Investigation of seismic signature induced by grain-bed impact considering the grain size distribution of flow-type landslides

Flow-type landslides are rapid, fluid-like movements of soil or debris down a slope, posing significant risks to infrastructure and safety. It consists of grains with various grain size distribution, ranging from millimeters to meters. Recent advancements in seismic sensing have proven to be valuable for characterizing flow-type landslides. Existing physical seismic impact models link flow-type landslides to seismic signatures, thereby enhancing the measurement and inversion of the landslides. However, most models rely on prior knowledge of grain size distribution, and also the application of effective diameter can overlook some information of the grain size distribution. This oversight leads to inaccuracies both within the models themselves and the inversions of grain size distribution derived from these models.

Integrating experimental methods with analytical theory, our study aims to elucidate the relationship between grain size distribution and the seismic signatures generated by grain-bed impacts, refining the seismic impact model considering grain size distribution. A newly developed free-fall experimental apparatus has been employed to conduct both single-grain and dual-grain falling tests as unit tests. Building upon the findings from unit tests, we carried out multi-grain experiments with varying grain size distributions. The frequency components and power spectral density of the seismic data can effectively differentiate between different grain size distributions. A new grain size distribution parameter has been proposed. Combing the experimental results, we utilized the elastic impact model to analyze the seismic signatures of individual grains. Additionally, the superposition method was investigated to account for the spatial and temporal variations of grain impacts, thereby revealing the seismic response associated with different grain size distributions. Ultimately, we propose a modified seismic impact model that incorporates grain size distribution for flow-type landslides. This study provides significant insights for practitioners by leveraging seismic signals to elucidate the characteristics of flow-type landslides.