1.0 INTRODUCTION SCOPE OF WORK EXECUTION OF FIELD WORK LABORATORY TESTS FINDINGS OF THE GEOTECHNICAL INVESTIGATION 9

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1 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 SCOPE OF WORK EXECUTION OF FIELD WORK LABORATORY TESTS FINDINGS OF THE GEOTECHNICAL INVESTIGATION DISCUSSIONS AND RECOMMENDATION SAMPLE CALCULATION REFERENCES 27 A B C D E F G ANNEXURE LOCATION PLAN BORE LOGS TRIAL PIT LOGS STATIC CONE PENETRATION TESTS DYNAMIC CONE PEENTRATION TESTS LABORATORY TEST RESULTS SUB SOIL PROFILE

2 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. 1

3 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 Transporting the selected soil and rock samples to the laboratory for conducting tests as per the scope of the work Analysis and interpretation of field & laboratory test data for the preparation of Geotechnical investigation report 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. 2

4 3.2 Period of Execution: The fieldwork was commenced on and completed on FIELD METHODOLOGY OF INVESTIGATION 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 Boring in Overburden Boring was done in accordance with IS: 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 3

5 precautionary measures for protecting concrete and reinforcement steel can be decided based on these chemical results 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 Standard Penetration Test (SPT) : SPT s were conducted as per IS 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 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 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 4

6 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: 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. 5

7 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 Depth of Thickness of Termination S NO Borehole No R. L (m) GWT(BGL) in m Over burden BGL(m) depth BGL (m) 1 BH BH BH BH BH BH BH BH BH

8 TABLE 2 TABLE SHOWING SUMMARY OF STATIC CONE PENETRATION TESTS SR NO SCPT NO GROUND R.L LOCATION (m) 1 SCPT NEAR BH-1 FOR PROPYLENE BULLET 2 SCPT NEAR BH-3 FOR PROPYLENE BULLET 3 SCPT FOR LPG BULLET 4 SCPT NEAR BH-5 FOR LPG BULLET 5 SCPT 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 DCPT FOR PROPYLENE 5.1 BULLET 2 DCPT FOR PROPYLENE 5.24 BULLET 3 DCPT NEAR BH-4 FOR 5.1 PUMP HOUSE 4 DCPT FOR LPG BULLET DCPT FOR LPG BULLET 4.7 7

9 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 X 2.5 X 1.8 FOR PROPYLENE 1.80 BULLET NEAR DC-1 TP X 2.5 X 2.0 FOR PUMP 1.90 HOUSE NEAR BH4 TP X 2.5 X 1.5 FOR LPG BULLET 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 8

10 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) IS2720 Specific Gravity determination (Part III) d) Natural moisture content and in-situ density tests on UDS samples IS 2720 (Part II) e) IS 2720 (Part Shear strength and consolidation tests on UDS samples 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 k) Engineering classification of soil IS 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 9

11 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 C u (Tuu) Kg/cm to 1.03 Angle of Internal Friction ø (Tuu) Degrees 2.86 to 3.60 Cohesion C u (UC) Kg/cm 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 10

12 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 / cm to 648 Soaked Point load Index strength kg / cm to 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. 11

13 Table -7 Summary of laboratory test results of Moderately weathered to Slightly weathered Rock Core Samples Parameter Unit Range Soaked Uniaxial compressive strength kg / cm to 1306 Soaked Point load Index strength kg / cm to Porosity % 0.08 to 2.89 Water Absorption % 0.03 to 1.42 Dry density gm/ cc 2.03 to 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 ( 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 12

14 SCPT NO following correlation between SCPT results and SPT N values can be utilized (Reference No. 5): SPT N value = Ckd/C, Where C = 2. GROUND R.L (m) SCPT SCPT Table -8 Summary of the SCPT test results PRESSURE AT TERMINATED LOCATION TERMINATED DEPTH BGL (m) CORRECTED CORRECTED CONE SHAFT RESISTANC RESISTANCE E (kg/cm2) (kg/cm2) NEAR BH-1 FOR PROPYLENE BULLET NEAR BH-3 FOR PROPYLENE BULLET SCPT FOR LPG BULLET SCPT NEAR BH-5 FOR LPG BULLET SCPT NEAR BH-7 FOR LPG BULLET 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. 13

15 Table -9 Summary of the DCPT test results DCPT NO GROUND LOCATION REFUSAL R.L (m) DEPTH BGL (m) Ncbr AT REFUSAL DCPT FOR PROPYLENE BULLET DCPT FOR PROPYLENE BULLET DCPT NEAR BH-4 FOR PUMP HOUSE DCPT FOR LPG BULLET DCPT FOR LPG BULLET

16 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 TP X 2.5 X 1.8 TP X 2.5 X 2.0 TP X 2.5 X 1.5 LOCATION GROUND WATER TABLE (m) FOR PROPYLENE 1.80 BULLET NEAR DC-1 FOR PUMP 1.90 HOUSE NEAR BH4 FOR LPG BULLET 1.40 Strata description Clay with sand up to 1.0m BGL Stiff Clay up to 1.80m BGL Clay with sand up to 1.0m BGL Stiff Clay up to 2.00m BGL Clay with sand up to 1.0m BGL Stiff Clay up to 1.50m BGL 15

17 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 m 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/m 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/m 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. 16

18 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/m 2 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 /m 2 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 /m 2 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. 17

19 Sample calculation to calculate chisel energy are given below For example Consider a Pile of 500 mm diameter. Area of Pile 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 /m 2 is converted into equivalent energy for 500 mm dia of Pile. Equivalent energy = 2250 x = 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)

20 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/m 2. Pile foundations are more suitable at this location 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 Breadth SBC (t/m2) Settlement Allowable bearing (m) (m) (mm) pressure (ABP) for 40mm settlement 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 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 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. 19

21 6.15 Parameters for design of dynamic foundations (footing area > 10m 2 ) installed in accordance with Table B above are given below (Reference IS2974). Coefficient of Elastic Uniform Compression (C z ) = 4 x 10 3 t/m 3 Coefficient of Elastic Non-Uniform Compression (C θ ) = 2C z = 8.0 x 10 3 t/m 3 Coefficient of Elastic Uniform Shear (C γ ) = 0.5C z = 2 x 10 3 t/m 3 Coefficient of Elastic Non-Uniform Shear (C ψ ) = 0.75C z = 3 x 10 3 t/m 3 Poisson s Ratio = 0.33 Dynamic Shear Modulus = G = 1850 t/m 2 P.S.Bansod Director- Technical 20

22 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 , 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. Dia of Pile Safe vertical Safe Uplift Safe lateral (mm) capacity of Capacity of capacity of Pile (tons) Pile (tons) Pile (tons) 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. 21

23 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. Proposed foundation depth BGL (m) Net Safe Bearing pressure (SBP) for 25mm permissible settlement (t/m2)ed Size of footing ( m x m ) 2 x 2 4 x T. V. Suresh Kumar Manager Geotechnical DBM Geotechnics and Constructions Pvt Ltd Santacruz, Mumbai 22

24 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> m Highly weathered rock, N> m m Moderately to slightly weathered 23

25 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/m 3 (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 = 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 = t/m2 Bearing capacity factor : N c = 5.14, Shape Factors : S c = 1.30 Inclination factors : iq = iγ = 1.0 Depth Factors : d c = 1.28 The net ultimate bearing Capacity, q nu = Cu x Nc x Sc x ic x dc = x 5.14 x 1.30 x 1.0 x 1.28 = t/m 2 Consider factor of safety = 3 The net safe bearing Capacity q ns = 85.53/3 = 28.5 t/m2 say 25 t/m2 24

26 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 = ρ c1 = H/CI x log (σo + σo) / σo Where H = 2.00m γ = 1.80 t/m 3 σo = 3.6 kg/cm2 σo = t/m 2 Compression index = 0.18 Initila void ratio = e0 = 0.37 Settlement = ρ c1 = Cc /1+ e0 x H x log (σo + σo) / σo = 202 mm II) Completely weathered rock from 5.50m to m below ground surface Immediate settlement, δ i = (q*b *(1-µ 2 )*m*is*if)/e (Ref: Foundation analysis and design, Bowles) say, N = 50 for soft rock Where, q = 13.5 t / m 2 B = 1.25 m µ = 0.30 m=4 For H/B = 8.4 and L/B = 28 & D/B = 1.8 I 1 = and I 2 = Is= If = 1.0, considered conservatively Taking E = 50 (N + 15) = 3250 t / m 2, for average N value 50 Therefore δ i = mm 25

27 III)Highly weathered rock from 16.00m to m below ground surface Immediate settlement, δ i = (q*b *(1-µ 2 )*m*is*if)/e (Ref: Foundation analysis and design, Bowles) say, N = 100 for highly weathered rock Where, q = 3.56 t / m 2 B = 1.25 m µ = 0.30 m=4 For H/B = 4.08 and L/B = 28 & D/B = 1.8 I 1 = and I 2 = Is= If = 1.0, considered conservatively Taking E = 50 (N + 15) = 5750 t / m 2, for N value 100 Therefore δ i = 1.52 mm IVI) Moderately weathered rock from 21.1 m to 30m below ground surface Where, q = 2.5 t / m 2 B = 1.25 m µ = 0.30 m=4 For H/B = 7.1 and L/B = 28 & D/B = 1.8 I 1 = and I 2 = Is= If = 1.0, considered conservatively Taking E =20000 t/m2 Therefore δ i = 0.41 mm TOTAL SETTLEMENT UNDER SBC OF 25 t/m2 AT CENTER OF LPG BULLET = = mm 26

28 REFERENCES 1) IS: , 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, 4 th Edition, ) Foundation Analysis and Design, J. Bowles, 4 th Edition 27