Electronic Theses and Dissertation

Abstrak indonesia memiliki kondisi geologi kompleks akibat interaksi tektonik aktif yang mempengaruhi variasi litologi, geomorfologi, dan stabilitas lereng. di lokasi penelitian, litologi regional terdiri atas anggota batugamping lam kabeue (qtpsl), batuan gunungapi lam teuba (qtvt), lahar dalam batuan gunungapi lam teuba (qvtl), formasi indrapuri (qpin), hingga endapan aluvium (qh). penelitian ini bertujuan untuk melakukan pemetaan geologi guna mendetailkan sebaran litologi serta mengevaluasi kestabilan lereng pada ruas jalan tol sigli banda aceh km 54, desa cot kareung, yang diidentifikasi berada pada zona bahaya tanah longsor sedang hingga tinggi berdasarkan peta bahaya longsor bnpb (2025). metode penelitian meliputi pemetaan geologi lapangan pada skala lokal untuk mengidentifikasi satuan batuan dan bentuklahan, serta pengujian parameter mekanika tanah di laboratorium. analisis stabilitas lereng dilakukan menggunakan metode fellenius melalui pemodelan komputer dengan software slide 6.0 dan perhitungan manual sebagai pembanding. parameter utama yang digunakan meliputi kohesi, sudut geser dalam, dan berat isi tanah berdasarkan kondisi aktual di lapangan. hasil penelitian menunjukkan daerah penelitian tersusun atas empat satuan geomorfologi, yaitu satuan kaki lereng fluvial gunung api atas (v6), satuan perbukitan dan lereng karst denudasional (k3), satuan dataran denudasional (d5), dan satuan dataran tuff (v12). kemudian, satuan geologi yang berkembang terdiri atas satuan batupasir formasi seulimeum (qtps), satuan batugamping anggota lam kabeue (qtpsl), satuan tuff formasi gunungapi lamteuba (qtvt), satuan endapan pasir dan konglomerat formasi indrapuri (qpin), serta satuan breksi laharik (qvtl). analisis stabilitas lereng menunjukkan kondisi aman dengan nilai faktor keamanan (fk) dari software slide 6.0 sebesar 1,738, serta hasil perhitungan manual pada tiga penampang berturut turut sebesar 1,698; 1,747; dan 1,661. nilai tersebut memenuhi kriteria bowles (1986) dan sni 8460:2017. mitigasi berupa sistem drainase telah diterapkan, namun direkomendasikan pemeliharaan drainase secara berkala, penerapan bioengineering melalui vegetasi berakar dalam, serta pemasangan instrumen monitoring seperti inklinometer dan piezometer untuk mendukung deteksi dini pergerakan lereng dan perubahan tekanan air pori. kata kunci: pemetaan geologi, geologi teknik, stabilitas lereng, metode fellenius, jalan tol sigli-banda aceh.

ABSTRAK Indonesia has complex geological conditions resulting from active tectonic interactions that influence variations in lithology, geomorphology, and slope stability. At the study site, the regional lithology consists of the Lam Kabeue Limestone Member (QTpsl), the Lam Teuba Volcanic Rocks (Qtvt), lahars within the Lam Teuba Volcanic Rocks (Qvtl), the Indrapuri Formation (Qpin), and alluvial deposits (Qh). This study aims to conduct geological mapping to detail the distribution of lithologies and evaluate slope stability along the Sigli–Banda Aceh Toll Road at KM 54, Cot Kareung Village, which has been identified as being in a moderate-to-high landslide hazard zone based on the BNPB Landslide Hazard Map (2025). The research methods included local-scale field geological mapping to identify rock units and landforms, as well as laboratory testing of soil mechanical parameters. Slope stability analysis was performed using the Fellenius Method through computer modeling with Slide 6.0 software and manual calculations for comparison. The main parameters used included cohesion, angle of internal friction, and unit weight of soil based on actual field conditions. The results of the study indicate that the study area consists of four geomorphological units, namely the Upper Volcanic Fluvial Slope Unit (V6), the Denudational Karst Hills and Slopes Unit (K3), the Denudational Plain Unit (D5), and the Tuff Plain Unit (V12). Furthermore, the developed geological units consist of the Seulimeum Formation Sandstone Unit (QTps), the Lam Kabeue Member Limestone Unit (QTpsl), the Lamteuba Volcanic Formation Tuff Unit (Qtvt), the Indrapuri Formation Sand and Conglomerate Deposits Unit (Qpin), and the Laharik Breccia Unit (Qvtl). Slope stability analysis indicates a safe condition with a Safety Factor (SF) value from the Slide 6.0 of 1.738, as well as manual calculations for three consecutive cross sections yielding values of 1.698, 1.747, and 1.661. These values meet the criteria of Bowles (1986) and SNI 8460:2017. Mitigation measures in the form of a drainage system have been implemented; however, periodic drainage maintenance, the application of bioengineering through deep-rooted vegetation, and the installation of monitoring instruments such as inclinometers and piezometers are recommended to support early detection of slope movement and changes in pore water pressure. Keywords: Geological Mapping, Engineering Geology, Slope Stability, Fellenius Method, Sigli-Banda Aceh Toll Road.