SUBSURFACE INVESTIGATIONS
CONTENTS CHAPTER 1 GEOTECHNICAL INVESTIGATIONS 1 1 INTRODUCTION 1 1 2 IMPORTANCE 2 1 2 1 IMPORTANCE ON ACCOUNT OF SAFETY 3 1 2 2 IMPORTANCE ON ACCOUNT OF ECONOMY 5 1 3 STAGES IN GEOTECHNICAL INVESTIGATION 6 1 3 1 GEOTECHNICAL INVESTIGATION DURING 7 RECONNAISSANCE SURVEY 1 3 2 PRELIMINARY GEOTECHNICAL INVESTIGATION 9 1 3 3 DETAILED GEOTECHNICAL INVESTIGATION 9 1 4 METHODS OF INVESTIGATION 10 1 4 1 OPEN TRIAL PITS 10 1 4 2 SUB SURFACE SOUNDING 11 1 4 3 EXPLORATORY BORING 11 1 5 INVESTIGATION SCHEME 15 1 5 1 DISPOSITION OF BORE HOLES TRIAL PITS 15 1 5 2 DEPTH OF EXPLORATION 16 1 5 3 WATER TABLE MONITORING 19 1 6 CORROSIVE SOILS WATER AND EFFLUENTS 20 1 7 COST OF THE GEOTECHNICAL INVESTIGATION 20 1 8 SUMMARY 21 CHAPTER 2 FIELD TESTING OF SOIL 2 1 INTRODUCTION 22 2 2 SUB SURFACE SOUNDING METHODS 23 2 2 1 STANDARD PENETRATION TEST SPT 23 2 2 2 STATIC CONE PENETRATION TEST PT SCPT 30 2 2 3 DYNAMIC CONE PENETRATION TEST DCPT 34 2 3 TEST FOR INDIRECT DETERMINATION OF SOIL STRENGTH 38 2 3 1 SAND REPLACEMENT METHOD 38 2 3 2 CORE CUTTER METHOD 43 2 4 TEST FOR DIRECT DETERMINATION OF SOIL STRENGTH 46 2 4 1 PLATE LOAD TEST 46 2 4 2 FIELD VANE SHEAR TEST 52 2 5 GEOPHYSICAL METHODS 59 CHAPTER 3 SOIL SAMPLING AND PREPARATION OF TEST SAMPLES 3 1 INTRODUCTION AND IMPORTANCE 65 3 2 TYPE OF SAMPLE 66 3 2 1 DISTURBED SAMPLE 66 3 2 2 DISTURBED BUT REPRESENTATIVE SAMPLE 67 3 2 3 UNDISTURBED SAMPLE 68 3 2 4 UNDISTURBED SAMPLING CRITERIA 69 3 3 SOIL SAMPLING DURING FIELD TESTING 70 3 3 1 IN OPEN PITS 70 3 3 2 DURING STANDARD PENETRATION TEST 72 3 4 SEALING OF SAMPLING TUBES 73 3 5 SAMPLE PREPARATION FOR VARIOUS LABORATORY TESTS 74 3 5 1 TEST SPECIMEN FROM UNDISTURBED SAMPLE 74 3 5 2 TEST SPECIMEN FROM DISTURBED SAMPLE 76 CHAPTER 4 DETERMINATION OF INDEX PROPERTIES OF SOIL 4 1 INTRODUCTION 78 4 2 WATER CONTENT DETERMINATION 78 4 2 1 WATER CONTENT DETERMINATION USING OVEN DRY METHOD 78 4 3 GRAIN SIZE ANALYSIS 80 4 3 1 DETERMINATION OF SPECIFIC GRAVITY 80 4 3 2 WET AND DRY SIEVE ANALYSIS 84 4 3 3 GRAIN SIZE DISTRIBUTION USING HYDROMETER 88 4 4 DETERMINATION OF ATTERBERG LIMITS 94 4 4 1 DETERMINATION OF LIQUID LIMIT 94 4 4 2 DETERMINATION OF PLASTIC LIMIT 98 4 5 TESTS FOR DENSITY DETERMINATION 101 4 5 1 STANDARD PROCTOR OR LIGHT COMPACTION TEST 101 4 5 2 MODIFIED PROCTOR OR HEAVY COMPACTION 105 4 5 3 RELATIVE DENSITY TEST 110 CHAPTER 5 TESTING FOR DETERMINATION OF ENGINEERING PROPERTIES OF SOIL 5 1 INTRODUCTION 115 5 2 LABORATORY TEST FOR DETERMINING THE 116 ENGINEERING PROPERTIES 5 2 1 DIRECT SHEAR TEST 116 5 2 2 TRIAXIAL TEST UNCONFINED COMPRESSIVE 124 STRENGTH UCS 5 2 3 TRIAXIAL TEST UNCONSOLIDATED 130 UNDRAINED UU 5 2 4 TRIAXIAL TEST CONSOLIDATED 137 UNDRAINED CU 5 2 5 TRIAXIAL TEST CONSOLIDATED DRAINED CD 142 5 2 6 LAB VANE SHEAR TEST 145 5 3 CALIFORNIA BEARING RATIO CBR TEST 150 5 4 TEST FOR SETTLEMENT ESTIMATION 158 5 4 1 CONSOLIDATION TEST OEDOMETER TEST 158 CHAPTER 6 TEST ON PROBLEMATIC TYPE OF SOIL 6 1 INTRODUCTION 168 6 2 PHYSICAL TESTS 168 6 2 1 FREE SWELL INDEX TEST 168 6 2 2 SWELL PRESSURE TEST 171 6 2 3 SHRINKAGE LIMIT TEST 176 6 3 OTHER TESTS 180 REFERENCES 181 CHAPTER 1 GEOTECHNICAL INVESTIGATIONS 1 1 INTRODUCTION GEOTECHNICAL INVESTIGATION IS A PREREQUISITE FOR ANY CIVIL ENGINEERING PROJECT AS IT PROVIDES SAFE ECONOMIC AND FEASIBLE METHOD OF CONSTRUCTION AS PER BS 5930 1981 THE OBJECTIVE OF GEOTECHNICAL INVESTIGATIONS ARE I SUITABILITY TO DETERMINE THE SUITABILITY OF THE SITE AND THE ENVIRONMENT FOR THE PROPOSED WORK II DESIGN TO ENABLE AN ADEQUATE AND ECONOMIC DESIGN INCLUDING TEMPORARY WORKS DESIGN WHICH CAN BE PROVIDED III CONSTRUCTION METHOD TO PLAN THE BEST CONSTRUCTION METHOD DEPENDING ON THE SOURCES OF MATERIALS WASTE IV EFFECT OF CHANGES TO DETERMINE THE CHANGES THAT WILL OCCUR IN THE SOIL AND SURROUNDING CIRCUMSTANCES EITHER NATURALLY OR BECAUSE OF WORK V SITE SELECTION WHEN THERE IS A SITE OPTION TO PROVIDE ADVICE AND GUIDANCE APART FROM ABOVE REQUIREMENT THERE ARE ENGINEERING TECHNICAL REQUIREMENTS ALSO THE TECHNICAL OBJECTIVE OF THE INVESTIGATIONS CAN BE DEFINED AS I DETERMINE THE SEQUENCE THICKNESS AND LATERAL EXTENT OF THE SOIL STRATA AND WHERE APPROPRIATE THE LEVEL OF BEDROCK II OBTAIN REPRESENTATIVE SAMPLES OF THE SOILS AND 1