KAJIAN KLASIFIKASI MASSA BATUAN DAN ANALISIS STEREOGRAFIS TERHADAP STABILITAS LERENG PADA OPERASI PENAMBANGAN TAMBANG BATUBARA AIR LAYA, DESA TANJUNG ENIM, KABUPATEN MUARA ENIM, SUMATERA SELATAN

Abstract

Slope stability problems on an open pit mine is a very important issue because it involves issues of human safety, mining equipment, and other infrastructure that is located around the excavation slopes. PT. Pamapersada is a coal mining contractor company that uses open pit system. Based on experience, sometimes avalanches or cracks occur in excavated slopes. To determine the relationship between the classification of the rock mass and slope stability slope forming material is necessary to do a research on the matter. Research sites located in  Tambang Air Laya pit. This is because the TAL Pit excavation area that has considerable variation in complex geological structures.

Geological mapping carried out to determine the distribution of lithology and geological structures contained in the Tambang Air Laya Pit. Geotechnical mapping carried out to classify the rock mass based on Rock Mass Rating.

From the field observations, the study area was divided geologically into four lithologic units, sandstone, mudstone, andesite, and coal. Based on the classification of the rock mass, the study area was divided into 4 types of rock mass: Type 1 rock mass composed of andesite with RMR value of 92 (very good rock), rock mass composed of type 2 rather weathered sandstone with RMR value of 80 (good rock), rock mass type 3 is composed of moderately weathered sandstone 50-70 RMR value (fair rock), type 4 is composed of claystone with 44-62 RMR value (fair rock).  Slope stability analysis using the program Slide Ver. 5, was conducted to determine the stability of existing slopes, changes in slope geometry, and simulated slopes formed by a type of rock mass. The results of the analysis showed that the TAL Pit slope design is in a state unsafe with Fk between 1:19 - 1,248.