Liquefaction Potential Analysis on Pandansimo Bridge using Nonlinear Site Response Analysis

The construction of bridges is one of the infrastructures that support the Trans South-South Java Road in Yogyakarta Province, including the Pandansimo Bridge. This bridge is located in a high liquefaction vulnerability zone near the coastal area with a shallow groundwater table, composed of saturated sandy soil and less than 10 km from the active Opak fault.

The study aims to evaluate the liquefaction potential in the Pandansimo Bridge area with the scenario of the 2006 Yogyakarta earthquake of 6.3 Mw.

The evaluation used eight modified pairs of ground motion to obtain peak ground acceleration values through nonlinear calculations with site-specific response analysis. Furthermore, the liquefaction potential analysis was conducted based on these results using simplified procedure methods.

The results show that each soil layer’s peak ground acceleration value ranged from 0.30 g to 0.49 g. Liquefaction potential is at a depth of 1 m to 16 m, with various thicknesses for each borehole depending on the soil properties, with vulnerability levels varying from very low to very high.

The findings indicate that liquefaction potential occurs at several borehole locations at Pandansimo Bridge. This liquefaction condition may serve as a reference for mitigating strategies applicable in case of probable liquefaction in the infrastructure.