Slope stability analysis of the drainage tunnel portal in Tanju Dam, Dompu District, West Nusa Tenggara

This paper presents design results of the tunnel portal slopes at Tanju Dam, Dompu, West Nusa Tenggara. The objective this research was to analyse stability using circular failure chart (CFC) method, limit equilibrium method (LEM), and finite element (FEM). Input parameters were obtained from drill core evaluations laboratory tests. By considering rock mass rating (RMR) values masses, which are categorized as class II, two slopes, adjustments for cohesion inner friction angle made. inlet slope (IL) have 350 kPa 40º outlet (OL) 400 45º angle. CFC shows that IL OL safety factor (FS) 3.5 3.44, respectively. LEM FS 3.69 3.65, Meanwhile, FEM 4.78 4.79, analysis indicate designed stable.