Relative Comparison of Foundations Designed on the Basis of Standard Penetration Test

RELATIVE COMPARISON OF FOUNDATIONS DESIGNED ON THE BASIS OF STANDARD PENETRATION TEST, UNCONFINED COMPRESSION TEST AND DIRECT SHEAR TEST

A PROJECT REPORT IS SUBMITTED TO THE DEPARTMENT OF CIVIL ENGINEERING OF WORLD UNIVERSITY OF BANGLADESH IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF BACHELOR OF SCIENCE IN CIVIL ENGINEERING.

SUBMITTED BY

Md. Zahid Bin HossenID No-10/09/36/1071Arafat JahanID No-10/09/36/1074Sonia AkterID No-10/09/36/1084Batch: 36thApproval of Thesis Serial No- 124Department of Civil EngineeringWorld University of Bangladesh.

SUPERVISORS.M TANVIR FAYSAL ALAM CHOWDHOURYLecturerDepartment of Civil Engineering World University of Bangladesh

November, 2013

TABLE OF CONTENTS

CONTENTSPage no

List of contentsI

List of figuresiii

List of TableV

Letter of transmittal vii

Declarationviii

CertificationIx

AcknowledgementX

Abstractxi

Notificationxii

CHAPTER 1: INTRODUCTION1

1.1 General1

1.2 Background3

1.3 Objectives3

1.4 Necessities of soil test4

1.5 History of soil test4

CHAPTER 2: LITERATURE REVIEW7

2.1 Introduction7

2.2 Definition of soil and bearing capacity8

2.3 Foundation 2.3.1 Shallow Foundation 2.3.2 Deep Foundation151516

2.4 Different type of soil test16

2.4.1 Standard Penetration Test (SPT)17

2.4.2 Unconfined Compression Test (UCT)22

2.4.3 Direct Shear test24

2.5 Major Problems and solution of the soil test.25

CHAPTER 3: METHODOLOGY27

3.1 Introduction27

3.2 Data source27

3.3 Project area location Map27

3.4 Test procedures (with equipment)30

3.4.1 Standard Penetration Test (SPT)30

3.4.2 Unconfined Compression Test (UCT)34

3.5 Direct Shear Test37

CHAPTER 4: ANALYSIS, RESULTS AND DISCUSSIONS42

4.1 Evaluation bearing capacity and comparison of Shallow Foundation. 42

4.2 Cost effect on foundation 4.2.1 Standard penetration test cost effect on Foundation. 4.2.2 Unconfined compression test cost effect on foundation 4.2.3 Evaluation bearing capacity and comparison of Deep Foundation. 4.3 Calculation of bearing capacity for the deep foundation from standard penetration test and unconfined compression test with comparison: 4.4 Result and discussion 4.5 Direct shear test calculation 51515254

586569

CHAPTER5: CONCLUSIONS AND RECOMMENDATIONS80

5.1 Conclusions80

5.2 Recommendations81

REFERENCE'S83

APPENDIXE'S84

LIST OF FIGURES

Figure NoDescriptionPage

Fig:- 1.1.1General Soil Map2

Fig:- 2.2.1Sand10

Fig:- 2.2.2 Clay soil10

Fig:- 2.2.3Silt soil11

Fig:- 2.2.4Mica soil11

Fig:- 2.2.5Organic soil12

Fig:- 2.2.6Cohesive soil12

Fig:- 2.2.7Cohesion less soil13

Fig:- 2.3.1Shallow foundation15

Fig :-2.3.2Deep foundation16

Fig:-2.4.1.1Standard penetration test (SPT)17

Fig:-2.4.1.2Driving sequence in an SPT18

Fig:-2.4.1.3Terzaghis Bearing capacity factors21

Fig:-2.4.2Unconfined compression test Machine23

Fig:-3.3.1Project area location Map for soil test -127





Fig:-3.4.1.1Tri pod & hammer30

Fig:-3.4.1.2Spilt spoon31

Fig:-3.4.1.3Total Equipment of SPT32

Fig:-3.4.1.4Spilt spoon sampler33

Fig:-3.4.1.5Disturbed soil sample collection33

Fig:-3.4.2.1Unconfined compression test (UCT)35

Figure NoDescriptionPage

Fig:-3.4.2.2Spilt cutting shoe36

Fig:-3.5.1Direct shear test38

Fig:-3.5.2Denky pump40

Fig:-3.5.3Hammer40

Fig:-3.5.4Height of fall41

Fig:-3.5.5Split spoon41

Fig:-3.5.6Soil collection41

Fig:-3.5.7Disturb soil sample collection41

Fig:-4.2.3.1Cost effect of foundation area54



Fig:-4.2.3.4 Cost effect of foundation area57

LIST OF TABLETABLE NODESCRIPTIONPAGE NO

Tab.2.2.1Empirical Values for Consistency of Cohesive Soil14

Tab.2.4.1.1Terzaghis bearing capacity factors21

Tab.2.4.1.2Approximate Relationship Between N and for Cohesion less Soil.22

Tab.2.4.1.3Correlation Between Soil Conditions and Standard Penetration Test N-Value22

Tab.3.5.1Physical properties of the tested sample.39

Tab.4.1.1Calculation of Bearing Capacity for the Shallow Foundation from Standard Penetration Test an Unconfined Compression Test with Comparison.43

Tab.4.1.2Calculation of Bearing Capacity for the Shallow Foundation from Standard Penetration Test an Unconfined Compression Test with Comparison43






Tab.4.1.8Calculation of Bearing Capacity for the Shallow Foundation from Standard Penetration Test an Unconfined Compression Test with Comparison.49

Tab.4.2.1.1Standard penetration test cost effect on foundation.51




Tab.4.2.2.1Unconfined compression test cost effect on foundation.52




Tab.4.2.3.1Foundation cost Effect between Standard Penetration Test and Unconfined Compression Test.54




Tab.4.3.1Deep Foundation cost Effect between Standard Penetration Test and Unconfined Compression Test.56

Tab.4.4.1.1 Shallow Foundation results summary.68

Tab.4.5.1 Skin Friction & End Bearing Design Chart.69

Tab.4.5.2 Skin Friction & End Bearing Design Chart.70

Tab.4.5.3Skin Friction & End Bearing Design Chart70







LETTER OF TRANSMITTAL

Date: November 16, 2013

ToS.M Tanvir Faysal Alam ChowdhouryLecturerDepartment of Civil EngineeringWorld University of BangladeshDhaka, Bangladesh.

Subject: Submission of project paper.

Sir,It is a great pleasure to submit herewith the project report on Relative Comparison of Foundations Designed On the Basis of Standard Penetration Test (SPT), Unconfined Compression Test (UCT) And Direct Shear Test (DST). This project report will have an overview on the current cost effect of foundation area based on soil test in Bangladesh. It has been great pleasure for us to work on such an important topic. This project work has been done according to the requirement of the World University of Bangladesh for the degree of B. Sc in Civil Engineering.

We would be very happy to provide any assistance in interpreting any part of the paper whenever necessary.

Sincerely yours

Md. Zahid Bin HossenID No. WUB10/09/36/0171

Arafat JahanID No. WUB10/09/36/1074

Sonia AkterID No. WUB10/09/36/1084

DECLARATION

We, do hereby, solemnly declare that the work presented in the project report has been earned out by us and so far know, none has yet submitted similar work in any University/College/Organization for an academic qualification.

We, hereby guarantee and ensure that the work that has been presented by us, does not breach any existing copyright.

We, further undertake to indemnify the University against any loss or damage arising from breach of the foregoing obligation.

Md. Zahid Bin HossenID No. WUB10/09/36/0171

Arafat JahanID No. WUB10/09/36/1074

Sonia AkterID No. WUB10/09/36/1084

WORLD UNIVERSITY OF BANGLADESHDepartment of Civil Engineering

CERTIFICATION

This is to certify that the project report on Relative Comparison of Foundations Designed On the Basis of Standard Penetration Test (SPT) And Unconfined Compression Test (UCT), Direct Shear Test is the bonafide record of Project work done by Md. Zahid Bin Hossen and others for the partial fulfillment of the requirements for the degree of B. Sc in Civil Engineering from the World University of Bangladesh (WUB).

This project work has been carried out under my guidance and supervision and is a record of successful work.

Supervisor

S.M Tanvir Faysal Alam ChowdhouryLecturerDepartment of Civil EngineeringWorld University of Bangladesh

ACKNOWLEDGEMENT

All praises and profound gratitude to the Almighty Allah who is the most beneficent and the most merciful for allowing great opportunity and ability to bring this effort to fruition safely and peacefully.

We are thankful to Professor Dr. Abdul Mannan Chowdhury, the honorable vice chancellor of the world University of Bangladesh for creating such opportunity of higher education.

The author would like to express their deepest gratitude, sincere appreciation and indebtedness to their supervisor S.M Tanvir Faysal Alam Chowdhury, Lecturer, Department of Civil Engineering, World University of Bangladesh for his constant supervision, continuous guidance, helpful criticism, affectionate encouragement and invaluable suggestions, generous help and unfailing enthusiasm at all stages of their project work. His active interest in this topic and valuable advice was the source of the authors inspiration.

The authors are grateful to Prof. A.F.M Abdur Rauf, Advisor, Department of Civil Engineering, World University of Bangladesh for his suggestions and comments that have contributed to this project work.

The authors are also grateful and wish to express thanks to Associate Professor Engr. Rabindra Ranjan Saha P Engr, Head of the Department of Civil Engineering, and Professor Sekandar Ali, Department of Civil Engineering, and Associate Professor Zahid Husain Khan, World University of Bangladesh for their valuable suggestions, cooperation and comments that have contributed to this project work.

The authors pay their deepest homage to their parents, whom they believe to be the cardinal source of inspiration for all their achievements. Their constant support throughout this project work was phenomenal and exemplary.

Authors

ABSTRACT

For subsurface geotechnical investigations the Standard Penetration Test (SPT),Unconfined Compression test and Direct Shear test have become industry standards in small diameter ( 60

Weak rock(except chalk)N600-80Very weakweakModerately weak to verystrong

80-200> 200

ClaysN600-25Very weakweakModerately weakModerately strong to verystrong

25-100100-250> 250

Note : N1 N60 (N1)60is SPT N value corrected to 100 kPa effective overburden pressure is SPT N value corrected to 60% of theoretical free-fall hammer energy is SPT N value corrected for both vertical effective stress and input energy

..........(6)

Classification is the process used during ground investigation to divide soil and rock into a limited number of groups, each of which contains materials expected to have broadly similar engineering behaviour. The engineering parameters which are of most importance in estimating behaviour are strength, compressibility and permeability and rate of consolidation. The methods most commonly used for classification are sample description, Moisture content and plasticity testing (for cohesive soils) and particle size distribution (for granular soils). Classification with the SPT is made possible because the test combines both a sampler (albeit of very poor quality and unable to sample coarse granular soils) and a penetrometer.(8)

Sand:Sand is a coarse grained soil, having particle size between 0.075mm to 4.75mm. The particle are visible to naked eye. It is a naturally occurring granular material composed of finely divided rock and mineral particles. The composition of sand is highly variable.

Figure 2.2.1: Sand

Clay soil:It consists of microscopic and sub-microscopic particles derived from the chemical decomposition of rocks. It contains a large quantity of clay minerals. It exhibits considerable strength when dry clay is fine grained soil. It is a cohesive soil. The particle size is less then 0.002mm.

Figure 2.2.2: Clay soil

Silt Soil: Silt is a fine grained soil. It granular material of a size somewhere between grained soil and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment (also known as suspended load) in a surface water body. It may also exist as soil deposited at the bottom of a water body. Silt particles range between 0.0039 to 0.0625 mm, larger than clay but smaller than sand particles. The particles not visible to naked eye.

Silt Soil

Figure 2.2.3: Silt Soil

Mica Soil:The mica group of sheet silicate (phyllosilicate) minerals includes several closely related materials having close to perfect cleavage, it is explained by the hexagonal sheet like arrangement of its atoms.

Mica Soil

Figure 2.2.4: Mica soil

Organic Soil:A sample composed primarily of vegetable tissue in various stages of decomposition and has a fibrous to amorphous texture, a dark-brown to black color, and an organic odor should be designated as a organic soil.

Organic Soil

Figure 2.2.5: Organic Soil

Cohesive Soil:Cohesive soils are fine-grained materials consisting of silts, clays, and organic material. These soils exhibit low to high strength when unconfined and when air-dried depending on specific characteristics. Most cohesive soils are relatively impermeable compared with cohesion less soils. Some silts may have bonding agents between particles such as soluble salts or clay aggregates. Wetting of soluble agents bonding silt particles may cause settlement.

Cohesive Soil

Figure 2.2.6: Cohesive Soil

Cohesion less Soil:Cohesion less soil is composed of granular or coarse grained materials with visually detectable particle sizes and with little cohesion or adhesion between particles. These soils have little or no strength, particularly when dry, when unconfined and little or no cohesion when submerged. Strength occurs from internal friction when the material is confined. Apparent adhesion between particles in cohesion less soil may occur from capillary tension in the pore water. Cohesion less soils are usually relatively free draining compared with cohesive soils.Cohesive less Soil

Figure 2.2.7:Cohesion less SoilCohesion of Soil (c):Cohesive soils are clay type soils. Cohesion is the force that holds together molecules orlike particles within a soil. Cohesion (c) is usually determined from the laboratory. Unconfined Compressive Strength Su can be determined in the laboratory using the Unconfined Compressive Strength Test. There are also correlations for Su with shear strength as estimated from the test.Cohesion of Soil (c)= Su/2 Where,c = Cohesion (kN/m2, lb/ft2).Su = Unconfined Compressive Strength (kN/m2, lb/ft2).

Empirical Values for Consistency of Cohesive Soil, (from Foundation Analysis, Bowels)Table 2.2.1:- Empirical Values for Consistency of Cohesive Soil, (from Foundation Analysis, Bowels)(3)SPT Penetration (blows/ foot) NEstimated ConsistencySu (kips/ft2)

0-2Very Soft0-0.5

2-4Soft0.5-1.0

4-8Medium1.0-2.0

8-16Stiff2.0 - 4.0

16-32Very Stiff4.0 - 8.0

>32Hard>8

Ultimate Bearing Capacity (qu):Ultimate bearing capacity is the theoretical maximum pressure which can be supported without failure.Allowable Bearing Capacity ( qa ):The allowable bearing capacity (qa) is the ultimate bearing capacity (qu) divided by an appropriate factor of safety (FS).qa=qu/FS Where,qa = Allowable Bearing Capacityqu = Ultimate Bearing CapacityFS = Factors of SafetyFS is often determined to limit settlements to less than 1 inch and it is often in the range of 2 to 4.Factor of Safety:Factors of Safety's are conservative and will generally limit settlement to acceptable values, but economy may be sacrificed in some cases.

(a) FS selected for design depends on the extent of information available on subsoil characteristics and their variability. A thorough and extensive subsoil investigation may permit use of smaller FS.

(b) FS should generally be 2.5 and never less than 2.Christopher, Barry R., et al., Reinforced Soil Structures, Volume I: Design and Construction Guidelines, FHWA-RD-89-043, 1990.(10)

2.3 FOUNDATIONA foundation is the lowest and supporting layer of a structure. Foundations are generally divided into two categories. 1.Shallow foundation 2.Deep foundation.2.3.1. Shallow Foundation:A foundation is shallow if its depth (d) is lets than or equal to its width later investigators, However have suggested. That foundation with (d) equal to 3 to 4 times width may be defined as shallow foundation.Shallow foundations, often called footings, are usually embedded about a meter or so into soil. One common type is the spread footing which consists of strips or pads of concrete (or other materials) which extend below the frost line and transfer the weight from walls and columns to the soil or bedrock.Another common type of shallow foundation is the slab-on-grade foundation where the weight of the building is transferred to the soil through a concrete slab placed at the surface. Slab-on-grade foundations can be reinforced mat slabs, which range from 25 cm to several meters thick, depending on the size of the building, or post-tensioned slabs, which are typically at least 20 cm for houses, and thicker for heavier structures.

Shallow Foundation

Figure 2.3.1: Shallow Foundation

2.3.2 Deep Foundation:A deep foundation is used to transfer the load of a structure down through the upper weak layer of topsoil to the stronger layer of subsoil below. There are different types of deep footings including impact driven piles, drilled shafts, caissons, helical piles, and earth stabilized columns. The naming conventions for different types of footings vary between different engineers. Historically, piles were wood, later steel, reinforced concrete, and pre-tensioned concrete.

Deep Foundation

Figure2.3.2: Deep Foundation2.4 DIFFERENT TYPE OF SOIL TESTSoil tests are performed to determine specific soil properties and how the soil responds to imposed conditions. Types of behavior depend on the strength, compressibility, permeability, corrosively, and index properties. Geotechnical policies and procedures manual to determine the desired properties, depending on the soil type and application. The Geotechnical engineer should observe the quality of Standard penetration test N-value and undisturbed samples when they are extruded from the sampling tubes in the laboratory. The geotechnical engineer determines the number, types, and requirements of needed tests. The geotechnical engineer should be familiar with each test procedure and should verify that the tests are being performed according to his/her directions. Familiarity with testing procedures and the soil samples helps the geotechnical engineer to appropriately apply the test results in his/her subsequent geotechnical analyses.(6)Tests shall be performed in accordance with ASTM D3441 (mechanical cones) and ASTM D 5778 (electronic friction cones andpiezocones).

2.4.1. Standard Penetration Test (SPT):Around 1902 Colonel Charles R. Gow, owner of the Gow Construction Co. in Boston, began making exploratory borings using 1-inch diameter drive samplers. Up until that time, contractors used wash borings with cuttings, similar to the methods presently used in advancing water wells. During the late 1920s and early 1930s, the procedure was standardized by Harry Mohr, one of Gows engineers, then with Raymond Concrete Pile Co. (H.A. Mohr, 1940, Exploration of Soil Conditions and Sampling Operations: Bull 269, Graduate School of Engg, Harvard University). Mohr developed a slightly larger diameter split-spoon drive sampler and recorded the number of blow counts per foot of penetration on an 18-inch deep sample round, using a 140-lb hammer dropping 30 inches, pushing a 2-inch outside diameter sampler, while recovering a 1-3/8 inch diameter sample. The value recorded for the first round of advance is usually discarded because of fall-in and contamination in the borehole. The second pair of numbers are then combined and reported as a singlevalue for the last 12 inches (1 foot). This value is reported as the SPT blow count value, commonly termed N.(4)

Figure2.4.1.1: Standard penetration test (SPT)

Not everyone used Gows sampler, which originated in the Boston area, but Karl Terzaghi liked it. Terzaghi and Arthur Casagrande vigorously sponsored adoption of the split spoon sampling procedure through the auspices of ASCEs Committee on Sampling and Testing of the Soil Mechanics and Foundations Division of ASCE, formed in 1938. The work of this committee was carried out at Harvard by JuulHvorslev, and pretty much standardized by 1940, when Hvorslev wrote The Present Status of the Art of Obtaining Undisturbed Samples of Soils, included as an 88-page appendix to the Purdue Conference on Soil Mechanics and Its Applications.Terzaghis concept of using standard blow counts to estimate soil properties was not realized until 1947, when he sat down with Harry Mohr and developed correlations between allowable bearing pressure and [SPT] blow counts in sands, while completing his draft of Soil Mechanics in Engineering Practice.(8)Later that year Terzaghi christened the 2-inch Gow sampler the Standard Penetration Test, in a presentation titled Recent trends in subsoil exploration, which he delivered to the 7th Conference on Soil Mechanics and Foundation Engineering at the University of Texas. The first published SPT correlations appeared in Fig. 177 on p. 423 of Soil Mechanics in Engineering Practice (First Ed.) by Terzaghi and Peck, published in 1948.Tri PodHeight of FallHammer

Figure 2.4.1.2: Driving sequence in an SPT

The standard drive sampler test was subsequently adopted by ASCE and The Corps Engineers in Hvorslevs Subsurface Exploration and Sampling of Soils for Civil Engineering Purposes, which appeared in November 1949 (reprinted by The Engineering Foundation in 1962 and 1965). Sprague and Henwood began producing the Mohr 2-inch diameter split spoon sampler in the early 1950s and it became a nation-wide standard in 1958 when the apparatus and procedures were officially adopted by ASTM as Test Method D1586 (and last revised in 1984)Baseline References on the SPT procedure Many of the SPT correlations have been explored, and there exist no small number of problems, requiring considerable judgment.(4)

Most of these problems are discussed in the following articles:For evaluation of liquefaction potential, raw SPT blow counts must be corrected to (N1)60 values, as described in the following sections. Burmisters (1948) input energy correction. Despite all the encouragement to adopt TerzaghisSPT test, most people went on using whatever devices they had previously, until more and more of Casagrandes students infiltrated the ranks of foundation engineering. In the New York area the favored device was the 3.625-inch diameter Moran & Proctor, or M & P Sampler; which had been developed by Carlton Proctor for the firms exploration of the San Francisco Bay Bridge project (C. S. Proctor, 1936, The Foundations of the San Francisco-Oakland Bay Bridge: Proceedings of the Intl Conference on Soil Mechanics and Foundation Engineering, Harvard Univ., v.3 p. 183-193). The M & P sampler allowed recovery of a much larger 3-inch diameter samples, using 5000 in-lbs. per blow in lieu of the SPT 4200 in-lbs. Moran & Proctor engaged Professor Don Burmister of Columbia University to develop a scheme for correlating M & P sampler blow counts with those of Mohrs SPT sampler, This could be rewritten to provide input energy and diameter correction for other tests to correlate with the SPT (ASTM D-1586).(4)

[N* = NR (W 1bs) (H in) [ (2.0 in)2 - (1.375 in)(1401b)(30in)(D0)2-(Di)2Where W is the hammer weight, H is the height of the drop, D0 is the outside diameter of the sample barrel, Di is the diameter of the drive sample, Nr is the raw blow count, and N* is the blow count reported as the equivalent SPT value. The Bur mister energy correction takes the raw SPT blow count value and multiplies it by an appropriate fraction, derived from the relationship above. The corrected blow count value is usually denoted by an asterisk (*) on the boring log, with a note explaining that the blow counts have been adjusted. If we apply Burmisters simple equation to the Modified California sample barrel, with an outside diameter of 3.0 inches and a sample diameter of 2.4 inches, the calculated correction would be 0.65. This means the equivalent SPT N values would be about 65% of those recorded with the Modified California apparatus. Most workers cite Burmisters 1948 correction for adjusted blow counts recorded with larger diameter drive samplers, or for lower energy hammers (such as the 70-lb hammer used with Mobile Drillings Minuteman portable drilling rig).(6)

Formula for Standard Penetration Test:Karl von Terzaghi was the first to present a comprehensive theory for the evaluation of the ultimate bearing capacity of rough shallow foundations. This theory states that a foundation is shallow if its depth is less than or equal to its width. Later investigations, however, have suggested that foundations with a depth, measured from the ground surface, equal to 3 to 4 times their width maybe defined as shallow foundations (B.M. Das, 2007).Terzaghi developed a method for determining bearing capacity for the general shear failure case in 1943.(5)Terzaghis Bearing capacity equations: Where,Strip footings:C: Cohesion of soil,

qu = cNc+ DNq + 0.5 BN* 1.1: unit weight of soil,Square footings:D: depth of footing,

qu=1.3cNc+ DNq + 0.47 BN* 1.2B: width of footingCircular footings:

qu=1.3cNc+ DNq + 0.3 BN* 1.3

Nc, Nq, N: Terzaghis bearing capacity factors depend on soil friction angle,

Teraghis Bearing Capacity Factors:Table 2.4.1: Terzaghis bearing capacity factors

NcNqN

05.710

57.31.60.5

109.62.71.2

1512.94.42.5

2017.77.45

2525.112.79.7

3037.222.519.7

3557.841.442.4

4095.781.3100.4

Terzaghi's Bearing Capacity Factors

Nc. Nq. N

Figure2.4.1.3:Terzaghis Bearing Capacity Factors.

Approximate Relationship Between N and for Cohesion less Soil:

Table2.4.2:Approximate Relationship Between N and for Cohesion less Soil.N Value*Relative Consition of SoilApproximate Value of

0-4Very Loose250-320

4-10Loose300-400

10-30Medium350-450

30-50Dense400

50very dense

* Values in this table refer to soil sampling procedures where the efficiency of the drop hammer is approximately 60%.

Correlation Between Soil Conditions and Standard Penetration Test N-Value:Table2.4.3: Correlation Between Soil Conditions and Standard Penetration Test N-ValueSoilDesignationN Blows

Sand and SiltLoose0-10

Medium11-30

Dense31-50

Very denseOver 50

ClayVery soft0-2

Soft3-5

Medium6-15

Stiff16-25

*Based on results for drive hammers with 60 percent efficiency. Source: Acker Drill Company.(7)

2.4.2 Unconfined Compression Test (UCT):The Unconfined Compression Test is still used as a means of rapidly evaluating the shear strength of cohesive soils although it is gradually losing favors. The Unconfined Compression strength is the maximum load attained per unit area or the load at 15%axial strain, whichever occurs first on a cylindrical sample tested in compression. The shear is taken as equal to 1/2 the Unconfined Compressive Strength. In practice the test specimens are usually obtained by extruding thin-wall tube samples. The lengthto of the specimen should be between 2 and 3. Two types of loading devices are permitted, either strain controlled or stress controlled. In practice strain controlled is now almost universally used for this test. In the strain controlled test the rate of loading is controlled so as to produce a uniform axial strain. In the stress controlled test the rate of loading is controlled so as to produce a uniform increase in axial load. In this laboratory, strain control will be used and the compression machines will be adjusted to a rate of loading which will provide 15% axial strain on the sample in approximately 10 minutes. Sensitivity of a cohesive soil is defined as the undisturbed strength of the soil divided by the remolded strength. The sensitivity cannot be less than 1. For most local clays, the sensitivity is between 1 and 3. For some highly sensitive clays it can exceed 10 and, in some cases, be so high that it cannot even be accurately measured. The most accurate method of determining sensitivity involves use of the laboratory vane shear apparatus. Two devices used to check the unconfined strength or shear strength in the field are the torvane and the pocket penetrometrer. You will use both and compare the results with that obtained from the unconfined test. The results of this lab will also be compared to the results of a triaxial compression test performed in a later lab. It is therefore necessary to retain a copy of all the results from this lab.(7)

Figure2.4.2: Unconfined Compression Test Machine

Formula for Unconfined Compression Test:The primary purpose of this test is to determine the unconfined compressive strength, which is then used to calculate the unconsolidated untrained shear strength of the clay under unconfined conditions. According to the ASTM standard, the unconfined compressive strength (qu) is defined as the compressive stress at which an unconfined cylindrical specimen of soil will fail in a simple compression test. In addition, in this test method, the unconfined compressive strength is taken as the maximum load attained per unit area, or the load per unit area at 15% axial strain, whichever occurs first during the performance of a test.(7)

Significance:For soils, the untrained shear strength (Su) is necessary for the determination of the bearing capacity of foundations. The untrained shear strength (Su) of clays is commonly determined from an Unconfined Compression Test. The untrained shear strength (Su) of a cohesive soil is equal to one-half the unconfined compressive strength (qu) when the soil is under the f = 0 condition (f = the angle of internal friction). The most critical condition for the soil usually occurs immediately after construction, which represents untrained conditions, when the untrained shear strength is basically equal to the cohesion (c). This is expressed as: Su = c (or cohesion) = qu/2 the value c put in equation for calculation Bearing capacity.(7)2.4.3 Definition of Direct Shear TestA direct shear test is a laboratory or field test used by geotechnical engineers to measure the shear strength properties of soil or rock material, or of discontinuities in soil or rock masses. A detailed description of the testing equipment and procedure can be also found on geotechdata.info direct shear test page.The U.S. and U.K. standards defining how the test should be performed are ASTM D 3080 and BS 1377-7:1990, respectively. For rock the test is generally restricted to rock with (very) low shear strength. The test is, however, standard practice to establish the shear strength properties of discontinuities in rock.The test is performed on three or four specimens from a relatively undisturbed soil sample.A specimen is placed in a shear box which has two stacked rings to hold the sample; the contact between the two rings is at approximately the mid-height of the sample. A confining stress is applied vertically to the specimen, and the upper ring is pulled laterally until the sample fails, or through a specified strain. The load applied and the strain induced is recorded at frequent intervals to determine a stress-strain curve for each confining stress. Several specimens are tested at varying confining stresses to determine the shear strength parameters, the soil cohesion (c) and the angle of internal friction (commonly friction angle) (). The results of the tests on each specimen are plotted on a graph with the peak (or residual) stress on the x-axis and the confining stress on the y-axis. The y-intercept of the curve which fits the test results is the cohesion, and the slope of the line or curve is the friction angle.(6)Direct shear tests can be performed under several conditions. The sample is normally saturated before the test is run, but can be run at the in-situ moisture content. The rate of strain can be varied to create a test of untrained or drained conditions, depending whether the strain is applied slowly enough for water in the sample to prevent pore-water pressure buildup.The advantages of the direct shear test over other shear tests are the simplicity of setup and equipment used, and the ability to test under differing saturation, drainage, and consolidation conditions. These advantages have to be weighed against the difficulty of measuring pore-water pressure when testing in untrained conditions, and possible spuriously high results from forcing the failure plane to occur in a specific location.(6)

2.5 MAJOR PROBLEM AND SOLUTION OF THE SOIL TESTAccording to our study we see the allowable bearing capacity of Standard penetration Test is better than Unconfined Compression Test. Some time the following problem are occur in Standard Penetration Test, Unconfined Compression Test and Direct Shear Test.(12)

1) Height of fall: Labors of Standard Penetration Test team can not control the height of fall for there unskillness. Most of the time they are not aware of importance of height of fall. For these cases height of fall is more or less than the specified height of fall (30 inch = 76cm). When the height of fall is more or less then 30inch, the SPT N-value is more or less than actual value. The ultimate result is Allowable bearing capacity increases or decreases and foundation size will be unsafe or costly. For controlling this problem must be take right stapes likes marking and using nut on top of the guide rod, using auto trip hammer and providing skill labors in Standard Penetration test Team.(9)

2) SPT Spoon cutting shoe Thickness: In Bangladesh SPT spoon cutting shoe thickness is usually does not comply with ASTM most of the cases. Always conventional spoon is more or less sharper than the Standard spoon. If cutting shoe of SPT spoon is sharp, N-value will be less than actual value. So Allowable Bearing capacity decreases and foundation will be unsafe. For controlling this problem must be take right stapes likes must be use in SPT standard spoon, Before use should be check thickness and sharpeners of cutting spoon.(9)

3) Non Standard Shelby Tube: In field test non- standard Shelby tubes used by Soil Exploration Company in Bangladesh, if Shelby tube is not comply with standard- soil sample will be disturbed, disturbed soil sample looses shear strength and Finally Unconfined Compressive Test result vary from actual strength. For this is case Foundation design cost will be increases or decreases. For Controlling this problem must be use ASTM standard Shelby tubes.(9)

4) Collection, Preservation and Carrying sample: Some time undisturbed soil sample is not collection, preservation and carrying with standard procedure. So for Unconfined Compressive Test result is deferent from actual desirable result. This problem can be reducing by fowling standard sample collection, preservation and carrying procedure.(9)

CHAPTER-IIIMETHODOLOGY

3.1 INTRODUCTIONIn conformation with the objectives, the following procedure was followed:- Collection of soil test report from Soil Exploration Company. Study and data analysis. Calculation of bearing capacity based on Standard Penetration test, Unconfined Compressive test and Direct Shear Test. Comparison among those bearing capacity and cost effect of foundation area3.2 DATA SOURCE1.Imakas Engineering Limited.(Mirpur-10,Dhaka)2.Nila Engineering Limited.(Darussalam, Kallanpur, Dhaka)3.3 LOCATION MAP

Figure 3.3.1:Project area location Map for soil (House#66, Road#05, Monsurabad, Mohammadpur, Dhaka)

Figure 3.3.2:Project area location Map for soil(House#59, Siddheswari circular road, Dhaka)

Figure 3.3.3:Project area location Map for soil(House#550, Road#10, Adabor, Mohammadpur, Dhaka)

Figure 3.3.4:Project area location Map for soil (House#64, Siddheswari circular road, Dhaka)

Figure 3.3.5:Project area location Map for soil (House#37, Road#18, Sector#13, Uttara, Dhaka)

3.4 TEST PROCEDURES (With Equipment):3.4.1. Standard Penetration Test (SPT): Apparatus and Materials:

(i)Drilling equipment: Any drilling equipment is acceptable that provides a reasonably clean hole, which is at least 5 mm larger than the sampler or sampling rods, and less than 170 mm diameter.(ii) Sampling rods steel a rod is used to connect the sampler to the drive weight assembly. A rod should be used unless otherwise directed.(iii)Split-barrel sampler consists of 3 main parts, head, split-barrel and shoe. A core catcher should be installed to prevent loss of sample. Shoes which have been damaged should be replaced or repaired.(iv)Hammer63.5 kg weight driving head (anvil) (v)Jar - for sample collection, (vi)Tri Pod

Tri pod HammerFigure3.4.1.1:Tri pod & Hammer

Test Procedures:

Test Hole: The desired sampling depth has cleaned out by the drill. If a wet drill is used, flush out all cuttings.Assembling Equipment: Attach the split-barrel sampler to the A-rod and lower into the hole until it is sitting on the undisturbed material. Attach the drive weight assembly. Lift the 63.5 kg hammer approximately 0.76 m and allow it to fall on the anvil delivering one seating blow. Mark the drill rod in 3 successive

0.15m increments to observe penetration. Mark the drive weight assembly to indicate a 0.76 m hammer lift.(3)

Fig.-3.4.1.2: Diagram of standard split-spoon (split-barrel) sampler. BS 1377 split-barrel samplers (a) BS 1377: 1975, (b) BS 1377: 1990

Penetration Testing:Raise and drop the hammer 0.76 m successively by means of the rope and cathead, using no more than 2 .25 wraps around the cathead. The hammer should be operated between40 and 60 blows per minute and should drop freely.

Continue the driving until either 0.45 m has been penetrated or 100 blows has been applied.

Record the number of blows for each 0.15 m of the penetration. The first 0.15 m increments the seating drive. The sum of the blows for second and third increment of 0.15 penetration is termed penetration resistance or N-value.

If the blow count exceeds 100 in total, terminate the test and record the number of blows for the last 0.30 m of penetration as the N-value. If less than 0.30 m is penetrated in 100blows, record the depth penetrated and the blow count.

If the sampler advances below the bottom of the hole under its own weight, note this condition on the log.GEO 1997.Interim review of the standard penetration test procedures with reference to Hong Kong practice.Geotechnical Engineering Office, Hong Kong SAR.

Figure:3.4.1.3: Total Equipment of SPT

Handing SampleBring the sample to the surface and open it. Remove any obvious contamination from the ends or sides and drain excess water. Carefully scrape or slice along one side to expose fresh material and any stratification.

Figure3.4.1.4: A split-spoon sampler barrel must be recovered from the hole detached from the drill rod, and mechanically broken down, as shown at left.(Ireland)

A split-spoon sampler barrel must be recovered from the hole, Assessment of vegetation and soil water regimes in partial canopies with optical remotely sensed data. Remote Sensing of Environment, v. 32, 1990, p. 155-167.Detached from the drill rod, and mechanically broken down, as shown at left. The two halves of a typical Standard Penetration Test (SPT) sampler with entrained soil are shown at right.

Figure3.4.1.5: Disturbed Soil Sample Collection (Adabor Mohammadpur, Dhaka). Record the length, composition, color, stratification and condition of sample. Remove sample and wrap it or seal in a plastic bag to retain moisture. If the sample can be removed relatively intact, wrap it in several layers of plastic to strengthen it and seal ends with tape. Mark the sample top and bottom if applicable and label it with an identification number.

Reporting Results:Prepare a log of the bore hole, in the field, on the Field Bore Hole Log report form and show:(i) Name and location of job.(ii) Date, start and finish.(iii) Hole number.(iv) Elevation and stationing.(v) Sample number and depth.(vi)Drilling method and type of bit.(vii) Description of soil.(viii) Number of blows for each 5ft. penetration or partial increment. .(ix) Type of drilling equipment.

3.4.2. Unconfined Compression Test (UCT)The primary purpose of the Unconfined Compression Test is to quickly determine a measure of the unconfined compressive strength of soils that possess sufficient cohesion to permit testing in the unconfined state. This measure is then used to calculate the unconsolidated untrained shear strength of the clay under unconfined conditions. In the Unconfined Compression Test, the sample is placed in the loading machine between the lower and upper plates. Before starting the loading, the upper plate is adjusted to be in contact with the sample and the deformation is set as zero. The test then starts by applying a constant axial strain of about 0.5 to 2% per minute. The load and deformation values are recorded as needed for obtaining a reasonably complete load-deformation curve. The loading is continued until the load values decrease or remain constant with increasing strain, or until reaching 20% (sometimes 15%) axial strain. At this state, the samples is considered to be at failure. The sample is then removed for measurement of the water content. As for the results, the axial stress is usually plotted versus the axial strain. The maximum axial stress, or the axial stress at 20% (sometimes 15%) axial strain if it occurs earlier, is reported as the unconfined compressive strength Su.(12) The untrained shear strength then reads Su = qu/2Dr.K.R. Arora. Soil Mechanics and Foundation Engineering, 2003, Standard Publishers Distributors, Sixth Edition.

Figure 3.4.2.1: Unconfined Compression Test (UCT)Equipment:(i) Compression device,(ii) Load and deformation dial gauges,(iii) Sample trimming equipment,(iv) Balance,(v) Moisture can.(vi) Oven(vii) Stop Watch(viii) Split Mould(iv) Sample extractor(x) Knife (xi) venire Calipers

Test Procedures:(1)Extrude the soil sample from Shelby tube sampler. Cut a soil specimen so that the ratio (L/D) is approximately between 2 and 2.5. Where L and d are the length and diameter of soil specimen, respectively.Split Cutting Shoe

Figure: 3.4.2.2: Split Cutting Shoe(2)Measure the exact diameter of the top of the specimen at three locations 120 apart. and then make the same measurements on the bottom of the specimen. Average the measurements and record the average as the diameter on the data sheet.(3)Measure the exact length of the specimen at three locations 120 apart, and then average the measurements and record the average as the length on the data sheet.(4)Weigh the sample and record the mass on the data sheet.

(5)Calculate the deformation (L) corresponding to 15% strain (). Strain (e) = L/L0Where L0 = Original specimen length (as measured in step 3).(6)Carefully place the specimen in the compression device and center it on the bottom plate. Adjust the device so that the upper plate just makes contact with the specimen and set the load and deformation dials to zero.(7)Apply the load so that the device produces an axial strain at a rate of 0.5% to 2.0% per minute, and then record the load and deformation dial readings on the data sheet at every 20 to 50 divisions on deformation the dial.(8)Keep applying the load until 1.the load (load dial) decreases on the specimen significantly,2.the load holds constant for at least four deformation dial readings, or 3.the deformation is significantly past the 15% strain that was determined in step 5.(9)Draw a sketch to depict the sample failure.(10)Remove the sample from the compression device and obtain a sample for water content determination.Analysis:(1)Convert the dial readings to the appropriate load and length units, and enter these values on the data sheet in the deformation and total load columns. (Confirm that the conversion is done correctly, particularly proving dial gage readings conversion into load)

(2)Compute the sample cross-sectional area, Ao = (d2 )/4

(3)Compute the strain, e = L/Lo(4)Computed the corrected area, A' = Ao/(l - e)(5) Using A, compute the specimen stress, Sc = P/ A'(Be careful with unit conversions and use constant units).(6)Compute the water content, w%.(7)Plot the stress versus strain. Show qu as the peak stress (or at 15% strain) of the test. Be sure that the strain is plotted on the abscissa. See example data.(8)Draw Mohrs circle using qu from the last step and show the untrained shear strength, Su = c (or cohesion) = qu/2.(6)

3.5 DIRECT SHEAR TEST

Assessments of the stability of slopes, earth pressures on retaining walls, and the bearing capacity of foundations are often carried out using a Mohr-Coulomb strength model, based on the strength parameters and .

In free draining materials or situations where the rate of soil failure is likely to be slow, the effective strength parameters, and are used. These strength parameters are usually estimated from laboratory testing of representative sample.

Direct shear testing is a standard testing method employed for the estimation of soil shear strength parameters. An important advantage of this test is that it is possible to test larger soil samples with relative case, and so soils with large particle sizes can be tested under conditions that more closely approximate those in the field.(7)

Methods for carrying out direct shear tests for geotechnical engineering purposes are well established in practice. These methods have been formalized into testing standard documents such as ASTM D 3080-98 (1998) Standard Test Method for Direct Shear Test of Soils Under Consolidated Drained Conditions and AS 1289-9.2.2 (1998) Soil Strength and Consolidation Tests-Determination of the Shear Strength of a Soil-Direct Shear Test using a Shear Box.(9)

Direct Shear Test Machine

Figure 3.5.1: Direct Shear TestApparatus, Materials, and Sample Preparation:All direct shear testing for this study was carried out using multi-speed direct shear equipment. The equipment was instrumented for automatic logging of both shear load and displacements. All instrumentation data were digitally displayed during the test, and outputs were interfaced with a personal computer. The large shear box tests were carried out using a Prolab machine with a shear box of 300 mm by 300 mm by 190 mm deep. The small shear box tests were carried out using a WykehamFarrence direct shear machine, with a shear box of 60 mm by 60 mm by 50 mm deep.(10)

Q181C (2002) gives guidance as to the maximum particle size of samples that may be tested in a shear box of a given size. For the large shear box with a depth of 190 mm, a maximum particle size up to 19 mm was considered permissible, noting that after consolidation of the sample, the sample height is often reduced to around 130 mm. The bulk sample, prepared to a maximum size of 19 mm, could thus be tested directly. For the small shear box of 50 mm depth, a maximum particle size up to 5 mm was permissible.(10)The material employed in this testing program was a ripped silt-stone rock, slightly weathered, taken from the excavated overburden of an open-cut coalmine in the Hunter Valley. This material was selected as, at one time, it was proposed to use it as RE wall backfilling an infrastructure development at the mine. In its delivered state, the sample was described as silty sandy gravel, and it contained gravels up to cobble size. Before testing commenced, the bulk sample was screened to remove all particles greater than 19 mm (about 10 % of the raw sample). These were crushed to pass the 19 mm sieve, and they were then returned to and blended evenly through the sample. Small box testing was carried out on a sample that had been modified by the removal of all material retained on the standard 4.75 mm sieve.The particle size distribution curves for each of the prepared samples are shown in Figs. 1 (a) and 1 (b). According to the Unified Soil Classification System (USCS), the prepared coarse samples are classified as (CM) silty sandy GRAVEL, fine to medium, pale gray siltstone gravels, fine to coarse sand, low liquid limit silt, and a trace of pale gray clay of low plasticity. After removal of the 4.75-19 mm fractions, the sample was modified to (SM) silty gravelly SAND.Physical properties of the tested sample.Table 3.5.1:Physical properties of the tested sample.Atterberg limits (-4.75 m fraction)Standard compaction (whole soil)9.5 19 mm

Soil size, mmLiquid limit, %Plastic limit, %Plasticity index, %Maximum dry density, g/m3Optimum water content, %Los Angeles abrasion value, % dry mass

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Relative Comparison of Foundations Designed on the Basis of Standard Penetration Test

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