Studi Geoteknik pada Lereng Lowwall Pit Lisat PT Teguh Sinar Abadi di Desa Muara Bunyut, Kecamatan Melak, Kabupaten Kutai Barat, Provinsi Kalimantan Timur

Muhamad Iqbal Fauzan Arif, Yuliadi Yuliadi, Dono Guntoro

Abstract


Abstract. PT Teguh Sinar Abadi (PT TSA) is one of coal surface mining in East Borneo. Considering current coal prices, future forecasts and favorable reserves, PT TSA decides to mine in the block of Lisat 2. In order for mining to run optimally, the design of slope geometry covering the angle and height of the slope should be done appropriately in order to stabilize the slope. The stability of the slope is one of the technical aspects of mining that must be considered in the open mining system because it is very influential on other aspects in mining operations. Both technically and economically. Therefore, geotechnical studies are required in the form of slope stability analysis using the Limited Equilibrium Method and Slide probability analysis to obtain the right design so that the slope remains stable and is expected to safely support mining activities. Many factors that influence the stability of the slope, are as follows: Geometry of slope, the height and angle of the slope, Physical-mechanical properties, strength (especially strong shear) and the weight of the mass contents of slope-forming rocks. The general orientation of the structure discontinuity of the slope rock mass to the orientation of the slope of the mine. Groundwater within the mass of slope rock. External factors of the slope system, in the form of external load and / or vibration (earthquake and due to mine blasting).The constituent rocks of the study sites are sedimentary rocks dominated by Siltstone. From the results of laboratory testing, the characteristics of the constituent rocks are categorized into very weak rocks to medium strong rocks. Based on the measurement of groundwater level, the condition of the groundwater level are at a depth of 5-20 meters from the surface. Design pit that has been made, has to redesigned. Because with the geometry, the slope safety factor is in the range of from 0.7 to 1.12 with a probability of 27% -42.7%. The recommended safe geometry for the slopes of the lowwall pit The PT TSA lever is as follows the overall slope angle (OSA) at an angle of 220 or 230 height overall slope at ± 230 meters with safety factor ranging from 1,365 - 1.66 with 0% slope slope probability.

Keywords: Lowwall, Slope Stability, Limited Equilibrium Method

Abstrak. PT Teguh Sinar Abadi (PT TSA) merupakan salah satu tambang terbuka batubara yang berada di Kalimantan timur. Dengan mempertimbangkan harga batubara saat ini dan prakiraan harga kedepan dan jumlah cadangan yang masih menguntungkan, PT TSA memutuskan untuk melakukan penambangan di blok Lisat 2. Agar penambangan berjalan optimal, perancangan geometri lereng yang meliputi sudut dan ketinggian lereng harus dilakukan dengan tepat agar terjadinya kestabilan lereng. Kestabilan lereng adalah salah satu aspek teknis penambangan yang harus diperhatikan pada sistem penambangan terbuka dikarenakan sangat berpengaruh pada aspek lain dalam operasi penambangan. Baik secara teknis dan ekonomis. Maka karena itu, diperlukan adanya studi geoteknik berupa analisis kestabilan lereng dengan menggunakan metode kesetimbangan batas (Limited Equilibrium Method) dan probabilitas kelongsoran untuk memperoleh design yang tepat sehingga lereng tersebut tetap stabil dan diharapkan dapat menunjang kegiatan penambangan dengan aman. Banyak faktor yang berpengaruh terhadap kestabilan lereng, yaitu sebagai berikut: Geometri lereng, yaitu tinggi dan kemiringan lereng. Sifat fisik-mekanik, kekuatan (terutama kuat geser) dan bobot isi massa batuan pembentuk lereng. Orientasi umum struktur diskontinuitas massa batuan lereng terhadap orientasi muka lereng bukaan tambang. Air tanah di dalam massa batuan lereng. Faktor luar sistem lereng, berupa beban luar dan atau getaran (gempa bumi dan akibat peledakan tambang). Batuan penyusun lokasi penelitian adalah batuan sedimen yang didominasi oleh batulanau. Dari hasil pengujian laboratorium, karakteristik batuan penyusun lokasi penelitian termasuk kedalam batuan lemah sekali hingga batuan kuat menengah. Berdasarkan hasil pengukuran muka air tanah, kondisi muka air tanah di lokasi penelitian berada pada kedalaman 5 - 20 meter dari permukaan. Design pit yang sudah dibuat perlu dilakukan redesign karena dengan geometri tersebut, faktor keamanan lereng yang berkisar dari 0.7 – 1.12 dengan probabilitas kelongsoran sebesar 27% - 42.7%.Rekomendasi geometri yang aman untuk lereng lowwall pit Lisat PT TSA adalah sebagai berikut overall slope angle (OSA) pada sudut 220 atau 230 tinggi keseluruhan lereng pada ± 230 meter dengan faktor keamanan berkisar dari 1.365 – 1.66 dengan probabilitas kelongsoran lereng 0%..

Kata Kunci: Lowwall, Kestabilan Lereng, Limited Equilibrium Method


Keywords


Lowwall, Kestabilan Lereng, Limited Equilibrium Method

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DOI: http://dx.doi.org/10.29313/pertambangan.v0i0.9699

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