Correlation of excess pore water pressure ratio on flow liquefaction phenomenon in Sibalaya – Central Sulawesi Province

¹ Department of Civil and Environmental Engineering, Faculty of Engineering , Universitas Gadjah Mada, Yogyakarta 55281, Indonesia
² Directorate General Water Resources, Ministry of Public Works and Housing, South Jakarta 12110, Indonesia
³ Centre of Excellence of Technological Innovation for Disaster Mitigation (GAMA-Ina-TEK), Universitas Gadjah Mada, Yogyakarta 55281, Indonesia

^* Corresponding author: fikri.faris@ugm.ac.id

Abstract

On September 28, 2018, liquefaction in Sibalaya damaged irrigation canals and hit 51.2 hectares fields and roads. This phenomenon was triggered by an earthquake of magnitude 7.5 that shook Sigi Regency, Central Sulawesi Province. As an increase in soil pore water pressure is one of the causes of liquefaction, the pore water pressure ratio (r_u) at the study site was analyzed. Then, this figure is used as a point of reference to determine the liquefaction potential. Standard Penetration Test (SPT) data and laboratory tests from four boreholes resulting from soil investigations in 2021 with a maximum depth of 20 meters were utilized in this study, along with microtremor data down to the depth of bedrock from test results in 2023. Based on the data, the liquefaction potential was assessed using the one-dimensional nonlinear site response approach, the GQ/H + PWP model, and the DEEPSOIL V.7 program. At multiple layers of boreholes, r_u is more than or equal to 0.8, indicating that the Sibalaya liquefaction flow area is still susceptible to liquefaction.