A REPORT ON SUB SOIL INVESTIGATION WORK NEW HAJ TOWER COMPLEX HOOGHLY RIVER BRIDGE COMMISSIONERS

Transcription

1 A REPORT ON SUB SOIL INVESTIGATION WORK PROJECT : NEW HAJ TOWER COMPLEX LOCATION : REVISED CHANGED SITE ON PLOT NO. IIA/26, OF RAJARHAT NEW TOWN, KOLKATA Project Implementation Authority : HOOGHLY RIVER BRIDGE COMMISSIONERS PREPARED BY : PEC ENGINEERS & ASSOCIATES, 2/39, NETAJI NAGAR, KOLKATA ON BEHALF OF : GHERZI EASTERN LIMITED, 16, MAHANIRBAN ROAD, KOLKATA

2 PEC ENGINEERS & ASSOCIATES A REPORT ON SOIL INVESTIGATION WORK FOR THE PROPOSED NEW HAJ TOWER COMPLEX AT REVISED CHANGED SITE ON PLOT NO. IIA/26 OF RAJARHAT NEW TOWN, KOLKATA CONTENTS SHEET NO. A. TEXT : 1. INTRODUCTION 1 2. AIMS OF THE PRESENT INVESTIGATION 1 3. GENERAL GEOLOGICAL FEATURES OF THE AREA 1 4. PROGRAMME AND METHOD OF INVESTIGATION GENERAL SUB-SOIL STRATIFICATION AND PROPERTIES DISCUSSION ON SUITABLE FOUNDATIONS FOR THE PROPOSED PROJECT RECOMMENDATION AND CONCLUDING REMARKS B. ANNEXURE : 8. LOCATIONS OF BORE-HOLES A-1 9. BORE LOG DATA SHEET A-2 to A SUB-SOIL PROFILE WITH N VALUE Vs. DEPTH PLOT A SUMMARY OF TEST RESULTS A-7 to A GRAIN SIZE DISTRIBUTION CURVES A-12 to A VOID RATIO (e) Vs. LOG P CURVES A-21 to A MORE CIRCLE DIAGRAMS A-24 to A GRAPHS FOR DIRECT SHEAR TEST A-28 to A-33

3 A. TEXT

4 1 INTRODUCTION : PEC ENGINEERS & ASSOCIATES The New Haj Tower Complex is proposed to be constructed at revised changed site on Plot No. IIA/26, Rajarhat New Town, Kolkata. In this connection, Gherzi Eastern Limited assigned the soil investigation work to PEC Engineers & Associates of 2/39, Netaji Nagar, Kolkata vide Work Order No. K/WO/SNM/MDA/340/540 dated 26/11/2012. Accordingly, the field work was started on 26/11/2012 and was completed on 05/12/2012. Subsequently, the soil samples collected in the bore-holes were subjected to visual identification/examination and/or were tested in the laboratory to determine various relevant properties and parameters based on which as well as experienced engineering judgement, this final report has been prepared. 2 AIMS OF THE PRESENT INVESTIGATION : The present investigation is aimed at assessing the sub-soil stratifications and their characteristics with the help of bore-hole studies including in-situ tests and laboratory investigation. Finally, with the application of the findings of the investigation, suitable foundation systems for the proposed structures are to be recommended. 3 GENERAL GEOLOGICAL FEATURES OF THE AREA : The area of the present investigation belongs to the well known Bengal Basin, which is the southward extension of Indo-Gangetic Flood Plains. It consists of typical alluvial deposits comprising layers of sand, silt and clay and is believed to have been formed by Ganga- Brahmaputra River System. These deposits often have thickness of more than 100 m over the bed rock. The sub-soil of the upper strata, which is of immediate importance to civil engineers is of recent origin. Often, scattered concentrations of decomposed/semidecomposed vegetation and/or organic matters are also observed up to about 15 m depth. However, the alluvial deposits of the Bengal Basin may be broadly divided into two types : (i) Silty clays/clayey silts with or without sand admixture covering most of the area. These were formed by back-swamp of flooded water of rivers. (ii) River Channel Deposits comprising silty sands/sands of fine to medium grade occurring in stretches. These were formed by meandering of rivers in the past.

5 PEC ENGINEERS & ASSOCIATES 2 4 PROGRAMME AND METHOD OF INVESTIGATION : The programme of the present investigation work as drawn by the client consists of: i) Field Investigation and ii) Laboratory Investigation with Report on the entire work. 4.1 FIELD INVESTIGATION : In field investigation, a total of 4 (four) nos. of bore-holes were sunk. Borehole-wise maximum depths of investigation below the Existing Ground Level (E.G.L.) are as follows: Bore-hole No. Date of Commencement Date of Completion Maximum Depth of Investigation Below E. G. L. 1 26/11/ /11/ M 2 29/11/ /12/ M 3 02/12/ /12/ M 4 04/12/ /12/ M Location Plan of bore-holes is shown in sheet no. A-1. Field Bore Logs are shown in sheets A-2 and A-5. The following were the different parts of the field investigation: Sinking of Bore-holes : Bore-holes were advanced by Auger and Rotary Wash Method. 150 mm dia. bore- holes were initially (up to a depth of 3.0 m below E.G.L.) made by operating hand auger. After the auger was withdrawn, the bore-holes (150 mm dia.) were taken down by wash boring technique using a manually operated winch. In this technique, the hole was advanced by a chopping bit. The bit which was hollow, was screwed to a series of hollow drill rods supported on a tripod by a rope passing over pulley. A stream of water under pressure was forced through the rod(s) and the bit into the hole. Upon entering the bore-hole at its bottom end, the stream of water under pressure loosened the soil around and forced it up along the annular surface between the rod and the side of the hole. The soil suspension from the bore-hole was discharged into a tub. The particles in suspension settled down in the tub and the clear water overflew into a sump. The water washed into the sump was reused for circulation. Casing pipe for an initial length of 4.0 m and subsequently bentonite slurry were used to prevent the collapse of bore holes. As the bore-holes progressed Standard Penetration Tests were conducted and Disturbed & Undisturbed samples were taken at suitable intervals Standard Penetration Tests : Standard Penetration Tests were conducted within the bore-holes at suitable intervals and in accordance with the specifications laid down in IS: The number of blows required for middle 30 cm penetration of Split-spoon Sampler out of a total penetration of

6 PEC ENGINEERS & ASSOCIATES 3 60 cm driven by a 63.5 kg hammer falling freely from a height of 75 cm was recorded as N value. In sandy soil, this field N value is corrected for overburden and dilatancy (wherever applicable) to get the corrected N value. This is a very useful test which gives an idea about the consistency/compactness as well as the strength of the in-situ soil Disturbed Samples : After each standard penetration test, sufficient quantity of disturbed sample was collected from the split-spoon sampler. Samples from the augered material were also taken sometimes for visual identification. These samples were very carefully preserved in double polythene packets to avoid loss of moisture as far as practicable. These were then properly marked & labeled and kept ready to be sent to laboratory for identification and testing Undisturbed Samples : Undisturbed samples were collected generally from cohesive or predominantly cohesive soil deposits in accordance with the specifications laid down in IS : and IS : A two-tier 100 mm I.D. open tube sampling assembly having area ratio of around 15% was used to collect the samples. The sampling assembly was driven to the required depth manually with the help of jarring link. Samples collected in the lower tube were retained, properly sealed at both ends by wax, marked & labeled and kept ready to be sent to the laboratory for testing Standing Water Level : Standing Water Levels in the bore- holes were measured 24 hours after completion of boring in the respective bore hole and are shown in the bore logs. The average level was found to be approximately at 4.25 m depth below average E.G.L. of the boring locations. However, for calculation of load bearing capacities of soil, water level should not be considered below E.G.L. for the worst case. 4.2 LABORATORY INVESTIGATION : In order to have a comprehensive picture of the sub-soil characteristics which will help in selecting a suitable foundation system for the proposed structure, the following laboratory tests have been conducted on disturbed and undisturbed soil samples. The test programme was so prepared as to incorporate appropriate and suitable engineering judgement and requirement. All the tests have been carried out as per IS specifications. i) Determination of Natural Moisture Content. ii) Sieve and Hydrometer analysis to determine grain size distribution.

7 PEC ENGINEERS & ASSOCIATES 4 iii) Determination of Liquid Limit and Plastic limit. iv) Determination of Unit Weight. v) Determination of Specific Gravity. vi) Unconfined Compression, Triaxial Compression and Direct Shear Tests to determine shear strength parameters. vii) One-dimensional Consolidation Test to determine compressibility characteristics. 5 GENERAL SUB-SOIL STRATIFICATION AND PROPERTIES : As revealed by the field and laboratory investigations, the sub-soil at the site up to the maximum depth of investigation below Existing Ground Level (i.e., 40.6 m) may be broadly divided in the following strata of which the most common features of present interest are given below. 5.1 STRATUM - I : Borehole-wise approximate existence and thickness of the stratum are given below : B. H. No. Exists from Exists up to Thickness m below E.G.L m below E.G.L m m below E.G.L m below E.G.L m m below E.G.L m below E.G.L m m below E.G.L m below E.G.L m Average Thickness 1.35 m It consists of brownish grey / grey silty clay with rusty brown spots. It seems to be a filledup deposit and does not bear much significance in the present context since, any foundation shall be seated beyond this layer. However, for calculation of overburden pressure, its bulk unit weight may be considered as 1.90 t/m 3.

8 PEC ENGINEERS & ASSOCIATES STRATUM - II : It is found in all the boreholes. Borehole-wise approximate existence and thickness of the stratum are given below : B. H. No. Exists from Exists up to Thickness m below E.G.L m below E.G.L m m below E.G.L m below E.G.L m m below E.G.L m below E.G.L m m below E.G.L m below E.G.L m Average Thickness 5.15 m It consists of brownish grey/ greyish brown / grey silty clay / clayey silt, occasionally with traces of decomposed vegetation. The deposit is basically cohesive in nature having medium consistency in general. Plasticity of soil varies from moderate to high. As per I.S. Classification, it may be denoted as CH-CI. The relevant engineering properties of soil as obtained from selective tests are given below: Value Properties / Parameters Range Average Field N Value 3 to Corrected N Value N. A. N. A. Bulk Unit Weight (t/m 3 ) 1.88 to Natural Moisture Content (%) 24 to Dry Unit Weight (t/m 3 ) 1.41 to Liquid Limit (%) 52 to Plastic Limit (%) 22 to Plasticity Index (%) 28 to Cohesion from UU Test (t/m 2 ) 5.2 to Angle of internal friction from UU Test 0 to Cohesion from UC Test (t/m 2 ) 3.5 to Specific Gravity 2.65 to Initial Void Ratio to Co-efficient of Volume Decrease, m v (cm 2 /kg) Grain Size Pressure Range (kg/cm 2 ) to to to to to Gravel (%) 0 0 Sand (%) 1 to 4 2 Silt (%) 50 to Clay (%) 28 to 49 40

9 PEC ENGINEERS & ASSOCIATES STRATUM - III : It is found only in borehole 1. Borehole-wise approximate existence and thickness of the stratum are given below : B. H. No. Exists from Exists up to Thickness m below E.G.L m below E.G.L. 5.5 m 2 Not Found Not Found - 3 Not Found Not Found - 4 Not Found Not Found - Average Thickness 5.5 m* It consists of grey silty clay/clayey silt with decomposed vegetation scatteredly present. The deposit is basically cohesive in nature having high plasticity. Consistency of soil varies from soft to medium. As per I.S. Classification, it may be denoted as CH-OH. The relevant engineering properties of soil as obtained from selective tests are given below: Value Properties / Parameters Range Average Field N Value 3 to 5 4 Corrected N Value N. A. N. A. Bulk Unit Weight (t/m 3 ) 1.86 to Natural Moisture Content (%) 31 to Dry Unit Weight (t/m 3 ) 1.41 to Liquid Limit (%) 46 to Plastic Limit (%) 23 to Plasticity Index (%) 23 to Cohesion from UU Test (t/m 2 ) 3.0 to Angle of internal friction from UU Test 0 to Specific Gravity 2.63* 2.63* Initial Void Ratio 0.783* 0.783* Co-efficient of Volume Decrease, m v (cm 2 /kg) Grain Size *indicates solitary value Pressure Range (kg/cm 2 ) * * * * * * * * * * Gravel (%) 0 0 Sand (%) 2 to 3 3 Silt (%) 65 to Clay (%) 26 to 32 29

10 PEC ENGINEERS & ASSOCIATES STRATUM - IV : It is found only in borehole 1. Borehole-wise approximate existence and thickness of the stratum are given below : B. H. No. Exists from Exists up to Thickness m below E.G.L m below E.G.L. 6.0 m 2 Not Found Not Found - 3 Not Found Not Found - 4 Not Found Not Found - Average Thickness 6.0 m* It consists of bluish grey / mottled brown & bluish grey silty clay with calcareous nodules and occasional lenses of sand. The deposit is basically cohesive in nature with high plasticity. Consistency of soil is stiff. As per I.S. Classification, it may be denoted as CH. The relevant engineering properties of soil as obtained from selective tests are given below: Value Properties / Parameters Range Average Field N Value 7 to Corrected N Value N. A. N. A. Bulk Unit Weight (t/m 3 ) 2.02* 2.02* Natural Moisture Content (%) 25* 25* Dry Unit Weight (t/m 3 ) 1.62* 1.62* Liquid Limit (%) 69* 69* Plastic Limit (%) 24* 24* Plasticity Index (%) 45* 45* Cohesion from UU Test (t/m 2 ) 9.1* 9.1* Angle of internal friction from UU Test Specific Gravity 2.66* 2.66* Initial Void Ratio 0.562* 0.562* Co-efficient of Volume Decrease, m v (cm 2 /kg) Grain Size *indicates solitary value Pressure Range (kg/cm 2 ) * * * * * * * * * * Gravel (%) 3* 3* Sand (%) 2* 2* Silt (%) 54* 54* Clay (%) 41* 41*

11 PEC ENGINEERS & ASSOCIATES STRATUM - V : It is found only in borehole 1. Borehole-wise approximate existence and thickness of the stratum are given below : B. H. No. Exists from Exists up to Thickness m below E.G.L m below E.G.L. 1.5 m 2 Not Found Not Found - 3 Not Found Not Found - 4 Not Found Not Found - Average Thickness 1.5 m* It consists of medium dense greyish brown medium dense clayey sand. The deposit is basically C - φ in nature having both cohesion and angle of internal friction. As per I.S. Classification, it may be denoted as SC. The relevant engineering properties of soil as obtained from selective tests are given below: Properties / Parameters Value Range Average Field N Value - - Corrected N Value - - Bulk Unit Weight (t/m 3 ) 1.94* 1.94* Natural Moisture Content (%) 21* 21* Dry Unit Weight (t/m 3 ) 1.60* 1.60* Liquid Limit (%) 38* 38* Plastic Limit (%) 19* 19* Plasticity Index (%) 19* 19* Cohesion from CU Test (t/m 2 ) 4.0* 4.0* Angle of internal friction from CU Test 24 0 * 24 0 * Cohesion from UC Test (t/m 2 ) - - Specific Gravity - - Initial Void Ratio - - Co-efficient of Volume Decrease, m v (cm 2 /kg) Grain Size *indicates solitary value Pressure Range (kg/cm 2 ) Gravel (%) 0 0 Sand (%) Silt (%) Clay (%) 26 26

12 PEC ENGINEERS & ASSOCIATES STRATUM - VA : It is found in boreholes 2, 3 and 4. Borehole-wise approximate existence and thickness of the stratum are given below : B. H. No. Exists from Exists up to Thickness 1 Not Found Not Found m below E.G.L m below E.G.L m m below E.G.L m below E.G.L m m below E.G.L m below E.G.L m Average Thickness m It consists of grey sandy silt / silty fine sand, sometimes with admixture of clay. The deposit is predominantly cohesion-less and non-plastic in nature. Cohesion value, if any, may be neglected for all practical purposes and only φ value may be taken in design calculations. Compactness of soil varies from loose to medium dense. As per I.S. Classification, it may be denoted as ML-SM. The relevant engineering properties of soil as obtained from selective tests are given below: Value Properties / Parameters Range Average Field N Value 4 to Corrected N Value 3 to Bulk Unit Weight (t/m 3 ) 1.82 to Natural Moisture Content (%) 24 to Dry Unit Weight (t/m 3 ) 1.38 to Liquid Limit (%) 42* 42* Plastic Limit (%) 22* 22* Plasticity Index (%) 20* 20* Cohesion from CU Test (t/m 2 ) 2.0 to Angle of internal friction from CU Test 22 0 to Cohesion from CD Test (t/m 2 ) 0.08 to Angle of internal friction from CD Test 27 0 to Specific Gravity 2.63 to Initial Void Ratio to Co-efficient of Volume Decrease, m v (cm 2 /kg) Grain Size Pressure Range (kg/cm 2 ) to to to to to Gravel (%) 0 0 Sand (%) 29 to Silt (%) 16 to Clay (%) 14 to 21 12

13 PEC ENGINEERS & ASSOCIATES STRATUM - VI : It is found in all the boreholes. Borehole-wise approximate existence and thickness of the stratum are given below : B. H. No. Exists from Exists up to Thickness m below E.G.L m below E.G.L m m below E.G.L m below E.G.L m m below E.G.L m below E.G.L m m below E.G.L m below E.G.L m Average Thickness 17.5 m It consists of grey silty fine sand with mica in traces. The deposit is purely cohesion-less and non-plastic in nature having medium dense to dense compactness. As per I.S. Classification, it may be denoted as SM. The relevant engineering properties of soil as obtained from selective tests are given below: Properties / Parameters Value Range Average Field N Value 16 to Corrected N Value 11 to Angle of internal friction based on corrected N 30 0 to Bulk Unit Weight (t/m 3 ) 1.83 to Natural Moisture Content (%) 23 to Dry Unit Weight (t/m 3 ) 1.41 to Liquid Limit (%) N. P. N. P. Plastic Limit (%) N. P. N. P. Plasticity Index (%) N. A. N. A. Cohesion from DS Test (t/m 2 ) 0 0 Angle of internal friction from DS Test 32 0 to Specific Gravity 2.64 to Gravel (%) 0 0 Grain Size Sand (%) 71 to Silt (%) 6 to Clay (%) 0 0

14 5.8 STRATUM - VII : PEC ENGINEERS & ASSOCIATES 11 It is found in all the boreholes. Borehole-wise approximate existence and thickness of the stratum are given below : B. H. No. Exists from Continues to Exist at Thickness up to termination depth Average Thickness m below E.G.L m below E.G.L m 2.40 m m below E.G.L m below E.G.L m (up to m below E.G.L m below E.G.L m termination m below E.G.L m below E.G.L m depth) It consists of silty clay, occasionally with lenses of silt and decomposed vegetation. The deposit is purely cohesive in nature having stiff consistency in general. Plasticity of soil is high. As per I.S. Classification, it may be denoted as CH-OH. The relevant engineering properties of soil as obtained from selective tests are given below: Properties / Parameters Value Range Average Field N Value 14 to Corrected N Value N. A. N. A. Bulk Density (t/m 3 ) 1.94 to Natural Moisture Content (%) 27 to Dry Density (t/m 3 ) 1.51 to Liquid Limit (%) 57 to Plastic Limit (%) 22 to Plasticity Index (%) 35 to Cohesion from UU Test (t/m 2 ) 6.7* 6.7* Angle of internal friction from UU Test Cohesion from UC Test (t/m 2 ) 5.8* 5.8* Specific Gravity 2.64* 2.64* Initial Void Ratio 0.695* 0.695* * * Co-efficient of Pressure * * Volume Decrease, m v Range * * (cm 2 /kg) (kg/cm 2 ) * * * * Gravel (%) 0 0 Grain Size Sand (%) 1 to 7 4 Silt (%) 48 to Clay (%) 37 to NOTE : i) N. A. indicates Not Applicable, ii) UU indicates Unconsolidated Undrained, iii) CU indicates Consolidated Undrained, iv) DS indicates Direct Shear, v) CD indicates Consolidated Drained, vi) N. P. indicates Non-Plastic, vii) *value of any soil parameter indicates solitary value available of that parameter.

15 PEC ENGINEERS & ASSOCIATES 12 6 DISCUSSION ON SUITABLE FOUNDATIONS FOR THE PROPOSED PROJECT : 6.1 SUITABLE FOUNDATION FOR THE 12-STOREY MAIN BUILDING: Considering the sub-soil conditions vis-a-vis the expected column loads for the proposed 12-storey high main building, R.C.C. Bored Cast-in-Situ piles are considered to provide the most suitable foundation system in the present case. Pile Diameter : 600 mm, 750 mm, 800 mm & 1000 mm dia. piles are considered for calculation. Generalized Sub-soil Profile : As seen from the bore hole studies, there are major variations in soil stratification particularly those identified between B.H. 1 and the rest. Moreover, strata thicknesses and values of relevant engineering properties of soil between the bore holes also vary. Therefore, it is of prime importance to choose the soil stratification and design parameters of each stratum in such a way that the piles will be reasonably safe giving due consideration to the constraints and limitations of the present investigation as well as the worst conditions of the sub-soil as envisaged in it. Keeping this in mind, a generalized subsoil profile with soil properties is thought of, based on which calculation for pile capacity is made and the same is shown in Fig. 1 in page no. 14. Cut-off Level of Pile : Cut-off Level of piles is considered at 1.5 m below E.G.L., which is more or less even at the boring locations and elsewhere at the site. Tip Level of Pile : Examining the sub-soil stratifications and conditions as obtained from bore hole studies and keeping in mind various other factors relating to design and cost, piles may be considered to rest on stratum-vi which consists of silty fine sand/fine sand with medium dense to dense compactness. Thus, Tip Level of piles is considered at 27.0 m below E.G.L. Pile Shaft Length : From the above considerations of cut-off level and tip level of pile, pile shaft length becomes 27.0 m 1.5 m = 25.5 m

16 PEC ENGINEERS & ASSOCIATES 13 E.G.L. STRATUM-I Filled-up / Top Soil : Silty Clay γ = 1.85 t/m m CUT-OFF LEVL 1.5 m 3.0 m STRATUM-II Medium to Stiff Silty Clay, occasionally with lenses of silt and traces of decomposed vegetation C u = 4.0 t/m 2, φ u 0 0, γ = 1.90 t/m 3, Avg. N = 5 α = m 6.0 m 7.0 m STRATUM-III Soft to Medium Silty Clay / Clayey Silt with decomposed vegetation scatteredly present C u = 3.0 t/m 2, φ u 0 0, γ = 1.85 t/m 3, Avg. N = 4 α = 1.0 STRATUM-IV Stiff Silty Clay with calcareous nodules and occasional lenses of sand C u = 9.0 t/m 2, φ u = 0 0, γ = 2.0 t/m 3, Avg. N = 15 α = 0.48 STRATUM-VA Medium Dense Sandy Silt / Silty Fine Sand with admixture of clay C d Nil, φ d = 30 0, γ = 1.85 t/m 3, Avg. N = 16 (field) and 12 (corrected) k = 1.0, δ = 27 0 P I L E S H A F T 25.5 m STRATUM-VI Medium Dense to Dense Silty Fine Sand with mica in traces γ = 1.87 t/m 3. Overall, Avg. N = 39 (field), 20 (corrected) Consider for present calculation, Avg. corrected N = 17, Accordingly, Take: C d = nil, φ d = 32 0, δ = 29 0, k = 1.0 N q = 20 PILE TIP LEVEL 2.0 m 12.5 m 10.5 m STRATUM-VII Stiff Silty Clay, occasionally with lenses of silt and decomposed vegetation. C u 6.3 t/m 2, φ u 0 0, γ = 1.95 t/m 3, Avg. N = 19 Fig. 1 : Generalised Sub-soil Profile for calculation of pile capacities

17 PEC ENGINEERS & ASSOCIATES 14 Methods for determination of Pile Capacities : Vertical capacities of piles in compression are determined using the Static Capacity formula given in IS:2911(Part-1/Sec. 2) Accordingly, Ultimate Skin Friction (Q fu ) and End Bearing (Q bu ) are found out as, Q fu = α.c.a s + k.p D.tanδ.A s Q bu = N c.c p.a p + P D.N q.a p (neglecting N γ -term), where N c is usually taken as 9.0 Factor of safety considered = 2.5 Safe Horizontal Capacity of pile is calculated following the method given in Annex C of the above mentioned code. It is to be noted here that the capacities thus calculated are only tentative and one must get himself satisfied with the actual capacity at field with proper load test as per the latest revision of IS:2911(Part IV). Sample Calculations of Pile Capacities for 600 mm dia. R.C.C. Bored Castin-Situ Pile x 25.5 shaft length: Vertical Capacity in compression : Referring to Fig. 1 in the previous page, embedment of pile shaft (i) in strata-ii = 3.0 m (ii) in stratum-iii = 7.5 m (iii) in stratum-iv = 6.0 m (iv) in stratum-va = 7.0 m (v) in stratum-vi = 2.0 m Skin Friction in Stratum-II : (Q fu ) II = α.c.a s = 1.0 x 4.0 x π x 0.60 x 3.0 = 22.6 ton Skin Friction in Stratum-III : (Q fu ) III = α.c.a s = 1.0 x 3.0 x π x 0.60 x 7.5 = 42.4 ton Skin Friction in Stratum-IV : (Q fu ) IV = α.c.a s = 0.48 x 9.0 x π x 0.60 x 6.0 = 48.9 ton Skin Friction in Stratum-VA : Critical Depth, D c corresponding to φ = 30 0 is 15D = 15 x 0.6 = 9.0 m

18 PEC ENGINEERS & ASSOCIATES 15 Consider water level at G.L. for the worst case. Maximum effective overburden pressure calculated from C.O.L. and corresponding to D c = 9.0 m is (P Dmax ) VA = 3.0 x ( ) x ( ) = 7.80 t/m 2 Therefore, (Q fu ) VA = k.p D.tanδ.A s = 1.0 x 7.80 x tan27 0 x π x 0.60 x 7.0 = 52.4 ton Skin Friction in Stratum-VI : Critical Depth, D c corresponding to φ = 32 0 is 16D = 16 x 0.6 = 9.6 m Maximum effective overburden pressure calculated from C.O.L. and corresponding to D c = 9.6 m is (P Dmax ) VI = 3.0 x ( ) x ( ) = 8.31 t/m 2 Therefore, (Q fu ) VI = k.p D.tanδ.A s = 1.0 x 8.31 x tan29 0 x π x 0.60 x 2.0 = 17.4 ton Therefore, total Ultimate Skin Friction, Q fu = = ton End Bearing in Stratum-VI : Referring to Fig. 1 in page 13, the weaker layer, stratum-vii lies 10.5 m below pile tip. According to Tomlinson, the full value of end bearing in stratum-vi should be taken if the weaker layer exists at least 10D = 10 x 0.6 = 6.0 m below pile tip. Thus, unit end bearing capacity in stratum-vi = (P Dmax ) VI.N q = 8.31 x 20 = t/m 2 Therefore, (Q bu ) VI = x A p = x (π/4) x (0.60) 2 = 47.0 ton Total Capacity : Total ultimate capacity in Skin Friction and End Bearing, Q u = = ton Take Factor of Safety = 2.5 Safe capacity in compression = 230.7/ ton Horizontal Capacity : Consider : i) Grade of concrete : M35 ii) Nature of soil offering resistance: Mainly medium silty clay / clayey silt in strata-ii and III iii) iv) Head Condition: Restrained Free length of pile over ground: Nil E of pile concrete = 5000 f ck = 5000 x 35 = MN/m 2 I of pile cross section (only concrete) = (π/64) x (0.60) x 10-3 m 4. Considering the clayey soil as normally consolidated,

19 PEC ENGINEERS & ASSOCIATES 16 Stiffness factor, T = (EI/η h ) 1/5 = (29580 x x 10-3 /0.75) 1/5 = m (in absence of η h value in the code, the same has been taken from the book named Theory and Practice of Foundation Design by N. N. Som & S. C. Das) 4T = 4 x = m < 25.5 m (shaft length) Therefore, the pile will act as Long (Elastic) Pile. e = L 1 = 0. L 1 /T = 0. Correspondingly, L f /T = 2.2. L f = Z f = 2.2 x m Now, applying formula given in the code, horizontal load causing a deflection of 5 mm is found out as Q = 5 x (12 x x 10 3 x x 10-3 ) / {( ) 3 x 10 3 } = kn 3.93 ton In the present case, reduction factor for moment, m = Moment induced in pile, M = 0.83 x 3.93 x ( )/ Ton m It is to be noted here that in finding out the horizontal capacity, no contribution of reinforcing steel towards the Moment of Inertia of pile, I has been considered. This factor will certainly influence deflection of pile under horizontal load. Settlement of Pile Group consisting of 6 nos. 800 mm dia. Bored Piles : Settlement is calculated by the method given in the book Foundation Design and Construction by M. J. Tomlinson (ELBS sixth edition, 1995 : page ) Let, arrangement of piles in the group be 2 rows of 3 piles each. Considering pile spacing = 3D c/c, outer dimensions of pile group are L= 2 x 3 x = 5.6 m B = 3 x = 3.2 m Embedment of pile shaft in stratum-vi = 2.0 m By 4(vertical) : 1 (horizontal) load dispersion from top of stratum-vi, size of equivalent raft is L R = {2 x 2 x 2.0/(3 x 4)} 6.3 m, B R = {2 x 2 x 2.0/(3 x 4)} 3.9 m Total load of group, Q = 6 x 157 = 942 ton Pressure below equivalent raft = 942/(6.3 x 3.9) = t/m 2 Extent of pressure bulb below equivalent raft = 2 x 3.9 = 7.8 m Thickness of stratum-vi below raft = (2.0/3) = m settlement will occur in stratum-vi only which will be immediate in nature. Immediate settlement in stratum-vi Consider corrected N within the stress-influence zone (Pressure Bulb) below raft = 20 Elastic modulus, E = N (after D Appolonia) = x 20 = 440 kg/cm 2 Influence factor, I f = 1.40.

20 PEC ENGINEERS & ASSOCIATES 17 Fox s correction factor for depth = 0.55 Poisson s ratio of sandy soil = 0.3 Therefore, corrected immediate settlement of the group in stratum-vi, (S i ) VI = {p x B x (1 - µ 2 ) x I p /E} x correction factor = {3.834 x 390 x ( ) x 1.40/440} x 0.55 = 2.38 cm Therefore, estimated settlement of the group, S = 2.38 cm 24 mm Summary of Pile Capacities : Vertical capacities in compression and horizontal capacities as calculated based on formula given in IS:2911 (Part-1/Sec. 2) 2010 for R.C.C. Bored Cast-in-situ piles of various dia. considered suitable in the present context are shown in Table-1 below. Table-1: Summary of R.C.C. Bored Cast-in-situ Pile Foundation Vertical Capacity under compression Horizontal Capacity Dia. of Pile (mm) Cut-off Level (C.O.L.) below EGL in m Pile Tip Level below EGL in m Pile Shaft Length (m) Type of Pile Ultimate Skin Friction (ton) Ultimate End Bearing (ton) Total Ultimate Capacity )ton) Overall Factor of Safety Safe Capacity (ton) Grade of Concrete = M35 Safe Horizontal Load at C.O.L. for a deflection of 5 mm (ton) Moment induced in pile due to the Safe Horizontal Load (ton m) Bored Cast-insitu Bored Cast-insitu Bored Cast-insitu Bored Cast-insitu NOTE : Above pile capacities are tentative. These must be ratified at field by proper load tests as per the latest revision of IS:2911(Part IV).

21 PEC ENGINEERS & ASSOCIATES SHALLOW FOUNDATION : For buildings and structures, if any, imposing much lighter loads on the sub-soil than the main building, shallow foundation in the form of isolated and / or continuous strip footings may be thought of as the effective foundation system. Footings are considered to be placed on stratum-ii at 1.50 m below E.G.L. and the calculations are based on the generalized sub-soil profile as shown in Fig. 2 below. E. G. L. FOUNDING LEVEL 1.5 m Stratum-I Filled-up / Top Soil : Silty Clay. γ = 1.85 t/m m 7.5 m Stratum-II Medium to Stiff Silty Clay, occasionally with lenses of silt and traces of decomposed vegetation. C U = 3.5 t/m 2, φ U 0 0 γ = 1.88 t/m 3 m V = cm 2 /kg E = 210 kg/cm 2 µ = 0.50 Stratum-III Soft to Medium Silty Clay / Clayey Silt with decomposed scatteredly present. C = 3.0 t/m 2, φ U 0 0 γ = 1.85 t/m 3 m V = 0.05 cm 2 /kg E = 180 kg/cm 2 µ = 0.5 Fig. 2: Generalized Sub-soil Profile and Properties for calculation of bearing capacity and settlement of shallow foundation Bearing Capacity : Referring to IS : , ultimate net bearing capacity, q d (for φ = 0) of soil in stratum- II is given by, q d = C.N C.S C.d C.i C (i)

22 PEC ENGINEERS & ASSOCIATES 19 Where, C = Cohesion of soil in stratum-ii, N C = Bearing Capacity Factor and found out from table 1 of IS : , S C = Shape Factor and found out from table 2 of IS : , d C = Depth Factor and found out from Clause of IS : , S C = Inclination Factor and found out from Cl. : of IS : Now, for the present case, taking cohesion of soil in stratum II, C = 3.5 t/m 2 and using the above formula (i), ultimate and safe net bearing capacities for a few representative sizes of square, rectangular and strip footings are calculated and shown in Table-2 in the next page. Sample calculations are also given following the table, which will come handy for the designer to calculate safe net bearing capacity for any other size of footing not given in the said Table. Settlement : Referring to IS : 8009 (Part I) 1976, settlement is first calculated for pressure p. This settlement is then equated to the permissible settlement of 75 mm to find out p. Pressure bulb is considered to extend up to 2 x width of foundation below bottom of footing. Referring to Fig. 2 in page no. 18, it is seen that pressure bulbs for the sizes of footings considered will either remain within stratum-ii or will penetrate into stratum-iii causing settlements in those strata. Deposits in strata-ii & III being cohesive and plastic in nature, settlements in these strata will be mainly due long-term consolidation of soil. However, there will also be some immediate settlements on application of load which are to be considered as well. Immediate settlements in strata-ii & III are calculated by the formula, S i = p x B x (1 - µ 2 ) x I p /E (ii) Where, p = Pressure from footing at founding level, B = Width of footing, µ = Poisson s Ratio of soil, I p = Influence Factor, E = Elastic Modulus of soil Consolidation settlements in strata-ii & III are calculated by the formula, S c = m v x p x H (iii) Where, m v = Co-efficient of Volume Decrease of Soil, p = Increase in load intensity at H/2 due to superimposed load, H = Thickness of soil layer under compression.

23 PEC ENGINEERS & ASSOCIATES 20 Calculated values of settlements of footings corresponding to pressure equal to the respective safe net bearing capacity and allowable net bearing pressures satisfying both shear failure and permissible settlement criteria for a few representative sizes of square, rectangular and strip footings are shown in Table-2 below. Sample calculations are also given following the table, which will come handy for the designer to calculate settlement for any other size of footing not given in the said Table. TABLE-2 : Summary of Shallow Foundations Type of Footing Size of Footing (m) Depth of Foundation Ultimate Net Bearing Capacity in t / m 2 Factor of Safety Safe Net Bearing Capacity (SNBC) in t / m 2 Settlement for pressure = SNBC in mm permissible settlement considered in mm Allowable Net Bearing Pressure to be applied at founding level (ANBP) in t / m 2 Square Rectangular Continuous Strip 1.5 x x m x 2.5 below x 3.0 EGL x x x m below 2.5 x 3.0 EGL x B = B = m below B = 2.5 EGL B = Sample Calculation of Safe Net Bearing Capacity : Consider, i) Depth of foundation, D f = 1.5 m below E.G.L. ii) Design value of cohesion in stratum-ii, C U = 3.5 t/m 2 iii) Design value of angle of internal friction in stratum-ii, φ U = Nil

24 PEC ENGINEERS & ASSOCIATES 21 1) Case I : Square Footing Take, size = 2.0 m x 2.0 m N c = 5.14; S c = 1.3 For φ = 0 0, d c = 1 + [0.2D f x tan(45 0 +φ/2)]/b = 1 + (0.2 x 1.5 x tan45 0 )/2.0 = 1.15 i c = 1.0 (for vertical loading) Therefore, q d = 3.5 x 5.14 x 1.3 x 1.15 x 1.0 = t/m 2 Applying a factor of safety of 2.5, Safe net bearing capacity, q a = 26.89/ t/m 2 2) Case II : Rectangular Footing Take, size = 2.0 m x 2.5 m S C = B/L = x 2.0/2.5 = 1.16 As stated in the previous case, N c = 5.14; d c = 1.15 and i c = 1.0 Therefore, q d = 3.5 x 5.14 x 1.16 x 1.15 x 1.0 = 24.0 t/m 2 Applying a factor of safety of 2.5, Safe net bearing capacity, q a = 24.0/ t/m 2 3) Case III : Strip Footing Take, width = 2.0 m Here, S C = 1.0 and all other parameters remain the same as before. Therefore, q d = 3.5 x 5.14 x 1.0 x 1.15 x 1.0 = t/m 2 Applying a factor of safety of 2.5, Safe net bearing capacity, q a = 20.69/2.5 = 8.3 t/m 2 Sample Calculation for Settlement and Allowable Net Bearing Pressure : Consider, i) Depth of foundation, D f = 1.5 m below E.G.L. ii) Coefficients of Volume Decrease of Soil, m v is cm 2 /kg in stratum-ii and 0.05 cm 2 /kg in stratum-iii for appropriate pressure ranges. iii) Elastic Modulus, E of soil is 210 kg/cm 2 in stratum-ii and 180 kg/cm 2 in stratum-iii iv) Extent of pressure bulb = 2B below foundation v) Net pressure imposed at founding level = p kg / cm 2 vi) Pressure distribution below footing as per 2 : 1 method vii) Refer to Fig. 2 in page no. 18

25 PEC ENGINEERS & ASSOCIATES 22 1) Case I : Square Footing Take, size = 2.0 m x 2.0 m Pressure bulb extends up to 2 x 2.0 = 4.0 m below founding level. Immediate Settlement in strata-ii & III Let, Net pressure at founding level = p kg/cm 2 Poisson s ratio of soil, µ = 0.5 Influence Factor, I p = 1.12 Compressible thickness is 3.0 m in stratum-ii and ( ) = 1.0 m in stratum-iii Weighted average of Elastic Modulus of soil in strata-ii & III, E = (210 x x 1.0)/4.0 = kg/cm 2 Fox s correction factor for depth (considering flexible footing) = 0.78 Corrected immediate settlement in strata-ii & III, (S i ) II-III = {p x B x (1 - µ 2 ) x I p /E} x Fox s correction factor = {p x 200 x ( ) x 1.12/202.5} x 0.78 = 0.647p cm Consolidation Settlement in stratum-ii Compressible thickness in stratum-ii, H II = 3.0 m = 300 cm Considering 2 : 1 pressure distribution, Increase in pressure at middle of compressible thickness H II p II = p x / ( ) 2 = 0.327p kg/cm 2 Take, Fox s correction factor for depth = 0.78 pore water pressure correction factor = 0.85 Therefore, corrected consolidation settlement in stratum-ii, (S c ) II = x 0.327p x 300 x 0.78 x 0.85 = 2.927p cm Consolidation Settlement in stratum-iii Compressible thickness in stratum-iii, H III = = 1.0 m = 100 cm Considering 2 : 1 pressure distribution, Increase in pressure at middle of compressible thickness H III, p III = p x / ( ) 2 = 0.132p kg/cm 2 Fox s correction factor for depth = 0.78 Pore water pressure correction factor = 0.85

26 PEC ENGINEERS & ASSOCIATES 23 Therefore, corrected consolidation settlement in stratum-iii, (S c ) III = 0.05 x 0.132p x 100 x 0.78 x 0.85 = 0.438p cm Total Settlement Therefore, total settlement, S = (S i ) II-III + (S c ) II + (S c ) III = 0.647p p p = 4.012p cm Settlement for a pressure equal to safe net bearing capacity, i.e., 10.8 t/m 2 = x cm = 43 mm Allowable Net Bearing Pressure to be considered for design It is seen from above that a pressure = safe net bearing capacity of soil = 10.8 t/m 2 causes settlement of 43 mm which is within permissible limit of 75 mm. Therefore, considering both bearing capacity and permissible settlement criteria, Allowable Net Bearing Pressure that can be applied at the founding level = 10.8 t/m 2 2) Case II : Rectangular Footing Take, size = 2.0 m x 2.5 m Pressure bulb extends up to 2 x 2.0 = 4.0 m below founding level. Immediate Settlement in strata-ii & III Let, Net pressure at founding level = p kg/cm 2 Poisson s ratio of soil, µ = 0.5 Influence Factor, I p = 1.24 Weighted average of Elastic Modulus of soil in strata-ii & III, E = kg/cm 2 Fox s correction factor for depth (considering flexible footing) = 0.79 Corrected immediate settlement in strata-ii & III, (S i ) II-III = {p x B x (1 - µ 2 ) x I p /E} x Fox s correction factor = {p x 200 x ( ) x 1.24/202.5} x 0.79 = 0.726p cm Consolidation Settlement in stratum-ii Compressible thickness in stratum-ii, H II = 300 cm Increase in pressure at middle of compressible thickness H II p II = p x 2.0 x 2.5 / {( ) x ( )} = 0.357p kg/cm 2 Fox s correction factor for depth = 0.79 Pore water pressure correction factor = 0.85 Therefore, corrected consolidation settlement in stratum-ii,

27 PEC ENGINEERS & ASSOCIATES 24 (S c ) II = x 0.357p x 300 x 0.79 x 0.85 = 3.236p cm Consolidation Settlement in stratum-iii Compressible thickness in stratum-iii, H III = 100 cm Increase in pressure at middle of compressible thickness H III, p III = p x 2.0 x 2.5 / {( ) x ( )} = 0.152p kg/cm 2 Fox s correction factor for depth = 0.79 Pore water pressure correction factor = 0.85 Therefore, corrected consolidation settlement in stratum-iii, (S c ) III = 0.05 x 0.151p x 100 x 0.79 x 0.85 = 0.510p cm Total Settlement Therefore, total settlement, S = (S i ) II-III + (S c ) II + (S c ) III = 0.726p p p = 4.472p cm Settlement for a pressure equal to safe net bearing capacity, i.e., 9.6 t/m 2 = x cm = 43 mm Allowable Net Bearing Pressure to be considered for design It is seen from above that a pressure = safe net bearing capacity of soil = 9.6 t/m 2 causes settlement of 43 mm which is within permissible limit of 75 mm. Therefore, considering both bearing capacity and permissible settlement criteria, Allowable Net Bearing Pressure that can be applied at the founding level = 9.6 t/m 2 2) Case III : Strip Footing Take, width = 2.0 m Pressure bulb extends up to 2 x 2.0 = 4.0 m below founding level. Immediate Settlement in strata-ii & III Let, Net pressure at founding level = p kg/cm 2 Poisson s ratio of soil, µ = 0.5 Influence Factor, I p = 2.52 Weighted average of Elastic Modulus of soil in strata-ii & III, E = kg/cm 2 Considering the footing as rigid, rigidity correction factor = 0.8 Corrected immediate settlement in strata-ii & III,

28 PEC ENGINEERS & ASSOCIATES 25 (S i ) II-III = {p x B x (1 - µ 2 ) x I p /E} x rigidity correction factor = {p x 200 x ( ) x 2.52/202.5} x 0.8 = 1.493p cm Consolidation Settlement in stratum-ii Compressible thickness in stratum-ii, H II = 300 cm Increase in pressure at middle of compressible thickness H II p II = p x 2.0 / ( ) = 0.571p kg/cm 2 Rigidity correction factor = 0.8 Pore water pressure correction factor = 0.85 Therefore, corrected consolidation settlement in stratum-ii, (S c ) II = x 0.571p x 300 x 0.8 x 0.85 = 5.242p cm Consolidation Settlement in stratum-iii Compressible thickness in stratum-iii, H III = 100 cm Increase in pressure at middle of compressible thickness H III, p III = p x 2.0 / ( ) = 0.364p kg/cm 2 Rigidity correction factor = 0.8 Pore water pressure correction factor = 0.85 Therefore, corrected consolidation settlement in stratum-iii, (S c ) III = 0.05 x 0.364p x 100 x 0.8 x 0.85 = 1.238p cm Total Settlement Therefore, total settlement, S = (S i ) II-III + (S c ) II + (S c ) III = 1.493p p p = 7.973p cm Settlement for a pressure equal to safe net bearing capacity, i.e., 8.3 t/m 2 = x cm = 66 mm Allowable Net Bearing Pressure to be considered for design It is seen from above that a pressure = safe net bearing capacity of soil = 8.3 t/m 2 causes settlement of 66 mm which is within permissible limit of 75 mm. Therefore, considering both bearing capacity and permissible settlement criteria, Allowable Net Bearing Pressure that can be applied at the founding level = 8.3 t/m 2

29 PEC ENGINEERS & ASSOCIATES 26 7 RECOMMENDATION AND CONCLUDING REMARKS : (i) For the main 12-storey building, R.C.C. Bored Cast-in-situ Piles have been discussed in this report. Diameters of piles have been chosen considering appropriateness and suitability from expected design loads as well as construction points of view. Cut-off level of piles has been considered at 1.5 m below E.G.L. and the pile tips have been considered to rest on medium dense to dense silty fine sand in stratum-vi at 27.0 m below E.G.L. Safe vertical (in compression) and horizontal capacities of 600 mm, 750 mm, 800 mm and 000 mm nominal dia. piles are presented in Table-1 in page no. 17 following which are given the sample calculations as reference for any further modifications of pile dia. and / or pile shaft length to arrive at suitable design capacities. However, these capacities calculated are only tentative and may not tally with the actual capacities at field because they are not only based on generalized subsoil conditions determined from bore hole studies at only four points, some aspects of their construction, such as quality of workmanship, methodology and equipment used in construction and the level of supervision also greatly influence the performance of piles at field. Hence, the theoretical capacities must be ratified by proper load tests as per the latest revision of IS:2911(Part IV). Grade of concrete in pile has been considered as M35 for calculating horizontal capacity. (ii) For lightly loaded structures, if any, shallow foundation may be provided and it is considered to rest on stratum-ii at 1.5 m below E.G.L. Table-2 in page no. 20 shows calculated values of Allowable Net Bearing pressure satisfying both shear failure and assumed permissible settlement of 75 mm for a few representative sizes of square, rectangular and strip footings. Sample calculations are also presented following Table-2, which the designer may refer to in order to calculate allowable net bearing pressure for any other size of footing not given in Table-2 and also corresponding to any value of settlement he may allow for the proposed structure(s). Preferably, tie beams may be provided between footings and they should also be designed for, besides any other load, probable differential settlements of those footings. Shallow foundations can, under no circumstances, be placed on filling or loose soil deposits. In any case, if such deposits are encountered at the proposed founding level of footings, i.e., 1.5 m below E.G.L., the same shall be removed completely till the virgin soil is reached and the area up to the founding level shall be back-filled by properly compacted sand. A suitable guard wall shall be provided along the periphery of the sand-fill which will extend horizontally at least 0.5B beyond the sides of footing all around.

30 PEC ENGINEERS & ASSOCIATES 27 (iii) All works relating to construction of foundation shall be done as per specifications laid down in relevant IS codes and / or in any other literature(s) published in standard and accepted books/journal/manual under strict and thorough supervision of competent technical personnel. For PEC Engineers & Associates (S. Nath) BCE, MIGS, MIE, C. Eng. (I)

31 B. ANNEXURE

32

33 PEC ENGINEERS & ASSOCIATES BORE LOG DATA SHEET : LAND / MARINE SHEET NO. A-2 PROJECT : SUB-SOIL INVESTIGATION WORK FOR THE PROPOSED NEW HAJ TOWER COMPLEX AT REVISED CHANGED SITE ON PLOT NO. IIA / 26 OF RAJARHAT NEW TOWN, KOLKATA. B.H. NO. 1 FIELD TEST NOS. SAMPLES NOS. TYPE OF BORING PENETROMETER UNDISTURBED (U) 5 BORING ROTARY (SPT) AUGER SHELL 2. DISTURBED WASH VANE SHEAR (V) - a) PENETROMETER (P) 22 DIA (MM) b) OTHERS (D) 2 DEPTH (M) COMMENCED ON : 26/11/2012 COMPLETED ON : 29/11/2012 STANDING WATER LEVEL 4.80 M below E.G.L. GROUND R.L. : 99.5 M (approx.) (w.r.t. TBM-1 marked in the Survey Drawing) DESCRIPTION Filled up/top Soil : brownish grey silty clay with rusty brown spots Greyish brown/ brownish grey medium to stiff silty clay with lenses of silt Grey soft to medium silty clay / clayey silt with decomposed vegetation present scatteredly. Bluish grey / mottled brown & bluish grey stiff silty clay with calcareous nodules and occasional lenses of sand. Greyish brown medium dense clayey sand Grey medium dense to dense silty fine sand with mica in traces Grey stiff silty clay, occasionally with lenses of silt and decomposed vegetation STRATUM I II III IV V VI VII I.S. CLASSI- FICATION CH - CI CH - OH CH SC SM CH - OH DEPTH (M) THICK- SAMPLES N NESS FROM TO VALUE REF. NO. DEPTH (M) (M) 0.00 D D U P (Up to End of B.H.) U2 P2 P3 U3 P4 P5 U4 P6 P7 U5 P8 P9 P10 P11 P12 P13 P14 P15 P16 P17 P18 P19 P20 P21 P BORE-HOLE TERMINATED AT M DEPTH

34 PEC ENGINEERS & ASSOCIATES BORE LOG DATA SHEET : LAND / MARINE SHEET NO. A-3 PROJECT : SUB-SOIL INVESTIGATION WORK FOR THE PROPOSED NEW HAJ TOWER COMPLEX AT REVISED CHANGED SITE ON PLOT NO. IIA / 26 OF RAJARHAT NEW TOWN, KOLKATA. B.H. NO. 2 FIELD TEST NOS. SAMPLES NOS. TYPE OF BORING PENETROMETER UNDISTURBED (U) 5 BORING ROTARY (SPT) AUGER SHELL 2. DISTURBED WASH VANE SHEAR (V) - a) PENETROMETER (P) 22 DIA (MM) b) OTHERS (D) 1 DEPTH (M) COMMENCED ON : 29/12/2012 COMPLETED ON : 01/12/2012 STANDING WATER LEVEL 6.20 M below E.G.L. GROUND R.L. : 99.6 M (approx.) (w.r.t. TBM-1 marked in the Survey Drawing) DESCRIPTION Filled up/top Soil : brownish grey / grey silty clay with rusty brown spots Brownish grey / grey medium to stiff silty clay, occasionally with lenses of silt. Traces of decomposed vegetation found at m depth Grey loose to medium dense sandy silt / silty fine sand, sometimes with admixture of clay Grey medium dense to dense silty fine sand with mica in traces Grey stiff silty clay with decomposed vegetation STRATUM I II VA VI VII I.S. CLASSI- FICATION CH - CI ML - SM SM CH - OH DEPTH (M) THICK- SAMPLES N NESS FROM TO VALUE REF. NO. DEPTH (M) (M) 0.00 D P U P P (Up to End of B.H.) U2 P4 P5 P6 P7 P8 P9 U3 P10 P11 U4 P12 P13 P14 P15 P16 P17 P18 P19 P20 P21 P22 U BORE-HOLE TERMINATED AT M DEPTH