Ut~IVL<SITY OF HAWAII LIBRARY:
CORRELATION OF RESISTANCE VALUE (R-VALUE) WITH CALIFORNIA BEARING
RATIO (CBR) FOR USE IN THE DESIGN OF FLEXIBLE PAVEMENTS
A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAI'I IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
IN
CIVIL ENGINEERING
December 2005
by Reyn S. Hashiro
Thesis Committee:
Phillip SK Ooi, Chairperson Peter G. Nicholson Horst G. Brandes
We certify that we have read this thesis and that, in our opinion, it is satisfactory in
scope and quality as a thesis for the degree of Master of Science in Civil Engineering.
,,~==
Q111 .H3
no. 40221
THESIS COMMITTEE
0l{£1%~ Chairperson
11
ACKNOWLEDGEMENTS
I would like to offer my sincere thanks to my research advisor Dr. Phillip Ooi for
his patience, guidance and assistance throughout my research project. I would also like
to thank Dr. Peter Nicholson and Dr. Horst Brandes for their guidance and assistance
throughout my graduate studies. Much thanks goes to the State of Hawaii Department
of Transportation (HOOT) and the Federal Highway Administrations for funding this
research project.
I would like to thank my fellow graduate assistants Mr. Kealohi Sandefur and Mr.
Jianping Pu for their assistance in soil sampling and for performing and analyzing many
of the index tests performed on the soil samples. Also, a special acknowledgement
goes to Mr. Robert Fukuda (HOOT) for performing all R-Value tests for this research
project.
In addition, I would like to thank the following people, agencies and companies
for their contributions to the research project: Miles Wagner, Herbert Chu (HOOT),
Steven Ege (HOOT), Brandon Hee (HOOT), George Masatsugu (HOOT), Clarence
Miyashiro (HOOT), Richard So (Department of Public Works, City and County of
Honolulu), Michelle Sakamoto (Dick Pacific Construction Company Ltd.), Department of
Land and Natural Resources, Leonard Leong (Royal Contracting Company), Board of
Water Supply and Geolabs, Inc.
Finally I'd like to thank my wife and daughter for their love and support to finish
my master's program at the University of Hawai'i at Manoa.
1I1
ABSTRACT
The Resistance Value (R-value) is commonly used by the Hawaii Department of
Transportation engineers to design the thickness of flexible pavements. Direct
measurements of the R-value require equipment that is not readily available to most
practicing engineers in the State of Hawaii. Typically, the R-value is indirectly based on
the results of the California Bearing Ratio (CBR) tests. Knowing the CBR, the R-value
is estimated based on published correlations. However, these correlations were
established for soils outside the State of Hawaii. Moreover, these correlations were not
established for directly relating R-value and CBR, but rather for estimating other
parameters such as resilient modulus, soil support value or modulus of subgrade
reaction.
CBR, R-value and index tests were performed on tropical residual soils from four
locations on the island of Oahu in the state of Hawaii. Based on the test results, five
correlations were developed to estimate the R-value. Among these procedures is one
relating R-value to index properties alone, without reference to the CBR value. The
limitations of each procedure and the choice of method are discussed.
Some tropical residual soils can undergo irreversible changes upon drying. One
of the soils sampled had a relatively high natural water content. As a secondary
objective, this soil was tested at three different stages of drying: first at its natural or in
situ state, second after oven drying the soil and third after drying the soil to
approximately half its natural water content (intermediate). This material can be
regarded as three different soils corresponding to the various stages of drying.
iv
The CBR and R-value were observed to increase from the in-situ to the oven
dried samples. The oven-dried samples were excluded from the correlations described
above because these soils were dried to temperature extremes that regular soils do not
experience, and therefore, are judged to be inappropriate for inclusion in the
correlations. The intermediate samples were included in the correlations because soils
used as fill material may undergo some drying prior to compaction in the field.
v
TABLE OF CONTENTS
ACKNOWLEDGEMENTS
ABSTRACT
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
CHAPTER 1 INTRODUCTION
1.1 OBJECTIVES
CHAPTER 2 LITERATURE REVIEW
2.1 CBR TEST
2.2 R-VALUETEST
2.3 CORRELATIONS BETWEEN CBR AND R-VALUE 2.3.1 Liddle et. al. (1967) 2.3.2 Van Til et al. (1972) 2.3.3 Packard (1984) 2.3.4 Equations Relating CBR and R-value to Resilient Modulus 2.3.5 Correlation Between R-value and Index Properties
CHAPTER 3 SOIL INDEX TESTING
3.1 SOIL SAMPLE LOCATIONS
3.2 INDEX TESTS AND RESULTS
3.2.1 Atterberg Limits 3.2.2 Grain Size Distribution 3.2.3 Sand Equivalent 3.2.4 Activity 3.2.6 Swell Potential
CHAPTER 4 CBR TESTING AND RESULTS
4.1 TEST PROGRAM
4.2 EQUIPMENT
4.3 TEST PROCEDURE
4.3.1 Sample Preparation 4.3.2 Compaction 4.3.3 Soaking of Samples 4.3.4 Penetration Test
4.4 ANALYSIS OF TEST RESULTS
CHAPTER S R-VALUE TESTING AND RESULTS
5.1 TEST PROGRAM 5.2 TEST PROCEDURE
vi
III
IV
VI
VIII
IX
1
2
4
4 S 7 9
10 12 15 18
20
20 2S 25 28 30 33 34
36
36 37 38 38 39 41 45 45
S4
54 54
5.2.1 Equipment and Sample Preparation 5.2.2 Compaction 5.2.3 Exudation Pressure 5.2.4 Resistance-Value Testing
5.3 ANALYSIS OF TEST RESULTS
CHAPTER 6 CORRELATION ANALYSIS
6.1 CORRELATIONS BETWEEN R-VALVE AND CBR
6.1.1 Method 1 6.1.2 Method 2 6.1.3 Method 3 6.1.4 Method 4 6.1.5 Method 5
6.2 CHOICE OF CORRELATION METHOD
CHAPTER 7 SUMMARY AND CONCLUSIONS
7.1 SUMMARY
7.2 CONCLUSIONS AND RECOMMENDATIONS
7.3 SUGGESTIONS FOR FUTURE WORK
REFERENCES
APPENDIX
Vll
54 57 59 59 60
63
63 63 79 82 84 88 91
93
93 95 96
97
101
LIST OF TABLES
Table 2.1 Standard load for high quality crushed stone material 4 Table 2.2 R-value at 300 psi (2068 kPa) exudation pressure as a function of
plasticity index and percent passing #200 sieve (After Arizona State DOT) 19 Table 3.1 Summary of in situ water contents 23 Table 3.2 Atterberg limits test results 26 Table 3.3 Liquidity index 28 Table 3.4 Sand equivalent test results 30 Table 3.6 Activity of soils tested 34 Table 3.7 WES method of classifying swell potential of undisturbed soils (after
Reese and O'Neill, 1988) 34 Table 3.8 Swell potential classification of compacted soils (Uniform Building Code,
1997) 35 Table 6.1 Slope and intercept from linear regression of R-value versus CBR without
Wahiawa ovendry 77 Table 6.2 Comparison of measured R-value with those predicted using the Arizona
DOT chart at 300 psi exudation pressure 88 Table 6.3 Findings on methods to estimate R-value 92 Table Al Interpreted R-values and soil properties 101 Table A2 Measured R-values 101
Ylll
LIST OF FIGURES
Figure 2.1 Penetration portion of CBR test (porter, 1949) 5 Figure 2.2 Schematic of a Hveem stabilometer (Howe, 1961) 7 Figure 2.3 Correlation chart for estimating soil support (Liddle et aI., 1967) 9 Figure 2.4 Correlation chart for estimating soil support (Van Til et al., 1972) 11 Figure 2.5 Soil classification related to strength parameters (Packard, 1984) 13 Figure 2.6 Earlier version of Figure 2.5 (Portland Cement Association, 1966) 14 Figure 2.7 Resilient modulus as a function of CBR (Heukelom and Klomp, 1962) 16 Figure 2.8 Comparison of R-value vs. CBR relationship derived indirectly from
Heukelom and Klomp's (1962 - Equation 2.5) and Powell et al.'s (1984-Eq'uation 2.7) equations 17
Figure 3.1 Soil sampling locations 21 Figure 3.2 In situ water contents of sampled soils 24 Figure 3.3 Atterberg limits and plasticity chart 27 Figure 3.4 Grain size distribution for soils from (a) Waipio; (a) Kapolei; (b) Mililani
Mauka; and (d) Wahiawa 31 Figure 4.1 CBR penetration test apparatus and data acquisition system 38 Figure 4.2 Mechanical rammer used for compaction of CBR samples 40 Figure 4.3 Soaking of CBR specimens and monitoring of swell 42 Figure 4.4 Swell contours for (a) Waipio; (b) Kapolei; (c) Mililani Mauka and (d)
Wahiawa in situ 43 Figure 4.5 Swell versus CBR 45 Figure 4.6 CBR family of curves for Waipio (a) Dry unit weight versus moisture
content; (b) CBR versus moisture content; and (c) CBR versus dry unit weight at constant moisture content 47
Figure 4.7 CBR family of curves for Kapolei (a) Dry unit weight versus moisture content; (b) CBR versus moisture content; and (c) CBR versus dry unit weight at constant moisture content 48
Figure 4.8 CBR family of curves for Mililani Mauka (a) Dry unit weight versus moisture content; (b) CBR versus moisture content; and (c) CBR versus dry unit weight at constant moisture content 49
Figure 4.9 CBR family of curves for Wahiawa in situ (a) Dry unit weight versus moisture content; (b) CBR versus moisture content; and (c) CBR versus dry unit weight at constant moisture content 50
Figure 4.1 CBR family of curves for Wahiawa intermediate (a) Dry unit weight versus moisture content; (b) CBR versus moisture content; and (c) CBR versus dry unit weight at constant moisture content 51
Figure 4.11 CBR family of curves for Wahiawa ovendry (a) Dry unit weight versus moisture content; (b) CBR versus moisture content; and (c) CBR versus dry unit weight at constant moisture content 52
Figure 4.12 Effect of Drying on Compaction Curves for Wahiawa Soil (a) Slayers @ 56 blows (b) Slayers @ 25 blows (c) Slayers @ 10 blows and (d) 3 layers @ 56 blows 53
Figure 5.1 Kneading compactor for R-value testing 55
IX
Figure 5.2 Exudation indicator device and loading frame with soil press for R-value testing 55
Figure 5.3 Hveem stabilometer device for R-value testing 56 Figure 5.4 Water content and dry unit weight of R-value samples prior to exudation
(a) Waipio; (b) Kapolei; (c) Mililani Mauka; (d) Wahiawa in situ; (e) Wahiawa intermediate and (f) Wahiawa oven-dry 58
Figure 5.5 R-value versus exudation pressure for soils from (a) Waipio; (b) Kapolei; (c) Mililani Mauka; (d) Wahiawa 61
Figure 6.1 CBR vs. R-Value (Epl = 240 psi,S Layers @ 56 Blows, RC I = 100%) 64 Figure 6.2 CBR vs. R-Value (EP = 300 psi,S Layers @ 56 Blows, RC = 100%) 64 Figure 6.3 CBR vs. R-value (EP = 240 psi,S Layers @ 56 Blows, RC = 95% Dry) 65 Figure 6.4 CBR vs. R-value (EP = 300 psi,S Layers @ 56 Blows, RC = 95% Dry) 65 Figure 6.5 CBR vs.' R-value (EP = 240 psi,S Layers @ 56 Blows, RC = 95% Wet) 66 Figure 6.6 CBR vs. R-value (EP = 300 psi,S Layers @ 56 Blows, RC = 95% Wet) 66 Figure 6.7 CBR vs. R-value (EP = 240 psi, 5 Layers @ 25 Blows, RC = 100%) 67 Figure 6.8 CBR vs. R-value (EP = 300 psi, 5 Layers @ 25 Blows, RC = 100%) 67 Figure 6.9 CBR vs. R-value (EP = 240 psi, 5 Layers @ 25 Blows, RC = 95% Dry) 68 Figure 6.10 CBR vs. R-value (EP = 300 psi, 5 Layers @ 25 Blows, RC = 95% Dry) 68 Figure 6.11 CBR vs. R-value (EP = 240 psi, 5 Layers @ 25 Blows, RC = 95% Wet) 69 Figure 6.12 CBR vs. R-value (EP = 300 psi, 5 Layers @ 25 Blows, RC = 95% Wet) 69 Figure 6.13 CBR vs. R-value (EP = 240 psi, 5 Layers @ 10 Blows, RC = 100%) 70 Figure 6.14 CBR vs. R-value (EP = 300 psi, 5 Layers @ 10 Blows, RC = 100%) 70 Figure 6.15 CBR vs. R-value (EP = 240 psi, 5 Layers @ 10 Blows, RC = 95% Dry) 71 Figure 6.16 CBR vs. R-value (EP = 300 psi,S Layers @ 10 Blows, RC = 95% Dry) 71 Figure 6.17 CBR vs. R-value (EP = 240 psi,S Layers @ 10 Blows, RC = 95% Wet) 72 Figure 6.18 CBR vs. R-value (EP = 300 psi, 5 Layers @ 10 BlOWS, RC = 95% Wet) 72 Figure 6.19 CBR vs. R-value (EP = 240 psi, 3 Layers @ 56 Blows, RC = 100%) 73 Figure 6.20 CBR vs. R-value (EP = 300 psi, 3 Layers @ 56 Blows, RC = 100%) 73 Figure 6.21 CBR vs. R-value (EP = 240 psi, 3 Layers @ 56 Blows, RC = 95% Dry) 74 Figure 6.22 CBR vs. R-value (EP = 300 psi, 3 Layers @ 56 Blows, RC = 95% Dry) 74 Figure 6.23 CBR vs. R-value (EP = 240 psi, 3 Layers @ 56 Blows, RC = 95% Wet) 75 Figure 6.24 CBR vs. R-value (EP = 300 psi, 3 Layers @ 56 Blows, RC = 95% Wet) 75 Figure 6.25 CBR vs. R-value (EP = 240 psi, Kentucky CBR) 76 Figure 6.26 CBR vs. R-value (EP = 300 psi, Kentucky CBR) 76 Figure 6.27 Comparison of measured R-value versus predicted using Van Tilet al.
(1972) 79 Figure 6.28 Predicted versus experimental slopes of the R-value versus CBR curves 81 Figure 6.29 Predicted versus experimental intercepts of the R-value versus CBR
curves 81 Figure 6.30 Comparison of predicted and measured R-values using Method 2 82 Figure 6.31 Comparison of predicted versus measured R-values using Method 3 83 Figure 6.32 Normalized CBR versus water content for constant compactive effort 85 Figure 6.33 Normalized CBR versus water content for constant dry unit weight 86 Figure 6.34 Path to obtain CBR based on Modified Proctor when the CBR at other
compaction effort is known (Li and Selig, 1994) 87 Figure 6.36 Comparison of predicted versus measured R-values using equation 6.10 90
x
CHAPTER 1 INTRODUCTION
The resistance value or R-value is used by the Hawaii Department of
Transportation (HOOT) engineers to design the thickness of flexible pavements. Direct
measurements of the R-value require testing equipment that is not available to most
engineers in Hawaii. The typical engineering practice in Hawaii is to estimate the R
value indirectly based on the results of the California Bearing Ratio (CBR) test.
Knowing the CBR, the R-value is estimated based on published correlations. These
correlations were not established to directly relate R-value and CBR. Rather, they were
meant for estimating other parameters such as the resilient modulus, soil support value
or modulus of subgrade reaction based on the R-value or CBR. Moreover, these
correlations were established for soils outside of the State of Hawaii.
Some tropical residual soils found in Hawaii have been known to exhibit different
characteristics than soils from temperate regions on the U.S. continent. According to
Mitchell and Sitar (1982), tropical residual soils including those found in Hawaii are likely
to be less dense, less plastic, less compressible, stronger and more permeable than
temperate soils of comparable liquid limit. One complication to this research program is
that tropical soils rich in halloysite can undergo irreversible changes upon drying.
Halloysite consists of alternating kaolinite unit cells and one layer of water molecules
resulting in a much weaker bond between the kaolinite units (Mitchell and Sitar, 1982).
As weathering proceeds, the halloysite content decreases and the kaolinite content
increases. The halloysite particles are characterized by a tubular morphology. As a
result of heating or air-drying, the water layer in the halloysite is removed irreversibly,
i.e., the material will not rehydrate to its former amorphous state. The addition of water
to the dehydrated sample will result in different properties than the same undried soil of
equal moisture content. Since this study involved testing tropical soils, every effort was
made to preserve the moisture of the soil samples prior to testing. In the event that
drying of the soil is required during testing (e.g., during compaction), the soil was tested
from wet to dry.
1.1 Objectives
The objectives of this research program included the following:
1. Conduct a literature search to identify existing correlations that link CBR with R
values. Correlations between R-value and other soil parameters were also
included in the search.
2. Perform a series of CBR tests and R-value determinations for tropical residual
soils. CH soils were not considered in this research program because they are
typically not used as subgrade material. Instead, ML and MH soils, which are
more commonly found on the Hawaiian islands, were tested in this research
program.
3. Perform soil index tests on these soils.
4. Verify that the previously established correlations between CBR and R-value apply
to local soils. If not, propose a correlation between CBR and R-value for the soils
tested. Perform a study to see if R-values can be correlated to other soil
parameters.
5. Develop a database of R-values for the soils tested in the State of Hawaii.
2
The CBR and R-value tests are briefly reviewed in Chapter 2. A literature review
of correlations between CBR and R-value is also included in this chapter. In Chapter 3,
the soil sampling locations and results of the soil index tests are presented. The CBR
and R-value test results are contained in Chapters 4 and 5, respectively. Correlations
developed to estimate the R-value and a discussion on the choice of methods are
covered in Chapter 6. To conclude in Chapter 7, a summary of the work,
recommendations on the correlations and suggestions for future work are described.
3
CHAPTER 2 LITERATURE REVIEW
The principles of the CBR and R-value tests are first briefly described.
2.1 CBR Test
The equipment and test procedure are detailed in AASHTO T 193-99 and ASTM
01883-99. There are three stages in a CBR test. First, the specimen is dynamically
compacted in a 6-inch (152.4 mm) diameter mold. Second, the specimen is soaked for 4
days with a surcharge load applied. Soaking the sample simulates the worst-case
moisture scenario in the field and the surcharge simulates the overburden due to the
pavement. Third, with the same surcharge load applied, a standardized piston having an
area of 3 in2 (19.4 cm2) is used to penetrate the soil in the mold at a rate of 0.05 inch per
minute (1.27 mm per minute) (Figure 2.1). Generally, the load at 0.1-inch (2.54 mm)
penetration is used to compute the CBR. The CBR is defined as the ratio of the stress at
0.1-inch (2.54 mm) penetration to that of a standard value. Standard values correspond
to those for a high-quality crushed stone and are summarized in Table 2.1.
Table 2.1 Standard load for high quality crushed stone material
Penetration (inch) Standard Load for Crushed Stone _(psi) 0.1 1000 0.2 1500 0.3 1900 0.4 2300 0.5 2600
Note: Conversion factors: 1 In - 25.4 mm and 1 PSI - 6.895 kPa.
If the CBR at 0.2-inch (5.08 mm) penetration is found to be higher than at 0.1-inch (2.54
mm) penetration, the load value at 0.2-inch (5.08 mm) penetration is used if another test
confirms a similar result.
4
r---------.. c
Head
_ Penetration piston
Til per£'d lugs
6 In. cylindrical mold
Figure 2.1 Penetration portion of CBR test (Porter, 1949)
2.2 R·value Test
The equipment and test procedure are described in AASHTO T 190-02 or ASTM
02844-01. There are four stages in the R-value test. First, the specimen is compacted in
a 4-inch (101.6 mm) diameter steel mold using a kneading compactor, which alternately
applies and releases a pressure of 350 psi (2,413 kPa) during the last 100 tamps.
Second, the specimen is loaded in a steel mold with a testing press until enough moisture
squeezes out of the specimen to light up five of six bulbs on an exudation indicator
device. Third, the specimen is soaked for 24 hours. Fourth, the specimen is placed in a
5
Hveem stabilometer (Figure 2.2) to measure the R-value. This device consists of a
cylindrical shell, which has a portion of the inside walls hollowed out and a neoprene
rubber diaphragm fixed in position. The annulus behind the diaphragm is filled with a
hydraulic fluid and is connected to a pressure gauge. When the 2.5-inch (63.5 mm) high
x 4-inch (101.6 mm) diameter sample is loaded from the top, the portion of the vertical
load transmitted by the specimen to the liquid annulus can be read on the gauge. The
resistance offered by the soil is expressed as a function of the ratio of the lateral
transmitted pressure to the vertical pressure of 160 psi (1,103 kPa) applied with a testing
press. This ratio provides an indication of the resistance to plastic flow, arranged on a
linear scale of 0 to 100. In its simplest form, the R-value is defined as:
(2.1 )
where Ph and Pv are horizontal and vertical pressures, respectively. The lateral pressure
varies inversely with the internal resistance of the soil. For example, an R-value of 100
indicates a material that does not deform under the vertical load. On the other hand, an
R-value of 0 indicates that the material offers no shear resistance and behaves like a
liquid.
6
FOLLOWER FOR II.I'PL~ING
LOAD TO SPECI"'E H
VALVE
_IR
SMALL PRESSURE
jt::l:3=::- FLEXIBLE DIAPHRAGM
NOT TO SCALE
PLATEN OF TESTING MACHINE
Figure 2.2 Schematic of a Hveem stabilometer (Howe, 1961)
2.3 Correlations between CBR and R-value
In the design of flexible pavements, the value of CBR after construction is desired.
If the subgrade soil is subjected to moisture changes, knowledge of the CBR after
undergoing a change in the field moisture content is desirable. To facilitate this, a
relationship between the moisture content, dry unit weight and CBR is needed. This
involves preparing CBR samples at a range of moisture contents and dry unit weights,
i.e., developing a "family of curves." Unlike the CBR, the R-value test data do not directly
permit selection of field compaction conditions. The R-value test is measured over a
range of exudation pressures by varying the moisture content. The R-value specimens
are usually prepared wet of optimum (Asphalt Institute, 1982) because of the uniqueness
of the exudation portion of the test, where the soil is loaded until moisture is squeezed
from the soil specimen. This pressure is called the exudation pressure. The design R-
7
value is selected based on a value of exudation pressure that best represents the worst
condition likely to be reached in place within the subgrade several years after construction
(Howe, 1961). The representative exudation pressure is a function of several factors
including soil type, climate, drainage and highway construction conditions. For a given
soil, the R-value ,varies with exudation pressure. An exudation pressure of 240 psi (1,655
kPa) is used in California while an exudation pressure of 300 psi (2,068 kPa) is adopted
in Washington and Hawaii. As a result of this difference between the CBR and R-value, it
is important to know not only the correlation but also under what conditions are the
correlations applicable; e.g., CBR at optimum based on Standard Proctor versus R-value
at exudation pressure of 240 psi (1,655 kPa).
Direct correlations between CBR and R-value are not commonly available. Often,
CBR and R-value are individually correlated with (1) resilient modulus, (2) soil support
value or (3) modulus of subgrade reaction. The correlations between CBR and R-value
described below are indirectly derived by combining two relationships: one between CBR
and say, the resilient modulus and the other between R-value and the resilient modulus.
By eliminating the resilient modulus, the relationship between CBR and R-value is
obtained. An extensive literature review was performed but no recent literature was found
that provided correlations between the CBR and R-value.
8
2.3.1 Liddle et. al. (1967)
The Utah State Department of Highways Materials and Tests Division proposed
the correlation between the R-Value at two exudation pressures, three types of CBR
(dynamic, static and AASHTO 3 point) and the soil support value (Liddle et aI., 1967) as
shown in Figure 2.3. This correlation was later adopted in AASHTO's (1976) Interim
Guide for Design of Pavement Structures.
I
.--- -- tU,. '40 '20
.. 70
.- 00-,. 711- 1~5-
.. IS 7- 36-
30 3. • 25 25 ~ 20 e
6-0 - 0 ~-- 1'5, -
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Figure 2.3 Correlation chart for estimating soil support (Liddle et aI., 1967)
The various CBR tests differ in the method of compacting the test specimens.
Static compaction involves compacting the samples with a static compression load, while
the dynamiC and the AASHTO 3 point test utilizes a vertical moving rammer dropped onto
the sample. The compaction method affects the soil structure in fine-grained soils and
therefore, the strength and stiffness characteristics (Seed et aI., 1960). The current
9
AASHTO T 193-99 and ASTM 01883-99 specifications require dynamic compaction of
test specimens.
Liddle et al. (1967) performed CBR and R-value tests on four Utah soils. CBR
tests were performed over a wide range of dry unit weights and moisture contents. The
resulting CBR is widely variable and the mean was used in the correlation. This
methodology was repeated for each soil sample. The CBR obtained in this fashion is not
specific to a particular combination of moisture content and dry unit weight. Multiple R
value tests were performed to determine the R-value at exudation pressures of 240 and
300 psi (1654 and 2068 kPa). Each mean CBR and R-value for the four soils was then
correlated to the soil support value by first determining its equivalent dynamic CBR. This
dynamic CBR value was then correlated to the soil support number using a previous
relationship that was obtained from the Utah State Material's Manual. AASHTO (1972)
cautioned against using this correlation for soils other than those found in Utah.
2.3.2 Van Til et al. (1972)
Van Til et al. (1972) indicated that "the vertical compressive strain on the subgrade
was the most significant factor affecting the performance of the roads at the AASHO
Road Test." They also recognized the importance of layer theory and wanted to develop
a rational approach to estimate the soil support value based on the resilient modulus.
They proposed a correlation between the soil resilient modulus, R-value (at 240 and 300
psi (1654 and 2068 kPa) exudation pressures) and the CBR as shown in Figure 2.4. In
this chart, the CBR is measured in accordance with the method proposed by Drake and
Havens (1959). Developed in Kentucky, this method requires that the soil specimen be
molded at or near the optimum moisture content as determined by the standard Proctor
10
(AASHTO T 99-01 or ASTM 0698-91) compaction test. Then the soil is compacted in a
CBR mold using dynamic compaction, where a 10-pound (4.54 kg) hammer is dropped
from a height of 18 inches (46 cm). The soil is compacted in five equal layers with each
layer receiving 10 blows. The soil is then soaked for 4 days prior to testing. Note that the
Kentucky CBR test procedure is not the same as the CBR test in AASHTO T 193-99 or
ASTM 01883-99. This chart was adopted in the 1986 AASHTO Guide for the Design of
Pavement Structures.
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; (I) Th. CQr.-.hU_ I .... teh the .... , •• c,,'--...... \I.r Wlfonoh: u.sIO d •• 1p •• t .... h 1'~Lll-'O .... 04 .. ..daU_ p" ........ I .. 240".1. 5 ••• ,,"_, ".:01 •• _~ Id....a'. R,,)C •• "The factOr. IJad.nl~1I'I. til ..... tl .... &1 0 .. ' .... ISf 1'. __ H,K .',",c. BU. yolo 2. (l' •• ) pp. \01-136. {U The cOrT<OlatiOOI 11 ""til th .... dp tV"" ... 4 1>, 11..,11.10'1(_ DorIOt. of Hlp.,._: ...,aolaU .... p~ •• "n :I.. )1)0 pd. s •• "rl.&"tb~. ,.--.t Ou1p. Corulec1oo SUdy.ri 111\1 B .. l1. 13309561. (.)} Th. ct>rfthtl_ 11 "l.It tlte 011 01, .. , .. cu"-v'" cleve I..,." '" r:.".ucJi.,. s •• ~ ...... II •••• _cI H ..... IU. J.A., • ..... _C"'.l ... tt .... of ha".d<, rlodbl. P .. _ ... O .. lp C:rH.ri_." In, .. lull. 2ll ("~9) PI'. )).--S6. n.. (oll""~ to. ~""""tt1 __ ~"l:r to til. 16l>ornort-ModtU.d cal, .... e1_ .. I .. to IHI _l.t.d At IIf ....... ti,. O\ltl_ o"l.tun ",,,",,.at .. .t.t~....tll." by AASIIO T-": dya.1C .. ~ .... tlo .. II to b. _.d ... nll • n_r _lfht 'Or 10 111 ""'"ppod (ra. I h.I"'~ q.t I. , ... : .,. .. 1_0 I~ '0 h ~OIIIIuud 1 .. U ... • ",_1 l • .,..n "itll .0 ... 11 I.~.r r.".trtD, 10 1>1 __ : .'.cl .... I. <0 b •• ..u. .. ", (u , day •. (4) Thlo .tlh II ... ""'0 .. d ..... l_d by c_p.rh_ 1 .. 1t ....... (h. C£Ht"l'1\L. ~- ... lue .... " ,he Croup Illd.' "'Ura.I_" by ,ho ,ro,,04ue til h"",. lin ..... 1. 2~ (I"S) pp. )1'_"~. ---
Figure 2.4 Correlation chart for estimating soil support (Van Til et aI., 1972)
11
2.3.3 Packard (1984)
Based on unpublished data of R-value varying with the modulus of subgrade
reaction, and based on the relationship between the modulus of subgrade reaction and
CBR, Packard (1984) developed an empirical chart where the soil R-value may be
indirectly obtained from CBR test results (Figure 2.5). An earlier version of this chart was
published by the Portland Cement Association in 1966, a copy of which is shown in
Figure 2.6. Since the soil strength parameters were related to modulus of subgrade
reaction, these charts were developed for use in the design of rigid or concrete
pavements. These charts are useful in that they provide CBR and R-values for various
soil types. However, the soil physical state (combination of water content and dry unit
weight) at which the CBR is based on was not provided.
A recent publication by Hall et al. (1997) indicated that while there is a noticeable
relationship between the modulus of subgrade reaction and CBR, there is little or no
correlation between the modulus of subgrade reaction and R-value. Therefore, Packard's
correlation, if used to relate R-value to CBR, should be used with caution.
12
2 GAUfOl'lNlA a!ARING RATIO· caR'"
) " , • , • • 10 " 20 ~ to .., so to 10 10 to 100
ASTM
j I • • , , &
son. Cl.ASSlFteATlON SYSTEM ", I I I I I I I I
(\JIIII;'" C",".ficoh,,,,)
1 1 \ \ \ I i
, I AASHO son. Cl.ASSlflCATIONI' \ I I I
.1'
I I . .
I I I -- - -. . .. . . . . .. -Ft:O!RAI.. AVIATION ADMINISTRATION I I I I I I
SOIL I CI..ASSIFICATtr"' I . . . . . . . . .
I . I 1 . ,
, I I I I
I I ! RESISTANCE VALUE - R'"
, I to ~o "0 '0 55 10
I I I I I I
I MOCULUS OF Su8GRAOE REACTION' k P~' ,... '" "'j I I I 100 150 I zoo %50 ~o 400 sao 100 100,' 10
I I I I I I I \
I BEARING VAL VIE , ,,;,"'11 I
,
I (30-.ndiomet., pIGtt. O.Hn deftechon)
10 I 20 ,0 I <0 I 50 .0 '0
f I I I I ,
CA'I..I'Fo'RNIA BEARING RATIO', CB" I I I 3 " I , ., • , 10 20 Z5 )0 <0 '0 $0'0 00 90 000
(1) For the basic idea, see O.J. Porter. ~Foundatioris for Flexible Pavements.w Highway Research Board Proceedings of the Twenty-second Annual Meeting. 1942, Vol. 22. pages 100 - 136.
(2) ASTM Designation 02487. (3) ·Classification of Highway Subgrade Materials." Highway Research Board Proceedings of the Twenty-fifth Annual Meeting.
1945. Vol. 25. pages 376·392. (4) Airport Paving. U.S. Deparbnentof Commerce. Federal Aviation Agency. May 1948. pages 11-16. Estimated using values
given in FAA Design Manual for Airport Pavements (Formerly used FAA Classification. Unified Clasification now used.) (5) C. E. Wames. "Correlation Between R Value and k Value.ft Unpublished report. Portland Cement Association. Rocky
Mountain-Northwest Region. October 1971 (best fit correlation with correction for saturation) (6) See TA Middlebrooks and G.E. Bertram. 'Soil Tests for Design of Runway Pavements.ft Highway Research Board
Proceeding of the Twenty-second Aonual Meeting. 1942. Vol. 22. pages 152,
Figure 2.5 Soil classification related to strength parameters (Packard, 1984)
13
2
3
CALIFORNIA BEARING RATIO - C BR' I e , T ••• 0 .5 20 Z'J 110 40 eo eo 10 1010Il10
UNIFIED I SOI( CLASSIFicATION'
Corps of EnVin .... U5.Army " and
u.~. Bureau of jeclimafion
AASHO SOIL CLASSIFICATION
Bureau of Public Roads I I I I, J
FEDERAL AVIATION AGENCY
SOIL
I CLASSIFICAT1'Oj.J !
i I I I , . I I
I
IR~SISTANCE VALUE - R
40 \ 50 55 60 20 lO
i I , r
.. . ..-
70 80
MODULUS OF'SUBGRADE REACTION· k psi pe; in. .'
I
I I
100 1200
, , I 300 400 soc 600 :700 1,,10 250 150
I i i I BEARING VALU'E , p~i
10 I (30, in.di ome •• r plate. 0 . !-in. deflection I
! 20 30 40 50 I
60 70
I I i I , , CALIFORNIA BEARING RATIO- CBR I
5 6 7 8 9 10 15 20 Z5 30 40· 60 eo TO 8010 IDO
•
Figure 2.6 Earlier version of Figure 2.5 (Portland Cement Association, 1966)
14
2.3.4 Equations Relating CBR and R-value to Resilient Modulus
The R-value can also be indirectly related to the CBR using an equation relating
the resilient modulus and CBR, and using an equation relating the resilient modulus and
R-value. A relationship between the resilient modulus of the soil and the CBR value was
proposed by Heukelom and Klomp (1962) as follows:
M, = 1500CBR (2.2)
where M, = resilient modulus of the soil in psi. Figure 2.7 illustrates the data used to
develop the correlation. The constant of proportionality of 1500 can vary quite
considerably from 0.5 to 2 times that amount. Heukelom and Klomp (1962) obtained field
measurements of the resilient modulus based on vibratory loading.
A relationship between the resilient modulus and the R-value was derived from
data collected in the San Diego County Experimental Base Project (Asphalt Institute,
1982) as follows:
M, (psi) = 772 + 369R (2.3)
This equation was subsequently revised to the following (Asphalt Institute, 1982):
M, (psi) = 1155 + 555R (2.4)
By equating the right-hand sides of equations 2.2 and 2.4 to eliminate M" the R-value can
be related to the CBR as follows:
R = 1500CBR-1155 555
(2.5)
15
MSHTO (1993) indicated that equations 2.2 and 2.4 are valid for a limited range of CBR
and R-values, respectively. Equation 2.2 is valid for CBR values of less than about 10,
while equation 2.4 is valid for R-values of less than about 20 .
4 .// Mr (MPa)=20 CBR /~ 0,,0 / 2
Mr (psl)=3000 CBR,,/' ;~// 2
/o/,f ~1 00
/ 0 0 /o~.B0 o~ ~ y~O 0/
• /~/cP.~ // ./.. 0 /
/ ~ -/ Qs i / Mr (MPa) = 10 CBR
/'7'*'. :(: // Mr (psI) = 1500 CBR / /6 / . lh ~ 0 .
6 /~Mr(MPa)=5 CBR
4 / Mr (psI) =750 CBR /
6
4
2
6
4
2
2 5 10 20 50 100 200 500 CBR VALUE
• <n 3 :l o o ~
Figure 2.7 Resilient modulus as a function of CBR (Heukelom and Klomp, 1962)
Another relationship between CBR and resilient modulus was proposed by Powell et
a\. (1984) for British soils as follows:
M, (psi) = 2552CBRo 64 (2.6)
16
In the UK, the CBR is measured on samples that are prepared at the dry unit weight and
water content that are likely to be in the field without soaking (Croney and Croney, 1998).
Combining equations 2.4 and 2.6, and eliminating Mr, R-value can be related to CBR as
follows:
2552CBR064 -1155 R = ----=-=:-::---
555 (2.7)
A comparison of the effects of using equations 2.5 and 2.7 is shown in Figure 2.8. At
CBR values less than 5, the two methods yield similar R-values. When the CBR value
exceeds 5, equation 2.7 is found to be more conservative.
70
60
50 ~
~ .. -40 GI :I
~ 30 • IX
20
10
0
0 5 10
.. .. .. .. .. .. .. ..
15
CBR (%)
.. .. .. .. .. ..
--Equation 2.5 Equation 2.7 --
20 25 30
Figure 2.8 Comparison of R-value vs. CBR relationship derived indirectly from Heukelom and Klomp's (1962 - Equation 2.5) and Powell et al.'s (1984-Equation 2.7) equations
For a given soil, the resilient modulus is a function of the soil stress state (confining
and deviatoric stresses) as well as the soil physical state (water content and dry unit
17
weight). The CBR is a function of the surcharge loads and soil physical state. The R
value is a function of exudation pressure (which is related to the soil physical state).
Correlations between the resilient modulus, CBR and R-value will be most useful if these
other variables are included or addressed but yet, they are excluded in many of the
correlations in the literature.
2.3.5 Correlation Between R-value and Index Properties
The R-value has been directly related to soil index properties. One such
correlation is provided in Table 2.2 used by the Arizona Department of Transportation
(Miyashiro, 2000) where the R-value is related to the plasticity index of the soil and the
percent passing the #200 sieve.
18
Table 2.2 R-value at 300 psi (2068 kPa) exudation pressure as a function of plasticity index and percent passing #200 sieve (After Arizona State DOT)
PERCENJ PASSING .200 SIEVE
0369UB~n~V~~~~~~~~~~m~~~n~~&~~rooo~ fl o 100 96 9l ea assl ~ 75 n ~ !i6 ~ 61 sa 56 S4 52 49 41 45 44 41 40 3937 3S 34 33 31 30 29 2S 27 196~W~&~~nM!i6M~saS6S4SZ~~~44~40~D~~n313OM2SVU 2~~~~m~nM!i6M~~S6~SZ~~~44~40~D~~nD3Oa2SVU~ 3~~&~~nMPM~~S6S4SZ~~~44~40~»~~n~3O~~VM~~ 4~~~~n~QMM~S6S4SZ~~~44~~~D~~~~~~2SVM~~n 5&~mn~PM~~~S4SZ~~~44~41~D~MnU3O~2Sv~~~nn 6~mn~PMU~~~52m~~~~~~v~~nU3O~~VM~~nn21 7~n~QMQ~~~SZ~~~44U41~~~~nUD~2SVM~~nn~ro 8n~Q~~~~~SZ~~~44uu~~~unU31~2Svu~~nu~ro~ 9~Q~~~~~~~~~~Q~~~~~~un~~vu~~nn~mWI9 WMM~~~~g~UG~QU~~~~nUn302SVM~~DU2Im~wrn IIM~~~~g~GG~QU40~~~nUD302SV2S~~nn2ImWI9rnI7 12 6J ~ 58 55 r.J 51 49 47 45 43 41 40 ~ ~ 35 ~ 32 31 30 2S 27 2S 2S 24 23 22 21 m 20 19 18 17 17 13~saS5~~UG~Q4140~D~MUD3O~V2S2S~nU~mm~rnI717~ 14 58 55 r.J 51 49474543 41 40 ~ 31 ~ 34 32 31 30 zg 27 2S 25 24 2322 21 21 m 19 18 17 17 1615 ~S6r.J~4941~Q~40~D~34UD3O~V~2S~n22n2Iro~rnllll~~15 16 r.J 51 49 47 45 4342 40 ~ 11 3S 34 n 31 30 29 28 M 2S 24 13 22 21 11 ZO 19 18 11 17 16 IS 15 14 17~UG~44~40~V~34nD~~2S2S~~DU22~m~~17VI6g1514H 18 49 47 45 44 42 40 39 37 35 34 n 31 ~ 29 28 Z1 2S 24 D 22 zz 21 m 19 18 18 17 16 IS 15 14 14 \3 19 ~ 46 44 42 40 ~ 37 36 34 n31 ~ ~ 2S 27 z,; 24 Z3 n 22 11 ZO 19 18 18 17 16 16 IS 14 14 13 13 zo ~ 44 42 40 ~ 37 ~ 34 II 31 30 29 28 27 26 ~ 24 Z3 ZZ 21 ZO 19 18 1817 16 16 IS 14 14 13 13 12 n44.4039~3634n32~~2SV~2S"Z322~ZOI9mrn17~16~14H\313UI2 lZ 42 4' 19 11 36 34 n 32 ~ 29 28 21 26 ZS 24 Z3 22 ZI m 19 18 18 17 16 16 IS 14 14 13 \3 12 \2 \I 23 41 39 31 ~ 34 II 32 30 ~ 28 21 ~ 25 24 23 ZZ 21 ZO 19 181817 16 16 15 14 14 13 13 12 12 II II 24 39 37 ~ 35 ~ 3Z ~ ~ 28 27 26 25 24 Z3 22 21 ZO 19 19 18 17 16 16 IS 14 14 13 13 12 12 11 II 10 25 l8 ~ lS n 32 31 29 2S 27 U 25 24 n ZZ 21 m 19 19 IS 17 16 16 15 l4"14 13 1112 12 11 11 1010 26 36 35 II 3Z 31 29 2S 27 2S 25 24 Z3 ZZ 21 ro 19 19 18 17 16 16 15 IS 14 13 II 12 ,12 11 11 10 10 10 21 ~ II 3Z 31 ~ 28 21 26 25 24 Z3 Z2 21 ZO 19 19 18 17 16 16 IS IS 14 13 13 12 12 11 II 10 10 10 9 28 3l 32 31 ~ 28 27 26 2S 24 Z3 ZZ 21 ZO 19 19 18 17 17 16 15 IS 14 13 13 12 12 11 11 10 10 10 9 9 ~' 3Z 3\ ~ 28 Z) 26 2S 24 21 Z2 21 ZO ZO 19 18 17 II 1& 1$ 15 14 11 13 12 12 II II 10 10 10 9 9 9 ~ 31 3028 Z7 26 ZS 24 Z3 22 21 ZO 20 19 18 17 17 16 IS IS 14 13 13 12 12 11 II II 10 10 9 9 9 8 11 ~ 2927 26 25 24 23 ZZ 21 20 20 19 18 17 17 16 15 IS 14 14 1] 12 12 11 II II 10 10 9 9 9 8 8 32: 29 2126 25 24 23 Z2 21 21 20 19 18 17 II 16 IS IS 14 14 Il 12 12 II II 11 10 10 9 9 9 8 8 8 3l 27 26 2S ~ 23 ZZ 21 21 20 19 18 11 17 16 15 IS 14 14 13 13 12 12 11 II 10 10 9 9 9 8 8 8 7 l4 26 25 24 23 zz 21 21 20 19 18 II 17 16 IS IS 14 14 13 13 12 12 II 11 10 10 9 9 9 8 8 8 1 1 35 ~ 24 Z3 ZZ ZZ 21 20 19 18 II II 16 IS IS 14 14 13 13 12 12 11 II 10 10 9 9 9 8 8 8 7 1 7 36 24 D 2Z 22 21 ZO 19 18 18 17 16 IS 15 14 14 13 II 12 12 11 II 10 10 9 9 9 8 8 8 7 7 7 6 37 Z3 23 2Z 21 20 19 18 18 17 16 16 15 14 14 1l 13 12 12 II 11 10 10 9 9 9 8 8 8 7 7 7 I 6 38 Zl Z2 21 ZO 19 18 18 17 16 16 15 14 14 13 13·12 12 II II 10 10 9 9 9 8 8 8 7 7 7 7 6 6 ~ 22 21 ZO 19 18 18 17 16 1& 15 14 14 13 11 12 1211 II 10 10 9 9 9 8 8 8 7 7 7 7 6 6 6 40 21 ZO 19 18 18 17 16 16 IS 14 14 13 13 12 12 II II 10 10 10 9 9 8 8 a 7 7 7 7 6 6 6 6
; 42 19 19 18 17 16 16 IS 14 14 13 13 12 IZ II 11 10 10 10 9 9 8 8 8 7 7 7 7 6 6 6 6 5 5 44 18 17 1616 IS IS 14 13 13 12 12 11 11 10 10 10 9 9 88 8 7 7 7 7 6 6 6 6 5 5 5 5 ~ 1716 1515.14 13 11 12 12 11 \I 10 10 10 9 9 9 8 8 8 ? 7 7 6 6 6 6 5 5 S ~ 5 4 ~ IS IS 14:13 13 12 12 11 II II 10 10 9 ,9 9 8 8 8 1 7 7 6 6 6 6 5' 5 5' 5 5 4 4 4 m 14 14 1312 12'11 II 111010 9 9 9 8 8 8 1 7 7 6 6 6 6 5 5 5 5 S 4 4 4 4 4 52 13 13 12 12 II II ;10 10 9 .9 9 8 8 8 7 7 7 6 6 6 6; 5 5 5 5 5 4 4 4 4 4 4 1 S4 12 12 II II 10 10 9 9 9 8 8 8 7 1 7 6 6 6 6 5 5 5 5 5 4 4 4 4 4 4 1 3 3 !6 II II 10 10 9 .9 9 8 8 8 ) 7 7 7 6 6 6 6 5 5 5 5 4 4 4 4 4 4 3 3 3 3 3 58 10 10 10 9 9 8 8 8 I 7 7 7 6 5 5 6 5 5 5' 5 5 4 4 4 4 4 4 1 3 3 3 3 3 60 10 9 9 8 8 8 7 7 7 7 , 5 , 6 5 5 5 5 5 4 4 4 4 4 4 3 3 3 3 3 3 3 3 62 9 8 88) 1 1 7 6 6 6 6 555 5 5 4 4 444 4 3 3 3 3 3 3 3 3 2 2 64 8 8 8 7 7 7 6 666 5 5 5 5 544 4 4 4 4 3 3 1 1 1 3 3 3 2 222 66 8 1 7 7 6 666 5 5 5 5 5 4 4 4 4 4 4 333 3 3 3 3 3 2 2 2 2 2 2 6B 7 7 6 6 .6 6 5 5 5 5 5 4 4 4 4 4 4 3 1 3 3 3 3 3 3 2 2 2 2 2 2 2 2 70 6 6 6 6 ,'5 5 5 5 5 4 4 4 4 4 4 3 1 3 3 3 3 3 3 2 2 2 2 2 2 2 2 2 2 72 6·6 5 5 5 5 5 4 4 4 4 4 4 3 1 1 3 1 3 1 3 1 2 1 2 2 2 2 2 2 2 2 2 ~ 655 5 5 4 4 4 444 3 J 3 3 3 3 3 3 322 2 2 2 222 2 2 2 2 1 ~ 5 5 554 4 4 4 4 4 3 333 3 3 3 3 2 2 2 2 2 2 2 2 222 2 1 I 1
19
CHAPTER 3 SOIL INDEX TESTING
3.1 Soil Sample Locations
Soil samples from four different locations on the island of Oahu were collected for
testing. The site locations (Figure 3.1) and the date of sampling are as follows:
1) Waipio - February 1, 2001
2) Kapolei - May 24, 2001
3) Mililani Mauka - September 25, 2001
4) Wahiawa - February 7, 2002
A trench was dug at each site to expose the less desiccated soil for sampling. To
preserve the in situ moisture content, the soil samples were placed into plastic bags,
which were then placed into 5-gallon plastic buckets. Prior to storage, moisture contents
were recorded on the day of sampling. After heat-sealing the plastic bags, each bucket
was sealed with a lid containing an a-ring, which provided a watertight seal. The buckets
were then stored in a 100%-humidity curing room located in the structures laboratory in
Holmes Hall at the Department of Civil and Environmental Engineering, University of
Hawaii. These steps were necessary to avoid possible irreversible changes in the soil
properties that could occur upon drying.
20
KAENA POINT
NO SCALE
(a) Island map
(b) Waipio
HALEIWA
WAIALUA
• Kapolei
Wahiawa •
• Mililani Mauka
.Waipio AIEA
POINT
96789 MILILANI
TOWN TMK. 9-4
PACIFIC
PUNALUU
~~
KAHALUU
DIAMOND HEAD
.. -
~&:!1'" ' ./
_. --.Q>u<. • c
l
Figure 3.1 Soil sampling locations
21
OCEAN N
KAILUA
KAI
96797 WAIPIO TMK9-4
ITE
•
• !
-~ /-
---'" / "" -
.. --.- .: . .l
•
(c) Kapolei I
-, ./' r_ .... I -' ,
i \
,
, / I ( \ r
( - ) / -" ) --l
I ( ~
/
J .
/ ~ SITE \
.f I
iJ"
/ K rl,"W"IW
F " ..... ~ ..
O\~_..- C ~
\ ---~C" 1/ ,6 ..... ~. , ., ( '
• ,
\ flII.1
""' ... PrqOOll1t
I c
I "'y,,,,. 1 .. , .............. / I
,f,.",t'/f'II'f11 ,
C , Pac"..:. .T..cIl\lDt18 ,
(d) Mililani Mauka
•
'00 ,
.Q -
Makakllo
Golf _-_'-~ __ E'Course
,. ~~~ ...
96706 E WA
-'"
•
,
96789 MILILANI MAUKA
TMK 9-5
\
SITE
, •
Naval REtservallo n
96707 KAPOLEI
TMK 9 - 1
•
/ • •
/ • •
I , , I • • ,
• •
I • •
( • • I i • •
\. % .... ~
l • ~
Figure 3.1 Soil sampling locations (continued)
22
,-
ti A"' • • • E
TM
~ I" . J -S ., ...... , , _.;<::.-;z:~~ I'~
I ,
I
(e) Wahiawa
I
,
,
•
I
•
1
, \ •
•
96786 WAHIAWA
TMK 7-6
,
Schofield
Barracks
M ilitary
Reservation
,
I • , , ,
.. - ,, ' -
( • 96789 ,.,.,~
M ILILANI· .... ,/. MAUKA TMK 9-S
Figure 3.1 Soil sampling locations (continued)
E W A
/ FOREST ,,-RES~Ve
"-\ I '" ..... /
,
Nuclear gauge (courtesy of Geolabs, Inc.) and sand cone testing were performed
at each site to measure the in place dry unit weight and moisture contents. Only the
results of the in situ moisture contents are presented herein . The in situ moisture
contents are summarized in Table 3.1 and Figure 3.2.
Table 3.1 Summary of in situ water contents
Soil Water Content' % Sand Cone NuclearG~e
Ra~e Mean Ra~e Mean Waipio 27.9 26.5 to 28.9 25.2 to 28.5+ 27.0 K~olei 18.9 to 21.3 20.1 22.2 to 26.2 23.6
Mililani Mauka 28.1 to 33.4 30.5 30.9 to 37.7 34 .5 Wahiawa 50.6 to 56.9 52.5 54.1 to 63.7 58.3
Note: (1) In this report, in situ moisture contents refer to those obtained from the in situ material that was removed during sand cone testing . Nuclear density testing at Kapolei , Mililani Mauka and Wahiawa were performed in a trench whereby the trench walls could affect the moisture content as the standard count was obtained from outside the trench .
23
70r-------------------------------------~
-C 60 CI> CI CIS CI 50 ... CIS CI> (j ::::I 40 I:
E ,g 30 --I: CI> -I: 20 0 u ... CI> - 10 CIS ::
0
0 10 20 30 40
o Waipio Gentry 6 Kapolei ¢ Mililani Mauka OWaihiawa
50 60
Water content from sand cone testing (%)
Figure 3.2 In situ water contents of sampled soils
70
Compared to the other soils, the Wahiawa soil was found to have the highest in
situ moisture content ranging from 51% to 57%. This soil was tested at various stages of
drying to study the effects drying had on the various soil properties. The Wahiawa soil
was subjected to the following stages of drying:
1. Testing at the in situ moisture content (Samples were required to be tested at
lower moisture contents than the in situ moisture content. These samples were
tested from wet to dry to reduce the effects of drying on the soil; i.e., the samples
were never rewetted after drying down). These samples are referred to as
Wahiawa in situ.
24
2. Drying to approximately half the in situ moisture content or - 26% (Samples were
then tested from dry to wet if the target moisture contents were higher. If the target
moisture contents were lower, then they were tested from wet to dry). These
samples are referred to as Wahiawa intermediate.
3. Testing after oven-drying the soil (Samples were tested from dry to wet). These
samples are referred to as Wahiawa oven-dry.
Waipio, Kapolei and Mililani Mauka soils had lower in situ moisture contents
compared to the Wahiawa soil. Increasing in situ moisture contents generally are
characteristic of soils from higher elevations and wetter climates on Oahu. The soils
were tested from dry to wet if the target moisture contents were higher than the in situ or
from wet to dry (without rewetting) if the target moisture contents were lower. Also, a few
tests were performed on oven-dried samples to see if they underwent irreversible
changes upon drying. Test results are presented next.
3.2 Index Tests and Results
The following laboratory index tests were performed on each soil sample:
• Atterberg limits
• Grain size distribution
• Sand equivalent
• Specific gravity
3.2.1 Atterberg Limits
Liquid and plastic limits were determined in accordance with ASTM Standard
04318-00 and are summarized in Table 3.2. The test results are also summarized in a
plasticity chart shown in Figure 3.3. Based on the Unified Soil Classification System
25
(uses), soils from Waipio and Kapolei are classified as low plasticity silt, or ML. Soils
from Mililani Mauka and Wahiawa are classified as high plasticity silt, or MH. Based on
the AASHTO classification system, the Waipio and Kapolei soils are A7-6 while the
Mililani Mauka and Wahiawa soils are A7-5.
Upon drying, the Atterberg limits generally trend down the A-line, with the shift
more pronounced for the high plasticity soils.
Table 3.2 Atterberg limits test results
Soil Atterberg Limits Type Determinations Avg. Ovendry
1 2 3 4 5 6 Liquid Limit 45.4 43.4 47.6 46.0 -- -- 45.6 42.8
Waipio Plastic Limit 25.0 26.7 37.7 29.3 -- -- 29.7' 30.9' Plasticity Index 20.3 16.7 9.8 16.7 -- -- 15.9 12.0 Liquid Limit 42.2 40.4 41.7 41.4 41.2 -- 41.4 36.6
Kapolei Plastic Limit 26.2 28.5 26.4 27.6 27.8 -- 27.3 24.9 Plasticity Index 16.0 12.0 15.3 13.7 13.4 -- 14.1 11.7
Mililani Liquid Limit 96.9 88.4 95.5 100.0 -- -- 95.2 57.7
Mauka Plastic Limit 46.8 43.9 38.8 47.2 -- -- 44.2 37.5 Plasticity Index 50.1 44.4 56.7 52.7 -- -- 51.0 20.2
Wahiawa Liquid Limit 93.7 97.4 96.5 108.6 96.6 -- 98.6 --In situ Plastic Limit 44.1 48.5 49.4 49.1 44.6 -- 47.1 --
Plasticity Index 49.6 48.9 47.1 59.5 52.1 -- 51.4 --Wahiawa Liquid Limit 89.7 84.7 87.6 -- -- -- 87.3 --
Intermediate Plastic Limit 41.1 42.1 43.6 -- -- -- 42.3£ --Plasticity Index 48.6 42.6 44.0 -- -- -- 45.1 --
Wahiawa Liquid Limit 71.0 60.3 68.6 54.6 64.6 62.5 63.6 --
Ovendry Plastic Limit 47.5 43.5 43.6 42.2 43.0 45.4 44.2£ --Plasticity Index 23.5 16.8 25.1 12.4 21.7 17.2 19.4 --
Note 1. Plastic limit of the oven dry soil is higher than the average for the in situ soil.
The difference is not significant, it's well within the margin of error and may be attributable also to variability in the soil.
2. The average plastic limit of the oven dry soil is higher than the intermediate soil. The difference is not significant, it's well within the margin of error and may be attributable also to variability in the soil.
26
60r-----------------------.---------__ ------------~~m
40 ~. o ~
X Q) "0 C
;:. ·0 :;:;
'" «l
a. 20
o Kapolei OWaipio <> Mililani rv1auka !J. Wahiawa Sa"""le - In s ~u X Wahiawa Sal1l'le - Interrrediate + Wahiawa Sal1l>le • Ovendry • Kapolei - Ovendry • Waipio - Ovendry • Mililani Mauka - Ovendry
ML
+
~Une
• ++
A-Lineo
CH
MH
O+-~~~~~~~~~~~~T-~~~~~~~~~-W
o 20 40 60 80 100
Liquid Limit (%)
Figure 3.3 Atterberg limits and plasticity chart
The liquidity index (LJ) relates the natural moisture content of the soil in the ground
to the plastic limit and plasticity index. It is defined as
LJ = w-PL PI
(3.1 )
where w = natural moisture content, PL = plastic limit and PI = plasticity index. Values of
LJ are summarized in Table 3.3.
27
Table 3.3 Liquidity index
Soil Natural Moisture Plastic Limit Plasticity Index Liquidity Index ContenU%) (%) (Oio)
Waipio 27.9 29.7 15.9 -0.11 Kapolei 20.1 27.3 14.1 -0.51 Mililani 30.5 44.2 51.0 -0.27 Mauka
Wahiawa 52.5 47.1 51.4 0.11
The LI provides an indication of the soil's consistency and sensitivity. If LI is
approximately equal to 0, the natural moisture content is close to the plastic limit. This
indicates that the soil sensitivity (undisturbed strength divided by remolded strength) is
low and the soil consistency may be relatively stiff. On the other hand, if LI approaches
unity, the soil is close to the liquid limit. This is an indication that the soil is sensitive. If LI
is less than 0, this is an indication that the soil is desiccated and hard. Three of the four
soils had negative liquidity indices. Only the Wahiawa soil had a positive LI. However, its
LI is relatively low (0.11).
3.2.2 Grain Size Distribution
Grain size distributions were obtained by performing hydrometer testing and wet
sieve analyses in accordance with ASTM Standard D422-63 (2002). Three variations of
the wet sieve/hydrometer tests were used on the Kapolei soil to assess the sensitivity of
each method:
Method 1.
1. Soil from a bucket were divided into two 100g (0.22 Ibs) portions.
2. Several moisture contents of the soil were then measured on each portion.
3. Using the moist weight from (1) and the moisture content from (2), the total dry
weight was then calculated.
28
4. One portion was wet sieved through a stack of sieves (No. 40, 60, 100 and
200). The material retained on the sieves was ovendried to determine the dry
weights.
5. The portion passing the No. 200 sieve was not collected but the dry weight of
the percentage passing the No. 200 sieve can be estimated by subtracting the
sum of all the dry weights from (4) from the total dry weight from (3).
6. The second portion of the soil from (1) was wet sieved through the No. 200
sieve and the fines and water were collected.
7. The collected soil/water mix from (6) was then dried to a moisture content that
is near, but not less than the in situ value.
8. After determining the moisture content. a portion of the moist fines equivalent
to a dry weight of approximately 50g (0.11 Ibs) was subjected to hydrometer
testing. The actual dry weight of soil used in the hydrometer test was
determined at the conclusion of the hydrometer test.
9. The results from the wet sieve analyses and the hydrometer test were then
combined to yield the complete grain size distribution.
Method 2.
This method is identical to method 1 except for steps 1 and 5. In step 1, only one
portion of sample was used for wet sieving. In step 5, all the fines passing the No.
200 sieve were collected for the hydrometer test.
Method 3.
This method is identical to method 2 except that the soil retained on the No. 40, 60,
100 and 200 sieves were mixed with a 100 ml standard sodium hexametaphosphate
solution for several hours and stirred in a mechanical mixer. The deflocculated
material was wet sieved through the stack of the four finest sieves again. The
material retained on the sieves was oven-dried to determine the dry weights while the
fraction passing the No. 200 sieve was collected and dried to a moisture content near
the in situ value. After determining the moisture content. a portion of the moist fines
equivalent to a dry weight of 50g (0.11 Ibs) was subjected to hydrometer testing.
29
The results from all three methods are plotted in Figure 3.4b for the Kapolei soil.
Methods 2 and 3 are the most reliable but they are the most tedious to perform because a
significant amount of water had to be evaporated prior to hydrometer testing. When the
results from the methods were compared, they all yielded similar results, although method
3 resulted in the finest grain size distribution because of the use of the deflocculant prior
to wet sieving through the four smallest sieves. Because the differences are relatively
insignificant and because methods 2 and 3 are time consuming, the grain size
distributions of the soil from the other three locations were obtained using method 1.
The grain size distributions for all four soils are plotted in Figures 3.4a through
3.4d.
3.2.3 Sand Equivalent
The sand equivalent test is used to determine the characteristics of the finer
grained portion of cohesion less soils. Typically, clays have sand equivalents between 0
and 5, silty clays between 6 and 10, clayey silts between 11 and 30, clayey fine sands
between 30 and 40, and silty fine sands above 40. Sand equivalent tests were performed
in accordance with AASHTO T 176-02, the results of which are summarized in Table 3.4.
The test results below confirm that the soils tested were predominantly clayey silts.
Table 3.4 Sand equivalent test results
Soil Sand Equivalent Determinations Average Ovendry 1 2 3 4 5
WaipJo 8 11 13 17 -- 12 12 Kapolei 8 8 7 10 -- 8 12
Mililani Mauka 11 9 10 16 11 11 10 Wahiawa In situ 14 14 13 18 -- 15 --
Wahiawa Ovendry 21 21 19 19 20 20 --
30
100~~~~--------~~~L---------------------~
80
~
o e::.. 60 .... Q) t:
u::: "E 40
~ Q)
Q. 20
10 (a) Waipio
1
, • •
0.1 0.01
Particle Diameter (mm)
Sieve #4 Sieve #200
---- In-situ • Ovendried
0.001 0.0001
100~-r----~&S~~=-~-------------------,
80
~
~ 60 ~
.~ u.. "E 40 ~ Q) Q.
20
10 (b) Kapolei
1
o Method 1} o Method 2 In situ 6 Method 3
- - - - - - Ovendried
. .
0.1 0.01 Particle Diameter (mm)
--
0.001 0.0001
Figure 3.4 Grain size distribution for soils from (a) Waipio; (b) Kapolei; (c) Mililani Mauka; and (d) Wahiawa
31
100
80
~
~60 .... Ql c::
u::: C 40 ~ Ql a.
20
o
Sieve #4
10 (C) Mililani Mauka
100
80
~60 o ~ .... Ql C
~ 40 c:: Ql e Ql
a. 20
o
Sieve #4
10 (d) Wahiawa
1
Sieve #200
• In-situ • • - - - Ovendried • • •
• , \
• , '. ~
~
~~
0.1 0.Q1 0.001 0.0001
Particle Diameter (mm)
Sieve #200
...... . "
In-situ . - --- Intermediate , . '. . ..... Ovendried ,
--\
'. , . . " .... ........ .
..... ........... . . '. .
' . . . . . . , '.
0.1 0.01 0.001 0.0001 Particle Diameter (mm)
Figure 3.4 Grain size distribution for soils from (a) Waipio; (b) Kapolei; (c) Mililani Mauka; and (d) Wahiawa (continued)
32
3.2.4 Specific Gravity
The specific gravity of the soils was measured in accordance with ASTM Standard
0854-98, the results of which are summarized in Table 3.5.
Table 3.5 Specific gravity test results
Soil Specific Gravity Determinations Average Ovendry
1 2 3 4 5 Waipio 2.82 2.99 2.90 2.90 -- 2.90 2.90 Kapolei 2.96 2.90 3.09 3.04 -- 3.00 3.06
Mililani Mauka 2.96 2.94 3.01 3.01 -- 2.98 3.00 Wahiawa In Situ 2.99 3.06 3.20 3.22 2.94 3.08 --
Wahiawa Ovendry 3.09 2.94 3.17 3.25 - 3.11 --
In general, oven drying the soils did not lead to significant changes in the specific
gravity.
3.2.5 Activity
Activity is the ratio of plasticity index to % clay (% finer than 0.002 mm). The
plasticity index is related to both the mineralogy and the amount of clay present. For
example, a soil rich in kaolinite may have a similar plasticity index as another soil with
little montmorillonite. The effects can be separated by the activity of the soil, which is
related to the specific surface area of the clay mineral. According to Mitchell (1993), the
activity is approximately 0.5 for kaolinite, between 0.5 and 1 for illite and between 1 and 7
for montmorillonite. The activity of the soils sampled is summarized in Table 3.6.
The activity of the ML soils increased minimally after ovendrying while the activity
of the MH soils decreased significantly after ovendrying. At its natural state, the activity of
the Wahiawa soil is 0.83. It decreased by about 18% when the natural water content was
halved and it decreased by about 55% after oven drying.
33
Table 3.6 Activity of soils tested
Soil Plasticity Index Clay Fraction Activity (0;(» (%)
Waipio 15.9 48.0 0.33 Waipio ovendry 12.0 33.0 0.36 Kapolei 14.1 38.0 0.37 Kapolei ovendry 11.7 26.0 0.45 Mililani Mauka 51.0 64.0 0.80 Mililani Mauka ovendry 20.2 47.0 0.43 Wahiawa in situ 51.4 62.0 0.83 Wahiawa intermediate 45.1 67.0 0.67 Wahiawa ovendry 19.4 52.5 0.37
3.2.6 Swell Potential
The Waterways Experimental Station (WES) provides a useful classification for
identifying in situ soils with a swell potential based on Atterberg limits. The swell potential
can be classified as low, marginal or high as summarized in Table 3.7. These
classifications are based on volume change measured from oedometer testing of
undisturbed soils.
Table 3.7 WES method of classifying swell potential of undisturbed soils (after Reese and O'Neill, 1988)
LL PI Suction Pressure Potential Swell Potential Swell Classification (%) -(%) (tst) (%l > 60 > 35 >4 > 1.5 HiQh
50-60 25 - 35 1.5 - 4 0.5 -1.5 Maroinal < 50 < 25 < 1.5 < 0.5 Low
Based on the Atterberg limits and Table 3.7, the potential swell classifications for
the ML soils (Waipio and Kapolei) and MH soils (Mililani Mauka and Wahiawa) are low
and high, respectively. The swell potential of compacted soils is provided in the 1997
Uniform Building Code in Table 3.8. These classifications are also based on volume
change measured from oedometer testing.
34
Table 3.8 Swell potential classification of compacted soils (Uniform Building Code, 1997)
Percent Swell Potential Swell Classification (%) >13 Very High
9.1 -13 High 5.1 -9 Medium 2.1 -5 Low 0-2 Very Low
35
CHAPTER 4 CBR TESTING AND RESULTS
Highlights of the CBR test procedures that deviate from AASHTO T 193-99 and
ASTM D1883-99 or features that pertain to this project are discussed below.
4.1 Test Program
CBR tests were performed on the soil samples prepared using several compactive
efforts and a variety of phySical states. They are as follows:
1. 5 layers at 56 blows per layer (compaction effort equivalent to the Modified
Proctor or AASHTO T 180-01 Method B or ASTM D1557-02 Procedure C)
2. 5 layers at 25 blows per layer
3. 5 layers at 10 blows per layer
4. 3 layers at 56 blows per layer (compaction effort equivalent to the Standard
Proctor or AASHTO T 99-01 Method B or ASTM D698-00 Procedure C)
5. Kentucky CBR
For the first four test series, the CBR was measured on at least 5 samples with varying
physical states along the compaction curve (one at or close to the optimum moisture
content, two dry-of-optimum and two wet-of-optimum). The Kentucky CBR was
measured at only one physical state. This method required that the soil specimen be
molded at or near the optimum moisture content as determined by the Standard Proctor
(AASHTO T 99-01 or ASTM D698-00) compaction test. The soil is then compacted in a
standard 6" CBR mold using dynamic compaction, where a 10 pound (4.536 kg) hammer
is dropped from a height of 18 inches (45.72 cm). The soil is compacted in five equal
layers with each layer receiving 10 blows.
36
4.2 Equipment
The CBR testing equipment consisted of a loading frame supporting a piston that
penetrated the soil within the mold (Figure 4.1). A data acquisition system was used to
record the load and displacement during the penetration portion of the CBR test. These
readings were checked with manual readings of the load using a 6000-lb (2721 kg) rated
proving ring and displacements using a Soiltest Inc. LC-8 dial gauge for quality
assurance. The data acquisition system consisted of the following equipment:
1. 3000-lb (1360 kg) rated load cell (Sensortronics 60001-3K)
2. Two linear variable differential transducers (L VDT) with a range of ±1 inch
(25.4 mm) (Schaevitz 1000MHR)
3. Signal conditioner (PMG Precision Instruments SC-5B AC Transducer)
4. Computer with analog to digital (AID) board (Metra byte )
5. ATS software (Version 3.1)
During testing, the voltage output from the load cell and LVDT's were transmitted to the
signal conditioner, which converted the voltage to an analog output (in bytes). The
analog output is then translated by the AID board to load and displacement units. The
load cell and LVOT's were calibrated periodically to ensure that the correct load and
displacement were recorded by the ATS software. The L VDT's were placed diametrically
opposite, and the measured displacement was taken as the average of both L VOT
readings.
37
Figure 4 .1 CBR penetration test apparatus and data acquisition system
4.3 Test Procedure
The CBR tests were performed in accordance with ASTM D1883-99 and AASHTO
T 193-99. A few modifications were made to the testing procedure and sample
preparation. These are described below.
4.3.1 Sample Preparation
As stated in ASTM D1883-99, if the material passed the % in (19-mm) sieve then
the entire sample shall be used for testing. All of the soil samples tested passed the No.
38
4 sieve. Extraneous materials such as roots and other materials which may alter the
results of the CBR test were removed prior to testing.
Based on the moisture contents determined during the initial field sampling, two 5-
gallon buckets of soil with similar moisture contents were thoroughly hand mixed, passed
through a No.4 sieve, placed back into the plastic bags which were then heat sealed, and
restored in the 1 OO%-humidity concrete curing room to ensure a uniform soil and moisture
distribution. Moisture content checks on the samples were taken to ensure no moisture
lost occurred during sample preparation.
Two 5-gallon buckets (approx. 40 Ibs) of moist soil were required for a series of
CBR tests at each compactive effort. Prior to testing the soil from both buckets were
again emptied into a large pan and mixed thoroughly. Also, any soil clumps were broken
apart at this time and another series of moisture content checks were performed to
ensure no moisture loss occurred after soil mixing.
4.3.2 Compaction
Compaction of the CBR test samples were performed in accordance with ASTM
D1883-99 and AASHTO T 193-99 with several minor modifications. The soil required for
each lift was prepared separately rather than in a single batch. For each lift, the required
amount of water and soil was mixed thoroughly in a pan prior to compaction. Moisture
contents were determined using soil samples from lifts 1, 3 and 5 for soils compacted in 5
layers, or every lift for soils compacted in 3 layers. Additional soil was added to each
batch to allow moisture content determinations to be made. Soil for the subsequent lifts
were prepared during compaction of a lift to minimize drying of the soil.
39
A Boart Longyear 8-335 mechanical compactor (Figure 4.2) was used to prepare
the soil for the following series of tests:
1. 5 Layers at 56 Blows per layer.
2. 5 Layers at 25 Blows per layer.
Figure 4 .2 Mechanical rammer used for compaction of CBR samples
40
The mechanical compactor used a pie-shaped rammer, and was bolted to concrete floor.
Prior to testing, the mechanical compactor was calibrated in accordance with ASTM
02168-02 by comparing the defonnation of lead cylinders using both the mechanical
compactor and a manual compactor.
For the remaining test series (5 Layers at 10 blows per layer using a 10-lb (4.54
kg) hammer, 3 Layers at 56 blows per layer using a 5.5-lb (2.5 kg) hammer and the
Kentucky CBR), the samples were compacted manually. These test series were
compacted manually because it was determined that the mechanical compactor did not
provide equal compactive effort to each lift when the number of blows per lift is low (Le.
10) and when using the 5.5 Ibs (2.5 kg) rammer. In these instances, pockets of
uncompacted soil were observed when using the mechanical compactor.
4.3.3 Soaking of Samples
Volume change below road pavements occur upon loading as well as upon
changes in moisture content. The focus of this section is on wetting-induced volume
change rather than the load-induced variety. Volume change, especially in expansive
and collapsing subgrades, can cause pavement distress, and should ideally be
minimized. Generally, volume change tends to be higher when soils are compacted dry
of optimum (Seed, 1959 and Lawton et aI., 1989).
After compaction, each sample was placed into a tub of water and soaked for four
days. The soaking was necessary to simulate the worst-case scenario in the field. A 15-
Ib (6.8 kg) surcharge load was placed on the specimens during soaking (Figure 4.3) to
simulate the effect of the pavement overburden stress. Measurements of swell were
taken for each sample. If the sample swelled within the first hour, measurements were
41
taken every hour for four hours. Measurements were then taken on a daily basis during
the four day soaking period . Using swell measurements after the 4-day-soaking period ,
the volumetric expansion was calculated as the swell divided by the original sample
height for each point, and contour lines of percent volume change were generated as
shown in Figure 4.4. In general , volume change decreased as the molding water content
increased. Also the maximum volume change occurred dry of optimum. To minimize
volumetric expansion in compacted soils, they should ideally be compacted on the "wet
side". However, using too high a moisture content can compromise the strength (CBR) of
the soil (see later) .
Figure 4 .3 Soaking of CBR specimens and monitoring of swell
42
110 -.----."...-------,
105
100 a;::-&. 95 -~90 UI
i 85· o ~80. o
75 -• 5 layers @ 56 blOws • 5 layers @ 25 blows
70
65-~-~--~-,--~
• 5 layers @ 10 blows • 3 layer'S @ 56 blows
- Zero air void curve
15 20 25 30 Moisture Content (%)
(a)
35
11 d -,-------------,
105 -
100 -1i c. 95 -~ 90 UI
i 85-o ~ 80-· a
75 _.
• 5 layers @ 56 blows • 5 layers @ 25 blows 4 Siayers@ 10 blows • 3 layers@ 56 blows
-Zero air void curve
70 -
65+-~-~~~r_~~
,,20 30 40
Moisture Content (%) (e)
50
110 "r----. ___ T-'------,
105
100 a;::-&. 95 ---~ 90 UI
i 85·" o ~ 80·· a
1% O. %
75 - • 5Iaye",@56blows • 5 layers @ 25 blows
70 . • 5Iaye",@ 10 blow. • 3 layers @ 56 blows
-Zero air void curve 65+--~-_r-~-~
15 20 25 30 Moisture Content (%)
(b)
35
11 0 .r-----~--"-''--__,
105 -
100
g: 95 -~ 90 UI
• 5 layers @ 56 blows • 5 layers @ 25 blows • slayers @ 10 blows • 3 layers @56,bIOWS
- Zero air void CUrie
~ 85-
~ 80-· ........ -~~~ c
75·"
70 -
65-r. -~~--r--~-~ 20 30 40 50
Moisture Content (%) (d)
60
Figure 4.4 Swell contours for (a) Waipio; (b) Kapolei; (c) Mililani Mauka and (d) Wahiawa in situ
43
A plot of percent swell versus CBR is shown in Figure 4.5. The swell is higher for
the high plasticity soils (Le., Wahiawa and Mililani Mauka). The maximum values
recorded for the percent swell were: 7.5%, 6.9%, 2.9% and 2.2% for Wahiawa, Mililani
Mauka, Kapolei and Waipio, respectively. The maximum values recorded for the percent
swell were: 7.5%, 5.1 % and 3.0% for Wahiawa in situ, intermediate and ovendry.
According to the UBC method of classifying swell potential of soils, the Kapolei and
Waipio soils that swelled 2.9% and 2.2%, respectively, can both be classified as having a
low swell potential. While the Wahiawa and Mililani Mauka soils that swelled 7.5% and
6.9%, respectively, have a medium swell potential. The UBC potential swell
classifications are based on swells measured in oedometer testing. It is expected that
CBR swells will be less than those measured from oedometer testing as the CBR
samples are significantly thicker and larger in diameter. Hee (2005) indicated that it is not
uncommon to assume that CBR swells are approximately half of those from oedometer
testing. Using this assumption, the potential swell classification based on CBR swells can
be approximated as follows:
Potential Swell (%)
0-2.5 2.5-4.5 4.5 - 6.5
> 6.5
Swell Classification
Low Medium
High Very High
Therefore, the Kapolei and Waipio soils that swell 2.9% and 2.2% can be classified
as having a medium and low swell potential, respectively, while the Wahiawa and Mililani
Mauka soils that swell 7.5% and 6.9%, respectively, have a very high swell potential.
44
8~--------------------------------------------~
7 o
6
5 x ~ x 0 '#. -=4 6
CD 6X :it
II) ~x 3 °x+ x+
~~~ x
2 0 0 -n6
x6 6 60
1 Cb 6 ¢lxo +OJO o x + x
0 000 0 o
~ Of. [] +0 0
0 5 10 15 20
CBR (%)
Figure 4.5 Swell versus CBR
4.3.4 Penetration Test
oWaipio o Kapolei o Mililani Mauka 6 Wahiawa in situ + Wahiawa ovendry X Wahiawa intermediate
o + +
25 30 35
The 15-lb (6.8 kg) surcharge load remained in place during the CBR test. Two sets of
readings were recorded: one set was taken manually and the second was recorded using
the data acquisition system. Overall, the readings from both sets were very consistent.
Upon completion of the CBR test, a moisture content determination was made.
4.4 Analysis of Test Results
The load versus displacement curves were plotted to determine if corrections are
needed. If the initial portion of the load-deflection curves concaved upward, a zero
correction as specified in ASTM 01883-94 was made. Then, the bearing ratio was
45
calculated at 0.1- (2.54 mm) and 0.2-inch (5.08 mm) deflections, and the greater of the
two was recorded as the CBR.
Compaction curves were also plotted based on the measured dry unit weight and
moisture content. A family of CBR curves was then generated for each soil. These
curves are contained in Figs. 4.6 through 4.11. It should be noted that the soils,
compacted in accordance with standard Proctor (56 blows in 3 layers), were not used to
generate the family of curves. From Figs. 4.6b through 4.11 b, CBR increases with
increasing dry density until the optimum moisture content is reached, where a peak CBR
is observed. Wet of optimum, the CBR decreases with decreasing dry density. In Figs.
4.6c through 4.11 c, the CBR is plotted against dry density at constant moisture content.
At low moisture contents, the CBR increases with increasing dry unit weight. At high
moisture contents, the reverse is true where the CBR decreases with increasing dry
density. This reduction is associated with water contents that are wet of the peak CBR.
Therefore, a decrease in CBR can occur as a result of over-compaction (too large a
compaction effort resulting in excessive dry unit weight) especially at high moisture
contents.
Two interesting observations on the Wahiawa soil can be made. First, drying
results in a shift of the compaction curve up and to the left, with the exception of the soils
compacted in 5 layers at 56 blows per layer (Fig. 4.12). In this case, the maximum dry
unit weight for the "intermediate" soil is higher than the oven-dry soil. Second, as the
sample is dried out, the CBR values tend to increase (see Figs. 4.9 through 4.11). For
example, the peak CBR for the 56-blow, 5-layer soils increased from about 15 for in situ
to 19 for intermediate to 38 for oven-dry.
46
1~r-------------------------~
.5 Layers@ 56 Blows • 5 Layers@ 25 Blow • • 5 Layers@ 10 Blows
110}-------~._----------------_1
~ ~ ~100 -I----:/--~--"...._---___1
'" c :> ~ o
16 21 26 31 36 Moisture Content (%)
(a)
30r---------------~--~~~_. • 5 Loyersl56 Blows • 5 Layers 25 Blows • 5 Layers 10 Blows
25}_-------J~------------__1
20-1-------+--++---------------1
t ~15}_------~_+4_*_------------_1 III o
16 21 26 31 36 Moisture Content (%)
(b)
~r-----------------------~
25
.22% .23%
.~%_------------------~~ 025% 026% D 2.7%
~}_----------~7L~~----~
80 85 90 95 100 105 Dry Unit Weight (pcf)
(c)
Figure 4.6 CBR family of curves for Waipio (a) Dry unit weight versus moisture content; (b) CBR versus moisture content; and (c) CBR versus dry unit weight at constant moisture content
47
120 r-~";';"'--":"'-----"----,
0:: III
• 5 Layers @ 56 Blows 1 5 Layers @ 25 Blows .5 Layers @ 10 Blows
110 -I---"""~-------I
90~---il-----~----1
80 -!-. --...,....-.....-,......._~..,...;;~
16
25
20
21 26
Moisture Content (%) Ca)
31
f'I • 5 Layers 156 Blows 1 5 Layers 25 Blows .5layers 10 BIoY!S
.. /
36
() 10 r.
II / \ 1\ l /~
5
o 16 21 26 31 36
Moisture Content (%) (b)
25 -,--------------, ,22% 123%
20 -' 24% _______ -1--___ --1 '25%
~15-1----------~~-----1 '$ ~
0:: al U 10~-------~1~+_------~
5·~---~~-+~---~
O~, __ ~~~ __ ~_~
80 90 100 110 Dry Unit Density (pel)
(e)
120
Figure 4.7 CBR family of curves for Kapolei (a) Dry unit weight versus moisture content; (b) CBR versus moisture content; and (c) CBR versus dry unit weight at constant moisture content
48
95~------------------------~ • 5 layers @ 56 Blows .5 Layers @ 25 Blows &5 Layers@ 10 Blows
90~~~~~~~---+--------~
'[ .... ·I----}~~-*+----'-I - !8S-:c ',!l' ~ . .. c :> SO .I--------I----__ ---c/-,~~\______i 5
751--------------4JL---------~
70~~~~ ________ --________ _4
.15 20 25 30 35 40 45 50
25
20
15
10
5
o 15
Moisture Content (%)
(a)
• .5layers'@10Blows .5 layers @25 Blows & 5 Layers @ 56 Blows
J"j
,
I I) ~ --:JIJ 25 35
Moisture Content (%)
(b)
- .
, 45
25:~-------------------------~ .33% .35% &37% .39%
~ .. ~ ___ Q~4~1~%~ ____ ~ ________ r_--~
151-------------------1-4-----1
~ rr III o
10 ·I------------------.A~-I_-----I
o~----~--______ --__ --~~ 60 70 80
Dry Unit Weight (pel)
(c)
90
Figure 4.8 CBR family of curves for Mililani Mauka (a) Dry unit weight versus moisture content; (b) CBR versus moisture content; and (c) CBR versus dry unit weight at constant moisture content
49
90~--------~----------~
85~----~~~+---------~
70 -I-----,--------''-----~ • 5 Layers @ 56 Blows 15 Layers @ 25 Blows '5 Layers @ 10 Blows
65~----~~~~--~~~
15 25 35 45 Moisture Content (%)
(a)
55 65
18 ---------------------......, ,5 Layers@ 10 Blows 16 1 ______ IS Layers@25Blows _
'" ~ 5 Layers @ 56 Blows
14~----~~~---~
12-1----~~1~~------1
~ 10 I------I--y-J.'-----I -II: m 81-----1--~~k_---~1 o
15 25 35 45
Moisture Content (%) (b)
55 65 75 80 85
Dry Unit Weight (pet) (c)
90
Figure 4.9 CBR family of curves for Wahiawa in situ (a) Dry unit weight versus moisture content; (b) CBR versus moisture content; and (c) CBR versus dry unit weight at constant moisture content
50
.100 .,.....-------------,
70 . 25 30
20 •
15
-.,e ~
~ 10 III 0
25 .30
35
.5 Layers @ 56 BloWs 15 Layers @ 25 Blows 15 Layers@ 10 Blows
40 45
Moisture Content ('10)
(a)
15 Layers @ 10 Blows 15 Layers @ 25 Blows .5 Layers @ 56 Blows
•
35 40 45 ., '"' ,-,.-.~
Moisture Content ('!o)
(b)
50
50
20 .32% 134% 136%
15 1380/, 0400/, [J42% - 1144% .,e
;; 10 III 0
51----------~~~--~~--_1
o·~~~-------~~--~~ 70 75 80. 85
Dry UnK Weight (pel) (c)
. 90
Figure 4.1 CBR family of curves for Wahiawa intermediate (a) Dry unit weight versus moisture content; (b) CBR versus moisture content; and (c) CBR versus dry unit weight at constant moisture content
51
C' u II. -~ 0 ~ , c ~ c
100
+ 5 Layers @ 50 Blows 15 Layers @ 25 Blows A 5 Layers @ 10 Blows
90
80
70 +--~~""""-""""'~'""'i-'---! 25 30 35 40
Moisture Content (%) (a)
45 50
40r-------------------~
. ' A5 Layers@ 10 Blows 15 Layers @ 25 Blows + 5 Lilyers @ 56 BloWs
30~------~Yrr_--------~
~ ~201------~_+_+~---------1 III I)
10r-----~~--~r~------~
25 30 35 40 45 ' 50 . Moisture Content (%)
(b)
-'f.
40r-~------------------~ +32% 134% A 36% '38%
30 -MO%--------------1-a 042%
~20r-------------~~--7_--1 III I)
10r---------------1
75 80 85 Dry Unit Weight (pc~
(c)
90
Figure 4.11 CBR family of curves for Wahiawa ovendry (a) Dry unit weight versus moisture content; (b) CBR versus moisture content; and (c) CBR versus dry unit weight at constant moisture content
52
95,-~----~---------.
90 0;:-,\,I Co -85 .. .c 01
~ 80 :!:! C :J 75 ~ c
70, -' -", ,5@56blowsinsiju
"\ '-I~' ,'~ "- 5 @ 56 blows intermediate ., . "
65 ·:·:·;5@56blo,wsovendry
20 25 .30 35 40 '45 50 Water Content (%)
(a) 95
90
!fi' Co - 85 .. .c 01
~ 80 /', ....... ;,-..;... .. ",. ~, '2 '" .' :J 75 ;1/
~ c
70 -, -5@10blowslnsitu - - 5 @ 10 blows intermediate
65 ...... 5 @ 10 blows ovendry
20 25 30 35 40 45 50 Water Content (%),
(c)
55
55
95,-------__ ----------~
90 !fi' Co - 85 -.c 01
~ 80 .... '2 :J 75 ~ c
70 -5@ 25 blows in situ - -5@ 25 blows Intermediate ······5 @ 25 blows ovendry
65+--r--r--r~r--r--~4
20 25 30 35 40 45 50 55
Water Content (%) (b)
95
90
!fi' Co -- 85-.. .c .~
~ 80 .',
.... -:,..,.:..." :!:! .. '",. '"
c .... / \, :J 75 - ':' , ~ c
70 -3 @ 56 blows in situ - -3@ 56 blows intermediate
65 ...... 3 @ 56 blows ovendry
20 25 30 35 40 45 50 55 Water Content (%)
(d)
Figure 4.12 Effect of Drying on Compaction Curves for Wahiawa Soil (a) 5 layers @ 56 blows (b) 5 layers @ 25 blows (c) 5 layers @ 10 blows and (d) 3 layers @ 56 blows
53
CHAPTER 5 R-VALUE TESTING AND RESULTS
5.1 Test Program
R-value tests were performed at the Hawaii Oepartment of Transportation (HOOT)
Materials Testing and Research Laboratory. A HOOT certified technician, Mr. Robert
Fukuda, performed all R-value tests in accordance with ASTM 02844-01. Between 6 and
15 tests were performed for each soil sample over a wide range of exudation pressures to
provide sufficient data to determine R-values at exudation pressures of 240 psi (1,655
kPa) and 300 psi (2,068 kPa). In the following section, adopted procedures that deviate
from ASTM 02844-01 or features that pertain to this project are discussed below.
5.2 Test Procedure
5.2.1 Equipment and Sample Preparation
Major components of the R-value test equipment include:
1. kneading compactor (Figure 5.1)
2. exudation indicator device and loading frame with soil press (Figure 5.2)
3. Hveem stabilometer (Figure 5.3)
A single 5-gallon bucket of soil (approx. 40 Ibs (18.14 kg) moist soil) was required
to perform R-value tests for each soil. Prior to testing the soil was passed through the
No. 4 sieve to remove non-soil particles, mostly roots and other debris. After sample
preparation was completed, the soil was placed back into the plastic bags re-sealed to
minimize moisture loss. Moisture content tests were again performed on the soil sample
upon completion of sample preparation to ensure no moisture loss occurred.
54
Figure 5.1 Kneading compactor for R-value testing
Figure 5.2 Exudation indicator device and loading frame with soil press for R-value testing
55
HClI COIll" tit
•
Figure 5.3 Hveem stabilometer device for R-value testing
56
•
An individual R-value test sample was prepared by weighing 1000 grams (2.205
Ibs) of moist soil. An initial R-value test was performed to obtain a baseline reading of the
exudation pressure corresponding to the in situ moisture content. Based on this result,
subsequent samples were prepared by adjusting the moisture accordingly to achieve the
desired range of exudation pressures (i.e., 100 psi (689 kPa) to 800 psi (5516 kPa))
required to provide R-values at 240 psi (1,655 kPa) and 300 psi (2,068 kPa) exudation
pressures.
5.2.2 Compaction
The soil was compacted using a kneading compaction in accordance with ASTM
Standard D2844-01. Moisture contents of the same batch of soil as the test specimen
were determined. Following compaction, the weight and height of the sample was
measured to enable estimation of the dry unit weight prior to exudation portion of the test.
The physical state of the soils prior to exudation were observed to be mostly wet of
optimum (Figure 5.4), which is consistent with the statement in the Asphalt Institute
(1982) that "because of the exudation pressure requirements, specimens for R-value
determinations are compacted wet of the line of optimum."
57
110 110 105 105
tf100 '51 00 Q. 95 .e: 95 -~ 90 ~ 90 III • rn C 85 c 85 CD CD
o 80 • 5 layers @ 56 blows
o 80 • 5 layers @ 56 blows
g 75 ~ • 5 tayera C 25 blows • 5 layers @ 25 blows -0 75 .. 5 layers @ 10 blows .. 5 layers @ 10 blows
70 • 3 layers @ !5e blows 70 • 3 laye", C 56 blowli
-Zero air void curve -zero air void curve
65 ¢ R."aluI/II sample prior to exudation
65 00 R· ... alue sample, prior to exudation
15 20 25 30 35 15 20 25 30 35 Moisture Content (%) MOisture Content (%)
(a) (b)
110 110 • 5 layers @ 56 blows • 5 la~re @ 56 blows
105 • 5 layers C 25 blows 105 • 5 layera @ 25 blows
'ti1OO .. 5 layers @ 10 blows .. 5 layers@ 10 blows
• 3 layers @ 56 blows <;:-100 • 3 Ia:;era @ 56 blOW'll -Zero air void curve ... - Zero air void curve .e: 95 oR-value sample prior to slI:udatlon .s 95 <0 R-value sample priOf to exudation
~ 90
~ ~ 90
rn III C 85 • c 85 ,!: CD
80 c 80 ~
~ ~ 0 75 c 75
70 70 65 65
20 30 40 50 20 30 40 50 60
Moisture Content (%) Moisture Content (%) (e) (d)
110· 110 • 5 layers @ 56 blows • 5 layers C 56 blows
105 • 5 layers rm 25 blows 105 • 5 ~rs @ 25 blows .to 5 layers @ 10 blows .. Slayers@ 10 blows
'ti1OO • 3 layers @ 56 bk:tw3 <;:-100 • 31ayers @ 56 blows -Zero air void curve ... -Zero elr 'J01d curve
.e: 95· c R-valul!t sample prior to exudation Q. 95 -~ 90 ~ 90 rn • ·iii c: 85·- c 85 ,!: CD
80· • c 80 ~ ~ c 75 • 0 c 75
0
70·· 70 65· 65
20 30 40 50 60 20 30 40 50 60
Moisture Content (%) Moisture Content (%) (e) (f)
Figure 5.4 Water content and dry unit weight of R-value samples prior to exudation (a) Waipio; (b) Kapolei; (c) Mililani Mauka; (d) Wahiawa in situ; (e) Wahiawa intermediate and (f) Wahiawa oven-dry
58
5.2.3 Exudation Pressure
After measuring the weight and height of the soil specimen, a phosphor-bronze
plate and filter paper were placed on top of the specimen. The mold was inverted and
then placed on the exudation device. Prior to pushing the sample down and commencing
the exudation pressure test, a light grade oil was placed on the inside of the mold to aid in
the sample push down. The coating of oil was used for the higher plasticity samples
because the specimen were found to stick to the steel mold, thus deforming the sample
during exudation and rendering the sample useless for R-value testing.
Upon completion of the exudation pressure test, the specimen was placed on the
expansion apparatus and the initial height of the sample was determined. 200mL of
water was then placed in the mold for 24 hours. Expansion pressure measurements
were not recorded for this research project because access to the facilities were not
available after business hours.
5.2.4 Resistance-Value Testing
After 24 hours, the water was drained and the specimen was air-dried. It was
observed that during extrusion of the higher plasticity specimens from the mold to the
stabilometer, the specimen would stick to the sides of the neoprene rubber diaphragm
causing it to bulge at the bottom. This was observed during testing of the Mililani Mauka
and Wahiawa samples but not the Waipio and Kapolei samples. Therefore, for the
Mililani Mauka and Wahiawa samples, the neoprene rubber diaphragm was coated with a
light grade oil to aid in advancing the specimen into the Hveem stabilometer.
After the specimen was extruded, a vertical pressure was applied at a rate of 0.05
inches per minute (1.27 mm per min) until it reached 160 psi (1,103 kPa) or 2000 Ib (907
59
kg). At this stress, the horizontal pressure was recorded. Then the vertical load was
reduced by half followed by a reduction in the horizontal pressure to 5 psi (35 kPa) using
the displacement pump (see Figure 2.2 and Figure 5.3). The number of turns required to
increase the horizontal pressure to 100 psi (689 kPa) was determined. According to
Oglesby and Hicks (1982), the intent of this displacement procedure is to measure the
penetration of the diaphragm into the interstices of the sample. Without this correction,
any roughness of the surface of the specimen could result in an error on the R-value.
5.3 Analysis of Test Results
The R-value was calculated using the following equation:
R=100 100
2.5(P, -1)+1 D Ph
(5.1 )
where R = resistance or R-value, P, = vertical pressure (160 psi or 1,103 kPa), Ph (psi) =
horizontal pressure at Pv = 160 psi (1,103 kPa), and D = turns displacement reading. If
the specimen height is not between 2.45 (62.23 mm) and 2.55 (64.77 mm) inches, a
correction for the R-value is required. This chart can be found in ASTM Standard D2844-
01. The R-value was plotted versus exudation pressure so that values at exudation
pressures of 240 psi (1,655 kPa) and 300 psi (2,068 kPa) can be interpolated (Figure
5.5). Based on these tests, the R-value samples at an exudation pressure of 300 psi
(2,068 kPa) were prepared at relative compaction values of between 87% and 99%, and
moisture contents of +4% to +13% above optimum. One interesting observation on the R-
values for the Wahiawa soil can be made. As the sample is dried out, the R-values tend
to increase (see Figs. 5.5). For example at an exudation pressure of 300 psi (2,068 kPa),
the R-values varied from 8.3 for the in situ to 10 for intermediate to 20.6 for the oven-dry.
60
Exudation Pressure (psi)
800 700 600 500 400 300
& .- -----: ~
(a)
Exudation Pressure (psi)
800 700 600 500 400 300
I
~ I
~I
(b)
200 100
•
200 100 o
I
...
o 60
50
40
" " 30 ~
20
10
o
60
50
40
.. " 30 ;;
~ 20
10
o
Figure 5.5 R-value versus exudation pressure for soils from (a) Waipio; (b) Kapolei; (c) Mililani Mauka; (d) Wahiawa
61
800 700 600
Exudation Pressure (psi)
500 400 300
• •
200 100 o 60
50
40 ., :::J
-----30 ~
•• ~ • -.. I' 20
10
o (c)
Exudation Pressure (psi)
800 700 600 500 400 300 200 100 a
• -------~~,--------~,---------------+_---1-------------------50
Ovendry
1---------------'~--------~----------c--~----------------_+40 , Intermediate --"" '
~
" " ~~--+---~----------------t30 ~
<&----~~---+--------------_+20
• +Insitu ~~.r~~------------+10
• Intermediate .. Oven Dry
L---=-----~------------------~--~~~~------~O
(d)
~
Figure 5.5 R-value versus exudation pressure for soils from (a) Waipio; (b) Kapolei; (c) Mililani Mauka; (d) Wahiawa (continued)
62
CHAPTER 6 CORRELATION ANALYSIS
6.1 Correlations between R·value and CBR
Based on test results on Waipio, Kapolei, Mililani Mauka, Wahiawa in situ and
Wahiawa intermediate, four methods of correlating R-value and CBR are presented. A
fifth method is also proposed that relates R-value to index properties alone. The
Wahiawa oven-dry samples were excluded from the correlation analyses because the
samples were dried to temperature extremes that regular soils do not experience, and
therefore are judged to be inappropriate for inclusion in this work. Nevertheless, the
data provided useful insight into the effects of drying on the measured properties.
6.1.1 Method 1
Linear relationships between R-value and CBR are plotted in Figs. 6.1 through
6.26. Charts were developed for 3 relative compactions (95% dry-of-optimum, 100% or
optimum, and 95% wet-of-optimum), 4 compaction efforts (5 layers at 56 blows, 5 layers
at 25 blows, 5 layers at 10 blows and 3 layers at 56 blows) and 2 exudation pressures
(240 psi (1654 kPa) and 300 psi (2068 kPa) giving a total of 24 figures. The remaining
2 of the 26 figures are for correlations between the Kentucky CBR and R-value at 2
exudation pressures. There was insufficient data to generate charts for 90% relative
compaction as the limited quantity of soil available precluded the extension of the
compaction curves.
As a result of omitting the Wahiawa oven-dry points, only five data points were
used in each regression analysis. The slopes and intercepts are summarized in Table
6.1 along with the coefficients of determination or R2.
63
25,----------------------------------------,
20
5
o
I
I J
, 1/
// f
.1 'J
:j I. :/
I
/ .'
/
/
I I
I
10
I
I I
I
/
I I
I I
I I
I I
I
20
CBR(O/O)
o
• Waipie • Kapolei '" Mililani X Wahiawa - in situ • Wahiawa - intermediate o Wahiawa - ovendry
Unear Regression wlo 00 Wahiawa
- - Equation 2.5 - •• - Equation 2.7 - - - Equation 6.4
30 40
Figure 6.1 CBR vs. R-Value (Ep1 '" 240 psi, 5 Layers @ 56 Blows, RC1
'" 100%)
25
• I 20 /
• . I I
r J
, . III 15 1/
. :::I ~ // >
" 10 f J I
i' I
:1 I
5 I. I
I :/
0
0 10
/ . . / . .
I I
I 1
I , I
I I
I
1 I
I I
20
CBR (0/0)
o
• Walpio • Kapolei .. Mililani :c Wahiawa· in situ
• Wahiawa· intermediate o Wahiawa - ovendlY
Linear Regression w/o 00 Wahiawa Equation 2.5
- - - - Equation 2,7 - - - Equation 6.4
30 40
Figure 6.2 CBR vs. R-Value (EP = 300 psi, 5 Layers @ 56 Blows, RC = 100%)
Note 1. EP = exudation pressure and RC = relative compaction.
64
25.----------------------------------------,
20
(j) 15 :::I
~ 0:: 10
5
•
o
. I /
I I . ... I / To / •
Ii / /
10
/
20
CBR ('Yo)
• Walplo
• Kapolei
.. Mililani
o Wahiawa - ovendry Linear Regression w/o 00 Wahiawa
Equation 2.5 - •• - Equation 2.7
- - - Equation 6.4
30 40
Figure 6.3 CBR vs. R-value (EP = 240 psi, 5 Layers @ 56 Blows, RC = 95% Dry)
25.----------------------------------------,
20
(j) 15 :::I
~ ... 10
5
o
o
/ /
/. /
I. '/ ./
i/ r f •
/ .f / i' / .'1
/ ./ /.
:/ I
/
/
10
.' /
/ /
• Walpio • Kapolei
.t. Mililani o Wahiawa - ovendry
---I Linear Regression wlo 00 Wahiawa Equation 2.5
- •• - Equation 2.7 - - - Equation 6.4
20
CBR ('Yo)
30 40
Figure 6.4 CBR vs. R-value (EP = 300 psi, 5 Layers @ 56 Blows, RC = 95% Dry)
65
25~----------------------------------------.
20
GI 15 :::I
~ 10
5
,
• I , I , /
1 1/ 1 0 '/
\ l 1 ' .. I', ...
:7\ I. 1::1( •
:/ I
1 1 ,
/ /
/ "
/
/
• Waipio • Mililani • Kapolei o Wahiawa - ovendry X Wahiawa - in si1u • Wahiawa - intermediate
Equation 2.5 - - - - Equation 2.7 - - - Equation 6.4
O+-~~~~-r~~~~-+~~~~~r-~L-~~
o 10 20
CBR (%)
30 40
Figure 6,5 CBR vs. R-value (EP = 240 psi, 5 Layers @ 56 Blows, RC = 95% Wet)
25~--------------------------------------~
20
GI 15 .2
~ ... 10
5
o
... o I
• I / , /
•
10
/ , '
20
CBR (%)
• Waipio ... Mililani
• Kapolei o Wahiawa. - ovendry X Wahiawa - in situ • Wahiawa - intermediate
Equation 2.5 - - - - Equation 2.7 - - - Equation 6.4
30 40
Figure 6.6 CBR vs. R-value (EP = 300 psi, 5 Layers @ 56 Blows, RC = 95% Wet)
66
25.----------------------------------------,
20
GI 15 :::I
~ 10
5 "
I
, , I , I
I : ~ • •
1/ .. p' , .,
I' i ••
./
/
I
o • Waipio • Mililani
• Kapolei :t:: Wahiawa· in situ
• Wahiawa· Intermediate o Wahiawa· o'Jendry
Linear Regression w/o 00 Wahiawa
Equation 2.5
- •• - Equation 2.7 - - - Equation 6.4
o+-~~~~+-~~~~~~~~~~~~~~
o 10 20
CBR (%)
30 40
Figure 6.7 CBR vs. R-value (EP = 240 psi, 5 Layers @ 25 Blows, RC = 100%)
25~--------------------------------------~
20
GI 15 :::I
~ 10
5
o
"
4 .. 1/
I
I
I ,/ , , ' 1/
// , J
/ /
/
I I
I
10
/
"
/ I
I
~
./
I I
I /
I I
/ I
I o
• Waipio A. Mililani
• Kapolei :c Wahiawa· in situ
• Wahiawa - intermediate o Wahiawa - ovendry
Linear Regression w/o 00 Wahiawa
- - Equation 2.5
20
CBR ('Yo)
- •• - Equation 2.7 - - - Equation 6.4
30 40
Figure 6.8 CBR vs. R-value (EP = 300 psi, 5 Layers @ 25 Blows, RC = 100%)
67
25~---------------------------------------.
20
CI) 15 ::::I C\I
~ .... 10
/
/
• Waipio ... Mililani
• Kapolei • Wahiawa - intermediate o Wahiawa - ovendry
5 linear Regression wlo 00 Wahiawa Equation 2.5
o 10
- •• - Equation 2.7
- - - Equation 6.4
20
CBR (%)
30 40
Figure 6.9 CBR vs. R-value (EP = 240 psi, 5 Layers @ 25 Blows, RC = 95% Dry)
25~--------------------------------------~
20
CI) 15 ::::I
~ 10
5
0 0
o
• , I . .t
I I.' :1 I,
:/ I
/
10
/
20
CBR(%)
• Walpio
• Mililani
• Kapolei • Wahiawa - intermediate o Wahiawa - ovendry
---I Linear Regression w/o 00 Wahiawa - • Equation 25 - •• - Equation 2.7 - - - Equation 6.4
30 40
Figure 6.10 CBR vs. R-value (EP = 300 psi, 5 Layers @ 25 Blows, RC = 95% Dry)
68
25~----------------------------~----------.
20 -
GI 15-:::I
~ ... 10
5
o
, \0
I , '
I / J
• I / .
'J
\ P , , -\i
,,1, // \« " ' . ,
I ,
10
/
/
/
20
CBR(%)
• Mililani
• Kapolei :c Wahiawa - in situ • Wahiawa - intermediate o Wahiawa - ovendry
Equation 2.5
- a - - Equation 2.7 - - - Equation 6.4
30 40
Figure 6.11 CBR vs. R-value (EP = 240 psi, 5 Layers @ 25 Blows, RC = 95% Wet)
25~--------------------------------------~
20
GI 15 :::I
~ c::: 1 0
5
o
• o I
• , I \ 'I' \ I /
.\l i" )K
:7 '. I.
:/ 1
" J
/
10
J
/
20
CBR (%)
• Mililani
• Kapolei X Wahiawa - in situ • Wahiawa - intermediate o Wahiawa - ovendry
Equation 2.5 - - - - Equation 2.7
- - - Equation 6.4
30 40
Figure 6.12 CBR vs. R-value (EP = 300 psi, 5 Layers @ 25 Blows, RC = 95% Wet)
69
25~---------------------------------------,
20
<II 15 :::I
~ 10
5
o
•
• I
1 r
I;'
• ''0 1"" f
J // :l /.
:/ I
I
I
/ . / I
I
10
I I
/
I I
r " / ,
I
" r /
/
20 CBR (%)
/ J
I
" /
• ... • lK
•
Waipio Mililani Kapolei Wahiawa - in situ Wahiawa - Intermediate
o Wahiawa· ovendry Linear Regression w/o 00 Wahiawa Equation 2.5
- •• - Equation 2.7 - - - Equation 6.4
30 40
Figure 6,13 CBR vs. R-value (EP = 240 psi, 5 Layers @ 10 Blows, RC = 100%)
25~--------------------------------------,
• I
20 01 I
• , /
I I I
. . / r / •
<II 15 1/ , I
:::I , / iii " /
~ r I ./ I • Waipio 10 I ... Mililani
J / • Kapolei
// I lK Wahiawa - in situ
:l I • Wahiawa - intermediate
5 I 0 Wahiawa - ovendry /. I linear Regression wlo 00 Wahiawa :/ I Equation 2.5
I / - - - - Equation 2.7 - - - Equation 6.4
0 0 10 20 30 40
CBR (%)
Figure 6.14 CBR vs. R-value (EP = 300 psi, 5 Layers @ 10 Blows, RC = 100%)
70
25~--------------------------------------~
20
CD 15 :s
0 iii > , 0:: 10
IC 1/
5 •• // I
0 0
/
10
• Waipio .. Mililani
• Kapolei • Wahiawa - intermediate o Wahiawa - ovendry
---linear Regression w/o OD Wahiawa Equation 2.5
- •• - Equation 2.7 - - - Equation 6.4
20
CBR (%)
30 40
Figure 6.15 CBR vs. R-value (EP = 240 psi, 5 Layers @ 10 Blows, RC = 95% Dry)
25~--------------------------------------~
20
CD 15 :s
~ 0:: 10
5
o
• o
/ ;' J..i • "
f. /
~/Aft~ I ,.t
I.' .-7 I. :/
I
,
I
/ .. /
I
10
• Waipio .. Mililani
• Kapolei • Wahiawa - intermediate o Wahiawa - ovendry
Linear Regression w/o OD WCihlawa - • Equation 2.5 - - - - Equation 2.7 - - - Equation 6.4
20
CBR(%)
30 40
Figure 6.16 CBR vs. R-value (EP = 300 psi, 5 Layers @ 10 Blows, RC = 95% Dry)
71
25.------------------------------------,
20
GI 15 :::I
~ ... 10
5
o
, / .. I • / ,
1 ./ , . \ 1./ \0 -/
" r I I
-f'! • I I. I ,', \
I I
10
/
20 CBR(%)
• Waipio • Mililani
• Kapolei o Wahiawa - o'Jendry ::c Wahiawa - in situ
Equation 2.5 - .... - Equation 2.7 - - - Equation 6.4
30 40
Figure 6.17 CBR vs. R-value (EP" 240 psi, 5 Layers @ 10 Blows, RC" 95% Wet)
25~--------------------------------------_,
20
GI 15 :::I
~ r:i:. 10
5
o
• o •
• I
\ I / \ "
" 1/ I , .
\ t/ - &I! t
.f\ ·f \
I. \
/' I
10
/ .'
/
/
20
CBR (%)
• Waipio .. Mililani • Kapolei ::K Wahiawa - in situ o Wahiawa - ovendry
Equation 2.5 - ~ .. - Equation 2.7 - - - Equation 6.4
30 40
Figure 6.18 CBR vs. R-value (EP" 300 psi, 5 Layers @ 10 Blows, RC" 95% Wet)
72
25,--------------------------------------.
20
GI 15 ::::I
~ 060 10
5
o
I , I , r
1/
i/ , .! •
:l I. :/
I
/
/
/ .'
/ .
IJ../ /
/ /
/
10
/
/ /
/ /
/ /
/
/ / 0
/ /
/
• ... • X
Waiplo Mililani Kapolei Wahiawa· In situ Wahiawa - Intermediate • o Wahiawa - olJendry
---Linear Regression w/o 00 Wahiawa - - Equation 2.5 - • - - Equation 2.7 - - - Equation 6.4
20
CBR (%)
30 40
Figure 6.19 CBR vs. R-value (EP = 240 psi, 3 Layers @ 56 Blows, RC = 100%)
25.---------------------------------------,
20
GI 15 ::::I
~ 10
5
o
I •
I , .' 1/
i/ 1
l' :7 I. :/
I
/
/ /
/
10
/ ... ..
/ /
IJ..
/ /
/ /
/ /
, /0
/
• Waiplo • Mililani
• Kapolei X Wahiawa - in situ
• Wahiawa - intermediate o Wahiawa - ovendry
---I Linear Regression w/o OD Wahiawa Equation 2.5
- - - - Equation 2.7
- - - Equation 6.4
20
CBR (%)
30 40
Figure 6.20 CBR vs. R-value (EP = 300 psi, 3 Layers @ 56 Blows, RC = 100%)
73
25.----------------------------------------,
20
GI 15 ::J
~ 10
5
0 0
• I: .e.
1 :/
10
• Walpio • Mililani
• Kapolei • Wahiawa ~ intermediate o Wahiawa· ovendry
Linear Regression w/o 00 Wahiawa
Equation 2.5 - •• - Equation 2.7 - - - Equation 6.4
20
CBR (%)
30 40
Figure 6.21 CBR vs. R-value (EP = 240 psi, 3 Layers @ 56 Blows, RC = 95% Dry)
25.---------------------------------------~
20
GI 15 ::J
~ .... 10
5
o
• o
1/ // "., .
I ./
:7 I. :/
1
/
1
/
/
1
10
• .t.
• •
WaipiO Mililani Kapolei Wahiawa - Intermediate
o Wahiawa - ovendry Linear Regression w/o 00 Wahiawa Equation 2.5
- - - - Equation 2.7 - - - Equation 6.4
20
CBR(%)
30 40
Figure 6.22 CBR vs. R-value (EP = 300 psi, 3 Layers @ 56 Blows, RC = 95% Dry)
74
25
, 20 • I ,
1 , . 15 I 1/
I CII :l \
jij I 0 " \
~ \ f \
10 I I IJ
jf.'
5 - i4\ :/ I
I I
o
. / . .
/ . /
/
10
/ .
20
CBR (%)
• Waiplo .. Mililani :.: Wahiawa· in situ • Wahiawa - intermediate o Wahiawa - ovendry
Equation 2.5 - •• - Equation 2.7 - - - Equation 6.4
30 40
Figure 6.23 CBR vs. R-value (EP = 240 psi, 3 Layers @ 56 Blows, RC = 95% Wet)
30
25
• 20 - 0 ,
CII I I I :l \ ,
C':I 15 - \ / --r
> I , I r .I 0::: I •
10 -.; :::t:: /'1 }I
5 I, ' :/
1
0
0
. ~
I /
/ .-
10 20
CBR (%)
• Waiplo .. Mililani X Wahiawa - in situ • Wahiawa - intermediate o Wahiawa - ovendry
Equation 2.5 - - • - Equation 2.7 - - - Equation 6.4
30 40
Figure 6.24 CBR vs. R-value (EP = 300 psi, 3 Layers @ 56 Blows, RC = 95% Wet)
75
25,-~------------------------------------,
20
GI 15 ::I
~ 10
5
25
20
GI 15 ::I iU > • a:: 10
5
0
o
0
o
1 , 1 . /
1/ -/ r
I
• /
• .J // 1&
/
/
• Waipio • Kapolei ... Mililani Mauka X Wahiawa· in situ • Wahiawa - intermediate o Wahiawa - ovendry ] )I( • :,
I
---Linear Regression w/o OD Wahiawa
10 20
CBR(%)
- - Equation 2.5 - •• - Equation 2.7
30
Figure 6.25 CBR vs. R-value (EP = 240 psi, Kentucky CBR)
, , I , I
I ,
0 • /
1/ ,
• .1& )I(
:, I
10
./ • . . ./
, / ,
• Waipio • Kapolei ... Mililani Mauka
X Wahiawa - in situ
• Wahiawa - intermediate o Wahiawa - ovendry
---linear Regression w/o 00 Wahiawa Equation 2.5
- •• - Equation 2.7
20
CBR ("!o)
30
Figure 6.26 CBR vs. R-value (EP = 300 psi, Kentucky CBR)
76
40
40
Table 6.1 Slope and intercept from linear regression of R-value versus CBR without W h· d a lawa oven lry
Compaction Effort Physical State
5 layers, 56 blows 95% RCD dry of optimum 5 layers, 56 blows 95% RC dry of optimum 5 layers, 56 blows 100% RC 5 layers, 56 blows 100% RC 5 layers, 56 blows 95% RC wet of optimum 5 layers, 56 blows 95% RC wet of optimum 5 layers, 25 blows 95% RC dry of optimum 5 layers, 25 blows 95% RC dry of optimum 5 layers, 25 blows 100% RC 5 layers, 25 blows 100% RC 5 layers, 25 blows 95% RC wet of optimum 5 layers, 25 blows 95% RC wet of optimum 5 layers, 10 blows 95% RC dry of optimum 5 layers, 10 blows 95% RC dry of optimum 5 layers, 10 blows 100% RC 5 layers, 10 blows 100% RC 5 layers, 10 blows 95% RC wet of optimum 5 layers, 10 blows 95% RC wet of optimum 3 layers, 56 blows 95% RC dry of optimum 3 layers, 56 blows 95% RC dry of optimum 3 layers, 56 blows 100% RC 3 layers, 56 blows 100% RC 3 layers, 56 blows 95% RC wet of optimum 3 layers, 56 blows 95% RC wet of optimum
,£ Note a. R - coeffiCient of determination b. RC '" relative compaction
Exudation Pressure
(psi) 240 300 240 300 240 300 240 300 240 300 240 300 240 300 240 300 240 300 240 300 240 300 240 300
Slope Intercept R£ a
m c
1.65 3.45 0.539 1.55 6.14 0.433 1.52 -21.3 0.822 1.37 -15.4 0.766 -2.53 22.8 0.374 -1.77 21.7 0.210 1.74 2.23 0.624 1.33 6.98 0.411 1.63 -16.7 0.896 1.42 -10.4 0.442 -1.05 10.8 0.862 -0.194 10.3 0.127 2.40 -0.329 0.685 1.83 5.01 0.453 2.40 -13.5 0.691 2.27 -9.26 0.702 -4.23 19.8 0.324 -3.36 20.2 0.208 2.23 0.553 0.590 1.66 5.89 0.369 1.18 -1.33 0.493 1.13 2.04 0.517 -6.75 24.6 0.475 -5.43 25.0 0.369
Note that the trend lines for the wet-of-optimum plots have a negative slope
indicating that as CBR increases, R-value decreases. This seems counterintuitive and is
perhaps an indication that the CBR for wet-of-optimum samples is less reliable for use in
correlating with R-value.
To determine the R-value at a particular exudation pressure, the CBR
corresponding to one of the above four compactive efforts and one of the above three
77
relative compactions is needed. The R-value is obtained using a linear equation (R = m
CBR + c) where m = slope and c = intercept from Table 6.1 or by reading the value from
the appropriate graph. The linear regression line was also plotted in Figure 6.1 through
6.26. These lines were omitted for the wet-of-optimum charts because they have a
negative slope. Also shown for comparison are curves for equations 2.5 and 2.7. In
general, for the range of R-values that was measured (i.e., < 25), equations 2.5 and 2.7
are reasonable for dry-of-optimum soils, overpredict the R-value for soils at optimum, and
underpredict the R-value for wet-of-optimum soils.
The R-values detenmined using Van Til et ai's (1972) correlation with the Kentucky
CBR is shown in Figure 6.27. Superimposed on this plot are the data obtained from this
testing program. While the Van Til et al. correlation predicted the R-value reasonably well
for the Kapolei soil, the R-value was overestimated for the remaining 4 soils.
78
35 Van Til et al. (1972) 240 psi Exudation Pressure
-- - Van Til et al. (1972) 300 psi Exudation Pressure 30 • • Measured 240 psi Exudation Pressure • • • Measured 300 psi Exudation Pressure • • 25 • Waipio ,
I
• • • Q) 20 ,. • ::I iii I
I
> Ii: 15 Wahiawa Mililani
Wahiawa intermediate Mauka • in situ 10 • • • •
5 • • 0
0 2 4 6 8 10 12 14
Kentucky CBR (%)
Figure 6.27 Comparison of measured R-value versus predicted using Van Til et al. (1972)
6.1.2 Method 2
In this method, a linear regression was performed on the slopes (column 4 of
Table 6.1) and intercepts (column 5 ofTable 6.1) obtained from Method 1. The slope
and intercept were each related to the following dependent variables: energy ratio,
relative compaction, moisture content relative to optimum, and exudation pressure. The
energy ratio is defined as the compaction energy per unit volume used for the actual
test normalized by the compaction energy per unit volume for the Standard Proctor test
according to Procedure A of ASTM 0698-00. The compaction energy per unit volume
in ft-Ibs/fe is defined as:
79
ER = No. of blows per layer x No. of layers x Wt. of Hammer x Hammer Drop Height (6.1) Mold Vol.
The energy ratios are 4.53, 2.02, 0.808 and 0.996 for 5 layers at 56 blows, 5 layers at
25 blows, 5 layers at 10 blows and 3 layers at 56 blows, respectively. A wetness factor
was established as follows: 0 for optimum, -1 for wet-ot-optimum and +1 for dry-of-
optimum.
The slopes (m) and intercepts (c) are related to the energy ratio (ER), relative
compaction (RC), wetness factor (WF) and the exudation pressure (EP in psi) as
follows:
m = 0.1693ER + 2.482WF + 0.4599RC + 0.00224EP - 45.34 (6.2)
c = -0.9051ER - 7.834WF - 4.458RC + 0.0515EP + 423.1 (6.3)
The coefficients of determination for equations 6.2 (Figure 6.28) and 6.3 (Figure 6.29)
are 0.782 and 0.857, respectively. These two equations were then combined and used
to predict the R-value for each of the CBR test as follows:
R= (0.1693ER+ 2.482WF + 0.4599RC+ 0.00224EP-45.34)cBR
-0.9051ER-7.834WF -4.458RC+0.0515EP+ 423.1 (6.4)
The resulting calculated R-values are plotted versus the measured values in Figure
6.30.
80
8 -
6
4 Y = 0.7826x
E 2 -R2 = 0.7823
"CI ,S!
0 .!:! "CI 4 6 f!! -2 D..
-4
-6
-8
Experimental m
Figure 6.28 Predicted versus experimental slopes of the R-value versus CBR curves
30
20 D D
U 10 "CI ,S!
0 u '5 f!! -20 10 20
D.. -10 D
D
-20 Y = 0.8714x R2 = 0.8572
-30
Experimental c
Figure 6.29 Predicted versus experimental intercepts of the R-value versus CBR curves
81
50
40 0
CII 0 :::J
Ol:b iii 30 y = 1.0668x > El Ol ~ • R' = 0.0406 It: 0 061 "'C 20 8 CII
9 - r::l ~ 0
"'C 10 0 8 e § 0
D- EL 0 0
o 10 15 20 25 30 35 -10
Measured R-Value
Figure 6.30 Comparison of predicted and measured R-values using Method 2
It can be seen that there is considerable variability in the predicted versus
measured R-values. This is because all the CBR data points were used in this
comparison irrespective of the relative compaction and the moisture content with
respect to optimum while the correlation was derived using only CBRs at 100% and
95% relative compaction, the latter at both dry- and wet- of optimum. The suitability of
this equation can be further evaluated by comparing how this equation plots relative to
the data in Figures. 6.1 through 6.24. In general, it can be concluded that this equation
is more suited to "dry-of-optimum" soils and less suitable for "optimum" and "wet-of-
optimum" soils.
6.1.3 Method 3
A simple relationship between R-value and CBR was developed involving the
exudation pressure and the activity of the fine-grained soil by trial and error. Use of
82
other parameters were explored but the resulting correlation coefficient was highest with
the following relationship:
(6.5)
where A = activity (expressed as numeric and not in %), EP = exudation pressure (in
psi), and K1 through ~ are constants obtained by using a solver to find the values that
gave a minimum objective function . The objective function was defined as the sum of
the square of the differences between the measured and predicted R-values. A
coefficient of determination of 0.6196 was obtained based on the following values of K1
through K 4 when forcing the regression line through the origin : K 1 = 0.00652, K 2 =
0.04708, K 3 = -1 .675 and K4 = 1.096 (Figure 6.31). This correlation was derived using
CBR values interpreted at 95% and 100% relative compactions.
30
25 . Q) y= x ::::I
R2 = 0.6196 Waipio (EP ; 240 psi) - 20 • '" > • Kapolei (EP ; 240 psi) • a:: I 'tI 15 • Mililani Mauka (EP = 240 psi)
Q) - • Wahiawa In Situ (EP = 240 psi) 0 .-'tI 10 X Wahiawa Intermediate (EP = 240 Q) ...
W~iPiO (EP ; 300 psi) a.. • 0
5 · , 0 6 0 Kapolei (EP ; 300 psi)
t. Mililani Mauka (EP = 300 psi) 0
0 5 10 15 20 25 30 35 40
Measured R-Value
Figure 6.31 Comparison of predicted versus measured R-values using Method 3
83
6. 1.4 Method 4
This procedure is based on the method of Li and Selig (1994) to estimate the
resilient modulus at a given physical state (combination of dry unit weight and water
content) of a soil. The eventual objective of this method is to relate the CBR at optimum
corresponding to the Modified Proctor compaction effort (5 layers with 56 blows) to the
R-value because of the high coefficient of determinations between CBR and R-values
(0.822 and 0.766 for 240 and 300 psi exudation pressures, respectively) at this relative
compaction. If the CBR at another energy ratio is available rather than the modified
Proctor CBR at optimum, then several steps are needed to correlate CBR with R-value.
These steps require two relationships: one between the optimum CBR at any
compaction effort and the equivalent Modified Proctor CBR at constant dry unit weight
and the second relating the CBR at any physical state on a compaction curve to the
CBR at optimum along the same compaction curve. The equation for paths of constant
energy ratio or compactive effort is as follows:
CBR CBRopt
sec h[2.623ERo.2037Plo.s36 (w - wopt
)] (6.6)
Note that sech refers to the hyperbolic secant of the term in the parentheses and sech x
= 2/(eX + e·X). This regression equation yields a coefficient of determination of 0.721
when comparing the predicted and measured normalized CBRs. It is plotted in Figure
6.32 using a PI of 50%. The PI and energy ratios are included in the regression
equation because they affect the width of the base of the CBR versus water content
plots. As can be seen in Figures 4.6 through 4.11, the width of the base increases with
increasing plasticity index (MH soils have broader bases than ML soils) and decreasing
84
compactive effort. Also shown on the plot is the data obtained from this testing
program.
The equation for paths of constant dry unit weight is given by:
CBR mod = sech[0.2899(w - wopt
) - 0.4837]+ 0.1 065 CBRopt
(6.7)
This equation relates the CBR at optimum corresponding to a given compactive effort
with the CBR at Modified Proctor along lines of constant dry unit weight. Therefore , if
the CBR corresponding to 100% relative compaction based on Standard Proctor is
known , then the CBR corresponding to Modified Proctor at the same dry unit weight can
be obtained using the above equation. This equation is plotted in Figure 6.33 along with
the data generated in this study.
1.2
1
C. 0.8 0
0:: III 0.6 0 ii III 0 0.4
0.2
• o
-20 -15 -10
•
• .... • •
-5
•
o
•
• •• • •
w - wopt (%)
•
5
5@56 Regression --5@25 Regression --5@10 Regression --3@56 Regression
• 5 layers 56 blows • 5 layers 25 blows • 5 layers 10 blows
3 layers 56 blows
• • • 10 15 20
Figure 6.32 Normalized CBR versus water content for constant compactive effort
85
1.2 .
• Dry of optimum
1 • Wet of optimum Trendline -Co
0 0.8 . a:: III U • - 0.6 • ." • 0
E a:: •• III 0.4 . • U •• • .... 0.2
• • o ·'------------------~, ----~------------------~
-25 -20 -15 -10 -5 o 5 10
W - wopt (%)
Figure 6.33 Normalized CBR versus water content for constant dry unit weight
Note that equation 6.7 is applicable only to dry-of-optimum samples . With the wet-of-
optimum data points in Figure 6.33 , the normalized CBR increases with increasing
water content. At the optimum water content, the normalized CBR must revert back to
unity; i.e. , the plot must curve back to (0, 1.0) , which means that there exists two
possible values of the normalized CBR for a given value of w - Wopt. This further
reinforces the fact that the R-value should not be correlated to wet-of-optimum CBRs.
If a CBR is available for a specimen prepared at a relative compaction other than
Modified Proctor, then the following procedure can be used to estimate the CBR at
optimum Modified Proctor:
1. For a given compactive effort, measure the CBR corresponding to a physical
state.
2. Use equation 6.6 to estimate the CBR at optimum for the same compactive effort.
l!6
3. Use equation 6.7 to estimate the CBR corresponding to Modified Proctor at
constant dry unit weight.
4. Use equation 6.6 again to estimate the Modified Proctor CBR at optimum.
The following figure and two scenarios are described to better illustrate this procedure.
1. If the CBR at Point Q in Figure 6.34 is required and the CBR is known at Point 0,
then Path OQ = Path OA + Path AQ. Estimate the CBR at Point A using equation
6.7. Using the value of CBR at Point A, estimate CBR at Point Q using equation
6.6.
2. If the CBR at Point Q is required and the CBR is known at Point C, then Path CQ =
Path CO + Path OA + Path AQ. First, using the CBR at Point C, estimate the CBR
at Point 0 using equation 6.6. The CBR at Point Q can now be estimated using
Step 1.
Reference points Q
Water Content
Figure 6.34 Path to obtain CBR based on Modified Proctor when the CBR at other compaction effort is known (Li and Selig, 1994)
This procedure was used to estimate the R-value by first estimating the Modified
Proctor CBR at optimum for all the CBR tests performed at or dry of optimum. Then the
following regression equations between R-value and CBR were used to estimate the R-
value.
87
For exudation pressure = 240 psi, R = 1.52CBR - 21.3 (6.8)
For exudation pressure = 300 psi, R = 1.37CBR - 15.4 (6.9)
Even though this model appears rational, the R-values predicted using this method was
very widely divergent (Figure 6.35). This is because the spread in the original data itself
is quite variable and only a limited number of R-values are available for correlation.
6.1.5 Method 5
In this procedure, the R-value is correlated to index properties (specifically the
activity) and the exudation pressure. This method was developed in light of the Arizona
DOT procedure, which did not provide reliable R-values for the tropical soils tested (Table
6.2).
Table 6.2 Comparison of measured R-value with those predicted using the Arizona DOT h d c art at 300 psi exu ation pressure
Soil PI % Passing #200 R-value from ADOT R-value (%) Sieve Chart (Table 2.2) measured
Waipio 15.9 89 15 22.5 Kapolei 14.1 99 15 9.7 Mililani Mauka 51.0 99 3 10.2 Wahiawa in situ 51.4 98 3 8.3 Wahiawa intermediate 45.1 100 4 10 Wahiawa ovendry 19.4 100 12 20.6
88
Exudation Pressure = 240 psi (1655 kPa)
70 B QI 60 :::l []
[] iU 50 [] [] > • Il: 40 [] Y = 1.5093x []
"C R2 = 0.1552 []
QI 30 ~ -(.) '6 20 [] QI [] [] ..
11. 10 0-8 8 []
0
0 5 10 15 20 25
Measured R-value
Exudation Pressure = 300 psi (2068 kPa)
70
60 B QI :::l [] iU 50 B =l' []
Y = 1.3758x Il: 40 [] []
"C R2 =0.1397 []
.S! 30 -El (.)
'6 20 []
!!! [] []
11. 10 I3tJ § 0
0 5 10 15 20 25
Measured R-value
Figure 6.35 Comparison of predicted and measured R-values using Method 4
89
Use of other parameters were explored but the resulting correlation coefficient was
highest with the following relationship that relates R-value with activity (A) and exudation
pressure (EP):
(6.10)
where constants C1 = 0.005616, C2 = -1.71 and C3 = 1.131. Equation 6.10 has a similar
form as equation 6.5 except that the CBR term is eliminated. A comparison of the
predicted and measured R-values is shown in Figure 6.36. The coefficient of
determination obtained was 0.6114, approximately the same as that obtained with
equation 6.5. From this exercise, it appears that the R-value is more dependent on the
soil characteristics and the exudation pressure and less dependent on the value of CBR.
25
~ 20 <II .. u '6 15 l!! Q. <II 10 :I C"CI >
5 , 0::
/ ¢
y-x ~¢ ¢
R2 = 0.6114
~ ~~ ¢ ¢
o ,
o 5 10 15 20 25
R-value measured
Figure 6.36 Comparison of predicted versus measured R-values using equation 6.10
90
6.2 Choice of Correlation Method
The choice of method to use to correlate CBR with R-value depends on the
physical state at which the CBR is measured. Methods 1, 2 and 3 were developed based
on interpreted CBRs at 95% and 100% relative compaction. Method 4 was developed
based on all the actual test data rather than values of interpreted CBR at 95% and 100%
relative compaction.
Method 1 is the recommended procedure for estimating R-value if the CBR is
available at any of the following relative compaction, physical state and compactive effort:
95% relative compaction dry-of-optimum, 100% relative compaction or at optimum, and
95% relative compaction wet-of-optimum, and compactive efforts of 5 layers at 56 blows
(Modified Proctor), 5 layers at 25 blows, 5 layers at 10 blows and 3 layers at 56 blows
(Standard Proctor). If the CBR is not available at any of the above relative compaction,
physical states and compactive efforts, then the other methods should be used.
Methods 2 and 4 are appropriate only for dry-of-optimum soils. Method 3 is more
versatile but the exponent for CBR is 0.04708 implying that the R-value is not very
sensitive to CBR. However, among methods 2, 3 and 4, method 3 produces results that
have least variability.
Method 5 relates R-value to the exudation pressure and activity only and is useful
if CBR values are not available.
Limitations and general comments on each method are summarized in Table 6.3.
91
Table 6 3 Limitations of the methods to estimate R-value Method Limitations Comments
1 1. Valid only for CBR measured 1. This is the recommended procedure on samples compacted using for use in design of flexible 4 specific energy ratios and 2 pavements. relative compactions (95% 2. Simple to use correlations provided and 100%). in charts as well as in the form of
2. Not valid for CBR measured linear equations. on wet-of-optimum samples. 3. Correlations established based on
CBR values interpreted at 95% and 100% relative compaction.
2 1. Valid for CBR measured on 1. Correlation in the form of one dry-of-optimum samples equation. only. 2. Correlations established based on
2. Very low coefficient of CBR values interpreted at 95% and determination. 100% relative compaction.
3. Can be used on compactive efforts and relative compactions other than the ones used to derive this correlation but extrapolation required.
3 1. Valid only for CBR measured 1. Correlation in the form of one on samples compacted using equation. 4 specific energy ratios and 2 2. Correlations established based on relative compactions (95% CBR values interpreted at 95% and and 100%). 100% relative compaction.
3. Exponent for CBR is very low indicating R-value is more correlated to activity and exudation pressure and less correlated to CBR.
4. Valid tor CBR measured on dry-ot-, at- and wet-ot-optimum samples.
4 1. Valid for CBR measured on 1. More general correlation in the form dry-ot-optimum samples only. of several equations that can be
2. Very low coefficient of used to estimate the R-value frOni a determination. CBR obtained on samples prepared
at any relative compaction and energy ratio.
2. Correlations established based on all CBR test data.
5 1. Simple correlation in the form of one equation.
2. Correlation independent of CBR.
92
CHAPTER 7 SUMMARY AND CONCLUSIONS
7.1 Summary
CBR, R-value and laboratory index tests were conducted on samples collected
from four different locations on the island of Oahu: Waipio, Kapolei, Mililani Mauka and
Wahiawa. The Waipio and Kapolei soils were classified as ML (AASHTO A7-6) while the
Mililani Mauka and Wahiawa soils were classified as MH (AASHTO A7-5). The Wahiawa
soil was significantly wetter than the other three with water contents in excess of 50%.
The liquidity index for the Wahiawa soil was 0.11 while the other three soils had negative
liquidity indices, an indication that they are desiccated.
Due to the higher water contents, the Wahiawa soil was tested at three different
stages of drying: first at its natural or in situ state, second after ovendrying the soil; and
third after drying the soil to approximately half its natural water content (termed Wahiawa
intermediate). Therefore, the Wahiawa soil can be regarded as three different soils
corresponding to three different stages of drying.
CBR tests were performed at several compactive efforts. At each compactive
effort, the CBR was measured over a range of molding water contents, thereby enabling
a family of curves to be plotted. Swell was also measured after soaking the soil for 4
days. Maximum volumetric expansion of about 2% and 7% were observed in the ML and
MH soils, respectively.
The CBR family of tests involves preparing samples over a range of moisture
contents and dry unit weights. Unlike the CBR, the R-value test data do not directly
permit selection of field compaction conditions. The R-value test is measured over a
93
range of exudation pressures by varying the water content, and the design R-value is
selected based on a value of exudation pressure that best represents the worst condition
likely to be reached in place in the subgrade several years after construction (Howe,
1961). As a result of this difference between the CBR and R-value, it is important to know
not only the correlation between the two parameters but also under what conditions are
the correlations applicable.
Existing correlations between CBR and R-value have limited applicability. With the
exception of the Van Til (1972) correlation, the physical state at which the CBR is
measured and correlated to R-value is not defined. The performance of "indirect"
correlations such as Equations 2.5 and 2.7 was found to be reasonable for dry-of
optimum soils, overpredict the R-value for soils at optimum, and underpredict the R-value
for wet-of-optimum soils. The Van Til et al. procedure results in an overprediction of the
R-value in 4 of the 5 soils tested. The Arizona DOT correlation between R-value and
index properties also showed poor agreement with measured data.
New correlations to estimate R-values were developed as part of this study. In
deriving these correlations, the Wahiawa ovendry data was excluded because these soils
were dried to temperature extremes that regular soils do not experience, and therefore,
are judged to be inappropriate for use. Nevertheless, the data provided useful insight into
the effects of drying on the measured properties. For the Wahiawa soil, the CBR and R
value increased with increasing degree of drying indicating that the soil underwent
irreversible changes upon drying.
94
7.2 Conclusions and Recommendations
A total of 5 correlations are included in this report. The first is a simple linear
regression between R-value and CBR. Separate correlations were developed for various
relative compactions, compactive effort and exudation pressures. These correlations
(Figs. 6.1 through 6.26) are direct and are recommended for use by HDOT in the design
of flexible pavements. However, these correlations are more suitable for CBR samples
prepared at- or dry-of-optimum. Wet-of-optimum samples yielded negative slopes,
implying that R-value decreases with increasing CBR. Seemingly counterintuitive, it is
therefore less desireable to correlate wet-of-optimum CBR with R-value.
Other correlations were developed but they are less direct and should only be
used if the CBR is available at a physical state different than the ones used to develop
Figs. 6.1 through 6.26. A second correlation resulted in an equation (6.4) that relates the
R-value at a desired exudation pressure to the CBR measured at a given relative
compaction and compactive effort. This equation was developed by performing linear
regression on the slope and intercept from method 1, where they were made functions of
the relative compaction, compactive effort, exudation pressure and a wetness factor. This
correlation appears to be valid only for dry-of-optimum samples.
A third correlation relates R-value to CBR, activity and exudation pressure with
appropriate exponents. The exponent for CBR is 0.04708 implying that the R-value is not
very sensitive to CBR. The coefficient of determination was 0.62 when comparing the
measured and predicted R-values.
The first three correlations were established based on CBR values interpreted at
95% and 100% relative compaction. A fourth method was developed based on all the
95
CBR data rather than interpreted CBR values. This procedure appears rational, has
significant scatter in the results, and again is not applicable for wet-of-optimum CBRs.
The fifth method relates R-value to the activity of the soil and exudation pressure.
It is useful for estimating R-value when CBR data is not available. The coefficient of
determination was 0.61.
7.3 Suggestions for Future Work
The scope of work included testing of a limited number of soil types (ML and MH),
based on which the correlations were developed. Additional tests (e.g., on CL soils)
should be performed so that the correlations can be updated if necessary to include a
wider range of soil types.
Van Til's (Figure 2.4) correlation results in unconservative R-values (generally too
high) for a given Kentucky CBR. Equations 2.5 and 2.7 are reasonable for dry-of optimum
soils, overpredict the R-value for soils at optimum, and underpredict the R-value for wet
of-optimum soils. Additional research may be useful in assessing these consequences
on past flexible pavement designs.
For future flexible pavement designs, it is recommended that the HDOT specify
that CBRs be measured at a given physical state (say 100% relative compaction using 5
layers at 56 blows). Companion R-values should be determined at say 300 psi exudation
pressure by HDOT on the same soil, and the correlation in Figure 6.2 assessed and
updated on a regular basis (say once every five years).
96
REFERENCES
American Association of State Highway and Transportation Officials (1972). AASHTO
Interim Guide for Design of Pavement Structures. Washington, DC.
American Association of State Highway and Transportation Officials (1976). Interim
Guide for Design of Pavement Structures. Washington, DC.
American Association of State Highway and Transportation Officials (1986). AASHTO
guide for design of pavement structures. Volume 2. Washington, DC.
American Association of State Highway and Transportation Officials (1993). AASHTO
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Maryland.
Croney, P. and Croney, D. (1998). The design and performance of road pavements. 3rd
Edition, McGraw-Hili, New York.
Drake, W.B. and Havens, J.H. (1959). Re-evaluation of Kentucky flexible pavement
design criterion. HRB Bulletin 233. 33 - 56.
Hall, K.T., Darter, M.I., Hoerner, T.E. and Khazanovich, L. (1997). LTPP data analysis
Phase I: Validation of guidelines for k-value selection and concrete pavement
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97
Hee, S.H. (2005). Personal communication.
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98
Miyashiro, C. (2000). Personal communication.
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99
Uniform Building Code. (1997). Published by the International Conference of Building
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100
APPENDIX
R-Value Database
Table A1 Interpreted R-values and soil ~ro~erties Soil Specific Natural Water % % Plasticity Liquid USCS Interpreted R-Value
Gravity Content Fines Clay Index Limit Symbol (%) Exudation Pressure
Low High Mean (%) (%) 240 ~si 300 ~si Waipio 2.90 26 29 28 89 48 16 46 ML 20 22.5 Kapolei 3.00 19 21 20 99 38 14 41 ML 8.5 9.7 Mililani 2.98 28 33 31 99 64 51 95 MH 7.5 10.2 Mauka
Wahiawa 3.08 51 57 53 99 62 51 99 MH 5 8.3 in situ
Wahiawa 3.08 26 99 67 45 87 MH 5 10 intermediate
Wahiawa 3.11 0 99 53 19 64 MH 13.2 20.6 ovendr:t
Table A2 Measured R-values Soil Exudation Pressure R-Value w Prior to y, Prior to
Exudation Exudation (psi) (%) (pel)
Waipio 231 16.2 26.9 97.1 271 23.9 26.0 98.9 294 21.1 26.7 100.8 319 28.3 25.4 100.5 438 28.5 26.0 100.8 581 29.4 25.6 100.8 605 31.9 25.2 100.0 653 32.5 25.0 101.2
Kapolei 191 7.6 28.1 96.8 245 8.5 26.5 99.5 374 13.0 26.4 100.5 398 13.2 26.0 104.1 462 15.7 25.1 103.6 509 23.0 23.8 103.9
Mililani 255 6.7 44.6 77.7 Mauka 255 10.4 44.8 76.9
334 12.7 46.7 77.7 398 17.0 41.1 79.6 398 42.2 36.8 86.3 454 45.6 37.0 84.9 533 19.0 45.9 78.4 541 17.1 40.1 82.1 621 24.9 39.1 82.6
Wahiawa 143 3.3 53.5 70.7 In Situ 286 3.7 49.4 73.3
294 6.9 48.4 75.6 310 6.2 45.3 78.9 318 9.3 45.7 78.4 398 20.2 39.5 84.4
101
Soil
406 32.8 37.7 87.3 477 37.6 36.4 88.7
Table A2 Measured R-values (cont'd) Exudation Pressure ~ \/,," '" w Prior to 'Yd Prior to
i=vllrl"'inn Exudation (psi) (%) (pct)
,~"'~,,~ 199 3.4 51.2 73.2 Intermediate 1---__ 2=31 __ +---:20': .. 7;-+---,:5,=,0"7--7-t-_~7 4.~
2~ 9.7 45.4 79. 31 7. ..6 75. 3 5..9 75.! 318 7. 1.4 79. 350 90 44.7 77. 382 25.1 37.~ 87.~
12 3' .0 36.2 89.3 18 16. 41.5 82.0 o 15J 39.6 84.2
716 51 3 .. 3 88.5 nc .. ic"c 191 1 '.0 4 ;.6 74. Ovendry 223 14.3 4 .9 82.
263 14.2 ·.0 79. 263 16.5 :.6 81.1 286 16.7' .2 83.3 ~66 18 __ 8 39.6 83. 493 44.3 38.2 85. 541 59.6 36.4 84.
102
