THE GEOLOGICAL STRUCTURE EFFECTS ON SLOPES STABILITY AND TUNNELS OF METAMORPHIC ROCKS AT POBOYA GOLD MINE PALU
Abstract
Poboya area has many geological structures that result in distribution of strength and stress of rocks not evenly distributed, as a result, the rock mass strength becomes disturbed and slopes become unstable. The objective of the study was to determine the geological structure effect on slope stability and tunnel conditions on metamorphic rocks at the Poboya gold mine. The study was conducted in the Mantikulore sub-district, Palu, Central Sulawesi. Lithology composing study area is metamorphic rocks consisting of gneiss and schist, therefore, the analysis was carried out on both locations which have many geological structures. Numerical analysis was performed applying the finite element method with the RS2 program assistance. The findings show that the safety factor value of the existing slope at gneiss and schist location under static loading is 4.6 and 2.72, if there is an earthquake it becomes 1.07 and 0.77. The safety factor value under static loading with the joint is 4.58 and 2.03, while under dynamic loading with joint, it becomes 0.94 and 0.64. The geological structure effect which represented by the joint gave a big impact with a decrease of safety factor at gneiss about 0.43% under static loading and 80% under dynamic loading. Meanwhile, at schist, safety factor decreased 25% under static loading and 76% under dynamic loading. For tunnel stability, the existence of joint will increase the displacement of 65% at gneiss under static loading and 84% under dynamic loading, while at schist, it increases 25% under static loading and 54% under dynamic loading. This illustrates that geological structures under dynamic loading affect significantly slope stability of Poboya gold mine.
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