Analysis Of Recurrent Subsidence on A National Road Segment in Watuawu Village, Lage District, Poso Regency

Recurrent subsidence has occurred on the national road segment at Km 233+900 in Watuawu Village, Lage District, Poso Regency, Central Sulawesi, since 2016. This study aims to identify the mechanisms and causal factors of this phenomenon. The research employed a geotechnical investigation approach and secondary data analysis, comprising the results of Standard Penetration Test (SPT), soil laboratory testing, rainfall data, seismic activity, and the morphological conditions of the Poso River. Liquefaction potential was analyzed by comparing the Cyclic Resistance Ratio (CRR) with the Cyclic Stress Ratio (CSR) to obtain the factor of safety (FS). The results show that, at depths of 2–20 m, FS values range from 0.27 to 0.55, that is, less than 1, indicating liquefaction potential in the analyzed soil layers. The recurrent subsidence appears to be associated with a combination of slope-toe erosion caused by the flow of the Poso River, increased soil saturation due to rainfall, the geotechnical conditions of the soil layers, and regional tectonic activity. This study recommends remediation through ground improvement and riverbank protection based on further geotechnical investigation. The findings are expected to serve as a basis for consideration in mitigation planning and in improving the stability of national road segments in disaster-prone regions.