Numerical Study on the Liquefaction Potential Analysis Using Constitutive Models for Sand and Silt in Mamuju, West Sulawesi

Sulawesi Island, located in the Eastern Indonesian archipelago, is known for its high seismic activity. In 2021, West Sulawesi experienced an earthquake with a mainshock of 6.2 M_W, which resulted in liquefaction characterized by sand boil and lateral spreading at various locations, including near the North coast of Mamuju.

This study aims is to assess the potential for liquefaction at a nearshore location in Mamuju, West Sulawesi. The assessment focuses on the increase in pore water pressure in an area characterized by multiple layers of sand, silt, and clay soils.

Numerical analysis was conducted by modeling one-dimensional soil column using PM4Sand and PM4Silt constitutive models calibrated using PLAXIS 2D soil test feature with the Cyclic Direct Simple Shear (CDSS) test method. Furthermore, the study included spectral matching of the ground motion from the 2021 Mamuju earthquake to the spectral response at the research site as motion input.

Analysis results indicate the potential for liquefaction in silty sand and sandy silt soils with sand-like behavior, as evidenced by an excess pore water pressure ratio exceeding 0.8. Meanwhile, sandy silt and sandy clay soils, with a plasticity index (PI) greater than 7, showed no liquefaction potential at a peak ground acceleration of 0.478 g.

In conclusion, soil relative density plays an important role in influencing pore water pressure and liquefaction susceptibility, which should be considered when planning and designing in earthquake-prone areas, shallow groundwater tables, sand, silt, and clay layers.