Mitigation plan against liquefaction potential on Gumbasa Irrigation Canal around Jono Oge area after 2018 Central Sulawesi Earthquake

Abstract

Gumbasa Irrigation Area was one of the public infrastructures affected by the liquefaction and flow-slide. Restoring it to operate as before required a reconstruction plan with consideration on potential damage caused by the earthquake and liquefaction. The objective of this study was to assess the performance of the mitigation plan applied on Gumbasa Irrigation Area (canal and rice field). Two mitigation plans to be applied in the Gumbasa Irrigation Canal are evaluated, i.e., (1) implementing impermeable lining and geogrid; (2) applying impermeable lining and steel-sheet pile with drain. Each mitigation plan was compared using the finite element method to examine the stability and displacement mechanism. Based on the result, the first mitigation plan was identified as more effective to reduce displacement caused by earthquake and liquefaction potential. The lowering groundwater method was applied on Jono Oge rice fields area by maintaining the recommended groundwater level obtained from the simulation of groundwater level using the simplified method. We concluded that mitigation plans on irrigation canal by applying impermeable lining and geogrid and by lowering groundwater on the rice fields area were the best mitigation plan for Gumbasa Irrigation Area.