Analisis penanganan tanah lunak pada timbunan studi kasus pembangunan jalan hauling di Kalimantan Timur

Haul road construction in coal mining areas of East Kalimantan commonly encounters soft clay subsoil with low bearing capacity and considerable thickness. This condition becomes critical when high embankments are required to support heavy mining truck loads. This paper presents a case study on ground improvement design for a 12 m high haul road embankment constructed over soft clay deposits extending to a depth of approximately 8 m with N-SPT values lower than 10. Several ground improvement alternatives were evaluated, including shallow soil replacement up to 1 m and 2 m, as well as a combined system of 2 m soil replacement and timber piles (dolken). Bearing capacity evaluation was conducted using analytical methods, while global stability and deformation behavior were assessed through two-dimensional finite element analysis using PLAXIS 2D. The results indicate that the untreated condition and shallow replacement alternatives alone do not satisfy the required global safety factor (SF < 1.50), despite reducing settlement magnitude. Bearing capacity assessment identified a critical depth of approximately 9–10 m, indicating the need for deeper ground reinforcement. The selected alternative, consisting of 2 m soil replacement combined with 7 m long timber piles, successfully increased the static safety factor to 1.53 and the seismic safety factor to 1.26, while reducing maximum deformation to 0.2315 m. The study demonstrates that timber pile reinforcement provides an effective and economical solution for improving embankment stability on soft ground, particularly for temporary haul roads in mining operations.