Nonlinear site response analysis approach to investigate the effect of pore water pressure on liquefaction in Palu

On 28 September 2018, a M w 7.5 earthquake hit Donggala Regency, Indonesia province of central Sulawesi, resulting in extensive liquefaction, land subsidence, and flow slides. Extensive liquefaction is caused by an increased development of pore water pressure. During an earthquake, the development of pore water pressure (PWP) causes soil to become soft and potential liquefaction on loose sands. A PWP development model was combined with a generalized/Hyperbolic constitutive model (GQ/H+PWP) in a one-dimensional seismic site response to investigate pore water pressure development beneath the soil layer. This model provided reasonable estimates of pore water pressure increase and stress-strain role. Analysis was carried out for three boreholes in Balaroa, Petobo, and Jono Oge sites. The effective stress approach, nonlinear site response analysis was used to conduct a parametric study of soil profiles. The potential liquefaction at Balaroa and Petobo sites were 9 m and 10 meters in depth, respectively. With a groundwater level of 14 meters below the ground surface, the liquefaction potential in Jono Oge was 16-17 meters in depth. These results indicated that the liquefaction potential in Jono Oge was influenced by the infiltration of irrigation water from the surface which caused liquefaction to occur on the ground surface.