Disaster Advances Vol. 15 (6) June (2022) 33 Liquefaction Potential of Sites in Kalyani Region based on Shear Wave Velocity Data Kumar Sajjan 1 , Muley Pradeep 1 * and Syed N.M. 2 1. Department of Civil Engineering, Madan Mohan Malaviya University of Technology Gorakhpur, INDIA 2. Department of Civil Engineering, MANUU, Bangalore, INDIA *pmce@mmmut.ac.in Abstract Liquefaction hazard is one of the most catastrophic effects of an earthquake. When dynamic loading occurs, saturated sandy soil in undrained conditions loses its shear strength due to the development of excess pore water pressure. Therefore, it is imperative to evaluate a site for its susceptibility to liquefaction. The main objective of the present study is to calculate the liquefaction potential of 6 sites in Kalyani region which are located at around 50 km from the City of Kolkata in the State of West Bengal, India. For this purpose, six bore locations are selected in the All India Institute of Medical Sciences, Kalyani, Kolkata Campus. The liquefaction potential of the site is calculated at all the six locations for an earthquake of magnitude 7.5 and peak ground acceleration (PGA) of 0.16 g. The water table is considered at the ground level. Liquefaction potential in terms of Factor of Safety against liquefaction is calculated with the depth based on the shear wave velocity data. Further, liquefaction potential index is also evaluated for all the considered sites. It is observed that the possibility of liquefaction is very high at shallow depths. Moreover, a parametric study is carried out for various values of the magnitudes of earthquakes and PGA values to show its effects on liquefaction susceptibility. Keywords: Peak Ground Acceleration, Shear Wave Velocity, Liquefaction Potential, Liquefaction Potential Index, SPT N Value, Seismic Hazard. Introduction Geotechnical investigation is carried out to identify the properties of the soil, where any major civil engineering structure is to be constructed. If the investigation is done for the site which comes under the earthquake prone areas then it is necessary to establish whether the given site is liquefiable or not. Standard Penetration Test (SPT), Cone Penetration Test (CPT), Becker Hammer Test (BHT) and Multichannel Analysis Surface Wave (MASW) Test are some of the field methods used to measure the liquefaction potential of soil. Earlier, the liquefaction potential of a site was calculated by the simplified procedure developed by Seed and Idriss 35 using the Cyclic Resistance Ratio (CRR) value obtained by N values of SPT. Since then, the method has been continuously reformed and simplified by various authors. 36-38,47 Another popular method for the evaluation of the liquefaction potential using the CPT was given by Robertson and Campanella 32 . This method of evaluation has also been reformed and updated several times. 30,34,41 The shear wave velocity (Vs) method for determination of the liquefaction potential is preferable over other methods such as SPT, CPT etc. because it is not affected by large particles and is less sensitive toward soil compression and reduced penetration resistance due to the presence of fines, thus requiring minor corrections. 31 It is also a non- destructive test and can be used both in the field and in the laboratory. 14,44 In this method, shear wave velocity is considered as an index property of soil to determine liquefaction potential resistance. Both liquefaction potential resistance and shear wave velocity are similarly influenced by stress history, age of soil geology, void ratio and different states of stress. In the last two decades, many researchers have given relationships between liquefaction potential resistance and shear wave velocity. They have used different methods like field test, penetration –Vs correlation, numerical investigation, laboratory experiments etc. 3,6,10,12,20,24,33,37,43,44 All these evaluations were based on the simplified procedure of Seed and Idriss 35 method. Several corrections have been applied to Vs for overburden stress and an analytical expression is established with Cyclic Stress Ratio (CSR). Several seismic tests have been used to measure shear wave velocity in the field like CPT, MASW, suspension logger, down-hole and cross-hole. 22,47 Sensitiveness of the calculation and condition of soil are highly affected by the precision of the tests. Stokoe et al 42 and Belloti et al 5 have shown that the velocity achieved by the shear wave is equally dependent on the motion of the particle and principal stresses. The evaluation of liquefaction potential index (LPI) is required to mitigate the damages caused by liquefaction. Iwasaki et al 18 proposed LPI to overcome the limitations associated with Factor of Safety (FoS). LPI is frequently used by researchers to evaluate the liquefaction potential of soils. LPI offers an advantage by providing a single value for the entire location for liquefaction hazard maps instead of several factors at different layers. 11,40,46 LPI has been calibrated using SPT test data to characterize the liquefaction potential of sites. 11,29,40,45 Iwasaki et al 19 categorized levels of liquefaction severity as very low, low, high and very high