13-HPCL Vizag Soil Report-VOL.V

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


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.



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.



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



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



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.



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



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



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



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



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



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.



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



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.



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



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



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.



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.



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



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.



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



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



• 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



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



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



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



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


Taking E = 50 (N + 15) = 5750 t / m2, for N value 100


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


Taking E =20000 t/m2


TOTAL SETTLEMENT UNDER SBC OF 25 t/m2 AT CENTER OF LPG BULLET = 202 + 14.33 + 1.52 + 0.41 = 218.26 mm



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

13-HPCL Vizag Soil Report-VOL.V

Documents

split spoon

rock quality

core recovery

highly weathered

rock core

clients location

laboratory

proposed mounded