Effect of Artesian Pressure on Liquefaction-Induced Flow-Slide: A Case Study of the 2018 Sulawesi Earthquake, Indonesia

This paper discusses the trigger of the long-distance flow-slide that occurred in the 2018 Sulawesi earthquake, Indonesia. As a result of post-earthquake field surveys and interviews with local residents, it was confirmed that artesian groundwater existed before the earthquake in the area where the long-distance flow-slide occurred. This fact may be due to the liquefaction of the deep ground by the earthquake and the inflow of a large amount of groundwater from the aquifer below the liquefaction to the surface layer, which may have caused the long-distance flow-slide. In this study, the possibility of the presence of artesian pressure was examined by preparing a soil cross section of the affected areas estimated from the results of borehole surveys conducted after the earthquake and grain size analysis. In addition, the cyclic resistance ratio of the supposed liquefied soil was obtained by undrained triaxial cyclic loading test using in-situ undisturbed samples, and the effect of artesian pressure on the occurrence of liquefaction was examined by simplified liquefaction analysis.