Perancangan Struktur Perkuatan Lereng Menggunakan Gabion untuk Penanganan Longsor (Studi Kasus: Segmen Jalan di Dusun Wunut, Bantul)

Ethana Nurani Aisyah, Dr. Eng. Fikri Faris, S.T.,M.Eng.

2026 | Skripsi | TEKNIK SIPIL

Longsor pada segmen jalan di Dusun Wunut, Desa Sriharjo, Kecamatan Imogiri, Kabupaten Bantul, terjadi akibat kombinasi kondisi tanah lunak jenuh, gerusan Sungai Oya, dan aktivitas seismik karena lokasi berada di dekat Sesar Opak. Kondisi tersebut menyebabkan stabilitas lereng menurun sehingga diperlukan struktur perkuatan yang mampu meningkatkan faktor keamanan, mengendalikan deformasi, serta sesuai diterapkan pada tanah dengan daya dukung rendah. Perancangan ini bertujuan memberikan alternatif struktur perkuatan lereng, mengevaluasi kinerja teknisnya berdasarkan faktor keamanan dan deformasi pada kondisi statis maupun pseudostatis, serta menentukan alternatif desain yang paling sesuai berdasarkan aspek teknis dan ekonomi. Perancangan dilakukan menggunakan data investigasi tanah berupa pengeboran, Standard Penetration Test (SPT), dan pengujian laboratorium. Analisis beban gempa dilakukan menggunakan metode Site Specific Response Analysis (SSRA) untuk memperoleh koefisien gempa horizontal yang diterapkan pada analisis pseudostatis. Dua alternatif struktur perkuatan yang dirancang adalah Gabion Faced Geogrid Reinforced Retaining Wall (GF-GR-RW) dengan mini pile melalui pendekatan konsep dari Mechanically Stabilized Earth (MSE) Wall dan soldier pile dengan gabion. Evaluasi kinerja dilakukan melalui pemodelan numeris menggunakan Plaxis 2D dengan model tanah Mohr-Coulomb, sedangkan aspek ekonomi dianalisis melalui perhitungan Rencana Anggaran Biaya (RAB). Hasil analisis menunjukkan bahwa kedua alternatif memenuhi persyaratan faktor keamanan minimum pada kondisi statis dan pseudostatis. GF-GR-RW dengan mini pile menghasilkan faktor keamanan sebesar 1,855 pada kondisi statis dan 1,109 pada kondisi pseudostatis, sedangkan soldier pile dengan gabion menghasilkan faktor keamanan sebesar 3,321 dan 1,420. Hasil pemodelan juga menunjukkan bahwa deformasi kedua alternatif masih berada dalam batas yang diizinkan. Dari aspek ekonomi, biaya konstruksi GF-GR-RW dengan mini pile sebesar Rp2,713,785,000 lebih rendah dibandingkan soldier pile dengan gabion sebesar Rp4,078,457,000. Berdasarkan hasil evaluasi teknis dan ekonomi, GF-GR-RW direkomendasikan sebagai alternatif perkuatan lereng yang paling sesuai untuk lokasi perancangan.

Landslides occurred along a road segment in Wunut Hamlet, Sriharjo Village, Imogiri District, Bantul Regency, due to the combined effects of saturated soft soil conditions, erosion by the Oya River, and seismic activity associated with the nearby Opak Fault. These conditions reduced slope stability, necessitating a reinforcement system capable of improving the safety factor, controlling deformation, and performing effectively on soils with low bearing capacity. This study aims to develop alternative slope reinforcement designs, evaluate their technical performance based on safety factor and deformation under static and pseudostatic conditions, and determine the most appropriate design by considering both technical and economic aspects. The design was carried out using geotechnical investigation data obtained from borehole drilling, the Standard Penetration Test (SPT), and laboratory testing. Seismic loading was evaluated using the Site-Specific Response Analysis (SSRA) method to determine the horizontal seismic coefficient applied in the pseudostatic analysis. Two reinforcement alternatives were investigated: a Gabion Faced Geogrid Reinforced Retaining Wall (GF-GR-RW) incorporating mini piles based on the Mechanically Stabilized Earth (MSE) Wall concept, and a soldier pile system with gabion. The technical performance of both alternatives was evaluated through numerical modeling using Plaxis 2D with the Mohr-Coulomb constitutive model, while the economic aspect was assessed through a cost estimate. The results indicate that both reinforcement alternatives satisfy the minimum safety factor requirements under both static and pseudostatic conditions. The GF-GR-RW with mini piles achieved safety factors of 1,855 under static conditions and 1,109 under pseudostatic conditions, whereas the soldier pile with gabion achieved safety factors of 3,321 and 1.420 respectively. The numerical analysis also showed that the deformation of both alternatives remained within the allowable limit. Economically, the construction cost of the GF-GR-RW with mini piles was IDR 2,713,785,000, which is lower than that of the soldier pile with gabion at IDR Rp4,078,457,000. Considering both technical performance and construction cost, the GF-GR-RW based on the MSE Wall concept with mini piles is recommended as the most suitable slope reinforcement alternative for the study area.

Kata Kunci : Gabion, Mechanically Stabilized Earth (MSE) Wall, Site Specific Response Analysis (SSRA), Soldier Pile, Stabilitas Lereng.