Evaluation of Liquefaction Potential of Kolkata City, India, Using LPI and LSN Approaches

Soil liquefaction is a phenomenon that occurs when soil strength and stiffness are reduced due to fast loading, such as shaking from an earthquake. Several approaches to evaluating the intention of initiating liquefaction have developed over the years. The present study aims to evaluate the liquefaction potential index (LPI) for Kolkata city based on the shear wave velocity (V_s) approach using IS 1893: Part 1 (Criteria for Earthquake-Resistant Design of Structures, Part 1: General Provisions and Buildings, Bureau of Indian Standards, New Delhi, pp 1–44, 2016). The shear wave velocity (V_s) of Kolkata city has been calculated through the empirical correlations between V_s and uncorrected SPT N values. The location of Kolkata indicates a moderate to high seismic alert since it is on the edge of seismic zones III and IV. The study involved the creation of LPI contour maps and LPI hazard maps for Kolkata city for different earthquake magnitudes with a_max/g = 0.24. Also, calculation of liquefaction severity number (LSN) for many boreholes around Kolkata based on the CPT approach for different earthquake magnitudes is carried out. The study shows that Kolkata’s susceptibility to liquefaction varies based on the magnitude of the earthquake M_w. As the liquefaction potential index (LPI) and the liquefaction severity number (LSN) values increase, the liquefaction potential also increases.