Feature and mechanism analysis of dispersive soil disintegration impacted by soil water content, density, and salinity

Dispersive soil has caused innumerable water-induced erosion failures of earthen structures in arid regions up to now, among which disintegration, as the first response process, is commonly deemed as the primary inducement but with inadequate understanding. In this study, the disintegration characteristics of a compacted dispersive lean clay with sand were investigated by carrying out laboratory disintegration tests under a water immersion regime. Soil mass water content (omega), dry density (rho(d)) and total soluble salt content (eta) were considered. Results suggest that for dispersive soil, (1) the disintegration process exhibited two distinct modes, which was divided by the omega near the optimum water content; (2) higher rho(d) delayed disintegration monotonously; (3) increasing eta first weakened and then enhanced the disintegration, in which pattern the eta at the inflection point increased with increasing rho(d), showing a density dependence. Evolutions of representative soil morphology were illustrated. More importantly, the underlying influential mechanism of omega and eta to disintegration were elaborated emphatically: (1) the initial clay dispersion level, soil consistency change, and conceptual "constraint force " exerted by soil matric suction jointly determine the disintegration modes; (2) increasing eta makes the soil pore solution concentration higher and microstructure simpler, competition between the two leads to nonmonotonic change patterns of disintegration completion time (T-d) and defined velocity (V-d); the interactive effect of rho(d) and eta manifests that eta produces an additional influence on the base of microstructure created by rho(d). Finally, the grey relation entropy analysis was introduced to evaluate the contributions of the three test variables to T-d and V-d. The obtained results and proposed perspectives are expected to be conducive to a deeper comprehension of the same or relevant behaviours of dispersive soils in the presence of water, so as to provide new insights for the targeted prevention and control of dispersive soil catastrophes.