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A Geotechnical Investigation Report
For
Proposed Natural Gas Pipeline Dia 16 inch
Client. -MM
Consultant.Petro Chemical Engineering Consultant
EPC Contractor. Petro Con Pvt.Ltd
May, 16, 2015
Geo Tech Report prepared byPEC Licence # 41987
House no-19 Mah-e- Nor Vills Nisheman Iqbal Lahore.042-35228238
An overview
The Geo technical Investigation Report prepared by GDE for Natural Gas Pipeline of FFC focuses on the
various Geotechnical aspects such as computation of safe bearing capacity, review of site condition
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SUBSURFACE INVESTIGATION AND LABORATORY TESING FOR THEProposed Natural Gas Pipeline dia 16 inch
TABLE OF CONTENTS
1.0 Introduction 2
2.0 Purpose and scope of work 3
3.0 Field investigation 4
3.1 Drilling of boreholes 4
4.0 Laboratory testing. 5
4.1 Soil classification tests
4.2 Specific gravity of soil 54.3 Unit weight 5
5.0 Results of the investigation 7
5.1 The subsurface strata 7
5.2 Groundwater conditions 7
6.0 Geotechnical parameters 7
6.1 Unit weight 7
6.2 Shear strength parameters 76.3 Modulus of elasticity (es) 9
6.4 Selection of foundation type 9
6.5 Depth of foundation 9
6.6 Allowable bearing pressures 10
6.7 Guidelines for placing the foundations 11
SEPERATORS
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1. INTRODUCTION
Geo Drillers Engineering (GDE), was engaged by the Petro chemical
Engineering Consultant, to carry out a subsurface soil investigationcampaign at the site of Proposed natural Gas pipeline. This report pertains
to the project a brief description of the geotechnical tasks performed at site
as well as results of the insitu field and laboratory tests. The report
presents an assessment of the general geotechnical conditions at the
investigated site. Specific recommendations for the foundation design are
included in this report.
The investigation was performed in accordance with the scope of work
stipulated by the client and comprised several tasks that included drilling of
boreholes to the designated depths below the existing ground level, in-situ
testing and sampling of the sub-soil through standard penetration tests
(SPTs) at different depth horizons, laboratory analysis. The scope of GDE
services also included preparation of a geotechnical report describing the
methodology and presenting results of all the geotechnical investigation,
recommendations for foundation design.
This report contains the results of field & laboratory investigation and a
brief description of the techniques employed during the field works as well
as methods used in performing the laboratory tests.
The evaluation of geotechnical parameters together with recommendations
for foundations and geotechnical work related to design & construction of
foundations is also included in this report.
The borehole logs and laboratory test results are presented in APPENDIX
respectively.
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2. PURPOSE AND SCOPE OF WORK
The purpose of the present investigation was to assess the prevailinggeotechnical conditions at the site and to verify the geo-engineering
properties of the deeper subsurface soil strata which will significantly affect
the foundations behaviour. The field investigation program comprised of
the following:
1. Drilling and sampling of a total of six (6) boreholes were drilled down
to a depth 10.0 m from surface level at the different locations
designated by the consultant.
2. In-situ testing and sampling of overburden soil by performing Standard
Penetration Tests (SPTs) at each1.0 m from surface down to maximum
borehole depth.
3. Conducting necessary laboratory tests on selected soil samples
retrieved from the boreholes.
4. Preparation of a geotechnical report presenting the investigation
procedures and the results of the in-situ and laboratory tests together
with recommendations for foundations design and construction.
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3. FIELD INVESTIGATION
A total of six (6) boreholes were drilled at site down to a depth 10.0 m from
surface level. The borehole logs are presented in APPENDIX-A.
3.1 DRILLING OF BOREHOLES
The drilling at each borehole location was carried out using percussion
drilling method. Drilling was carried out through a 5 hollow stem auger,
using augering method. The Standard Penetration Tests (SPTs) were
performed at surface and thereafter at a depth interval of 1.0 m in
accordance with ASTM D1586. The drive assembly of SPT consisted of
hammer of 140 lb. weight, a driving head and a guide permitting free fall of
30 inch. The assembly was equipped with split spoon sampler to collect the
disturbed samples for necessary identifications and testing. The samples
retrieved from the split spoon sampler were examined for their visual
identification, packed in airtight polyethylene bags and sent to the
laboratory for further evaluation and testing. A record of field observation
was maintained in the form of field logs describing the visual identifications
(ASTM-2488) of the subsurface materials encountered at different depths,
the sampling details and recording the blow count observed in the SPT.
These logs were later on refined by incorporating the laboratory test results
and are presented in APPENDIX-B.
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4. LABORATORY TESTING
Representative soil samples retrieved from the split spoon sampler (SPT)
were selected from each borehole. The representative SPT samples weretested in laboratory. The SPT samples were subjected to moisture content,
gradation and Atterberg limits in order to identify the subsurface materials.
The tests were performed according to relevant American society for
testing Materials ASTM. The laboratory test results are presented in
LABORATORY TESTING separator.
4.1 SOIL CLASSIFICATION TESTS (ASTM D422)
The classification test performed on selected representative samples of
subsurface materials consisted of determination of natural moisture
content (ASTM D2216), Liquid Limit and Plastic Limits (ASTM D4318) and
Grain-size Analysis (ASTM D422) and sedimentation test by Hydrometer
(ASTM D4221-99).
4.2 SPECIFIC GRAVITY OF SOIL (ASTM D 854-06)
Specific gravity tests were performed on selected representative samples of
subsurface materials according to (ASTM D854-06).
4.3 UNIT WEIGHT (AASHTO T233-02)
The soil samples retrieved from the boreholes were subjected to density
measurement according to AASHTO T233-02 measuring the weight and
volume by immersion in water.
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Measurements of soil properties in the Laboratory in Table-1 lists various
laboratory tests on Un disturbed and disturbed samples soil samples
collected from various depths to find physical properties and strength
characteristics.
Table 1 Measurements of soil properties
Sr.No Tests Performed
procedure
Type
sample
1 Sample preparation ASTM(D 2487) DS/UDS
2 Moisture content ASTM(D 2216) UDS
3 Dry unit weight ASTM(C 29) UDS
4 Specific Gravity ASTM(D 854 & C127) UDS
5 Grain size Analysis ASTM(D 422) DS/UDS
6 Direct shear test ASTM(D 3080) UDS
7 N- observed ASTM(D 2166) DS
8 Unconfined
compressive Strength
ASATM(D2166) UDS
9 LL & PL ASTM (D422) DS
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5. RESULTS OF THE INVESTIGATION
5.1 THE SUBSURFACE STRATA
The description of the subsurface soil strata is based on the inspection of
soil samples retrieved from the field and later refinements done after
laboratory test results. Based upon the results of the field investigation a
representative subsurface soil profile has been developed described as
follows:
Near Railway Track Change=14 +275
BH.no Layer
Encounter
Type of
soil
SPT-N
value
Layer
Up to
Total
thickness
1
Layer-1 SM 1~3 0~2.0 m 2 m
Layer-2 CL 3~5 2~7 m 5 m
Layer-3 ML 3 7~8 m 1m
Layer-4 SM 7~11 8~10 m 2 m
Groundwater was encountered at 1 m depth in the 1stweek of May 2015
Near Masu Wah Canal Change=13 +650
BH.no Layer
Encounter
Type of
soil
SPT-N
value
Layer
Up to
Total
thickness
2
Layer-1 CL 1~3 0~3.0 m 3 m
Layer-2 SM 4~6 3~8 m 5 m
Layer-3 SP-SM 7 8~10 m 2m
Groundwater was encountered at 2 m depth in the 1stweek of May 2015
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Near Canal Road Crossing Kandyaro change=10 +775
BH.no Layer
Encounter
Type of
soil
SPT-N
value
Layer
Up to
Total
thickness
3
Layer-1 SM 5 0~3.0 m 3 m
Layer-2 SP 1~3 3~4 m 1 m
Layer-3 CL 3~8 4~10 m 6m
Groundwater was encountered at 2.5 m depth in the 1stweek of May 2015
Near Dher wah lower, change=6 +825
BH.no Layer
Encounter
Type of
soil
SPT-N
value
Layer
Up to
Total
thickness
4
Layer-1 CL 3 0~4.0 m 4 m
Layer-2 ML 4~5 4~6 m 2 m
Layer-3 CL 5~8 6~10 m 4 m
Groundwater was encountered at 3 m depth in the 1stweek of May 2015
Near narli wah Canal change=1 +080
Near Mari Mani Fold Change =0+100
BH.no Layer
Encounter
Type of
soil
SPT-N
value
Layer
Up to
Total
thickness
5,6Layer-1 ML 3~4 0~3.0 m 3 mLayer-2 CL 3~5 3~5 m 2 m
Layer-3 SP-SM 6~14 5~10 m 5 m
Groundwater was encountered at 3 m depth in the 1stweek of May 2015
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6. GEOTECHNICAL PARAMETERS
The geotechnical parameters refer to the parameters related tocharacteristics of the subsurface materials for design and construction of
foundation and execution of earthwork. These parameters have been
developed on the basis of evaluation of the engineering characteristics of
the subsurface strata as determined through drilling records, field
exploration, in-situ testing (SPTs) and laboratory testing of the
representative samples of materials obtained from the boreholes. The
selection of parameters is discussed as follows:
6.1 UNIT WEIGHT
The unit weight of the subsurface material was estimated through
inspection and laboratory classification of the samples retrieved from
boreholes and through correlation with the SPT data. Typically, for the
purpose of calculations the bulk unit weight (bulk) of the representative soil
materials has been considered as 1.585 ~1.647 g/cm3. Following relation
should be used for submerged conditions.
(Sub= bulk- w) sub = Buoyant Unit Weight
w = Unit Weight of Water
In view of the fact that the site might be flooded or due to effects of future
rise in the groundwater table use of buoyant unit weight is recommended
for design purposes.
6.2 SHEAR STRENGTH PARAMETERS
The angle of internal friction applicable to the sub-soil layers encountered
at site has been estimated on the basis of N-values determined through
performance of SPTs at different locations in the area and at different
horizons within the layer. Most of the N-values determined in the subsoil
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fall in the range of to 22 blows/12 Inch. Corresponding to these values, a
value of 29.2 to 32.3 degrees is considered applicable to the sub-strata.
Conservative value of = 24 degrees has been adopted for calculation
purposes.
In case of select fill, the angle of internal friction should be taken as 32
degrees.
6.3 MODULUS OF ELASTICITY (Es)
The immediate settlement of foundation depends upon the elastic
properties of the load bearing strata, characterised by Modulus of Elasticity
(Es). The Modulus of Elasticity of soils is directly proportional to N-values
recorded in SPTs. The constant of proportionality depends upon the type of
soils in which the tests are carried out. For the strata, encountered in this
particular investigation, following relationship between Es and N-values
was used for calculation of immediate settlement:
Es= 500 (N + 15), kPa SAND layer
Es= (500 ~ 1,000), Su Clay layer
The above expression can also be used for select fill and N should be taken
as 15 in case select fill.
6.4 SELECTION OF FOUNDATION TYPE
Considering the anticipated structural loads and the load carrying
characteristics of the sub-soil strata at the site, Spread Footing/Mat footing
is considered technically feasible for the proposed Structures.
6.5 DEPTH OF FOUNDATION
All foundations must be laid at a safe depth that is free from the influence of
seasonal, climatic and environmental changes. Such safe depth must ensure
foundation safety and stability form the effects of wind erosion and erosion
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from surface run off. At the same time all foundations must be placed on
firm natural soil after removing any loose or undesirable soil. The
recommended minimum foundation depth for Spread footing/Mat footing
for the proposed structure is 3~5 feet measured from the existing ground
level.
Any loose and undesirable soil layer, if encountered during the excavation
for the foundations shall be replaced with structural backfill, rock fill or
lean concrete.
6.6 ALLOWABLE BEARING PRESSURES
The allowable bearing pressure for the design of foundations must not
exceed the allowable bearing capacity of the load carrying soil with respect
to shear failure. At the same time the settlement corresponding to the
allowable bearing pressure must not exceed the maximum allowable limit
of settlement for the particular foundation / structure system. In the
present case it is the allowable settlement criteria and not the shear failure
which will determine the allowable bearing pressure for design of
foundations.
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Allowable Bearing Capacity (qall) for Spread Footings(Near Railway Track Change=14 +275)
Depth ofFoundation (ft)
Width ofFoundation (ft)
SBC(ton/ft)
Settlement(mm)
2.5 4.0 0.53 13.52.5 5.0 0.61 23.02.5 6.0 0.75 25.134
Qult = cNc Sc + y DfNqSq+0.5yBNySyQall = Qult/FOS
Note:1. The calculations, presented above, are based on Terzaghis Bearing Capacity
equation.
2. The value of Ng ,Nq ,Nc in the formula was taken by (Vesic)
3. The value of Ng ,Nq ,Nc in the formula was taken by (Vesic)
4. Factor of Safety of 3 has been considered for the calculations above.
5. Settlement analysis have been made using Braja M. Das, (Principles of
Geotechnical Engineering, 5th
edition, 2002)
Recommendations
A. The tolerance of structures to settlement is function of type and size of
foundations.
The allowable total settlement for such structures as reported in the literature
Terzaghis Criteria of 25mm,which is considered maximum limit of the settlement
tolerable for spread/isolated footing.
B. Based on the project subsurface soil condition and bearing capacity analysisperformed, the recommended Allowable bearing capacity is restricted up to0.51 ton/ft based on the allowable settlement criteria.
C.Note
The Road Base layer should be of 0.25 m thickness each and compacted by avibrator system to achieve 95 % Modified proctor.
The degree of Compaction should be confirmed by In-situ Density tests.
Ground at foundation level should be properly compacted prior to laying of
structural fill.
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Allowable Bearing Capacity (qall) for Spread Footings
(Near Masu Wah canal Change=13 +650)
Depth ofFoundation (ft)
Width ofFoundation (ft)
SBC(ton/ft)
Settlement(mm)
4.5 4.0 0.51 17.54.5 5.0 0.61 25.04.5 6.0 0.75 27.11
Qult = cNc Sc + y DfNqSq+0.5yBNySyQall = Qult/FOS
Note:
6. The calculations, presented above, are based on Terzaghis Bearing Capacity
equation.
7. The value of Ng ,Nq ,Nc in the formula was taken by (Vesic)8. The value of Ng ,Nq ,Nc in the formula was taken by (Vesic)
9. Factor of Safety of 3 has been considered for the calculations above.
10.Settlement analysis have been made using Braja M. Das, (Principles of
Geotechnical Engineering, 5th
edition, 2002)
Recommendations
B. The tolerance of structures to settlement is function of type and size of
foundations.
The allowable total settlement for such structures as reported in the literature
Terzaghis Criteria of 25mm, which is considered maximum limit ofthe settlement
tolerable for spread/isolated footing.
B. Based on the project subsurface soil condition and bearing capacity analysisperformed, the recommended Allowable bearing capacity is restricted up to0.61 ton/ft based on the allowable settlement criteria.
C.Note
The Road Base layer should be of 0.25 m thickness each and compacted by a
vibrator system to achieve 95 % Modified proctor.
The degree of Compaction should be confirmed by In-situ Density tests. Ground at foundation level should be properly compacted prior to laying of
structural fill.
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Allowable Bearing Capacity (qall) for Spread Footings
(Near Canal road crossing Kandyaro Change=10 +775)
Depth ofFoundation (ft)
Width ofFoundation (ft)
SBC(ton/ft)
ImmediateSettlement
(mm)4 4.0 0.73 11.54 5.0 0.85 17.04 6.0 1.05 26.13
Qult = cNc Sc + y DfNqSq+0.5yBNySyQall = Qult/FOS
Note:
11.The calculations, presented above, are based on Terzaghis Bearing Capacity
equation.12.The value of Ng ,Nq ,Nc in the formula was taken by (Vesic)
13.The value of Ng ,Nq ,Nc in the formula was taken by (Vesic)
14.Factor of Safety of 3 has been considered for the calculations above.
15.Settlement analysis have been made using Braja M. Das, (Principles of
Geotechnical Engineering, 5th
edition, 2002)
Recommendations
C. The tolerance of structures to settlement is function of type and size of
foundations.
The allowable total settlement for such structures as reported in the literature
Terzaghis Criteria of 25mm, which is considered maximum limit of the settlementtolerable for spread/isolated footing.
B. Based on the project subsurface soil condition and bearing capacity analysisperformed, the recommended Allowable bearing capacity is restricted up to0.78 ton/ft based on the allowable settlement criteria.
C.Note
The Road Base layer should be of 0.25 m thickness each and compacted by a
vibrator system to achieve 95 % Modified proctor.
The degree of Compaction should be confirmed by In-situ Density tests.
Ground at foundation level should be properly compacted prior to laying of
structural fill.
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Allowable Bearing Capacity (qall) for Spread Footings
(Near Dher Wah Lower, Change=6 +825)
Depth ofFoundation (ft)
Width ofFoundation (ft)
SBC(ton/ft)
Settlement(mm)
5.0 4.0 0.63 18.55.0 5.0 0.71 24.19665.0 6.0 0.85 29.4
Qult = cNc Sc + y DfNqSq+0.5yBNySyQall = Qult/FOS
Note:
16.The calculations, presented above, are based on Terzaghis Bearing Capacity
equation.17.The value of Ng ,Nq ,Nc in the formula was taken by (Vesic)
18.The value of Ng ,Nq ,Nc in the formula was taken by (Vesic)
19.Factor of Safety of 3 has been considered for the calculations above.
20.Settlement analysis have been made using Braja M. Das, (Principles of
Geotechnical Engineering, 5th
edition, 2002)
Recommendations
D. The tolerance of structures to settlement is function of type and size of
foundations.
The allowable total settlement for such structures as reported in the literature
Terzaghis Criteria of 25mm, which is considered maximum limit of the settlementtolerable for spread/isolated footing.
B. Based on the project subsurface soil condition and bearing capacity analysisperformed, the recommended Allowable bearing capacity is restricted up to0.70 ton/ft based on the allowable settlement criteria.
C.Note
The Road Base layer should be of 0.25 m thickness each and compacted by a
vibrator system to achieve 95 % Modified proctor. The degree of Compaction should be confirmed by In-situ Density tests.
Ground at foundation level should be properly compacted prior to laying of
structural fill.
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Allowable Bearing Capacity (qall) for Spread Footings
(Near Narli Wah Canal Change=1 +080
Near Mari Mani Fold ,Change 0+100)
Depth ofFoundation (ft)
Width ofFoundation (ft)
SBC(ton/ft)
ImmediateSettlement
(mm)3 4.0 0.73 11.53 5.0 0.81 17.03 6.0 0.95 26.
Qult = cNc Sc + y DfNqSq+0.5yBNySyQall = Qult/FOS
Note:
21.The calculations, presented above, are based on Terzaghis Bearing Capacity
equation.
22.The value of Ng ,Nq ,Nc in the formula was taken by (Vesic)
23.The value of Ng ,Nq ,Nc in the formula was taken by (Vesic)
24.Factor of Safety of 3 has been considered for the calculations above.
25.Settlement analysis have been made using Braja M. Das, (Principles of
Geotechnical Engineering, 5th
edition, 2002)
Recommendations
E. The tolerance of structures to settlement is function of type and size of
foundations.
The allowable total settlement for such structures as reported in the literatureTerzaghis Criteria of 25mm, which is considered maximum limit of the settlement
tolerable for spread/isolated footing.
B. Based on the project subsurface soil condition and bearing capacity analysisperformed, the recommended Allowable bearing capacity is restricted up to0.80 ton/ft based on the allowable settlement criteria.
C.Note
The Road Base layer should be of 0.25 m thickness each and compacted by a
vibrator system to achieve 95 % Modified proctor.
The degree of Compaction should be confirmed by In-situ Density tests.
Ground at foundation level should be properly compacted prior to laying of
structural fill
For & on Behalf of Geo Drillers Engineering
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IN-Situ Testing on Proposed Site for Natural gas Pipeline