The Correlation of Liquefaction With Excess Pore Water Pressure in Langkat, North Sumatra

Abstract

An earthquake is a natural occurrence that has the potential to trigger liquefaction. In fine sandy soil layers with a shallow water table, earthquakes can cause a rapid increase in excess pore water pressure (PWP), compromising the soil's effective strength and increasing the risk of liquefaction. According to the Indonesian Liquefaction Vulnerability Zone, North Sumatra is categorized as a liquefaction area. Langkat is one of the regencies in North Sumatra that is categorized as having a moderate liquefaction vulnerability. Therefore, Langkat was chosen as a research area to investigate liquefaction potential using pore water pressure (PWP) with empirical methods by Yegian and Vitelli (1981) and numerically using Deepsoil V7.0. The study area consists mostly of sand with shallow groundwater levels due to its proximity to rivers and high seismic zones associated with the Sumatran fault. The analysis is based on Standard Penetration Test data and laboratory tests from 2 boreholes with a depth of 30 m. The lts show that full liquefaction potential exists at BH 01, a depth of 9-11 m below the ground surface with 𝑟𝑟𝑢𝑢 > 0.8 and a limit of γmax ≥ γ. Marginal liquefaction occurs at BH 02 at a depth of 3.5 m with 𝑟𝑟𝑢𝑢 > 0.8 and γmax < γlimit. Evaluation of the excess pore water pressure ratio in area prone to liquefaction is important because this condition can cause rapid damage. The low bearing capacity of the building foundation is proven by the 𝑟𝑟𝑢𝑢 value approaching 0.8.