ANALISIS PROBABILITAS KESTABILAN LERENG TAMBANG TIMAH PRIMER BLOK PEMALI, BANGKA, INDONESIA

Teguh Nurhidayat, Edo Syawaludin, Muchtar Arifin, Iwan Oktariansyah

Abstract


ABSTRAK

 

Studi geoteknik sangat penting pada tambang terbuka untuk menentukan geometri lereng dan kestabilan lereng tambang. Kestabilan lereng pada tambang terbuka sangat mempengaruhi kelangsungan produksi dan keselamatan pekerja pada tambang tersebut. Pada kasus tambang timah primer, material pembentuk lereng yang terdiri dari batuan induk berupa granit dan tanah dekomposisi dari granit. Hal ini dapat memberikan masalah dalam penentuan parameter kekuatan material dan analisis yang digunakan. Karena  parameter kekuatan yang berasal dari dekomposisi granit mempunyai variabilitas yang tinggi. Metode deterministik tidak cukup untuk memodelkan kestabilan lereng pada tambang timah primer. Sehingga dilakukan perpaduan antara penggunaan metode deterministik dan probabilistik dalam proses analisis kestabilan lereng. Pemboran geoteknik dilakukan dengan cara full coring. Parameter sifat fisik dan mekanik material lereng didapat dari hasil pengujian laboratorium. Nilai internal shear angle, unit weight dan cohesion diproses dengan simulasi Monte Carlo sebagai model variabel acak. Simulasi Monte Carlo melakukan evaluasi secara simultan dari kestabilan lereng. Simulasi juga dilakukan dengan variasi sudut lereng keseluruhan dan proses pengeringan air tanah. Hasil simulasi memperlihatkan lereng pada penampang 1 dengan sudut lereng keseluruhan sebesar 25o (pada keadaan dinamik, SF= 1.216, PF= 8.1%, RI= 1.419)  dengan proses pengeringan air tanah, penampang 2 pada sudut lereng keseluruhan 35 o(pada keadaan dinamik, SF= 1.44 , PF= 0% , RI= 3.535)  dan Penampang 3 pada sudut lereng keseluruhan 15o (pada keadaan dinamik, SF= 1.469 ,PF= 13.7%, RI= 1.079).  

 

Kata kunci: kestabilan lereng, probabilitas, timah primer

 

 

ABSTRACT

 

Geotechnical studies are very important in open pit mining to determine the slope geometry and stability of the mine slope. Slope stability at an open pit greatly influences the continuity of production and the safety of workers at the mine. In the case of primary tin mining, slope-forming material consisting of host rock in the form of granite and soil decomposition of granite. It can give problems in determining the strength parameters and the modeling used. Because the strength parameters derived from granite decomposition have high variability. The deterministic method is not enough to model slope stability in primary tin mines. So it is a combination of the use of deterministic and probabilistic methods in the process of modeling the slope stability. Geotechnical drilling is done by full coring. The parameters of physical and mechanical properties of slope material are obtained from laboratory test results. Internal shear angle, unit weight and cohesion values are processed by Monte Carlo simulation as a random variable model. Monte Carlo simulations carry out simultaneous evaluations of slope stability. Simulations are also carried out with overall slope angle variation and groundwater dewatering. Simulation results show that the slope at cross-section 1 at overall slope angle(OSA) 25o (under dynamic condition, SF = 1,216, PF = 8.1%, RI = 1,419) with groundwater dewatering process, cross-section 2 at with 35o(OSA) (SF = 1.44, PF = 0%, RI = 3,535) and Section 3 at 15o (SF = 1,469, PF = 13.7%, RI = 1,079).

 

Key word: slope stability, probability, primary tin

 


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DOI: https://doi.org/10.36986/ptptp.v1i1.89

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