[H-DS07] Landslides and related phenomena

[HDS07-P02] Impact of Diatom Fossil Particle Breakage on the undrained Shear behavior: Implication for coseismic diatomite landslides in the Noto Peninsula, Japan

*Junfan Liao¹, Gonghui Wang² (1.Graduate School of Science, Kyoto University, 2.Disaster Prevention Research Institute, Kyoto University)

Keywords:Diatomite, Particle Breakage, Shear Strength, Liquefaction, Microstructure

The Noto Peninsula, Japan’s largest diatomite-producing region, is widely covered with diatomaceous mudstone and experiences frequent geological activity. In weathered diatomaceous areas, where the soil is highly susceptible to disturbance, the risk of landslides is particularly high. During the 2024 Noto Earthquake, several diatomite landslides with distinct landsliding behavior occurred in Noto Peninsula. While previous studies on diatomite landslides have focused on examining the effect of diatom content on shear strength, the roles of diatom fossil particle breakage, shear strength evolution, and pore water pressure dynamics during earthquakes remain poorly understood. This study investigates diatomaceous soil taken from some diatomite landslide areas using a large-scale ring shear apparatus and SEM imaging to quantify the effects of mechanical stress, pore water pressure response, and microstructural particle breakage on the shear behavior of diatomite under drained or undrained conditions. The findings provide insights into the initiation and movement of landslides on diatomaceous mudstone during the 2024 Noto Earthquake.