GEOTECHNICAL INVESTIGATION REPORT INFRASTRUCTURE PVT LTD

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1 GEOTECHNICAL INVESTIGATION REPORT Client : TAEIN CONSTRUCTION & INFRASTRUCTURE PVT LTD Office address : Flat No.104, A -Wing,1st floor,gloria Park, Paranjape Scheme, Bavdhan Khurd, Chandni Chowk, Pune ,Maharashtra,India Structure : Proposed Industrial Shed Architect. Structural Consultant : Page 2

2 CONTENTS Page No. 1.0 Introduction Scope for Geotechnical Assessment Investigation Procedure and Standard code Provisions Result of Investigation and Laboratory Testing Engineering Analysis Geotechnical Evaluation and Opinion Safe Bearing Capacity Location Plan Bore-Logs Lab test results 29 Page 3

3 Chapter 1 INTRODUCTION TAEIN CONSTRUCTION & INFRASTRUCTURE PVT LTD. is planning to execute proposed construction of Industrial Structure with ancillary structures at Mahad and entrusted geotechnical investigation work at the project location to, Pune by work order No.TSFIPL Dated.15 th Dec Geotechnical investigation work was envisaged to assess the subsoil strata from safe bearing capacity point of view and to establish subsoil profile at the project location. Site investigation in one form or the other is required for every engineering project. Information about the surface and subsurface features is essential for the design of structures and for planning construction techniques. As a statutory requirement, client decided to carry out geotechnical investigation. Geotechnical investigation work consists of drilling and sampling in nine boreholes at the project location. TM Engineering Services, Chinchwad, Pune carried out fieldwork during December Selected soil and rock samples were tested in laboratory of TM Engineering Services, Chinchwad, Pune. Laboratory test results were obtained on Jan 01, This report has been prepared by TM Engineering Services, Chinchwad, Pune. This geotechnical investigation report is based on the data collected from three boreholes and from laboratory results and judgment of undersigned based on his experience. Scope of this investigation report is limited Page 4

4 to assess subsoil strata from safe bearing capacity point of view. It does not include site visits by the undersigned to confirm any aspects during construction phase. Professional judgments and recommendations are presented in this report. They are based partly on evaluation of the technical information gathered, partly on historical reports and partly on our general experience with sub-surface condition in the area. We do not guarantee the performance of the project in any respect other than that our engineering work and the judgments rendered meet the standard and care of our profession. It should be noted that the boring/trial pits may not represent potentially unfavorable subsurface conditions between boring. If during construction soil conditions are encountered that very from those discussed in this report or historical reports of if design loads and/or configuration change, we should be notified immediately in order that we may evaluate effects, if any, on foundation performance. The recommendations presented in this report are applicable only to this specific site. These data should not be used for other purposes. Page 5

5 Chapter 2 SCOPE FOR GEOTECHNICAL ASSESSMENT The purpose of this evaluation was to assess subsurface conditions at the site and to provide geotechnical recommendations for project. Objective of the site investigation was to obtain the information that may be useful for one or more of the following purposes: 1. To select the type and depth of foundation for a given structure. 2. To determine the bearing capacity of soil/rock layer. 3. To establish the ground water level. 4. To select the suitable construction technique. 5. To predict potential foundation problems. 6. To ascertain the suitability of the soil as a construction material. 7. To collect and transport the selected samples of soil and rock in testing laboratory and conduct relevant tests to determine properties. 8. Recommendations for soil-related construction conditions such as site preparation, earthwork construction, excavation slopes, and difficult excavation. Geotechnical investigation for proposed project was carried out by drilling three boreholes to examine subsurface profile. Depth of borehole to be drilled was determined using IS: section The lateral extent of exploration and the spacing of borehole depends mainly on the variation of the strata in horizontal direction. Representative of client decided the number and indicated location of bore hole in the field. Page 6

6 The scope of services included a site reconnaissance, site soil test, borings and soil sampling, laboratory soil testing, engineering evaluation of the field test data, and preparation of this report. Specifically, the scope of our engineering work for this site was to provide the following: 1. Soil nature and origin, including changes resulting from man s activities. 2. Depths, thickness and composition of soil strata that will be appreciably stressed by the intended construction. 3. Depths to encountered groundwater, dense soil strata, and rock that could affect the proposed construction. Collect undisturbed soil samples from cohesive soil stratum. 4. Conduct standard penetration tests at an interval of 1.0 to 1.5 metres and collect disturbed soil samples. 5. To prepare a geotechnical investigation report by compiling data collected from field, boreholes and results of laboratory tests. The scope of this investigation report did not include an environmental assessment or investigation for the presence or absence of hazardous or toxic material in the soil or groundwater or surface water within or beyond the site. Any statements in this report or on the soil test, boring logs regarding odors, staining of soils, or other unusual conditions observed are strictly for the information of our client. Page 7

7 Chapter 3 INVESTIGATION PROCEDURE AND STANDARD CODE PROVISIONS PLANNING A subsurface exploration program depends upon the type of structure to be built and also upon variability of the strata at proposed site. Sub-surface explorations are generally carried out in three stages. A) Reconnaissance: Prior to our field exploration, TM engineer visually evaluated the site and surrounding areas. His observations were used in planning exploration, in determining area of special interest, and in relating site conditions to know geologic conditions in the proposed project area. Subsurface exploration programme includes visit to a site and study the map and other relevant records. The information about the following features is obtained: i) General topography of the site. ii) Existence of underground water mains, power conduits, etc. at the site. iii) Existence of settlement cracks in structure already builds near site. iv) The evidence of landslides, creep of slope and shrinkage cracks. v) The satisfaction of soil observed from deep cuts near the site. vi) Depth of ground water table as observed in wells and drainage pattern. vii) Type of vegetation existing at the site. B) Preliminary Exploration: The aim of a preliminary exploration is to determine the depth, thickness, extent and composition of each soil stratum at the site. The depth of bedrock and the ground water table is also determined. The preliminary explorations are generally in the form of trial pits. Trial pits were not considered for these sub-surface investigations. Page 8

8 TRIAL PIT Trial pits are excavated at the site to inspect the strata. The size of the pit should be sufficient to provide necessary working space. IS: recommends a clear working space of 1.2m X 1.2m at the bottom of the pit. The depth of the pit depends upon the requirement of the investigation. Shallow pits up to a depth of 3m can be made without providing any lateral support. For deeper pits especially below the ground water table the lateral support in the form of sheeting and bracing system is required. Tests pits can be excavated manually in vertical bands or by other appropriate methods so as to expose a clean face of rock or soil. Measurements should be taken and recorded documenting the orientation, plan dimension, depth of the pit, and thickness of each stratum exposed in the pit. Adequate precaution should be taken against possible accidents due to caving of the ground. C) Detail Exploration: The purpose of detail exploration is to determine engineering properties of soil in different strata. It includes an extensive boring program, sampling and testing. Field test such as vane shear test, SPT, PLT, Permeability test are conducted to determine properties of soil in natural state. The tests for the determination of dynamic properties are also carried out, if required. DRILLING Location of the borehole is indicated on the attached Borehole Location Plan in the Annexure 6.1. On site location of borehole was specified by client. The boring was performed to maximum depth of 10m below the existing ground surface elevations. For drilling rotary type drilling rig was used. Rig was coupled with diesel engine, tripod and all drilling accessories. Drilling rig have tripod with suitable arrangement for driving as well as extracting casing. It was also used for conducting Standard Penetration Test (SPT), collection of Undisturbed Soil Samples (UDS) and Disturbed or wash Soil Sample (DS). Page 9

9 Initially casing of adequate diameter to suit boring of 100 mm boreholes was lowered and boring was commenced, when rock was encountered, diameter of boreholes was changed to N x (76mm) diameter. A core barrel and N x sized bits are used for drilling and recovering rock cores. Recovered rock cores were numbered serially and preserved in good quality sturdy wooden core boxes. Rock core recovery (CR) and Ro ck Quality Designation (RQD) were computed for every run of length drilled. Rock samples have been selected for laboratory test based on the probable founding elevation of the proposed structure. Standard Penetration test and Soil Sampling All soil sampling and Standard Penetration Testing (SPT) was performed in general accordance with IS: and ASTM Standard D 1586 and D The soil borings were advanced by rotary drilling methods. At regular intervals (1 to 1.5m), soil samples were obtained w ith a standard split-spoon. Sampler was first seated 15cm and then driven an additional 30cm with blows of a 63.5 kg hammer falling a distance of 75cm. The number of blows required to drive the sampler the final 30cm was recorded and is designated the standard penetration resistance or N value. Because the sampler may be damaged by driving it 12 to 18 inches into very dense soils, it is driven a few inches into such materials and the penetration, e.g. 100/3, 50/1, etc. Penetration resistance, when properly evaluated, is an index of the soil s shear strength, density, and foundation support capability. SPT N values are correlated with the relative density of non-cohesive soils and consistency of saturated cohesive soils, as shown in Annexure 6.5. Ground Water Ground water table was observed after dewatering the boreholes by suitable method and waiting for time period of 24 hours to allow for recuperation of ground water. Ground water samples were collected for chemical analysis [IS: 3025 (Part 24 and 32)] to determine their ph, Sulphate and Chloride content. Page 10

10 This is useful to predict corrosive effect of ground water on structures. Classification of water samples is based on the following table. In this case sample of ground water was not encountered and hence not tested. Laboratory Tests Lab tests are conducted (as per relevant IS code) on soil and rock samples to determine their properties, which may be used for design and geotechnical evaluation. Sr. Test Description Relevant IS/ASTM code No. A Soil Test 1 LL and PL IS: 2720 (Part 5) 1985; ASTM D ph of soil IS: 2720 (Part 26) 1987; ASTM D Soluble Sulphate in soil IS: 2720 (Part 27) 1977; ASTM D Specific Gravity test IS: 2720 (Part 3) 1980; ASTM D854 5 Grain size analysis IS: 2720 (Part 4) 1985; ASTM D422 6 Relative density of sand IS: 2720 (Part 14) Permeability test IS: 2720 (Part 17) 1986; ASTM D Proctor density test IS: 2720 (Part 7) 1980; ASTM D698 9 Direct shear test IS: 2720 (Part 13) 1986; ASTM D Triaxial text IS: 2720 (Part 10, 11, 12) 1973; ASTM D Consolidation test IS: 2720 (Part 15) 1986; ASTM D2435 B Rock Tests 1 Water absorption ASTM D 2 Porosity ASTM D 3 Dry density ASTM D 4 Crushing strength (UCS) ASTM D Point load test ASTM D 6 Triaxial test ASTM D2664 Elastic Modulus of Rock ASTM D3148 Point load strength index is often used to predict uniaxial compressive strength. On average, uniaxial compressive strength is 20 to 25 times point load strength. However, the ratio can very between 15 and 50, especially for anisotropic rocks. Logging Procedures: In logging the exploration pit / boreholes, a vertical profile should be made parallel with one pit wall or boreholes. The contact between Page 11

11 geological units should be identified and drawn on the profile, and the units samples as recommended disturbed samples and IS: (sand), IS: (fine grained soil) for undisturbed samples. Characteristic and type of soil or lithologic contacts should be noted. Variation within the geologic unit must be described and identified, and indicated on the pit / borehole log wherever the variation occurs. The sample locations should be shown in the respective log and their location written on a sample tag showing the station location and elevation. Ground water should also be noted on the exploration pit / borehole log. Page 12

12 Chapter 4 RESULTS OF INVESTIGATION AND LABORATORY TESTING A preliminary site model was developed using the information obtained from existing data and the site visit. The model should be divided into zones of interest (i.e., geotechnical units) based on the necessary design parameters and objectives. This model will obviously change as results of the detailed investigation are collected. Following information was collected during the site reconnaissance stage. Sr. Checklist Item Sub-Item Description No. 1 Accessibility Easy 2 Visit to site Date and time December 16 Visitors Weather condition Temperature Sunny 3 Ground cover Silty sandy gravel 4 Existing Terrain Plain 5 Site hydrology Surface water None conditions Subsurface water Water loss 6 Site drainage.. 7 Soil and rock Surface soil Silty sandy gravel conditions Subsurface soil Weathered rock Rock features Weathering 8 Investigative Operation Drilling in nine borehole 9 Prior information Interviews with Client 10 Geological information NA Boreholes observations and laboratory testing results for proposed structure are presented in this section. Boreholes were drilled up to maximum 10m depth from the existing ground level. Fieldwork is summarized in the following table. Page 13

13 Table 4.1 Summary of Boreholes Bore Hole No. Occurrence of Rock Strata Final Depth of Borehole Ground Water Table (m) BH m 10.0m Water loss BH m 10.0m Water loss BH m 10.0m Water loss BH m 10.0m Water loss BH m 10.0m Water loss BH m 10.0m Water loss BH07 0.5m 10.0m Water loss BH m 10.0m Water loss BH m 10.0m Water loss Representative of client decided number of borehole and indicated location of bore hole in field. Borehole log for the site is given in Chapter 7. SUB SOIL PROFILE: Sub-soil conditions described below are based on drilling and sampling in a total of three boreholes at the proposed site. A generalized sub-soil profile at the project location is described in various layers as follows. In the table thickness of various layers encountered (in mts) along with SPT N or RQD range as the case may be is tabulated. Subsoil at the project site may not be in the same order as tabulated. Layer I: Silty sandy gravel Layer II: Completely weathered rock (Hard murum) Layer III: Highly weathered fractured amyloidal basalt Layer IV:Slightly weathered & slightly fractured basalt Page 14

14 Bore Layer I Layer II Layer 3 Layer 4 hole no Thick Thick Thick Thick BH BH BH BH BH BH BH BH BH GROUND WATER LEVEL: Water level was encountered in the borehole as tabulated. In case it is required to determine ground water level it is advised to install piezometers and monitor over long period of time. Ground water is considered at foundation depth for design calculations. Ground water shall be considered at ground surface for calculating uplift pressure on bottom of raft of basement. LABORATORY TESTING: Sub stratum is mainly consists of backfill and weathered basalt. On completion of drilling samples were sent to the laboratory for further testing. Samples were classified in the laboratory and representative samples were selected for testing. Following tests were performed. Unconfined Compression Test Dry Density Tests were performed as per relevant IS standards, latest revision. Page 15

15 ENGINEERING ANALYSIS: Engineering analysis of the subsoil was performed to determine net safe bearing capacity. Parameters obtained are based on various field and laboratory tests. Foundations shall be placed on weathered rock Allowable stress intensity is determined as per the procedure given in IS12070 Code of practice for Design and Construction of Shallow Foundations on Rock. The procedure is based on RMR (Rock Mass Rating) concept. RMR is calculated as per the method given in IS (Part 1) Quantit ative Classification System of Rock Mass. Determination of RMR takes into consideration following properties of rock stratum Strength of Intact rock material Rock Quality Designation Spacing of Discontinuities Condition of Discontinuities Ground water condition Orientation of Discontinuities Joint Orientation It is mentioned in IS that if net allowable bearing capacity is determined based on RMR settlement of raft foundation upto 6m thickness to be less than 12mm. It shall be noted that for foundations placed on rock IS code does not specify any limit on width of foundations, type of foundations. Also there is no specific reference to factor of safety against shear failure. Page 16

16 Chapter 5 GEOTECHNICAL EVALUATION AND OPINION Conclusions and Recommendations are based on following accepted norms. Foundations should not fail in shear. It is mentioned in IS that if net allowable bearing capacity is determined based on RMR settlement of raft foundation upto 6m thickness to be less than 12mm Net safe bearing capacity to be adopted for pad (spread foundations or raft) placed at different depths below the ground surface existing at the time of investigation is tabulated below. Exact foundation depth will depend on up lift forces on the foundations. Bore hole no Depth of foundation Net safe bearing capacity BH1 1.5m 30T/m 2 2.5m 35T/m 2 3.5m 40T/m 2 4.5m 45T/m 2 BH2 0.5m 25T/m 2 1.5m 30T/m2 2.5m 35T/m 2 3.5m 35T/m 2 4.5m 40T/m 2 BH3 1.5m 30T/m 2 2.5m 35T/m 2 3.5m 35T/m 2 4.5m 40T/m 2 BH m 25T/m2 1.5m 30T/m m 35T/m 2 BH m 0.5m 35T/m 2 25T/m2 1.5m 30T/m m 35T/m 2 Page 17

17 BH m 25T/m2 1.5m 30T/m m 35T/m 2 BH m 25T/m2 1.5m 30T/m m 35T/m 2 BH m 25T/m2 1.5m 30T/m m 35T/m 2 BH m 25T/m2 1.5m 30T/m m 35T/m 2 Whenever foundations are placed on rock, it is essential to ensure that there are no loose pockets on rock surface. In case of loose pockets or over excavation, it shall be filled by plain cement concrete. Constrologix takes this opportunity to thank staff of Taein Constructions Mahad for their cooperation and support during execution of this work. Shirish Joag M. Tech. (Geotech). FIIB, FIGS, FIIE Geotechnical Consultant Page 18

SITE INVESTIGATION 1

SITE INVESTIGATION 1 Definition The process of determining the layers of natural soil deposits that will underlie a proposed structure and their physical properties is generally referred to as site investigation.