ABSTRACT
CONTENTS 2.1 Introduction to Subsurface Exploration........................................................................ 48
2.1.1 Preliminary Site Exploration............................................................................... 48 2.1.2 Site Exploration Plan............................................................................................ 49
2.1.2.1 Soil Boring............................................................................................... 49 2.2 Need for In Situ Testing................................................................................................... 53
2.2.1 Sample Disturbance.............................................................................................. 53 2.3 Geophysical Testing Methods ........................................................................................ 54
2.3.1 Ground Penetrating Radar .................................................................................. 54 2.3.2 Resistivity Tests..................................................................................................... 57
2.3.2.1 Seismic Refraction.................................................................................. 58 2.4 Physical Sampling and Penetration Tests..................................................................... 59
2.4.1 Standard Penetration Test ................................................................................... 59 2.4.1.1 SPT Correlations with Shear Strength Properties ............................ 59 2.4.1.2 Efficiency of Standard Penetration Testing ....................................... 62
2.4.2 In Situ Rock Testing.............................................................................................. 65 2.4.2.1 Timed Drilling ........................................................................................ 65 2.4.2.2 Coring Methods ..................................................................................... 65 2.4.2.3 In Situ Rock Strength Tests .................................................................. 67
2.5 Cone Penetration Test ...................................................................................................... 69 2.5.1 Cone Penetration Testing with Pore Pressure
Measurements (Piezocone)................................................................................ 73 2.6 The Field Vane Shear Test............................................................................................... 75 2.7 The Pressuremeter Test.................................................................................................... 75 2.8 The Dilatometer Test ........................................................................................................ 79
2.8.1 Measurement Procedure...................................................................................... 80 2.8.2 Determination of Foundation Design Parameters........................................... 81
2.9 California Bearing Ratio Test.......................................................................................... 82 2.10 Borehole Shear Test .......................................................................................................... 84
2.10.1 Test Procedure..................................................................................................... 84 References ..................................................................................................................................... 86
2.1.1 Preliminary Site Exploration
The designer of a super-structure foundation must invariably perform a detailed surface and subsurface (soil) exploration of the potential site prior to deciding on the nature and type of the foundation. The subsurface investigation program for a given site should account for the type, size, and importance of the proposed structure. These parameters help focus the design of the site exploration program by determining the quantity and depth of soil soundings (or borings) required. Planning for a site investigation should also include the location of underground utilities (i.e., phone, power, gas, etc.). As such, a local ‘‘call before you dig’’ service should be notified several days prior to the anticipated investigation. These services are usually subsidized by the various local utilities and have no associated cost.
