13-hpcl vizag soil report-vol.v
TRANSCRIPT
1686-HPCL/VIZAG REFINERY/FINAL/ TVS REPORTS
REPORT ON GEOTECHNICAL INVESTIGATION
FOR LPG MOUNDED STORAGE AT VISAKHA REFINERY, MALKAPURAM, VISAKHAPATNAM (A.P)
FOR HINDUSTAN PETROLEUM CORPORATION LIMITED
CONTENTS
SR.NO. DESCRIPTION PAGE NO.
1.0 INTRODUCTION 1
2.0 SCOPE OF WORK 2
3.0 EXECUTION OF FIELD WORK 2
4.0 LABORATORY TESTS 8
5.0 FINDINGS OF THE GEOTECHNICAL INVESTIGATION 9
6.0 DISCUSSIONS AND RECOMMENDATION 16
7.0 SAMPLE CALCULATION 21
8.0 REFERENCES 27
ANNEXURE A LOCATION PLAN
B BORE LOGS
C TRIAL PIT LOGS
D STATIC CONE PENETRATION TESTS
E DYNAMIC CONE PEENTRATION TESTS
F LABORATORY TEST RESULTS
G SUB SOIL PROFILE
1686-HPCL/VIZAG REFINERY/FINAL/ TVS REPORTS
Prepared by T.V.Suresh Kumar Reviewed by P.S.Bansod 1
REPORT ON GEOTECHNICAL INVESTIGATION FOR LPG MOUNDED STORAGE
AT VISAKHA REFINERY, MALKAPURAM, VISAKHAPATNAM (A.P)
FOR HINDUSTAN PETROLEUM CORPORATION LIMITED
1.0 INTRODUCTION
1.1 HINDUSTAN PETROLEUM CORPORATION LIMITED, VISAKHA REFINERY, VISKHAPATNAM plans construction of one LPG mounded bullet (proposed) and
one Propylene mounded bullet (future) storage as part of their refinery expansion
project. PDIL is the main consultant for this project. For this purpose it was
decided to conduct Geotechnical Investigation at the two mounded bullet
locations. Total nine boreholes were planned to be carried out for the
Geotechnical investigation and from that to obtain the relevant foundation design
parameters for the proposed mounded bullet.
1.2 Hindustan Petroleum Corporation Limited, Visakha have awarded the
contract to M/s. DBM Geotechnics and Construction Pvt. Ltd., (DBM) Mumbai to carry out the Geotechnical Investigation for the proposed mounded
Bullet structures.
1.3 DBM carried out fieldwork during September and November 2006 and
subsequently laboratory tests were conducted on selected disturbed soil (D/S),
undisturbed soil samples and rock core samples
1.4 Geotechnical investigation report is prepared based on the field investigation
data, laboratory test results, analysis and interpretation of all field and laboratory
test data.
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2.0 SCOPE OF WORK
2.1 To investigate the subsurface soil conditions at the site nine boreholes were
carried out. The detailed scope of investigation is as follows.
2.2 Setting up boring rig at each bore hole location and boring 150 mm diameter bore
holes through all kinds of soils.
2.3 Drilling vertically through the rock using ‘NX’ size (76 mm) with double tube core
barrel fitted with diamond studded drill bits. The boreholes were terminated in hard
rock.
2.4 Conducting Standard Penetration Tests (SPT) in over burden at an interval of
1.5m.
2.5 Collecting 100 mm undisturbed soil samples in suitable cohesive stratum
2.6 Conducting five no’s of Static Cone Penetration tests
2.7 Conducting five no’s of Dynamic cone penetration tests.
2.8 Conducting three no’s of Trial pits.
2.9 Arranging all soil samples and rock cores in the core boxes as per the borehole
logging, labeling properly in sequence indicating number of core sample, depth of
core sample and direction of drilling on each rock core piece.
2.10 Transporting the selected soil and rock samples to the laboratory for conducting
tests as per the scope of the work.
2.11 Analysis and interpretation of field & laboratory test data for the preparation of
Geotechnical investigation report.
2.12 Handing over all the rock core samples in core boxes to Client’s representative for
safe storage and future reference.
3.0 EXECUTION OF FIELD WORK 3.1 Location: All the nine boreholes were executed as per the Client’s location plan.
Location plan for the boreholes is enclosed in the Annexure.
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3.2 Period of Execution: The fieldwork was commenced on 14-09-2006 and
completed on 09-11-2006.
3.3 FIELD METHODOLOGY OF INVESTIGATION
3.3.1 Erecting and setting up of Boring rig
At each bore hole location as per the Client’s location plan, Calyx type boring rig
was shifted, assembled and erected.
3.3.2 Boring in Overburden
Boring was done in accordance with IS: 1892 -1979. Standard rotary type drilling
rig coupled with 8 H.P capacity diesel engine, which is fitted to a tripod frame and
with all drilling accessories was used for boring. The rig deployed was generally
suitable for all Geotechnical Investigation work and had an arrangement for
driving and extraction of casing, boring and drilling by mud circulation method.
Collecting D/S, UDS, conducting SPT and carrying out permeability test with this
rig was possible.
Rotary method of boring was used for boring in soil. Boring was commenced by
driving a SX casing in the upper layers of the borehole. Boring was carried out in
soil using 6” dia core barrel up to the top of the hard surface. Diameter of the
borehole in soil was 150mm. SX casing was lowered in overburden as boring
progressed. Advancement of borehole in soil was done by removing soil with help
of water circulation under rotary action of the Core barrel. Boring in all types of soil
was continued till the hard stratum was met with. Standard penetration tests were
conducted at an interval of 1.0m.
When ever the hard stratum was encountered the size of the borehole was
reduced from SX (150 mm) size to NX (76 mm) size. Drilling was carried out in
hard stratum / rock vertically, by using ‘NX’ size double tube core barrel fitted with
diamond studded drill bits. The boreholes were terminated in hard rock as per the
scope of work.
During investigation, soil and ground water samples were also collected for
chemical analysis to determine their pH, sulphates, and chlorides. Any
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precautionary measures for protecting concrete and reinforcement steel can be
decided based on these chemical results.
3.4.0 IN –SITU TESTS IN OVERBURDEN
Standard penetration tests were conducted in overburden and also in completely
weathered rock, wherever rock cores were not recovered. Disturbed soil samples
were collected through split spoon sampler of SPT test for field observations and
to determine the index properties from laboratory tests.
3.4.1 Standard Penetration Test (SPT) : SPT’s were conducted as per IS 2131-1981.
Disturbed Samples were collected through Split Spoon Sampler at 1.0 m or 1.5m
interval or wherever the Strata changed. A standard split spoon sampler was
driven at the bottom of the hole. The penetration resistance in terms of blows for
300mm penetration of the split spoon sampler was measured as ‘N’ Value. The
blows were imparted by a standard weight of 65 kg falling through a height of 750
mm. The resistance was measured for 150 mm, 300 mm and 450 mm
penetrations. The resistance of first 150 mm was ignored and the resistance of
next 300 mm was recorded as standard penetration value ‘N`. If the sampler was
driven less than 450 mm (total) then the penetration resistance was given for the
last 300 mm of penetration. If the penetration depth was less than 150 mm and
the blow count was more than 50 then the ‘N’ value was considered as ‘Refusal’
or more than 100 blows for less than 30cms penetration.
3.4.2 Undisturbed samples: In all boreholes undisturbed samples were collected.
These samples were packed suitably and transported to the laboratory for
conducting as per the scope of work.
3.4.3 Ground water table (G.W.T) : Ground water table is encountered in between
1.6m and 2.20m below existing ground level. Seasonal and annual fluctuations in
water levels can be expected to occur.
3.5 DRILLING IN HARD STRATUM / ROCK
Once the hard stratum or rock surface was met the size of the bore hole was
reduced to NX size (76mm). The hard stratum or top of the rock surface was
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confirmed, either by the refusal from standard penetration test N value or due to
resistance during the drilling operation. In this hard stratum further work was
carried out by using NX core drilling with TC/Diamond studded bits. The work
was done generally as per IS: 6926-1973. The maximum length of the drill (run)
was maintained as 1.50m. At the end of each run the drill rod string with core
barrel was extracted from the bore hole and core was recovered from the core
barrel. Recovered rock cores were numbered and labeled serially and carefully
transferred to in good quality, sturdy, wooden core boxes and preserved. The
core recovery percentage was recorded. Core Recovery percentage = {C.R. % =
(Length of Core / Length of run) x 100}. Rock Quality Designation (RQD) was
also recorded. Rock Quality Designation (RQD) = (Total Length of core pieces of
100mm & above in Length / length of run) x 100}. Core recovery percentage and
RQD were computed for every drilled run based on the length of cores retrieved.
3.6 INDIAN STANDARD CODES USED FOR THE FIELD INVESTIGATION
Field Geotechnical investigation was executed in accordance with the Indian
standard Codes listed below.
a) IS: 1892: Code of practice for subsurface investigation of foundation
b) IS: 1498: Classification and identification of soil for general engineering
purpose.
c) IS: 2131: Method for standard penetration test for soil
d) IS: 2132: Method for collecting undisturbed soil samples
e) IS: 4968( part -1): Method for subsurface sounding of soils by Dynamic cone
penetration tests
f) IS: 4968( part III): Method for subsurface sounding of soils by Static cone
penetration tests
d) IS: 5313: Guide for Core Drilling Observations
e) IS: 6926: Code of Practice for Diamond Core Drilling for Site Investigations
f) IS: 4078: Code of practice for indexing and storage of drill core.
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3.7 The summary of the field investigation results of boreholes and in situ tests are give
below.
TABLE – 1
The summary of field investigation results of boreholes
S NO
Borehole
No
R. L (m)
Depth of GWT(BGL)
in m
Thickness of Over burden
BGL(m)
Termination depth BGL
(m)
1 BH-1
7.609 2.20 11.00 24.30
2 BH-2
8.014 1.75 5.50 20.00
3 BH-3
8.349 2.15 6.05 25.50
4 BH-4
8.349 1.90 9.50 20.00
5 BH-5
8.789 3.00 5.50 23.25
6
BH - 6 9.174 1.60 4.50 21.00
7
BH-7 10.384 1.75 5.00 19.00
8
BH-8 10.499 1.75 7.00 13.00
9 BH-9 8.354 --
4.60 13.00
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TABLE – 2
TABLE SHOWING SUMMARY OF STATIC CONE PENETRATION TESTS
SR NO SCPT NO GROUND R.L (m)
LOCATION
1 SCPT1 7.614 NEAR BH-1 FOR
PROPYLENE BULLET
2 SCPT 2 9.993 NEAR BH-3 FOR
PROPYLENE BULLET
3 SCPT 3 8.754
FOR LPG BULLET
4 SCPT 4 9.154 NEAR BH-5 FOR LPG
BULLET
5 SCPT 5 10.319 NEAR BH-7 FOR LPG
BULLET
TABLE – 3
TABLE SHOWING SUMMARY OF DYNAMIC CONE PENETRATION TESTS
SR NO
DCPT NO GROUND R.L (m)
LOCATION REFUSAL DEPTH BGL
(m)
1 DCPT1
7.464 FOR PROPYLENE
BULLET
5.1
2 DCPT 2 8.134 FOR PROPYLENE
BULLET
5.24
3 DCPT 3
8.424 NEAR BH-4 FOR
PUMP HOUSE
5.1
4 DCPT 4 9.549
FOR LPG BULLET 5.05
5 DCPT 5 9.810
FOR LPG BULLET 4.7
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TABLE – 4
TABLE SHOWING SUMMARY OF TRIAL PITS
TP NO GROUND R.L (m)
SIZE (m) L X B X D
LOCATION GROUND WATER
TABLE (m)
TP 1
7.584 2.5 X 2.5 X 1.8 FOR PROPYLENE
BULLET
NEAR DC-1
1.80
TP 2 8.324 2.5 X 2.5 X 2.0 FOR PUMP
HOUSE NEAR BH4
1.90
TP 3
10.179 2.5 X 2.5 X 1.5 FOR LPG BULLET 1.40
4.0 LABORATORY TESTS
The laboratory tests are conducted in DBM’s well equipped soil testing laboratory
under the supervision of well qualified and experienced engineers.
The laboratory tests aim to obtain the following characteristics of different layers
a) Grain size analysis, hydrometer analysis, liquid limit, plastic limit, specific gravity
tests were conducted for obtaining Index properties of the disturbed soil samples.
b) For obtain cohesion, friction, natural density, compressible characters of soil etc,
tests were conducted as per the IS codes listed below.
c) Compressive strength, Porosity, water absorption, dry density and modulus of
elasticity tests were conducted on selected rock core samples and the results
were shown in the annexure
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Table -5 Summary of List of IS codes
a) Grain Size Distribution by Sieve Analysis and Hydrometer
Analysis
IS 2720
(Part –IV)
b) Consistency limit determination to obtain liquid limit and
plastic limit.
IS 2720
(Part – V)
c) Specific Gravity determination
IS2720
(Part –III)
d) Natural moisture content and in-situ density tests on UDS
samples
IS 2720
(Part – II)
e) Shear strength and consolidation tests on UDS samples
IS 2720 (Part –
XI, XII & XVI)
g) Chemical analysis of soil to determine pH, Sulphate (SO3)
and Chloride (Cl)
IS 2720 (Part –
XXIV& XXVI)
h) Chemical analysis of water to determine pH, Sulphate
(SO3) and Chloride (Cl) IS 3025
i) Soaked crushing strength of rock IS 9143
j) Porosity, Density and specific gravity test on rock IS 13013
k) Engineering classification of soil IS 1498
5.0 FINDINGS OF THE GEOTECHNICAL INVESTIGATION 5.1 Sub Soil Stratification
From nine boreholes investigation and their laboratory test results following sub
soil stratification is obtained.
Layer I : Residual Soil Layer II : Completely weathered to Highly weathered/ Khondalite
Amphibolite/Granite Gneiss Layer III : Moderately weathered to Slightly weathered Kondalite Layer I: Residual Soil: The top subsurface layer is Residual Soil. This layer is
observed in all the boreholes. This layer is consisting of Silty Clay and Clayey
Sand. Thickness of this layer is varying between 4.50m and 7.00m. Standard
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penetration tests were conducted in this layer and SPT values are varying
between 4 and 53. Disturbed soil samples were collected through split spoon
sampler and the samples were tested in the laboratory. Undisturbed soil samples
were collected by conducting separate borehole just adjacent to the boreholes at
an alternative depths with respect to the SPT depths below ground level. SPT
and UDS samples were tested in the laboratory and results are summarized
below.
Silty Clay
Gravel % 0 to 20
Sand % 21 to 45
Silt % 24 to 40
Clay % 16 to 38
Liquid limit % 35 to 49
Plastic limit % 13 to 23
Plasticity Index % 16 to 29
Cohesion Cu (Tuu) Kg/cm2 0.69 to 1.03
Angle of Internal Friction ø (Tuu) Degrees 2.86 to 3.60
Cohesion Cu (UC) Kg/cm2 0.70 to 2.27
Classification CI / SC
Silty Sand Gravel % 30 to 35
Sand % 51 to 52
Silt + Clay % 14 to 18
Engineering Classification SM
Layer II: Completely weathered to Highly weathered khondalites / Amphibolite/Granite Gneiss: Second layer of the subsurface layer is
Completely weathered to Highly weathered Amphibolite/ Granite. This layer
is encountered in all boreholes. Top level of this layer varies between 4.50m and
7.00m below the existing ground level bottom level of this layer is varying
between 10.10m and 23.00m below the existing ground level Standard
penetration tests were conducted in this layer and SPT “N” values are varying
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between 35 and Refusal. Rock Core Recovery of this Amphibolite/ Granite is
varying between Nil and 50%.Rock Quality Designation of this
Amphibolite/Granite is varying between NIL and 19.
Some rock samples were selected for conducting tests in laboratory. The results
are summarized below.
Table -6 Summary of laboratory test results of Highly weathered rock Core samples.
Parameter Unit Range
Soaked Uniaxial compressive strength kg / cm2 466 to 648
Soaked Point load Index strength kg / cm2 2.82 to 11.73
Porosity % 0.52 to 4.56
Water Absorption % 0.19 to 1.76
Dry density gm/ cc 2.56 to 2.93
Layer III: Moderately weathered to Slightly weathered Khondalite: The third
subsurface layer is Moderately weathered to Slightly weathered Khondalite. This layer is observed in all the boreholes. Top level of this layer is varying
between 13.10m and 24.30m. Top level of the layer varying between 2.00m and
3.60m and exist up to the termination depth of the boreholes. Rock Core
Recovery of this Khondalite is varying between 55% and 100%.Rock Quality
Designation of this Khondalite is varying between NIL and 72%. Rock samples
were tested and results of testing are summarized below Some rock samples were selected for conducting tests in laboratory. The results
are summarized below.
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Table -7 Summary of laboratory test results of Moderately weathered to Slightly
weathered Rock Core Samples
Parameter Unit Range
Soaked Uniaxial compressive strength kg / cm2 357 to 1306
Soaked Point load Index strength kg / cm2 0.00 to 11.73
Porosity % 0.08 to 2.89
Water Absorption % 0.03 to 1.42
Dry density gm/ cc 2.03 to 2.96
5.2 Static Cone Penetration Tests: Static Cone Penetration Tests were conducted
with 20 tones capacity hydraulic equipment and using a 60 degree cone of 10 sq.
cm base area. This cone was pushed vertically in to the ground by static thrust
required to cause a bearing capacity failure of soil immediately around the point
where the measurements were made. Such measurements were made for every
10 cm interval to provide a continuous bearing capacity profile and hence shear
strength profile of the soils around the test locations. The cone point was
advanced by two rod system. Outer mantle tube provides structural strength and
protects inner rod from soil friction and buckling. The protected inner rod
advances the point during the thrust. This thrust was measured using pressure
gauges. Cone resistance and friction are corrected and reported. The procedure
is generally in accordance with IS- 4968 ( Part III ) and the manufacturer’s
guidelines.
Results obtained from SCPT tests are consistent with borehole SPT N values.
Soil type as inferred from SCPT results is silty clay and clayey sand. The
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following correlation between SCPT results and SPT N values can be utilized
(Reference No. 5): SPT N value = Ckd/C, Where C = 2.
Table -8 Summary of the SCPT test results
PRESSURE AT TERMINATED DEPTH
SCPT
NO
GROUND R.L (m)
LOCATION
TERMINATEDBGL (m) CORRECTED
CONE RESISTANCE (kg/cm2)
CORRECTED SHAFT
RESISTANCE (kg/cm2)
SCPT1
7.614
NEAR BH-1 FOR
PROPYLENE
BULLET
5.80
900.525
8.225
SCPT 2
9.993
NEAR BH-3 FOR
PROPYLENE
BULLET
5.80
900.44
5.485
SCPT 3 8.754
FOR LPG
BULLET
5.00 900.44 6.855
SCPT 4 9.154 NEAR BH-5 FOR
LPG BULLET
5.60 880.44 16.444
SCPT 5 10.319 NEAR BH-7 FOR
LPG BULLET
5.00 900.44 2.746
5.3 Dynamic Cone Penetration Test (i.e. DCPT) : Dynamic Cone Penetration Test
were carried out at this site as per IS:4968. Using this procedure, a solid cone of
diameter 65mm and attached to the end of a rod is driven vertically downward into
the soil by a 65 kg. weight falling 75cm. The number of blows required to drive the
cone by 30 cms, is noted as the “Cone penetration resistance (Ncbr)”. This can be
correlated with SPT “N values” using relation Ncbr/1.5 = SPT N value.
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Table -9 Summary of the DCPT test results
DCPT NO GROUND R.L (m)
LOCATION REFUSAL DEPTH BGL
(m)
Ncbr AT
REFUSAL
DCPT1
7.464 FOR PROPYLENE
BULLET
5.1 209
DCPT 2 8.134 FOR PROPYLENE
BULLET
5.14 148
DCPT 3
8.424 NEAR BH-4 FOR
PUMP HOUSE
5.16 102
DCPT 4 9.549
FOR LPG BULLET 5.05 103
DCPT 5 9.810
FOR LPG BULLET 4.68 152
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5.4 TRIAL PITS Three Trial pits were excavated. The details of the trial pits were given in the
table below.
Table – 10
TABLE SHOWING SUMMARY OF TRIAL PITS
TP NO GROUND R.L (m)
SIZE (m) L X B X D
LOCATION GROUND WATER TABLE
(m)
Strata description
Clay with sand
up to 1.0m BGL
TP 1
7.584
2.5 X 2.5 X
1.8
FOR PROPYLENE
BULLET
NEAR DC-1
1.80
Stiff Clay up to
1.80m BGL
Clay with sand
up to 1.0m BGL
TP 2
8.324
2.5 X 2.5 X
2.0
FOR PUMP
HOUSE NEAR BH4
1.90
Stiff Clay up to
2.00m BGL
Clay with sand
up to 1.0m BGL
TP 3
10.179
2.5 X 2.5 X
1.5
FOR LPG BULLET
1.40
Stiff Clay up to
1.50m BGL
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6.0 DISCUSSIONS AND RECOMMENDATIONS 6.1 Three boreholes, ( BH1 to BH3) were carried out at the Future project (Mounded
bullet for propylene), two boreholes, BH-4and BH9 were carried out at Pump
house location and four bore holes, BH 5 to BH 8 were carried out at the
proposed Mounded bullet (for LPG storage) location. At present Visakha refinery
is planning to construct one mounded Bullet for LPG storage. Size of the
proposed mounded bullet area is 83m x 49.4m and height of the mound is
10.260m above ground level with 1:2500 downward slope. The maximum weight
under hydro test per bullet (LPG) is 3527 tones and for propylene is 2728 tones.
The approximate working load per LPG and propylene Bullets is worked out as
25 t/m2.
6.2 Based on the four bore hole investigation (BH-5 to BH-8) the top subsurface
layer is medium stiff to hard silty clay layer. BH-5 to BH-7 boreholes were carried
out with in the boundary of proposed LPG Bullet area and BH-8 borehole is
approximately 20m to 25m away from the boundary of proposed LPG plant.
Based on these three boreholes (BH-5 to BH-7), the top layer up to 3.50m is
medium stiff layer and SPT ’N’ values varies between 6 and 15. Very stiff layer is
observed from 3.50m to 5.50m BGL. Hence for the proposed LPG mounded
storage the stratum below 3.50m is capable to take the loads. The strata from
existing ground level to 3.50m is relatively more compressible hence this soil of
3.50m thickness should be replaced with sand layer. 6.3 The safe bearing capacity is calculated based on shear failure criteria and
settlement criteria. The foundation of LPG mounded storage may be designed for
25 t/m2.The settlements are calculated based on laboratory test results
6.4 The total vertical consolidation settlement is 218 mm and differential settlement is
81mm (based on laboratory test results) under the pressure of 25 t/m2.
6.5 If Open cast footing is considered, for an allowable pressure of 25 t/m2 and for
allowable differentials settlement of 50mm, the clay layer up to 5.0m should be
removed and filled with well compacted sand layers.
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6.6 Since the depth of excavation is about minimum 5.00m below existing ground
level and also considering the high ground water table (1.60m to 2.20m BGL),
extensive dewatering and protection to the sides in the form of shoring and
strutting for the excavation pits will be required. During excavation, first the top
compressible clay layer above ground water table will be removed. Later the
ground water should be lowered below the bottom of the proposed excavation
depth of 5.00m by using dewatering pumps located at the corners of the
proposed excavated area. After lowering the ground water below 6.00m BGL,
further excavation of the soil will be commenced. After completion of the
excavation, graded sand will be placed in loose layers of 225mm to 250mm
thickness and shall be compacted to 150mm by 10ton vibratory roller. The
degree of compaction should be 95% of the modified compaction achieved in the
laboratory. This process will continue till the sand bed comes to the ground level
or as per the design requirement.
6.7 Another option is adopting “Pile foundation” for the site. Considering the subsoil
stratification and also hydraulic conditions of the existing site, deep foundations
are more suitable than the shallow footing system. In these Pile foundations
Bored Cast-In-Situ Concrete Piles as per IS-2911 (part 1/sec-2) are
recommended and installed preferably by direct mud circulation (DMC) method.
The Safe structural Pile capacity should be limited to 500 t/m2 acting on the
nominal Pile cross section.
6.8 Weathering of rock strata at this site is completely to highly weathered form up to
the depth of approximately 20m below existing ground level. Hence Pile lengths at
this site would vary depending upon the core recovery, RQD, Crushing strength of
rock etc. The chisel penetration response test is suggested to evolve a pile
termination level. Chiseling criteria can be utilised to determine the level of hard
bedrock. Hard bedrock can be inferred when chisel penetration is less than 10cms
for chisel energy of 2250 t-m /m2 of Pile cross section. A minimum of 2 trials
should be carried out to determined Pile termination. Wherever the chiseling
energy of 2250 t-m /m2 per less than 10cms is confirmed, socketing of the pile may
be adopted with minimum 1 x D length in this stratum. Where, D is the dia of Pile.
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Sample calculation to calculate chisel energy are given below For example – Consider a Pile of 500 mm diameter.
Area of Pile – 0.19625 m2
Let, Weight of chisel – 1.0 tons
If fall of chisel is limited to 2.0m, energy of each blow
= 1.0 x 2.0 = 2.0 ton –m
The energy of 2250 t-m /m2 is converted into equivalent energy for 500 mm dia of
Pile.
Equivalent energy = 2250 x 0.19625 = 440 t - m
To achieve this, no of blows required of 1.0 ton chisel with 2.0m fall = 440/2 = 220
blows.
The no. blows are increased to account for submerged weight of chisel with weight
of 1.0 ton tension while releasing the chisel. So , chiseling criteria for 500mm dia
will be as follows.
The penetration shall be less than 10cms for 260 blows of chisel with weight of 1.0
ton and falling through a height of 2.0 meters.
Generally, 300 blows can be applied within 30 minutes. While checking the
chiseling criteria, the chisel shall be with drawn after 30 minutes, hole cleaned and
penetration measured.
6.9 The safe load carrying capacity of different dia of piles is given in table below.
Table – 11
Dia of pile
(mm)
Safe load carrying capacity of pile (tons)
500 100
600 140
750 200
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6.10 FOR PROPYLENE BULLETS For this mounded structure the foundation may be placed at a depth of 6.00 m
below existing ground level. Allowable bearing pressure may be considered
25t/m2. Pile foundations are more suitable at this location.
6.11 Spread and continuous foundations for retaining wall and other structures at this
site will be installed at a depth of minimum 2.0m below ground surface. The
allowable bearing for different breadths are given below.
Table 12
Depth BGL(m)
Breadth (m)
SBC (t/m2) Settlement (mm)
Allowable bearing pressure (ABP) for 40mm settlement
2.0
25 67.19 15
3.0
3.0
23.16 72.08 12
6.12 Lateral Earth pressure The retaining walls to mound the soil will subject to lateral earth pressures due to
retained earth. A total soil unit weight and lateral earth pressure parameter (Ka)
of 2.0 t/m3 And 0.33, respectively, can be used for design of retaining wall.
6.13 Pump Houses
Excavations below ground will be required to complete proposed pump houses.
Shallow groundwater table of between 1.6m and 2.2m below ground surface, was
encountered at this site. Hence, extensive dewatering will be required. Adequate
uplift resistance in the form of dead weight or anchors should be provided on pump
house rafts.
6.14 Temporary excavation sides below water table should be sloped at a maximum
slope of 2:1 (horizontal: vertical) or flatter to minimize side sloughing and
collapse. Excavations above water table can be maintained near vertical.
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6.15 Parameters for design of dynamic foundations (footing area > 10m2) installed in
accordance with Table B above are given below (Reference IS2974).
Coefficient of Elastic Uniform Compression (Cz) = 4 x 103 t/m3
Coefficient of Elastic Non-Uniform Compression (Cθ) = 2Cz = 8.0 x 103 t/m3
Coefficient of Elastic Uniform Shear (Cγ) = 0.5Cz = 2 x 103 t/m3
Coefficient of Elastic Non-Uniform Shear (Cψ) = 0.75Cz = 3 x 103 t/m3
Poisson’s Ratio = 0.33
Dynamic Shear Modulus = G’ = 1850 t/m2
P.S.Bansod Director- Technical
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FINAL RECOMMENDATIONS FOR FOUNDATION TYPE FOR PROJECT OF MOUNDED LPG & PROPYLENE FACILTES AT HPCL, VISKHA REFINERY Subsequent to the earlier submitted draft final report along with addendum sent on 27-11-2006, following is the final recommendations as regards Pile capacity and SBC of shallow foundations for minor structures. We are recommending only Pile Foundations based on soil investigation data for the mounded storage (LPG and Propylene area), Pump House and for all major heavily loaded structures, Equipment foundations. The details are as follows.
• Recommended foundation type is – RCC Cast in Situ Bored Pile foundations
• Safe Vertical, lateral and uplift capacity of different dia of Piles are given below in
table.
• All Piles should be terminated in moderately weathered rock o0nly. (Layer lll as
discussed in soil investigation). In LPG, Pump house and propylene area. The
minimum length of pile will be 20m / up to moderately weathered rock, which ever
is higher.
• Socketing of Pile should be minimum 3x Dia in Moderately weathered rock.
Dia of Pile (mm)
Safe vertical capacity of Pile (tons)
Safe Uplift Capacity of Pile (tons)
Safe lateral capacity of Pile (tons)
300 35 25 3.4
400 50 45 4.6
450 70 50 5.2
500 1000 55 538
600 140 70 6.9
750 2000 836 86
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• The pile capacity has also taken in to account maximum permissible deflection of
12 mm. As per soil data the maximum differential settlement has been found to be
9mm in propylene and LPG mound area.
• For minor (lightly loaded ) foundations shallow foundations may be used as per
Soil bearing capacity given in table below. However a cushion of minimum 230mm
thick boulder soling has to be kept with 230mm projection all along below the
shallow foundation.
Net Safe Bearing pressure (SBP) for 25mm permissible settlement (t/m2)ed
Size of footing ( m x m )
Proposed
foundation depth BGL (m)
2 x 2 4 x 4
1.0 2.5 4.0
1.5 3.3 4.5
2.0 3.9 5.0
T. V. Suresh Kumar Manager – Geotechnical DBM Geotechnics and Constructions Pvt Ltd Santacruz, Mumbai
1686-HPCL/VIZAG REFINERY/FINAL/ TVS REPORTS
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7.0 SAMPLE CALCULATION FOR ALLOWABLE BEARING CAPACITY
FOR LPG MOUNDED BULLET REFERENCE BH – 5 (Considered on conservative side)
SUB SOIL STRATIFICATION G.L, 0.0 m
SILTY CLAY LAYER
SPT 1 at 1.50m N = 6
SPT 2 at 2.50m N = 10
UDS 1 at 3.20m Cu =10 t/m2
SPT 3 at 3.50m N = 15
SPT 4 at 4.50m N = 19
SPT 5 at 5.50m N = R
Completely weathered rock, N>50
- 16.00 m
Highly weathered rock, N>100
- 21.10 m
Moderately to slightly weathered - 23.25 m
1686-HPCL/VIZAG REFINERY/FINAL/ TVS REPORTS
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7.1 CALCULATION OF SAFE BEARING CAPACPCITY (SBC) A BASED ON SHEAR FAILURE CRITERIA
Type of Footing : Shallow and spread
Size of pedestal where Bullet rest
Breadth of LPG Bullet pedestal : 2.5 m
Length of LPG Bullet Pedestal : 70 m
Depth of Proposed Foundation : 3.50 m
Depth of Water Table : 0.00m (assumed conservatively
at ground level)
Load Inclination : 0°
Bulk Unit Weight : 1.8 t/m3 (Minimum value
considered from Laboratory tests)
Field ‘N’ Value : = 15 (Minimum considered
after checking with DCPT and SCPT by correlations)
Undrained Cohesion, Cu : 15/1.5 = 10.00 t/m2 (Based on N value)
Cohesion from lab tests (from BH 5 at 3.50m)
i) From Triaxial compression test, Cu = 10.3 t/m2
Minimum value is considered from above two, say cu = 10.00 t/m2
Bearing capacity factor : Nc = 5.14,
Shape Factors : Sc = 1.30
Inclination factors : iq = iγ = 1.0
Depth Factors : dc = 1.28
The net ultimate bearing Capacity, qnu= Cu x Nc x Sc x ic x dc
= 10.00 x 5.14 x 1.30 x 1.0 x 1.28 = 85.53 t/m2
Consider factor of safety = 3
The net safe bearing Capacity qns = 85.53/3 = 28.5 t/m2 say 25 t/m2
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B) SETTLEMENT AT THE CENTER OF BULLET ( Based on lab test results) {(Reference IS: 8009) I) Silty Clay – from – 3.50m to – 5.50m below ground surface
Consolidation Settlement = ρc1 = H/CI x log (σo + ∆σo) / σo
Where
H = 2.00m
γ = 1.80 t/m3
σo = 3.6 kg/cm2
∆σo = 17.61 t/m2
Compression index = 0.18
Initila void ratio = e0 = 0.37
Settlement = ρc1 = Cc /1+ e0 x H x log (σo + ∆σo) / σo
= 202 mm II) Completely weathered rock – from – 5.50m to - 16.00m below ground surface
Immediate settlement, δi = (q*B’*(1-µ2)*m*Is*If)/E (Ref: Foundation analysis
and design, Bowles) say, N = 50 for soft rock
Where, q = 13.5 t / m2
B’ = 1.25 m
µ = 0.30
m=4
For H/B’ = 8.4 and L/B = 28 & D/B = 1.8
I1 = 0.672 and I2 = 0.151
Is= 0.758
If = 1.0, considered conservatively
Taking E = 50 (N + 15) = 3250 t / m2, for average N value 50
Therefore δi = 14.33 mm
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III)Highly weathered rock – from – 16.00m to - 21.10m below ground surface
Immediate settlement, δi = (q*B’*(1-µ2)*m*Is*If)/E (Ref: Foundation analysis
and design, Bowles) say, N = 100 for highly weathered rock
Where, q = 3.56 t / m2
B’ = 1.25 m
µ = 0.30
m=4
For H/B’ = 4.08 and L/B = 28 & D/B = 1.8
I1 = 0.453 and I2 = 0.154
Is= 0.541
If = 1.0, considered conservatively
Taking E = 50 (N + 15) = 5750 t / m2, for N value 100
Therefore δi = 1.52 mm
IVI) Moderately weathered rock – from – 21.1 m to 30m below ground surface Where, q = 2.5 t / m2
B’ = 1.25 m
µ = 0.30
m=4
For H/B’ = 7.1 and L/B = 28 & D/B = 1.8
I1 = 0.628 and I2 = 0.152
Is= 0.715
If = 1.0, considered conservatively
Taking E =20000 t/m2
Therefore δi = 0.41 mm
TOTAL SETTLEMENT UNDER SBC OF 25 t/m2 AT CENTER OF LPG BULLET = 202 + 14.33 + 1.52 + 0.41 = 218.26 mm
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REFERENCES
1) IS: 6403- 1981, Code of Practice for Determination of Bearing Capacity of
Shallow Foundation
2) IS: 8009 (Part I) –1976, code of practice for calculation of settlements of
Foundations.
3) IS 456:2000 Code of Practice For Plain and Reinforced Concrete.
4) Foundation Design Manual, N V. Nayak, 4th Edition, 1996.
5) Foundation Analysis and Design, J. Bowles, 4th Edition