Abstract
Suffusion is one of the main modes of internal erosion leading to selective erosion and gradual migration of fine soil particles through the voids of soil skeleton formed by coarse soil particles under seepage flow. Suffusion may induce deterioration and even failure of hydraulic geo-structures, such as embankment dams, dikes, levees, as well as landslide dams, if they are formed by gap-graded cohesionless soils. Soil mass in the hydraulic geo-structures is always subjected to overburden load and seepage through the soil mass generally has a large component along the horizontal direction. In the literature, however, little attention has been paid to the horizontal seepage-induced suffusion under controlled vertical stress. In this study, horizontal seepage-induced suffusion tests were carried out using a testing apparatus with controllable vertical stress and hydraulic gradient. The seepage flux and eroded fine particle mass, as well as local hydraulic gradients can be measured. The effects of initial dry density and initial fines content on suffusion characteristics of a cohesionless soil were investigated. Test results showed that after the initiation of suffusion, alternate decrease and increase in the coefficient of permeability occurred possibly due to alternate clogging and dredging of soil pores by the movable fine particles. Uneven distribution of local hydraulic gradients along the flow path was observed and this could be regarded as a sign of the initiation of suffusion. Both initiation and failure hydraulic gradients increased with initial dry density and initial fines content.
Highlights
Suffusion is one of the main modes of internal erosion leading to selective erosion and gradual migration of fine particles through the voids of soil skeleton formed by coarse particles under seepage flow
Suffusion may lead to deterioration and even catastrophic failure of the hydraulic geo-structures which were formed by gap-graded cohesionless soils (Foster et al, 2000; Moffat and Fannin, 2006; Moffat et al, 2011; Ke and Takahashi, 2012; Peng et al, 2020b)
The possible reason was that the major part of overburden load was carried by the soil skeleton formed by gravel particles, while the sand particles were less involved in the load transfer chains
Summary
Suffusion is one of the main modes of internal erosion leading to selective erosion and gradual migration of fine particles through the voids of soil skeleton formed by coarse particles under seepage flow. The investigations showed that the parameters affecting suffusion characteristics included particle size distribution of soils (Kenney and Lau, 1985; Indraratna et al, 2011, 2015; Chang and Zhang, 2013; Moraci et al, 2014), hydraulic gradient (Salehi Sadaghiani and Witt, 2011; Ke and Takahashi, 2012; Song et al, 2018), seepage flow direction (Richards and Reddy, 2012; Hosseini and Pachideh, 2018), hydraulic loading history (Luo et al, 2013a; Rochim et al, 2017), fines content (FC, i.e., the mass ratio of fine particles to total weight of the soil specimen; Ke and Takahashi, 2012, 2014; Ouyang and Takahashi, 2015) and others. It is necessary to carry out experimental investigations on the horizontal seepage-induced suffusion under controlled vertical stress
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