Electronic Theses and Dissertation

ABSTRAK
Kabupaten Aceh Tengah terletak di zona geologi yang kompleks dengan topografi beragam, mulai dari dataran tinggi hingga pegunungan, dan merupakan bagian dari punggung Pegunungan Bukit Barisan. Daerah ini memiliki litologi batuan yang berumur dari Pra-Tersier hingga Kuarter-Tersier, di mana batuan metasedimen dan metamorf mendominasi lapisan lebih tua, sedangkan batuan vulkanik berasal dari aktivitas Gunung Geureudong, Gunung Salak, dan Gunung Telege. Lokasi penelitian terletak di Kecamatan Silih Nara, Kabupaten Aceh Tengah, Provinsi Aceh. Lokasi penelitian ini termasuk ke dalam iklim tipe B yang berarti musim kemarau terjadi lebih lama daripada musim hujan. Namun karakteristik curah hujan di lokasi penelitian termasuk tinggi, berkisar 1.700-2.000 mm per tahun, dengan tingginya intensitas curah hujan tersebut dapat menyebabkan maraknya peristiwa bencana alam seperti longsor. Dalam Peta Geologi Regional Lembar Takengon, daerah penelitian ini tersusun atas Formasi Bruksah (Tob), Formasi Bampo (Tlb), Formasi Salah Nama (Qvns), Endapan Aluvium Gunung api Klastika Tak Terpisahkan (Qhv), dan Endapan Aluvium (Qh). Keberagaman kondisi geologi pada lokasi ini dipengaruhi oleh aktivitas tektonik yang membuat lokasi penelitian memiliki struktur serta kemiringan lereng yang bervariasi, dari landai hingga curam. Struktur geologi tersebut memiliki dampak yang besar pada stabilitas lereng batuan. Penelitian ini bertujuan untuk mengetahui kondisi geologi pada permukaan yang mencakup struktur geologi, persebaran litologi, bentuk bentang alam pada lokasi penelitian, serta mengetahui nilai dari kualitas massa batuan dengan menggunakan metode klasifikasi Rock Mass Rating (RMR) dan nilai kestabilan lereng dengan menggunakan metode Slope Mass Rating (SMR). Pengamatan geomorfologi memberikan hasil berupa peta geomorfologi yang menggambarkan tiga bentuk lahan, yaitu denudasional, struktural, dan vulkanik. Litologi yang terdapat pada lokasi penelitian tersebar pada beberapa titik berupa satuan batupasir, satuan batuserpih, satuan batugamping, satuan batuan konglomerat, endapan aluvium, dan endapan aluvium gunung api klastika tak terpisahkan. Berdasarkan hasil dari perhitungan parameter RMR, didapatkan kelas massa batuan sedang dengan bobot RMR 56, serta hasil analisis kinematika menunjukkan bahwa lereng tersebut termasuk ke dalam jenis longsoran baji. Sedangkan klasifikasi SMR memberikan hasil berupa nilai lereng di lokasi penelitian yang termasuk ke dalam kategori kelas II dengan bobot massa berkisar 61 hingga 80, mengindikasikan bahwa lereng tersebut stabil dengan kemungkinan terjadi longsor sebesar 20%. Berkenaan dengan rekomendasi lereng, penambahan paritan pada kaki lereng, pemasangan pagar pada lereng, serta jala kawat, dan pemasangan titik baut perlu dilakukan demi menjaga kestabilan lereng tersebut.

Kata Kunci: Pemetaan Geologi, Silih Nara, Stabilitas Lereng, slope mass rating, rock mass rating.

ABSTRACT Central Aceh Regency is located in a complex geological zone with diverse topography, ranging from highlands to mountains, and is part of the Bukit Barisan Mountain Ridge ridge. The area has rock lithology that ages from Pre-Tertiary to Quaternary-Tertiary, where metasedimentary and metamorphic rocks dominate the older layers, while volcanic rocks come from the activity of Mount Geureudong, Mount Salak, and Mount Telege. The location of the research is located in Silih Nara District, Central Aceh Regency, Aceh Province. The location of this study is included in the type B climate which means that the dry season lasts longer than the rainy season. However, the characteristics of rainfall at the study site include high, ranging from 1,700-2,000 mm per year, with the high intensity of rainfall can cause the rampant occurrence of natural disasters such as landslides. In the Regional Geological Map of the Takengon Sheet, this research area is composed of the Bruksah Formation (Tob), the Bampo Formation (Tlb), the Misnamed Formation (Qvns), the Alluvium Deposits of the Inseparable Clastic Volcano (Qhv), and the Aluvium Deposits (Qh). The diversity of geological conditions at this location is influenced by tectonic activities that make the research site have a varied slope structure and slope, from sloping to steep. The geological structure has a great impact on the stability of the rock slope. This study aims to determine the geological conditions on the surface which includes geological structure, lithological distribution, landscape shape at the research site, as well as to determine the value of the quality of the rock mass using the Rock Mass Rating (RMR) classification method and the slope stability value using the Slope Mass Rating method(SMR). Geomorphological observations provide results in the form of geomorphological maps that describe three land forms, namely denudational, structural, and volcanic. The lithology found at the research site is spread at several points in the form of sandstone units, silica units, limestone units, conglomerate rock units, alluvium deposits, and alluvium deposits of clastic volcanoes inseparable. Based on the results of the calculation of RMR parameters, a medium rock mass class with an RMR weight of 56 was obtained, and the results of kinematic analysis showed that the slope was included in the type of wedge avalanche. Meanwhile, the SMR classification gave results in the form of slope values at the research site which were included in the class II category with a mass weight ranging from 61 to 80, indicating that the slope was stable with a 20% chance of landslides. Regarding slope recommendations, the addition of trenches at the foot of the slope, the installation of fences on the slopes, as well as wire meshes, and the installation of bolt points need to be carried out in order to maintain the stability of the slope. Keywords: Geological Mapping, Recih Nara, Slope Stability, slope mass rating, rock mass rating.