Landslide Management for Batu Tulis – Cross Bogor – Sukabumi Station Double Lane Project at STA 5+550

Abstract

In the implementation of the St. Batu Tulis – Lintas Bogor – Sukabumi STA 5+550 project, a significant challenge arose with the occurrence of an avalanche during construction, attributing landslides to substantial land subsidence caused by the destabilization of the slope's soil or rocks. This disruption significantly impacted construction planning, particularly in terms of cost considerations. This study conducted a comprehensive comparative analysis of the stability of the original embankment slope and slopes reinforced with gabions (measuring 2m x 1m x 0.5m), sheet piles (type W-400 A-1000), and bored piles (size D600). To evaluate the stability, it was imperative to determine the safety factor (SF) and slope deformation under applied loads. The Plaxis 8.6 program was employed for the analysis, incorporating all relevant soil parameter data. Safety factor values were calculated as 1.67 for the gabion-bored pile combination slope, 1.62 for the sheet pile-reinforced slope, and 1.63 for the bored pile-reinforced slope. Estimated costs for slope strengthening were as follows: IDR 3,525,789,199.92 for sheet piles, IDR 2,180,309,258.00 for bored pile-gabion combination, and IDR 6,689,603,822.00 for bored piles alone. The budget for slope reinforcement with gabions proved more economical by IDR 1,345,479,941.92 compared to sheet piles and IDR 4,509,294,564.00 compared to bored piles. The reinforcement type selection was based on a cost analysis, prioritizing lower expenses while ensuring construction feasibility. Gabions offer advantages such as economical prices, flexibility, and simple construction methods, but they have drawbacks, including susceptibility of galvanized coated wire to water conditions with high salt or acid content and requiring a wide area for construction due to their large size. Sheet pile reinforcement is resistant to corrosion, durable, and has good performance, but it is unsuitable for supporting very high soil due to the requirement of a large cross-sectional area and not suitable for use in rocky soils due to piling difficulties.