Electronic Theses and Dissertation

Pemetaan geologi adalah suatu kegiatan penelitian untuk menghasilkan peta geologi yang menggambarkan kondisi dan menjelaskan informasi geologi permukaan, bentang lahan (geomorfologi), persebaran litologi, dan struktur geologi. Lokasi penelitian terletak di Desa Ie Mirah Kecamatan Babahrot, Kabupaten Aceh Barat Daya, Provinsi Aceh. Lokasi penelitian secara geografis terletak berada pada titik koordinat 3˚ 53’ 19.06‖ - 3˚ 56’ 1.08‖ LU dan 96˚ 38’
45.31‖ - 96˚ 41’ 27.39‖ BT. Luas wilayah penelitian 5x5 km2 yang mencakup pemetaan geologi dan analisis kestabilan lereng. Berdasarkan Peta Geologi Regional Lembar Tapaktuan lokasi penelitian terdiri dari Formasi Babahrot (Muba), Formasi Meulaboh (Qpm) dan Formasi Alluvium (Qh). Kondisi geologi lokasi penelitian dipengaruhi oleh aktivitas gunung api sehingga muncul struktur geologi dan kemiringan pada lereng batuan. Lereng yang diteliti merupakan lereng batu filit yang memiliki banyak struktur kekar, kondisi air tanah yang basah sehingga rentan mengalami erosi dan pelapukan. Penelitian ini bertujuan untuk mengetahui kondisi geologi daerah penelitian dengan melakukan pemetaan geologi yang mencakup persebaran litologi, struktur geologi, bentuk bentang lahan, dan menganalisis kestabilan lereng untuk mengetahui jenis longsoran dan nilai dari probabilitas longsor menggunakan kelas massa batuan dengan metode slope mass rating (SMR). Pada peta geomorfologi terdapat tiga bentang lahan berupa bentang lahan struktural, denudasional, dan fluvial. Pada peta lintasan terdapat 79 STA dengan sebaran litologi berupa 10 STA batu filit, 30 STA endapan lanau, 38 STA endapan pasir dan 1 STA endapan pasir kerikil yang dizonasikan menjadi tiga formasi pada peta geologi yaitu satuan batu filit, satuan endapan lanau,dan satuan endapan pasir. Analisis kestabilan lereng menggunakan nilai kelas massa batuan (RMR), didapatkan nilai bobot RMR sebesar 52 masuk ke dalam kelas III dengan jenis longsoran berupa longsoran baji. Berdasarkan klasifikasi SMR lereng masuk dalam kategori kelas III dengan bobot 44,5 yang menunjukkan hanya sebagian lereng yang stabil dan probabilitas longsor sebesar 40%. Adapun rekomendasi untuk kestabilan lereng berupa pemberian paritan pada kaki lereng, pemasangan jangkar jala kawat, kabel baja, beton semprot, beton gigi/konvensional, dan dinding penahan beton.

Kata Kunci: Pemetaan Geologi, Lereng, Longsor, RMR, dan SMR.

Geological mapping is a research activity conducted to produce a geological map that depicts surface geological conditions and explains information on surface geology, landforms (geomorphology), lithological distribution, and geological structures. The study area is located in Ie Mirah Village, Babahrot District, Southwest Aceh Regency, Aceh Province. Geographically, the study area lies at coordinates 3°53′19.06″–3°56′1.08″ N and 96°38′45.31″–96°41′27.39″ E. The total area of investigation covers 5 × 5 km², encompassing geological mapping and slope stability analysis. Based on the Regional Geological Map of the Tapaktuan Sheet, the study area consists of the Babahrot Formation (Muba), Meulaboh Formation (Qpm), and Alluvium Formation (Qh). The geological conditions of the study area are influenced by volcanic activity, resulting in the development of geological structures and slope inclinations within the rock masses. The investigated slope is composed of phyllite rock characterized by numerous joint structures and wet groundwater conditions, making it highly susceptible to erosion and weathering processes. This study aims to determine the geological conditions of the study area through geological mapping, including lithological distribution, geological structures, landform characteristics, and slope stability analysis to identify landslide types and landslide probability values using rock mass classification with the Slope Mass Rating (SMR) method. The geomorphological map identifies three types of landforms, namely structural, denudational, and fluvial landforms. Along the traverse map, 79 stations (STA) were recorded, with lithological distribution consisting of 10 STA of phyllite, 30 STA of silt deposits, 38 STA of sand deposits, and 1 STA of gravelly sand deposits. These lithologies are zoned into three geological units on the geological map: phyllite unit, silt deposit unit, and sand deposit unit. Slope stability analysis based on the Rock Mass Rating (RMR) classification yielded an RMR value of 52, which falls into Class III and indicates a wedge-type failure. Based on the SMR classification, the slope is categorized as Class III with an SMR value of 44,5, indicating that only part of the slope is stable and has a landslide probability of 40%. Recommended slope stabilization measures include the construction of drainage channels at the slope toe, installation of wire mesh anchors, steel cables, shotcrete, conventional or toothed concrete, and concrete retaining walls. Keywords: Geological Mapping, Slope, Landslide, RMR, SMR.