Solid Concentration as a Main Proxy for Basal Force Fluctuations Generated by Highly Concentrated Sediment Flows

Abstract

Sediment flows generate ground vibrations by exerting force fluctuations on the riverbed. Linking force fluctuations to properties of highly concentrated sediment flows, however, remains particularly challenging due to complexities arising from grain-to-grain interactions. Here, we conduct downscaled flume experiments in which we specifically measure force fluctuations and local seismic vibrations together with flow properties of highly concentrated sediment flows at high spatial and temporal resolution. We observe hysteresis behaviors between force fluctuations amplitude and flow surface elevation and mass that occur during complex changes in internal flow dynamics. By contrast, force fluctuations amplitude exhibits a unique negative relationship with solid concentration. We suggest this is due to the rheology of dense granular flows, where solid concentration is a proxy for particle agitation. We therefore advance that solid concentration should be incorporated in seismic models of such sediment flows as a key parameter describing inter-particle collisions and impacts to the bed.