Post-liquefaction Analysis Using Standard Penetration Test Data and Grain Size Distribution Test at Irrigation Canal in Sidera Village

Liquefaction is a disaster caused by cyclic loads which can cause massive damage. One example is the 7.5 Mw earthquake that hit Palu Sigi, Indonesia, in 2018. Researchers agree that liquefaction is closely related to soil density and grain distribution. This study aims to get an overview of how far soil grain size distribution influences the risk of liquefaction in irrigation canals in the Sidera area. The analysis of this research is based on the grain size distribution test. The empirical analysis using the simplified procedures method, which refers to the Idris-Boulanger equation, is used to calculate the safety factor and post-melting completion and lateral displacement for each borehole in 6 (six) peak ground acceleration (PGA) scenarios based on Kanno attenuation. Based on soil grain size distribution test analysis, the soil is dominated by fine-grained sand and sandy silt. The liquefaction analysis shows that after the Palu-Donggala Earthquake in 2018, the affected area, as the location of this study, is still vulnerable to liquefaction at PGA values above 0.3 g. From the results of the post-thaw analysis, the largest lateral soil displacement at point BM-48 in the 0.6 g PGA range was 3.67 m, while the soil subsidence occurred 1.62 m.