Flow deformation characteristics of sandy soils under constant shear stress with water inflow

Previous researcher explained that the catastrophic long-distance flow-slide in Palu city, in which the surface ground laterally deformed up to several kilometers after the earthquake in the gently ground inclination (1-5%), might be promoted by the inflow of confined aquifer or fault water. This paper aims to investigate the flow behavior characteristics of Toyoura sand and in-situ sand by employing water inflow shear tests with a constant shear stress in the triaxial apparatus and the modified torsional shear apparatus. Through this experiment, rapid-flow behavior can be observed on both materials, even at a low initial static shear stress. This behavior depends on the volumetric strain development characteristics, which are also correlated with the material's initial densities. The dense specimen showed this rapid flow state at a higher volumetric strain level than the loose specimen. Besides, the flow rate during the rapid flow state was also measured. This rate is affected by the material's initial densities as well as the initial static shear stress. (C) 2022 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.