LIQUEFACTION POTENTIAL INDEX OF SOIL STRATUM BASED ON GEOTECHNICAL AND GEOPHYSICAL INVESTIGATIONS

Abstract

Liquefaction potential assessment at Narora and two sites at Roorkee has been attempted using “the Simplified approach.” In doing this, three investigating approaches are considered and iteratively, two methods are used, including SPT, CPT and Shear wave velocity. This study aims to determine the Liquefaction Potential Index (LPI) and vulnerability assessment of these areas. Shear wave velocity (Vs) data has been collected using the Multi-channel Analysis of Surface Waves (MASW) method. To calculate CRR and CSR, the SPT, CPT and MASW profiles are used. Vulnerability parameters LPI and LPIISH are also evaluated considering the adopted approach. The LPI approach is based on the factor of safety (FS) to the depth and thickness of the liquefiable layers. Selected approaches (LPI and LPIISH) gave quantified results and are used for evaluating the severity of liquefaction. The LPI and LPIISH data obtained for these sites were compared and found that the Narora site is more vulnerable to PGA values greater than 0.24g for an earthquake with a moment magnitude of 7.5. The site at IIT Roorkee shows minor vulnerability for 0.36g with SPT data, but shear wave velocity shows severe liquefaction. However, at CBRI Roorkee, SPT results show minor to moderate manifestation, but MASW predicts none to minor vulnerability at 0.24g. Considering these results, it can be said that the PGA value, which is likely to be uncertain, plays a significant role in liquefactioninduced damage predictions. Among all, the Narora site is found to be the most vulnerable to liquefaction.