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). According to the Indonesian Liquefaction Vulnerability Zone, North Sumatra is categorized as a liquefaction-prone area. Langkat is one of the regencies in North Sumatra that is categorized as having a moderate liquefaction vulnerability, Langkat was chosen as the study area to investigate liquefaction potential using nonlinear site response analysis with pore water pressure (PWP). This model provided reasonable estimates of PWP increase (ru) in the soil layers. The study area was predominantly composed of sand with a shallow groundwater table due to its proximity to the river and the high seismic zone associated with the Sumatran fault. The analysis was based on the Standard Penetration Test and laboratory test data from 2 boreholes with a depth of 30 m. The results showed that in the boreholes under a 6.6 Mw, full liquefaction potential was found at BH 01, a depth of 9-11 m below the ground surface with a ru > 0.8 and γmax ≥ γlimit. Marginal liquefaction occurs at BH 02 depth 3.5 m with ru > 0.8 and γmax < γlimit. Non-linear site response analysis is a good approximation to describe the possibility of soil liquefaction, which can help design earthquake-resistant structures.