Liquefaction potential hazard assessment and its effect on toll road construction in Seyegan Subdistrict, Yogyakarta

Toll road construction is a vital infrastructure connecting the two economic centers on Java Island. However, given the potential disaster risks in the region, it is essential to assess the geological and geotechnical conditions to determine the potential for liquefaction in the area. The special region of Yogyakarta is susceptible to earthquakes and associated disasters. One of the most significant earthquakes occurred on May 27, 2006 with a magnitude of 6.3 Mw resulting from the Opak Fault. Furthermore, the toll road is constructed above the Mataram Irrigation Canal, characterized by a shallow groundwater level and young volcanic deposits that are vulnerable to liquified. The study aimed to determine the potential for liquefaction in the area and predicted the vertical settlement caused by liquified soil. The analysis of liquefaction potential utilized the simplified procedure to obtain factor of safety and Liquefaction Severity Index (LSI) to assess the vulnerability index of liquefaction. Results indicated the research area had a very low to medium liquefaction susceptibility index. In addition, the calculation of vertical settlement using Idriss and Boulanger (2008) equation showed a predicted vertical settlement range of 0.4 cm – 44.64 cm. The predicted vertical settlement range underscores the importance of considering the potential for liquefaction to mitigate any adverse effects on the toll road’s construction and operation.