Study of Shallow Soil Deposit in East Coast of India by SPT, MASW, and Crosshole Tests

Abstract

In this study, a geophysical investigation is performed in the coastal city of Tuticorin in Tamil Nadu, India, at a location approximately 1.5 km west of the east coast. Standard penetration test along with hammer energy measurement was performed for sample collection and topographic identification. Later, Crosshole (CHT) and Multichannel Analysis of Surface Waves (MASW) tests were conducted to obtain the distribution of shear (S-) wave velocities in the shallow subsurface. The S-wave velocity (VS) profiles were coherent with the borelog showing the gradual increase in the velocity values from gravelly silty sand at the top to weathered limestone at the bottom of boreholes. However, VS profiles obtained from CHT showed higher values than those obtained from MASW. These data was subsequently used in liquefaction potential estimation of shallow subsurface layers, which is predominantly silty sand submerged under shallow groundwater. It was observed from analysis using SPT data that the subsurface soil is liquefiable at the peak acceleration of 0.2 g. However, the same observation was not prominent when evaluated using VS. Thus, a more detailed survey to establish the liquefaction susceptibility of the subsurface is needed. This study highlights the importance of carrying out multiple tests to interpret geotechnical site conditions more accurately, which is not possible to obtain using only one type of test.KeywordsLiquefactionIn-situ testingShear wave velocity