RESPONSE OF STABLE OVERALL SLOPE GEOMETRY OF OPEN PIT COAL MINE IN WARUKIN FORMATION TO DEWATERING AND PEAK GROUND SEISMIC IN SOUTH KALIMANTAN, INDONESIA

MAKALAH ILMIAH RESPONSE OF STABLE OVERALL SLOPE GEOMETRY OF OPEN PIT COAL MINE IN WARUKIN FORMATION TO DEWATERING AND PEAK GROUND SEISMIC IN SOUTH KALIMANTAN, INDONESIA RESPONS GEOMETRI LERENG MENYELURUH STABIL TAMBANG TERBUKA PADA FORMASI WARUKIN, AKIBAT PENYALIRAN DAN GEMPA DI KALIMANTAN SELATAN, INDONESIA Agus Wiramsya Oscar1*, Dicky Muslim2*, Nana Sulaksana2, Febri Hirnawan2 1Postgraduated Programe of Geological Engineering, Padjadjaran University, Bandung, Indonesia of Geological Engineering, Padjadjaran University, Bandung, Indonesia ; 2Faculty ABSTRACT Understanding of the response of the mine slope stability is very important regarding the safety of life and investment / productivity / environment, as anticipation of landslide prevention based on the latest research. Mine slope behavior previously discussed widely in terms of the response due to dewatering and seismic (Peak Ground Acceleration) as well through verification. This paper aims to obtain a broad dimension of design criteria that are not only unstable slopes, but the slope is stable under various conditions of the rock mass saturation (dewatering) and seismic condition. Response of slope stability per geotechnical rocks unit from different formations or any engineering formation as a result of environmental influences, for example, the same quake, will be different. This means that the geometry of the same slope in other formation will have different stability conditions (safety factor of the slope) due to the same seismic acceleration. This is also similar due to dewatering. The method used for this study is the deductive-probabilistic method with a hypothetical verification approach. The Standard statistical analysis is used to test the data normality and homogeneity, average and independent differences, as well as regression-correlation test. The research results show that dewatering activity can decrease ground water level (GWL/MAT) of the slope, so the durability of sliding along the sliding plane is reduced (increasing slope safety factor). At the same time earthquake reduces shear strength and increases driving force, so the safety factor of the slope suddenly downs. Slope stability decreased due to the earthquake, but dewatering improves slope stability. Thus, the slope in dewatering conditions will be kept stable through simulation to anticipate earthquake. Keywords: Overall slope, Safety Factor, dewatering, Peak Ground Acceleration ABSTRAK Pemahaman respon dari stabilitas lereng tambang sangat penting terkait keselamatan jiwa dan investasi / produktivitas / lingkungan, sebagai antisipasi pencegahan longsor berdasarkan penelitian terbaru. Perilaku lereng tambang dibahas sebelumnya secara luas dalam hal respon karena penyaliran dan seismic serta melalui verifikasi kualitatif. Makalah ini bertujuan untuk mendapatkan dimensi yang luas kriteria desain yang tidak hanya lereng yang tidak stabil, namun lereng stabil dalam berbagai kondisi dari kejenuhan massa batuan (penyaliran) dan kondisi seismik/getaran. Respon dari stabilitas lereng per unit satuan batuan geoteknik dari formasi yang berbeda atau pembentukan keteknikan satuan batuan Buletin Sumber Daya Geologi Volume 11 Nomor 1 - 2016 55 MAKALAH ILMIAH sebagai akibat dari pengaruh lingkungan, misalnya, gempa yang sama, akan berbeda. Ini berarti bahwa geometri lereng yang sama dalam formasi lainnya akan memiliki kondisi stabilitas yang berbeda (faktor keamanan dari lereng) karena percepatan gempa yang sama. Ini juga mirip karena penyaliran. Penelitian ini bertujuan untuk mengetahui respons geometri lereng menyeluruh stabil tambang batubara terbuka pada Formasi Warukin di Kalimantan Selatan akibat penyaliran dan gempa. Penelitian ini menggunakan metode deduktifprobabilistik dengan pendekatan verifikasi hipotetik. Analisis kemiringan lereng dilakukan untuk mengetahui faktor keamanan lereng di daerah penelitian. Analisis statistik seperti uji korelasi regresi yang sebelumnya telah dilakukan juga uji normalitas dan homogenitas data serta menguji perbedaan rata-rata dan independen. Hasil penelitian menunjukkan bahwa aktivitas penyaliran dapat menurunkan elevasi muka air tanah (MAT) di dalam tubuh lereng, sehingga daya tahan geser di sepanjang bidang gelincir menjadi turun (faktor keamanan lereng meningkat). Gempa menurunkan gaya tahan geser sekaligus menaikkan gaya dorong geser pada saat yang bersamaan, sehingga faktor keamanan lereng turun dengan tiba-tiba. kestabilan lereng menurun akibat gempa, tetapi penyaliran meningkatkan kestabilan lereng. Dengan demikian lereng dalam kondisi dewatering akan dapat dijaga tetap stabil melalui simulasi untuk mengantisipasi terjadinya gempa. Kata kunci: Lereng menyeluruh, faktor keamanan, dewatering, seismik dasar puncak INTRODUCTION Determination of the angle of comprehensive slope (overall slope), the largest stable at a maximum depth of an open pit mine is an aspect of the geotechnical part of mine planning, so that the mining operation is capable of producing optimal cost (recovery) for mineable reserves in a safe condition (slope with no landslide). Such circumstances should always be maintained, and is a joint responsibility of all parties involved in a mining organization. Therefore management of mine to maintain the condition of safety along with the acquisition of optimal production is in accordance with the government rules of mining techniques (Good Mining Practice). Rock formation genetically has specific physical and mechanical characteristics along with composition and variety of rock types with distinct physical characteristics, biological, and chemical, known as facies. This understanding is used as the basis for tracking the physical and mechanical characteristics in carrying out geotechnical mapping to the systematic division of geotechnical rock units. Dearman (1991) 56 explained the rank of geotechnical rock units in descending order: 1. engineering types (scale 1: 5,000 or greater), 2. lithological types (scale 1; 5000-1: 10,000), 3. engineering formations (scale 1: 10000-1: 200,000), 4. engineering groups (scale 1: 200,000 or smaller). In mining operations, which are generally large-scale geotechnical issues will involve large-scale map, so that the study of various phenomena of slope instability will focus on geotechnical rock units at the level of engineering formation until the lithological type. This research studies on all three levels of the units. Response of slope stability per unit geotechnical rocks of different formations or any engineering formation as a result of environmental influences, for example, the same seismicvibration, will be different. It means that the geometry of the same slope made in the formation of the others will have different slope stability conditions (safety factor) though the Peak Ground Acceleration (PGA) are the same. Buletin Sumber Daya Geologi Volume 11 Nomor 1 - 2016 : 55 - 72 MAKALAH ILMIAH Similarly, due to dewatering. Both factors c (...truncated)