Analisis Stabilitas dan Mitigasi Longsor Menggunakan Regeometri serta Sistem Perkuatan Soil Nailing pada Longsoran di Area Waduk Cirata
Abstract
Longsor pada kawasan waduk strategis seperti Waduk Cirata merupakan ancaman serius terhadap keberlanjutan operasional Pembangkit Listrik Tenaga Air (PLTA) serta keselamatan penduduk di sekitar daerah aliran sungai Citarum, Jawa Barat. Penelitian ini bertujuan untuk mengevaluasi stabilitas lereng eksisting yang telah mengalami longsor serta merancang sistem mitigasi yang efektif terhadap beban statik maupun dinamik menggunakan pendekatan forensik teknik sipil. Metode yang digunakan meliputi pemodelan numerik berbasis elemen hingga dengan perangkat lunak PLAXIS 2D melalui pendekatan Strength Reduction Method (SRM). Parameter tanah diperoleh dari uji laboratorium dan korelasi empiris, divalidasi melalui back analysis hingga mencapai kondisi kritis (SF ≈ 1,0). Simulasi dilakukan pada tiga skenario utama: kondisi eksisting, perbaikan geometri (regeometri) dengan sistem bench, serta kombinasi regeometri dan sistem perkuatan soil nailing serta shotcrete. Hasil penelitian menunjukkan bahwa lereng eksisting berada dalam kondisi tidak stabil dengan faktor keamanan (SF) 0,95. Regeometri berhasil meningkatkan SF statik menjadi 1,613, namun SF seismik hanya 1,065 (di bawah ambang batas). Setelah penambahan soil nailing dan shotcrete, SF statik meningkat menjadi 1,75 dan SF seismik menjadi 1,121, yang telah memenuhi kriteria keamanan minimum. Implikasi penelitian ini memberikan rekomendasi teknis bahwa mitigasi longsor di kawasan sesar aktif wajib mengintegrasikan perkuatan struktural aktif seperti soil nailing, karena regeometri saja tidak cukup terhadap beban gempa.
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