Liquefaction Potential Analysis of Irrigation Canals at Sidera Area-Sigi Regency

Abstract

An earthquake measuring 7.5 on the Richter scale that occurred in Palu on 28 September 2018 resulted in liquefaction where the soil lost its bearing capacity due to increased pore water pressure. The liquefaction disaster caused great damage to the Gumbasa Irrigation channel, a large part of which is in the alluvial fan area. This study aims to analyze the potential of liquefaction in irrigation canals in the Sidera village area, Sigi Regency. Using SPT (Standard Penetration Test) data from 2 boreholes with a depth of ± 20 m, MASW data, and Earthquake Risk Map. Researchers analyzed with the Seed Simplified Procedure approach, The researchers analyzed the Simplified Procedure method proposed by Seed, which uses a stress-based approach that uses the ratio of soil shear strength (CRR) and earthquake-induced soil shear stress (CSR). The results of the analysis using Peak Ground Acceleration (PGA) of 0.43 and groundwater level variations of -2.85 m (borehole BM 53) and -12.5m (Borehole BM 49) show that liquefaction occurs at depths of 4-8 m (BM 53) and 14-17 m (BM 49). The value of the Liquefaction Potential Index (LPI) increases and indicates a high liquefaction potential below the water table with the highest value of 17.88. The analysis shows that liquefaction is closely related to the shallow water table, soil type, and low N-SPT values. The high liquefaction potential requires prevention methods as a form of treatment.