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Prepared By: Date: Octo ber, 2015
RIDARC Drilling and Geo-Technical Pvt. Ltd.Sainbu VDC - 2, Bhaisepati, Lalitpur
Phone / Fax No: 01-5593065, Contract No: 9851016051, 9741137840E-mail:[email protected]&[email protected]
Detailed Soil Investigation ofTrishuli River Bridge,Ratmate-08, Khalte
to
Budhasingh-01, ChipletteNuwakot
Client:Department of Roads, Bridge Branch
Babarmahal, Kathmandu
REPORT
ON
Prepared For:
ANK- Lumbini- Himdung J/V
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Acknowledgement
Sainbu VDC - 2, Bhaisepati, Lalitpur, Contract No: 9851016051, 9741137840, E-mail:[email protected] Pagei
ACKNOWLEDGEMENT
We are grateful to M/s Bridge Branch, DoR and
ANK- Lumbini- Himdung J/V for providing us theopportunity to carry out these investigations.
The co-operation extended by their clientsEngineers, Sub- Engineers and other Field Staffduring field investigations is thankfully
acknowledged.
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Table of Contents
Sainbu VDC - 2, Bhaisepati, Lalitpur, Contract No: 9851016051, 9741137840, E-mail:[email protected] Pageii
Table of Content1. GENERAL INTRODUCTION ....................................................................................................... 1
1.1 Background .............................................................................................................................. 1
1.2 General Geology, Geomorphology and Seismicity.................................................................. 1
2. OBJECTIVES ................................................................................................................................. 2
3. Scope of Investigation..................................................................................................................... 2
4. Methodology ................................................................................................................................... 2
4.1 Field Tests ................................................................................................................................ 2
4.2 Sampling................................................................................................................................... 3
4.3 Ground Water Table ................................................................................................................. 4
4.4 Laboratory Tests ....................................................................................................................... 4
4.5 Strata Analysis.......................................................................................................................... 4
4.6 Bearing Capacity Analysis ....................................................................................................... 4
4.6.1 Depth of Foundation ......................................................................................................... 4
4.6.2 Bearing Capacity of Soil ................................................................................................... 5
4.6.3 Stress distribution in Soils ............................................................................................. 5
4.7 Bearing Capacity Calculation................................................................................................... 5
4.7.1 Bearing capacity From In-situ Test.............................................................................. 5
4.8 Liquefaction ........................................................................................................................... 10
5. OBSERVATIONS AND RESULTS ............................................................................................ 11
5.1 Field Investigation Results ..................................................................................................... 11
5.2 Laboratory Investigation Results ........................................................................................... 11
5.2.1 Index Properties ........................................................................................................... 11
5.2.2 Strength Parameters .................................................................................................... 12
5.3 Settlement ............................................................................................................................... 12
6. Analysis of Data ............................................................................................................................ 12
6.1 Bearing Capacity .................................................................................................................... 12
6.2 D50Calculations ..................................................................................................................... 19
7 DESIGN PARAMETERS ............................................................................................................ 19
8 RECOMMENDATION ................................................................................................................ 20
Annexes:Bore Hole LogsTest Result Summary Sheet
Laboratory Test ResultFiguresPhotographs
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Abbreviation
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LIST OF ABBREVIATION
SPT Standard Penetration Tests
DCPT Dynamic Cone PenetrationTestADB Asian Development BankADT Average Daily TrafficARE Assistant Resident EngineerASTM American Standards for Testing MaterialsAWBR All Weather Bituminous RoadAWGT All Weather Gravel TrackBM Benchmark/sBOQ Bill of QuantitiesCAD Computer Aided DraftingCBR California Bearing Ratio
CPM Critical Path MethodCV Curriculum VitaeDCP Dynamic Cone PenetrationDLP Defects Liability PeriodDOR Department of RoadsDTM Digital terrain ModelingEIA Environmental Impact AssessmentEMAP Environmental Management Action PlanEMG Environmental Management GuidelinesEPA Environmental Protection ActEPR Environmental Protection Rules
ESA Equivalent Single Axle/sEV Earned ValueFWET Fair weather Earth TrackFWGT Fair weather Gravel TrackGEU Geo-environmental UnitGON Government of NepalHRD Human resource DevelopmentICB International Competitive BiddingIEE Initial Environmental ExaminationIOW Inspector of WorksIRC Indian Roads CongressJV Joint VentureKm Kilometer/sMIS Management Information SystemNCB National Competitive BiddingNRRL Norwegian Road Research LaboratoryPAF Project Affected FamiliesPIP Priority Investment ProgramPOL Petroleum, Oil and LubricantPQ Pre-qualificationPWD Public work Directive
QAP Quality Assurance PlanRAP Resettlement Action PlanRMDP Road Maintenance and Development Project
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Trishuli River Bridge, Nuwakot
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Soil Investigation Works of Trishuli River Bridge, Nuwakot
1. GENERAL INTRODUCTION
This report is prepared in accordance with the agreement between Bridge Branch, DoR and
ANK- Lumbini- Himdung J/V and RIDARC Drilling & Geo-Technical Pvt. Ltd., Sainbu,
Lalitpur to determine the bearing capacity and subsurface exploration of bridge site at
Trishuli River at Ratmate-08, Khalte to Budhasingh-01, Chiplette, Nuwakot District.
Site has been proposed to make two bore holes for sub surface exploration, which is located
at Ratmate-08, Khalte to Budhasingh-01, Chiplette, Nuwakot District. The site is nearer to
the vehicular approach of Galchhi to Bidur link road.
1.1 Background
The main objective of this Soil Investigation is to explain geotechnical characteristics of the
sub-soil strata, (i) to express the engineering properties of the sub-soil (ii) to confirm the
value of bearing capacity of the soil.
1.2 General Geology, Geomorphology and Seismicity
The site is located at the latitude of 2751'25 N and longitude of 850328 E; of Nuwakot
in the lesser Himalaya region of Nepal which is a part of the metasediments. The geological
formation of the lesser Himalaya is different types of sedimentary and metamorphic rocks
such as sandstones, silt, conglomerates, lime stone, quartzites, schists, etc. The
formations are occasionally mixed with local sandstones, silt, conglomerates, lime stone,
quartzites and schists.
Geologically, the lesser Himalaya are covered by glaciers where boulders, sand and stone
brought by glacier are found. Glaciers in the lesser Himalaya are deposited by the rivers
originating and coming from the Himalaya and they make fan shape deposition at the exit
point of the river. It is also observed that the same pattern continued in earlier times for the
deposition of older sediment. From the depositional pattern it is found that boulder and
cobbles are deposited in the form of fan in the mouth of river, whereas fines are deposited
further away.
In lesser Himalaya the parent rocks being the lower and upper formation of metasedimentsconsisting of sandstones, silt, conglomerates, lime stone, quartzites, schists, etc. The land
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form of lesser Himalaya has been divided as metasediments and crystalline, the
metasediments where both erosion and deposition are not occurring.
Generally, the sandstones, silt, conglomerates, lime stone, quartzites and schists arecompact. Its bearing capacity is high. Locally this unit is not prone to erosion and flooding.
There is no liquefaction.
As a matter of fact, the project site is in a Himalaya area having sandstones, silt,
conglomerates, lime stone, quartzites, schists in their textures without any soft cohesive
traces in the vicinity of the site. The deposits are in loose to medium denseness in state.
So both banks are slightly eroded during rainy season. The river depth is low and flows in
the wider width at the bridge axis.
2. OBJECTIVES
The main objective of this investigation is to explore geotechnical characteristics of the
subsoil strata, (i) to assess the engineering properties of the sub-soil; (ii) to confirm the
assumed value of bearing capacity of the ground strata during design of foundation, and
(iii) to confirm the design parameters to be used during the detailed design of the foundation
of the proposed site.
3. SCOPE OF INVESTIGATION
The scope of work includes drilling of two boreholes, each of greater than 19.0 m deep,
along with dynamic cone penetration test, standard penetration test, retrieving samples
from the boreholes and evaluation of allowable bearing capacity of the foundation based
on field and laboratory test.
4. METHODOLOGY
The following are the methodology adopted to meet the objectives.
4.1 Field Tests
The SPT is done to find the strength of soil in field at every interval of 1.5 m in each BH.
Standard Penetration Tests: It consists of driving a Split Spoon sampler with an outside
dia. of 50 mm into the soil at the base of borehole. Driving is accomplished by a drop of
hammer weighing 63.5 kg falling freely through a height of 750 mm onto the drive head.
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First of all the spoon is driven 150 mm into the soil at the bottom of the borehole. It is then
driven further 300 mm and the number of blows (N values) required to drive this distance
is recorded.
Dynamic Cone Penetration Test (DCPT): It consists of driving a cone by blows of
hammers. The number of blows for driving the cone through a specified distance is a
measure of the dynamic cone resistance.
Dynamic Cone Penetration test are performed by a 50 mm cone. The driving energy is
given by a 63.5 kg falling freely through a height of 750 mm onto the drive head. First of
all the cone is driven 100 mm into the soil at the bottom of the bore hole. It is then driven
further 200 mm and the number of blows (Ncbrvalues) required to drive this distance isrecorded.
The result i.e., Ncvalues first corrected to the Standard Penetration Test (SPT) value (N)
and that provides and estimation of degree of compaction of soil strata, values of angles of
internal friction () and allowable bearing capacity. The dynamic cone resistance is
correlated with the SPT (N) as given below.
Nc = 1.5 N for depth up to 3 m
= 1.75 N for depth 3 to 6 m
= 2 N for depth greater than 6 m
4.2 Sampling
(i) Disturbed Sample:
Before any sample was taken, the borehole was cleaned up of loose disturbed soil
deposited during boring operation. The samples which were obtained from bailer and in the
SPT tube were preserved as representative disturbed samples for finding out index
properties. The samples thus obtained were placed in airtight double plastic bags, labeled
properly for identification and later transported to the lab for analysis.
(ii) Undisturbed Sample:
Undisturbed Sample was extracted by means of thin wall tube (Shelby tube). The tube was
pushed into the ground and the sample recovered mechanically. The tube was sealed with
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wax and wrapped with airtight polythene sheets and then bound by adhesive tapes and
properly labeled. The tube was properly packed in a wooden box so as to minimize the
disturbances during transportation to the laboratory and avoided the changes of moisture
content of sample. This sample was used for the determination of strength andconsolidation parameters.
But undisturbed samples could not be obtained in this site.
4.3 Ground Water Table
Ground Water Table (GWT) was not observed during the drilling, which is mentioned in the
borehole logs.
4.4 Laboratory Tests
Disturbed and Undisturbed samples collected in core boxes, were transported to lab in
Bhainsepati, Lalitpur for the following tests.
Index property Test
a) Sieve Analysis
b) Natural Moisture Contentc) Bulk Density & Dry Density
d) Specific Gravity
f) Atterbergs Limit
Strength Parameter Test
a) Direct Shear Test
4.5 Strata Analysis
The project area lies in the Nuwakot district. The area is found of sand and boulder with
some layers of clay.
4.6 Bearing Capacity Analysis
4.6.1 Depth of Foundation
Strata of site consists of sand and boulder along with a clayey gravel layer. A pile
foundation or pile foundation for varying depth is considered for SBC calculation, so that
the designer can choose the depth according to capacity required and scour depth
provision.
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4.6.2 Bearing Capacity of Soil
The stratum being non-homogeneous consisting with sand and boulder and sandy clay the
computation of bearing capacity of the strata for foundation is derived from the SPT testand laboratory method.
4.6.3 Stress distribution in Soils
The Boussinesq's equation can be used to get stress distribution analysis for stress at
depths below the foundation level.
L = 6 m, B = 6 m
L/B = 6/6 = 1.0
For square footing the effective pressure below B; (depth equal to width of footing, 6.0 m,
or 12.0 m below GL) below the foundation bed, the remaining pressure is reduce about
1/3rdof total value.
The investigation work is to 16 m. The stress distribution at a depth of 7.0 m below ground
level is only 1/3rdof stress developed at the foundation level and seems very low. So there
will not be any major geotechnical changes in the strata below the depth of investigation.
4.7 Bearing Capacity Calculation
4.7.1 Bearing capacity From In-situ Test
Correction of N value from SPT
i) Overburden Correction
for overburden, as suggested by Peck et.al. (1974).
N corr = 0.77 Nreclog (2000/v')
Where, v' = Effective Overburden pressure (KN/m2)
N rec = SPT value Recorded
ii) Dilatancy Correction
Terzaghi and Peak (1976) give correction for water pressure.
If, Nrec 15, then Ncorr= Nrec
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If Nrec 15, then Ncorr= 15+1/2(Nrcc15)
Then for bearing capacity analysis Ncorris used as the N in the Correlation provided
by different researcher.
iii) Standardize Field Penetration Value:
N60 = 60
RSBHrecN
Where,
N60 = Standard penetration number, corrected for field conditions to an
Average energy ration of 60%
Nrec = measured penetration number
H = hammer efficiency (%)
B = correction for borehole diameter
S = sampler correction
R = correction for rod length
iv) Using Meyerhof's (1965) & Bowles (1977) Correlation
qsafe = 11.98N 1
2
2528.3
128.3wd Rx
Sf
B
B
Where,
N = Standard Penetration Value
B = width (m)
S = Settlement (mm)
fd = 1+0.33 (D/B) 1.33
Rw1 = water correction factor = 0.5
Allowable Bearing Pressure
The allowable bearing pressure (qa) is the maximum pressure that can be imposed on the
foundation soil taking into consideration the ultimate bearing capacity of the soil and the
tolerable settlement of the structure. Analysis to determine the ultimate bearing capacity
and the pressure corresponding to a specified maximum settlement were performed and
the minimum pressure obtained from the two analyses were adopted as the allowable
bearing pressure.
ALLOWABLE BEARING PRESSURE BASED ON ULTIMATE BEARING CAPACITY
Since the soil in the vicinity of the foundation level has been found to be granular or non-
plastic, cohesion less sand through-out the site, the allowable bearing capacity has been
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analyzed using the N-values from SPT results. Empirical formula of Teng (1988) applicable
for this type of soils has been used to obtain the allowable bearing pressure with safety
factor equal to 3.
For Open foundation:
qa= 3 NBRw + 5(100+N)DRw (4.1)
qa= 2 NBRw+ 6(100+N)DRw (4.2)
For Bored Piles:
Qu= 133 N Ab+ 0.67 N As (4.3)
Where: qa =Q/4= net allowable bearing pressure, KN
N = SPT value corrected with respected to overburden
B = width of footing, ft
D = depth of footing, ft
Rw& Rw= correction factors for position of water level
Qu = Ultimate total load in KN
N= Average SPT value below pile tip
N = Average SPT value along pile Shaft
AS= Shaft Surface area of pile in m2
Ab= Base area of pile in m2
Qa= Qu/ 4
Qa= Safe load for pile
ALLOWABLE BEARING PRESSURE BASED ON TOLERABLE SETTLEMENT
The maximum allowable settlement for footings in sand is generally 40 mm and format
foundation in sand the allowable settlement is 65 mm (Skempton and MacDonald, 1955).
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The method of Teng (1988) has been employed for the analysis. This method is a
modification of the method of Terzaghi and Peck (1948) such that the allowable bearing
pressure could directly be obtained from the SPT values.
For open and well foundations:
AS per IS: 3935(1967), for well foundation
Allowable pressure (qa) = 0.054N2B+ 0.16(100+N2) D for cohesion less soil
For cohesive soil the laboratory method is used.
For Mat
qna= 1.75(N-3)Rw for 25 mm settlement
According to Is: 6403
qna= 1.27(N-3)for 65 mm settlement
For Bored Pile
qna = (133*N * Ab+ 0.67 * As* N)/3
Where,
N = SPT value at Base of Pile
N= Average SPT value across length of pile
Ab= Area of base of pile
As= Surface area of pile
Qna= allowable load for pile in KN
Where, qa is the net allowable bearing pressure in psf for maximum settlement of 25 mm.
The other notations are the same as in Eqs. 4.1.
The minimum average SPT values from the boreholes in each structure have been selected
for the analysis of bearing capacity of the relevant structure.
The allowable bearing pressure for a limiting settlement other than 25 mm (e.g. x mm) can
be linearly interpolated from the allowable bearing pressure for 25 mm settlement.
qa(x mm) = qa(25 mm)(x/25)
B
DRw
B
BNq 1'
2
1)3(720
2
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4.7.2 Bearing Capacity from Laboratory Tests
In sandy soil the failure is generally shear failure and the bearing capacity is governed bythe shear properties i.e. C and . Direct shear test from disturbed samples shows that the
average value of angle of friction is greater than 280. Then the failure condition of these
strata should be considered as general shear failure. This is the general rule that local
shear cannot occur in dense gravelly strata.
Considering the worst condition of water table at ground, either suitable correction factor
of Rw' (0.5) or submerged unit weight of the strata should be used for getting the ultimate
bearing capacity, assuming that the whole depth is saturated.
From Terzaghi's equation
For open Foundation
qult = 1.2 CNc + DfNq Rw1+ 0.4 BNRw2
qsafe = qult / F.S.
For pile foundation
Q = (CuNc + Df (Nq-1))*Ab+ (Cu+ K tan) As
Qa = qult / F.S.
Where,
AS= Shaft Surface area of pile in m2
Ab= Base area of pile in m2
= Adhesion factor
K = earth pressure factor
= angle of internal friction
Cu= Undrained cohesion = undrained shear strength
= unit weight of the soil (T/m3)
Nc, Nq& Nare bearing capacity factors
B = Width of foundation (m)
D = Depth of foundation (m)
F.S. = Factor of safety i.e., 3
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Rw1& Rw2 = Water correction factor = 0.5 for ground level
If local shear failure occurs,
Then, ' = tan-1[2/3 tan ]
C' = 2/3C
Bearing Capacity by Meyerhof's Correlation for Pile Foundation
Safe Load (Qall) =..SF
QQ sp
Where,
Qp = Ultimate point bearing capacity (KN)
Qs = Ultimate skin resistance (KN)Qp = ApqNq
Qs = CuP L (for cohesive soil layers)
Qs = pf L (for cohesion less soil layers)
Where,
p = Pile perimeter = Dp
f = Unit frictional (or skin) resistance
= Kotan
= 300(assumed for sandy layers)
Ap = Area of Pile
Cu = Undrained Cohesion = 30 KN/m2
= Co-efficient of adhesion (factor)
= 0.8
Nq = 50.0
L = Length of pile in clayey (70.0 m) or sandy strata (6.0 m)sat = 18 KN/m
3
Dp = Diameter of pile i.e. 0.5m
F.S. = Factor of safety i.e. usually 3 is taken
Results:The stratigraphy profiles of all boreholes at the proposed depth of pile foundation
level have in same order and (N) value also more or less same. So, a single average value is
taken for all boreholes.
4.8 Liquefaction
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When fine or medium, saturated, loose sand deposit is subjected to a sudden shock
(generated by an earthquake) the mass will temporarily liquefy. This phenomenon is
termed 'Liquefaction'. When liquefaction takes place in a particular soil then the bearing
capacity of the soil disappears and the structure built on it gets tilts or even sinks.The past big earthquakes, have shown that saturated sandy soils in a loose to medium
dense condition were liquefied during earthquakes varying in magnitude from 5.5 to 8.5
(Richter scale) and epicenter distance from several miles to hundreds of miles.
From the case studies, liquefaction potential characteristics of the soil depend on:
1) The soil contains less than 10 percent fines (silt and clay sizes)
2) D60 is between 0.2 mm and 1.0 mm
3) Cu (D60/D10) is between 2 and 5; and
4) The blow count per 30 cm standard penetration tests is less than 15.0
Where:
D60 = 60 percent of the soil grains smaller than that size.
D10 = 10 percent of the soil grains smaller than corresponding size
Cu = Coefficient of uniformity = D60/D10
5. OBSERVATIONS AND RESULTS
5.1 Field Investigation Results
Logging of the bore holes were carried out at the site during boring period. The logs were
reconfirmed and suitably corrected based on the laboratory test results. The logs of the
boreholes are provided in annexes show that clay with silt.
Measured SPT values are 39 to 75 in the in-situ soil strata at different levels. Measured
value shows that the layers are medium dense to very densely compacted.The seepage ground water table was not observed.
5.2 Laboratory Investigation Results
5.2.1 Index Properties
The results of physical and index properties of soil samples collected from various depths
are presented in the attached summary sheet.
The grain size distribution curves of soil sample are classified as USCS Soil Classification
System. As per USCS Soil Classification System most of the soils are in GP group.
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5.2.2 Strength Parameters
Direct Shear Test was conducted on undisturbed and representative disturbed samples.
The cohesion (c) and angle of internal friction () of the soil up to 19 m in BH1 and 25 m in
BH2 is found in the range of 0 to 7 KN/m 2 and 230 to 320 respectively. The strength
parameter leads to give medium to high shear strength value.
5.3 Settlement
For heavier and important structure consolidation settlement should be predicted by the
following equation.
SOc = Hi* (Cc/(1+eo) log {(p0 + p)/ p0}
Where, SOc= long term settlement, cm
Hi = thickness of each layer
Po = effective overburden pressure before load application
p = the excess pressure due to superposition of load
Cc = Compression index
eo= initial void Ratio
Then, Total settlement (Sc) = * SOc
Where, = average pore pressure coefficient
6. ANALYSIS OF DATA
6.1 Bearing Capacity
a The sample on the right bank (BH-2) consists of soft rock from 3 m depth. The rock samples
obtained were in pulverized or powder form. No RQD values could be obtained. So the soft
rock is treated as soil and the bearing capacity values are obtained as per below. However,
in the next section, the bearing capacity are calculated as per soft rock.
For open foundation, the Bearing Capacity values from field test results are summarized in
tabulated form:
Size of open foundation= 4.5 m X 4.5 m
BoreHoleNo.
Depth(m)
FieldrecordedSPT (N)Values
StandardizeN value N60
Meyerhofs(1965) &
Bowles (1977)(25mm
Settlement)(T/m2)
IS Code(2950-1956)
(25 mmsettlement)
(T/m2)
Lower BCValues for
25 mmsettlement
(T/m2)
BC valuesfor 40 mmsettlement
(T/m2)
BH-1
3 75 51.56 42.28 42.49 42.28 67.65
4.5 63 43.31 38.72 35.27 35.27 61.95
6 64 44.00 42.59 35.88 35.88 68.147.5 54 37.13 38.68 29.86 29.86 61.89
9 58 39.88 44.49 32.27 32.27 71.19
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BH-2
3 46 31.63 25.93 25.05 25.05 41.49
4.5 75 51.56 46.10 42.49 42.49 73.75
6 75 51.56 49.91 42.49 42.49 79.85
7.5 75 51.56 53.72 42.49 42.49 85.95
9 75 51.56 57.53 42.49 42.49 92.05
Size of open foundation= 5.0 m X 5.0 m
BoreHoleNo.
Depth(m)
FieldrecordedSPT (N)Values
StandardizeN value N60
Meyerhofs(1965) &
Bowles (1977)(25mm
Settlement)(T/m2)
IS Code(2950-1956)
(25 mmsettlement)
(T/m2)
Lower BCValues for
25 mmsettlement
(T/m2)
BC valuesfor 40 mmsettlement
(T/m2)
BH-1
3 75 51.56 41.00 42.49 41.00 65.59
4.5 63 43.31 37.28 35.27 35.27 59.65
6 64 44.00 40.76 35.88 35.88 65.22
7.5 54 37.13 36.83 29.86 29.86 58.939 58 39.88 42.18 32.27 32.27 67.49
BH-2
3 46 31.63 25.14 25.05 25.05 40.23
4.5 75 51.56 44.38 42.49 42.49 71.01
6 75 51.56 47.77 42.49 42.49 76.43
7.5 75 51.56 51.16 42.49 42.49 81.85
9 75 51.56 54.55 42.49 42.49 87.27
Size of open foundation= 6.0 m X 6.0 m
BoreHoleNo.
Depth(m)
Field
recordedSPT (N)Values
StandardizeN value N60
Meyerhofs(1965) &
Bowles (1977)(25mm
Settlement)(T/m2)
IS Code
(2950-1956)(25 mmsettlement)
(T/m2)
Lower BC
Values for25 mmsettlement
(T/m2)
BC values
for 40 mmsettlement
(T/m2)
BH-1
3 75 51.56 39.11 42.49 39.11 62.57
4.5 63 43.31 35.18 35.27 35.18 56.28
6 64 44.00 38.10 35.88 35.88 60.95
7.5 54 37.13 34.14 29.86 29.86 54.62
9 58 39.88 38.81 32.27 32.27 62.09
BH-2
3 46 31.63 23.99 25.05 23.99 38.38
4.5 75 51.56 41.88 42.49 41.88 67.00
6 75 51.56 44.64 42.49 42.49 71.43
7.5 75 51.56 47.41 42.49 42.49 75.86
9 75 51.56 50.18 42.49 42.49 80.29
Size of open foundation= 7.0 m X 7.0 m
BoreHoleNo.
Depth(m)
FieldrecordedSPT (N)Values
StandardizeN value N60
Meyerhofs(1965) &
Bowles (1977)(25mm
Settlement)(T/m2)
IS Code(2950-1956)
(25 mmsettlement)
(T/m2)
Lower BCValues for
25 mmsettlement
(T/m2)
BC valuesfor 40 mmsettlement
(T/m2)
BH-1
3 75 51.56 37.79 42.49 37.79 60.46
4.5 63 43.31 33.71 35.27 33.71 53.93
6 64 44.00 36.24 35.88 35.88 57.987.5 54 37.13 32.26 29.86 29.86 51.62
9 58 39.88 36.46 32.27 32.27 58.34
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BH-2
3 46 31.63 23.18 25.05 23.18 37.08
4.5 75 51.56 40.13 42.49 40.13 64.21
6 75 51.56 42.47 42.49 42.47 67.95
7.5 75 51.56 44.81 42.49 42.49 71.70
9 75 51.56 47.15 42.49 42.49 75.44
Size of open foundation= 8.0 m X 8.0 m
BoreHoleNo.
Depth(m)
FieldrecordedSPT (N)Values
StandardizeN value N60
Meyerhofs(1965) &
Bowles (1977)(25mm
Settlement)(T/m2)
IS Code(2950-1956)
(25 mmsettlement)
(T/m2)
Lower BCValues for
25 mmsettlement
(T/m2)
BC valuesfor 40 mmsettlement
(T/m2)
BH-1
3 75 51.56 36.81 42.49 36.81 58.90
4.5 63 43.31 32.63 35.27 32.63 52.20
6 64 44.00 34.87 35.88 34.87 55.80
7.5 54 37.13 30.89 29.86 29.86 49.429 58 39.88 34.74 32.27 32.27 55.58
BH-2
3 46 31.63 22.58 25.05 22.58 36.13
4.5 75 51.56 38.84 42.49 38.84 62.15
6 75 51.56 40.87 42.49 40.87 65.39
7.5 75 51.56 42.90 42.49 42.49 68.63
9 75 51.56 44.92 42.49 42.49 71.88
Size of open foundation= 9.0 m X 9.0 m
BoreHoleNo.
Depth(m)
Field
recordedSPT (N)Values
StandardizeN value N60
Meyerhofs(1965) &
Bowles (1977)(25mm
Settlement)(T/m2)
IS Code
(2950-1956)(25 mmsettlement)
(T/m2)
Lower BC
Values for25 mmsettlement
(T/m2)
BC values
for 40 mmsettlement
(T/m2)
BH-1
3 75 51.56 36.07 42.49 36.07 57.71
4.5 63 43.31 31.80 35.27 31.80 50.88
6 64 44.00 33.83 35.88 33.83 54.13
7.5 54 37.13 29.83 29.86 29.83 47.73
9 58 39.88 33.42 32.27 32.27 53.47
BH-2
3 46 31.63 22.12 25.05 22.12 35.40
4.5 75 51.56 37.86 42.49 37.86 60.57
6 75 51.56 39.64 42.49 39.64 63.43
7.5 75 51.56 41.43 42.49 41.43 66.29
9 75 51.56 43.22 42.49 42.49 69.15
Size of open foundation= 10.0 m X 10.0 m
BoreHoleNo.
Depth(m)
FieldrecordedSPT (N)Values
StandardizeN value N60
Meyerhofs(1965) &
Bowles (1977)(25mm
Settlement)(T/m2)
IS Code(2950-1956)
(25 mmsettlement)
(T/m2)
Lower BCValues for
25 mmsettlement
(T/m2)
BC valuesfor 40 mmsettlement
(T/m2)
BH-1
3 75 51.56 35.48 42.49 35.48 56.76
4.5 63 43.31 31.14 35.27 31.14 49.83
6 64 44.00 33.00 35.88 33.00 52.807.5 54 37.13 29.00 29.86 29.00 46.39
9 58 39.88 32.38 32.27 32.27 51.81
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BH-2
3 46 31.63 21.76 25.05 21.76 34.82
4.5 75 51.56 37.08 42.49 37.08 59.32
6 75 51.56 38.67 42.49 38.67 61.88
7.5 75 51.56 40.27 42.49 40.27 64.43
9 75 51.56 41.87 42.49 41.87 66.99
b The right bank (BH-2) consists of soft rock from 3 m depth. On the process of obtaining
samples, no such sample pieces required for obtaining RQD (core pieces greater than 10
cm) were obtained. The samples obtained were in pulverized form.
As per Bowles (1996), the Bearing capacity of rock can be obtained using Terzaghi
equations as,
qu= 1.3cNc+ qNq+ 0.4BN for square footing
where, the bearing capacity factors are calculated as:
)2
+45(tan5=N 4c
)2
+45(tan=N 6q
1+N=N q
The bearing capacity equation is for intact rock and does not account for the effect of
discontinuities. In our case, the sample obtained is pulverized, i.e. the sample is quite
discontinuous and the bearing capacity equation is not applicable.
Peck et al. (1974) have related the RQD to the allowable bearing pressure as
RQD qa(Mpa) qa(T/m2)
100 29 2900
90 19 1900
75 12 1200
50 6.25 625
25 3 3000 0.96 96
In our case, RQD=0, so allowable bearing pressure=96 T/m2
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c For well foundation, the Bearing Capacity values from field test results are summarized in
tabulated form:
Well Foundation For Borehole 1 (Left Bank)
BHno.
Diameter(B) (m)
Depth (D)(m)
Nvalues
IS 3955 (1967)(T/m2)
Terzaghi and Peck(1948) (T/m2)
Least Value(T/m2)
1
5 6 51.56 336.62 276.92 276.92
5 7.5 43.31 287.77 261.23 261.23
5 9 44.00 345.46 297.56 297.56
5 10.5 37.13 285.56 274.20 274.20
5 12 39.88 367.41 324.97 324.97
5 13.5 35.06 320.34 307.49 307.49
5 15 25.44 196.77 232.63 196.77
5 16.5 28.88 269.03 288.39 269.03
5 18 35.06 416.05 382.29 382.29
1
6 6 51.56 350.98 237.96 237.96
6 7.5 43.31 297.90 222.22 222.22
6 9 44.00 355.91 251.13 251.13
6 10.5 37.13 293.00 229.92 229.92
6 12 39.88 376.00 271.03 271.03
6 13.5 35.06 326.98 255.30 255.30
6 15 25.44 200.26 192.40 192.40
6 16.5 28.88 273.53 237.73 237.73
6 18 35.06 422.69 314.21 314.21
1
7 6 51.56 365.33 212.03 212.03
7 7.5 43.31 308.03 196.32 196.327 9 44.00 366.36 220.32 220.32
7 10.5 37.13 300.45 200.57 200.57
7 12 39.88 384.59 235.31 235.31
7 13.5 35.06 333.62 220.75 220.75
7 15 25.44 203.76 165.79 165.79
7 16.5 28.88 278.03 204.22 204.22
7 18 35.06 429.33 269.21 269.21
1
8 6 51.56 379.69 193.61 193.61
8 7.5 43.31 318.16 177.93 177.93
8 9 44.00 376.82 198.48 198.48
8 10.5 37.13 307.89 179.78 179.788 12 39.88 393.17 210.01 210.01
8 13.5 35.06 340.26 196.30 196.30
8 15 25.44 207.25 146.96 146.96
8 16.5 28.88 282.53 180.52 180.52
8 18 35.06 435.97 237.39 237.39
1
9 6 51.56 394.05 179.86 179.86
9 7.5 43.31 328.29 164.24 164.24
9 9 44.00 387.27 182.22 182.22
9 10.5 37.13 315.33 164.31 164.31
9 12 39.88 401.76 191.20 191.20
9 13.5 35.06 346.89 178.13 178.13
9 15 25.44 210.74 132.96 132.96
9 16.5 28.88 287.04 162.92 162.92
9 18 35.06 442.61 213.75 213.75
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Well Foundation For Borehole 2 (Right Bank)
BHno.
Diameter(B) (m)
Depth (D)(m)
Nvalues
IS 3955 (1967)(T/m2)
Terzaghi and Peck(1948) (T/m2)
Least Value(T/m2)
2
5 6 31.63 132.62 163.23 132.62
5 7.5 51.56 402.83 314.69 314.69
5 9 51.56 469.04 352.45 352.45
5 10.5 51.56 535.24 390.21 390.21
5 12 51.56 601.45 427.97 427.97
5 13.5 51.56 667.66 465.73 465.73
5 15 51.56 733.87 503.50 503.50
5 16.5 51.56 800.08 541.26 541.26
5 18 51.56 866.29 579.02 579.02
2
6 6 31.63 138.02 140.26 138.02
6 7.5 51.56 417.18 267.70 267.70
6 9 51.56 483.39 297.45 297.45
6 10.5 51.56 549.60 327.19 327.19
6 12 51.56 615.81 356.93 356.93
6 13.5 51.56 682.02 386.68 386.68
6 15 51.56 748.23 416.42 416.42
6 16.5 51.56 814.44 446.17 446.17
6 18 51.56 880.64 475.91 475.91
2
7 6 31.63 143.42 124.98 124.98
7 7.5 51.56 431.54 236.50 236.50
7 9 51.56 497.75 260.96 260.96
7 10.5 51.56 563.96 285.43 285.43
7 12 51.56 630.17 309.89 309.89
7 13.5 51.56 696.38 334.36 334.367 15 51.56 762.58 358.82 358.82
7 16.5 51.56 828.79 383.29 383.29
7 18 51.56 895.00 407.76 407.76
2
8 6 31.63 148.82 114.12 114.12
8 7.5 51.56 445.90 214.35 214.35
8 9 51.56 512.11 235.09 235.09
8 10.5 51.56 578.32 255.84 255.84
8 12 51.56 644.52 276.58 276.58
8 13.5 51.56 710.73 297.32 297.32
8 15 51.56 776.94 318.07 318.07
8 16.5 51.56 843.15 338.81 338.818 18 51.56 909.36 359.55 359.55
2
9 6 31.63 154.22 106.02 106.02
9 7.5 51.56 460.26 197.85 197.85
9 9 51.56 526.46 215.83 215.83
9 10.5 51.56 592.67 233.82 233.82
9 12 51.56 658.88 251.81 251.81
9 13.5 51.56 725.09 269.79 269.79
9 15 51.56 791.30 287.78 287.78
9 16.5 51.56 857.51 305.76 305.76
9 18 51.56 923.72 323.75 323.75
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d Considering Circular pile and pile cap (Mat) at 3.2 m from Surface
For Borehole 1 and 2 the Bearing Capacity values are tabulated as below:For 0.5 m Dia Circular Pile
Depth Qs Qb Qu FOS Qa( KN) Qa( T)
10 184.3 399.2 583.5 2.5 233.4 23.3
12 260.4 461.3 721.7 2.5 288.7 28.9
15 399.0 570.3 969.3 2.5 387.7 38.8
18 566.9 624.2 1191.1 2.5 476.4 47.6
20 695.1 691.0 1386.0 2.5 554.4 55.4
For 0.6 m Dia Circular Pile
Depth Qs Qb Qu FOS Qa( KN) Qa( T)
10 221.2 574.8 796.0 2.5 318.4 31.8
12 312.5 664.3 976.8 2.5 390.7 39.1
15 478.8 821.2 1300.0 2.5 520.0 52.0
18 680.2 898.8 1579.1 2.5 631.6 63.2
20 834.1 995.0 1829.0 2.5 731.6 73.2
For 0.7 m Dia Circular Pile
Depth Qs Qb Qu FOS Qa( KN) Qa( T)
10 258.0 782.4 1040.4 2.5 416.2 41.6
12 364.6 904.2 1268.8 2.5 507.5 50.8
15 558.6 1117.8 1676.4 2.5 670.6 67.1
18 793.6 1223.4 2017.0 2.5 806.8 80.7
20 973.1 1354.3 2327.3 2.5 930.9 93.1
For 0.8 m Dia Circular Pile
Depth Qs Qb Qu FOS Qa( KN) Qa( T)
10 294.9 1021.9 1316.8 2.5 526.7 52.7
12 416.7 1181.0 1597.7 2.5 639.1 63.9
15 638.4 1460.0 2098.4 2.5 839.3 83.9
18 907.0 1597.9 2504.9 2.5 1002.0 100.2
20 1112.1 1768.8 2880.9 2.5 1152.4 115.2
For 0.9 m Dia Circular Pile
Depth Qs Qb Qu FOS Qa( KN) Qa( T)
10 331.7 1293.3 1625.1 2.5 650.0 65.0
12 468.8 1494.7 1963.4 2.5 785.4 78.5
15 718.2 1847.8 2566.0 2.5 1026.4 102.6
18 1020.4 2022.4 3042.8 2.5 1217.1 121.7
20 1251.1 2238.7 3489.8 2.5 1395.9 139.6
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6.2 D50Calculations
Bore Hole Depth (m) thicknessweighted meansize (mm)
D50 as perborehole (mm)
D50for thesite (mm)
BH-1
0 4.94
13.73
15.1
0 - 0.5 0.5 17.50
0.5 - 1.0 0.5 16.07
1.0 - 1.5 0.5 3.39
1.5 - 3.0 1.5 2.24
3.0 - 4.5 1.5 25.00
4.5 - 6.0 1.5 25.00
6.0 - 7.5 1.5 0.79
BH-2
0 1.78
16.48
0 - 0.5 0.5 2.32
0.5 - 1.0 0.5 4.93
1.0 - 1.5 0.5 2.19
1.5 - 3.0 1.5 3.05
3.0 - 4.5 1.5 25.00
4.5 - 6.0 1.5 25.00
6.0 - 7.5 1.5 25.00
7 DESIGN PARAMETERS
Unit weight of soil = 1.7 t/m2
Angle of internal friction = 300
Ground Water table: At the surface level (Considering Worst Condition)
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8 RECOMMENDATION
The results are shown in safe bearing capacity, it is recommended that:
i The safe allowable bearing capacity (tons/m2) for 4.5, 5.0, 6.0, 7.0, 8.0, 9.0 and
10.0 m width Open foundation at 3.0, 4.5, 6.0, 7.5 and 9.0 m depths (measured
from existing ground level) of site locations are as given below:
Size DepthBH1 BH2
BC (25 mmsettlement)
BC (40 mmsettlement)
BC (25 mmsettlement)
BC (40 mmsettlement)
4.5 x 4.5 3 42.28 67.65 25.05 41.49
4.5 x 4.5 4.5 35.27 61.95 42.49 73.75
4.5 x 4.5 6 35.88 68.14 42.49 79.85
4.5 x 4.5 7.5 29.86 61.89 42.49 85.95
4.5 x 4.5 9 32.27 71.19 42.49 92.05
5.0 x 5.0 3 41.00 65.59 25.05 40.23
5.0 x 5.0 4.5 35.27 59.65 42.49 71.01
5.0 x 5.0 6 35.88 65.22 42.49 76.43
5.0 x 5.0 7.5 29.86 58.93 42.49 81.85
5.0 x 5.0 9 32.27 67.49 42.49 87.27
6.0 x 6.0 3 39.11 62.57 23.99 38.38
6.0 x 6.0 4.5 35.18 56.28 41.88 67.00
6.0 x 6.0 6 35.88 60.95 42.49 71.43
6.0 x 6.0 7.5 29.86 54.62 42.49 75.86
6.0 x 6.0
9 32.27 62.09 42.49 80.29
7.0 x 7.0 4.5 33.71 53.93 40.13 64.21
7.0 x 7.0 6 35.88 57.98 42.47 67.95
7.0 x 7.0 7.5 29.86 51.62 42.49 71.70
7.0 x 7.0 9 32.27 58.34 42.49 75.44
8.0 x 8.0 4.5 32.63 52.20 38.84 62.15
8.0 x 8.0 6 34.87 55.80 40.87 65.39
8.0 x 8.0 7.5 29.86 49.42 42.49 68.63
8.0 x 8.0 9 32.27 55.58 42.49 71.88
9.0 x 9.0 4.5 31.80 50.88 37.86 60.57
9.0 x 9.0 6 33.83 54.13 39.64 63.43
9.0 x 9.0 7.5 29.83 47.73 41.43 66.29
9.0 x 9.0 9 32.27 53.47 42.49 69.15
10.0 x 10.0 4.5 31.14 49.83 37.08 59.32
10.0 x 10.0 6 33.00 52.80 38.67 61.88
10.0 x 10.0 7.5 29.00 46.39 40.27 64.43
10.0 x 10.0 9 32.27 51.81 41.87 66.99
This bearing capacity values are calculated considering the discontinuous pulverized soft rock as
soil mass. However, the allowable bearing capacity values can be considered as 96 ton/m2for the
soft rock of Borehole 2 from the depth of 3.0 m.
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ii No consideration would be made for the consolidation settlement criteria.
iii Use an average friction angle of 30for soil and rock layers below the foundation
depth in both bore holes.
iv The value of D50 of the river bed material is 15.1 mm
v As the relatively high DCPT values are due to the presence of cobbles and boulders
in borehole location. Which may sometimes does not exactly represent the actual
site conditions and the above recommended bearing capacity may be unsafe. Thus,
it is recommended to check the average percentage of boulders and gravels and
weathered rock fragments including their denseness during the period of excavation
of the foundation. Provision of thicker PCC helps to reduce the weaker soil pockets
zones.
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Bore Hole Log
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Test Result Summary Sheet
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Laboratory Test Result
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Figures
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Photographs
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DCPT at Bore Hole1 (Right Bank)
DCPT at Bore Hole2 (Left Bank)
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Sample collection at BH-1 (Right Bank)
4.5 m
6.0 m
Loose sample for
sieve anal sis
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Sample collection at BH-2 (Left Bank)
3.0 m
7.5 m
20.0 m
12.0 m
17.5 m
mailto:[email protected]:[email protected]:[email protected]:[email protected]7/23/2019 Revised Geo Technical Reports of Trishuli River Bridge at Nuwakot
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Trishuli River Bridge, Nuwakot