Kajian Stabilitas Lereng pada Perencanaan Main Dam

Abstract

Main dam merupakan salah satu bangunan hidrolika pada suatu waduk/bendungan yang berfungsi sangat penting dalam menahan tampungan air, sehingga perlu diperhitungkan kekuatan dan keamanannya secara cermat. Penelitian ini bertujuan untuk melakukan kaji ulang stabilitas lereng pada perencanaan main dam berdasarkan muka air normal (MAN) dan muka air banjir (MAB). Hasil analisis debit inflow menunjukkan bahwa pada kondisi volume tampungan normal sebesar 10.40 juta m3/detik, elevasi muka air normal bendungan pada 94.27 mdpl. Pada elevasi tersebut, kedalaman bendungan adalah 29.27 m dari dasar bendungan. Hasil analisis debit banjir terpilih menggunakan metode HSS Nakayasu dengan distribusi hujan durasi 6 jam sebesar 189.82 m3/detik, sehingga diperoleh elevasi muka air banjir bendungan sebesar 95.72 mdpl. Pada elevasi tersebut, kedalaman bendungan setinggi 30.37 m dari dasar bendungan. Berdasarkan parameter muka air, beban akibat angin, kenaikan muka air akibat abnormal operasional pintu bangunan, dan tambahan tinggi jagaan berdasarkan tipe bendung, tinggi jagaan main dam yang diperoleh sebesar 2.97 m. Stabilitas lereng main dam aman dengan analisis faktor keamanan (FK) menggunakan software rocscience untuk kondisi MAN diperoleh sebesar 1.37 dan MAB diperoleh sebesar 1.25. Kondisi tersebut memenuhi syarat faktor keamanan minimum stabilitas dengan tambahan beban gempa (FK ≥ 1.2).

Main dam is one of the hydraulic structures in a dam which has a very important function in holding water reservoirs, so its strength and safety need to be carefully calculated. This study aims to review slope stability in main dam planning based on normal water level (MAN) and flood water level (MAB). Results of the discharge inflow analysis showed that normal conditions were 10.40 million m3/ sec, normal water level at 94.27 mdpl. At this elevation, the depth of the dam was 29.27 m from the bottom of the dam. The result of selected flood discharge analysis using the Nakayasu HSS method with a rainfall distribution of 6 hours duration was 189.82 m3/second, so that the flood water level of the dam was obtained at 95.72 mdpl. At this elevation, the depth of the dam was 30.37 m from the bottom of the dam. Based on water level parameters, wind loads, water level rise due to abnormal building door operations, and additional guard height based on the type of dam, guard height main dam obtained was 2.97 m. Slope stability of the main dam was considered good by factor of safety analysis (FK) using rocscience software for MAN conditions obtained by 1.37 and MAB obtained by 1.25. This condition met the requirements for the minimum safety factor of stability with additional earthquake loads (FK ≥ 1.2).