Utilizing the Limit Equilibrium Method: Slope stability analysis of the outlet diversion tunnel portal at Jatinegara Dam, Tegal District, Central Java

Abstract The purpose of the Jatinegara Dam is to irrigate agricultural land in the villages of Cacaban dan Rambut. Investigations involving engineering geology have been carried out, however a slope stability analysis is still required. The purpose of this study is to evaluate the stability of the slope at the outlet portal of the Jatinegara Dam using the Bishop Simplified and Morgenstern-Price limit equilibrium methods (LEM). These methods analyze the stability of the slope under both static and seismic loading, and the results are used to determine the value of Safety Factor (SF). The primary source of data was rock and soil evaluations taken from the surface and rock cores of the outlet tunnel portal. Rock quality assessment based on Geological Strength Index (GSI) and laboratory testing. The outlet portal slope consists of volcanic breccia, sandstone, and siltstone with quality ranges from very poor to good. The results of LEM show that the outlet portal slope is in stable condition under both static and seismic loads, as per the SNI 8460:2017 standards.