Reconnaissance of liquefaction case studies in 2015 Gorkha (Nepal) earthquake and assessment of liquefaction susceptibility

Abstract

The Gorkha (Nepal) earthquake of the moment magnitude Mw 7.8 occurred on 25 April 2015, with the epicenter 77 km north-west of Kathmandu at a focal depth of 13 km. After the main shock of the earthquake, a field investigation was carried out in the Kathmandu Valley to collect case histories of geotechnical and structural damages. This paper provides the observations of liquefaction case histories and the liquefaction potential assessment based on Standard Penetration Tests for liquefied and non-liquefied sites were performed. Recorded ground motions from the event are presented and the local site effect on the occurrence of liquefaction is described briefly. Observed liquefaction case studies are presented. Ejected soils at liquefied sites were collected and the particle size distributions of ejected soils were analysed. SPT blow counts and the soil profiles at eight liquefied and non-liquefied sites were obtained. The factors of safety against liquefaction with depth and liquefaction potential index of the eight sites were estimated and compared with observed liquefaction areas during Gorkha earthquake. The liquefaction potential indices obtained from the analysis were found to be consistent with the field observation.