Internal erosion process and its influence factors in widely graded
loose soils due to rainfall infiltration
Abstract
Widely graded loose soils (WGLS), a loose mixture comprising coarse and
fine particles, are widely distributed in the western mountainous areas
of China. Owing to rainfall infiltration, fine particles are eroded and
migrated through the skeleton formed by coarse particles, thus altering
the hydraulic and mechanical characteristics of WGLS. This paper intends
to uncover the internal erosion process and its influencing factors in
WGLS due to rainfall infiltration. To this end, a novel fixed-wall
permeameter is developed, capable of applying an inflow rate-controlled
condition and collecting effluent flowing out of the specimen. A
simplified and cost-effective testing protocol is proposed for
separating eroded silty clay particles, sandy gravel particles, and
seepage water from the collected effluent. Several seepage tests are
conducted on remolded specimens with different inflow rates and initial
porosity utilizing the newly developed experimental setup and testing
protocol. The results indicate four successive erosion stages in the
internal erosion process: the suffusion stage, the suffosion stage, the
piping stage, and the stabilization stage. Six critical hydraulic
gradients correspond to the onset of the various stages. The inflow rate
does not affect the critical hydraulic gradient for suffusion. However,
it significantly impacts the critical hydraulic gradient for suffosion
and subsequent internal erosion behavior. Increasing initial porosity
does not necessarily result in higher erosion potential. These results
are conducive to further understanding the formation mechanism of
internal erosion-induced geologic hazards.