This paper presents a site-specific seismic ground response evaluation through convolution-deconvolution analysis in the Balaroa-Petobo area during the 2018 Palu-Donggala Indonesia earthquake. The equivalent-linear ground response analysis for the earthquake time history recorded at Balaroa was carried out using DEEPSOIL software. The results of the analysis indicate that the EW component of the earthquake motion was amplified more severely (amax) than was the NS component, as it propagated to the Petobo surface. The amplification of the bedrock motion on the Petobo surface was more serious than that on the Balaroa surface, which appears to be due to the differences in the subsurface stratification and material properties of the two sites. The Fourier spectrum and response spectra also showed greater maximum spectral accelerations (Sa,max) and maximum Fourier amplitudes (Af) at the Petobo site than at the Balaroa site. The frequency of surface soil both the Petobo and Balaroa sites computed by using comparison between response spectra analysis and the local modes analysis VS/4*H was indicated the potential decline of surface soil stiffness at Petobo area appear to account for the structural damage and liquefaction flow slides during the 2018 incident.

Dispersive soil is susceptible to water erosion and could cause damage in geotechnical engineering or hydraulic engineering projects. Recycled clay brick powder (RCBP) was used as a modifier to improve the dispersivity and water stability of dispersive soil in this study. Pinhole tests, crumb tests, disintegration tests, particle analysis tests, exchangeable sodium percentage (ESP) tests, pH tests, conductivity tests, and X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were conducted to explore the modification effects and corresponding mechanisms of RCBP on dispersive soil. The results revealed that the dispersivity of the soil significantly weakened as the RCBP content increased and curing time extended. Specifically, adding 4% RCBP to the soil and curing for 7 days effectively transformed dispersive soil into nondispersive soil. Furthermore, the final disintegration time of the soil sample with 10% RCBP cured for 28 days was 273% longer than that of the soil sample without curing. Moreover, the treatment led to decreased fines content, ESP value, and pH value in the soil samples. The decrease in ESP value indicated the replacement of sodium ions adsorbed on the soil particle surfaces with calcium ions, resulting in a reduction in the thickness of the diffuse electric double layer of soil particles, and subsequently reduced soil dispersivity. Additionally, the decrease in pH also contributed to the reduction of the diffuse electric double-layer thickness. XRD and SEM analyses confirmed the formation of cementing materials between soil particles due to the modification, which filled gaps and cemented particles to create a waterproof barrier between soil particles. In conclusion, the utilization of RCBP as a modifier for dispersive soil could be a win-win measure with promising outcomes. It is recommended that more than 4% RCBP should be added in engineering applications.

Dispersive soil is a widely distributed problematic soil in arid or semiarid areas of the world and can cause pipe erosion, gully damage and other seepage failures. This study analyzed the effect of environmentally friendly enzyme-induced carbonate precipitation (EICP) on the dispersivity of dispersive soils. This methodology was tested for the stabilization of three dispersive soil types (two high-sodium soils, two low-clay-content soils, and two soils with both high sodium and low clay contents) to examine the impact on dispersivity based on the results of pinhole tests and mud ball tests. Physical, chemical, mechanical, and microscopic tests were also conducted to investigate the effects of the components in the EICP reaction solution on dispersive soil modification. The experiments showed that the concentration of the reaction solution and the curing time required to limit the dispersivity decreased with increasing clay content in the soil. Ca2+ limited the dispersivities of dispersive soils via four distinct mechanisms. The first mechanism was ion exchange; Ca2+ decreased the percentage of exchangeable sodium ions to less than 7% while reducing the thickness of the diffuse double layer such that the spacings between soil particles were reduced and the chemical dispersivity was limited. Second, Ca2+ increased the viscosity of the solution by salting out the organic matter present in the soybean urease. Subsequently, the D1-class physically dispersive soil was converted into an ND2-class nondispersive soil. Third, Ca2+ decreased the soil pH by reducing the CO32- content, which could hydrolyze to increase the soil alkalinity. Finally, the presence of Ca2+ led to the generation of cementitious minerals through the precipitation of CaCO3 crystals that continuously generated CO32-, filling and cementing soil particles and thereby limiting their physical dispersivity. These results indicated that a low-concentration EICP reaction solution efficiently controlled the dispersivities of the three dispersive soils.