ANALISIS LIKUEFAKSI PADA LAPISAN TANAH BERPASIR DI LOKASI PROYEK PABRIK, GRESIK, JAWA TIMUR

In this study, an analysis was conducted to evaluate the potential for liquefaction at a factory project located in Manyar, Gresik, East Java. The analysis aimed to determine whether the sandy soil layer in the factory area has liquefaction potential. Liquefaction potential was evaluated by comparing the earthquake-induced loading with the soil’s resistance to liquefaction. The potential was expressed as a factor of safety against liquefaction (FSL). In addition, Cyclic Stress Ratio (CSR) calculations were carried out. Two methods were used to determine the Cyclic Resistance Ratio (CRR) values in this project: the Ishihara method (1979), the Yoshimi & Tokimatsu method (1984), the Boulanger & Idriss method (2014) and Andrus & Stokoe method. The data used in this study included soil investigation reports, downhole seismic test results, and earthquake maps. Based on the liquefaction analysis, no liquefaction potential was found at borehole SPT B02. However, since the project location is near a fault (based on the geological map of Surabaya and Quadrangle, Java), further checks on site classification based on SNI 1726:2019 are recommended. Abstrak Penelitian ini melakukan analisis potensi likuefaksi pada proyek pabrik yang berlokasi di Manyar, Gresik, Jawa Timur. Analisis dilakukan untuk mengetahui apakah lapisan tanah berpasir di area pabrik berpotensi mengalami likuefaksi. Evaluasi potensi likuefaksi dilakukan dengan membandingkan beban gempa terhadap ketahanan tanah terhadap likuefaksi. Potensi likuefaksi dinyatakan sebagai faktor keamanan terhadap likuefaksi (FSL). Selain itu, dilakukan juga perhitungan Cyclic Stress Ratio (CSR). Terdapat empat metode yang digunakan untuk menentukan nilai Cyclic Resistance Ratio (CRR) pada proyek ini, yaitu metode Ishihara (1979), Yoshimi & Tokimatsu (1984), Boulanger & Idriss (2014) dan Andrus & Stokoe (2000). Data yang digunakan meliputi laporan penyelidikan tanah, hasil uji downhole seismic, dan peta gempa. Berdasarkan hasil analisis likuefaksi, tidak ditemukan potensi likuefaksi pada lokasi lubang bor SPT B02. Namun, mengingat lokasi proyek dekat dengan sesar (berdasarkan peta geologi Surabaya dan Quadrangle, Jawa), disarankan dilakukan pengecekan lebih lanjut mengenai klasifikasi situs berdasarkan SNI 1726:2019.