Assessment of Standard Penetration Test (SPT) based Liquefaction Potential Index of Gorakhpur City, Uttar Pradesh, India

ABSTRACT

The devastating 7.8 Mw seismic event that struck Nepal on April 25, 2015, led to extensive structural collapse and loss of life due to severe seismically induced liquefaction activity. The surrounding Tarai regions also experience the devastating effects of these cataclysmic catastrophes. Being located in the Tarai area near the seismically active Nepal Himalayan belt. Gorakhpur city, one of the biggest and fastest-growing, densely populated cities in eastern Uttar Pradesh (UP), was taken up for a standard penetration test (SPT)-based assessment of liquefaction potential. Field research and geotechnical analysis revealed the city’s susceptibility to earthquake-induced liquefaction and ground failure, posing significant risks to both life and property. This study aims to present the findings of the liquefaction susceptibility study in Gorakhpur city and its suburbs through safety factors and the liquefaction potential index (LPI). Using data from 30 boreholes, including ground acceleration from the 7.8M Nepal-Gorkha earthquake, SPT-N160 values, and groundwater table depth, the assessment indicates a high to very high seismic liquefaction potential (>5 LPI) in and around Gorakhpur city. Depth-wise analysis of boreholes identified six patterns of liquefiable and non-liquefiable layers up to 10.5 m deep. The study highlights a considerable portion of the city as prone to seismic liquefaction during strong earthquakes, attributed to shallow groundwater tables (2–9 m below ground level) and liquefiable sediment layers within 10 m depth, mainly consisting of fluvial, fine sand, and silt deposits. Understanding the severity and location of seismic liquefaction risks is crucial for urban planners and geotechnical engineers to develop infrastructure resilient to liquefaction-induced damage during earthquakes. By identifying vulnerable areas and implementing appropriate mitigation measures, cities like Gorakhpur can better prepare for and withstand future seismic events, ultimately reducing the impact on lives and property.