Abstract
Loess has the characteristics of complex structure and reduced mechanical strength after encountering water. In Chinese loess areas, irrigation, water storage, and rainfall affect the stability of the original loess structure and cause damage to the foundation. This paper analyzes the results of in situ water immersion test (in order to study the permeability of water storage in undisturbed loess), rainfall test (in order to study the permeability of rainwater in the backfill loess), and water storage test (in order to study the permeability characteristics of water storage in backfill loess) on the filling site and studies the permeability law of water in unsaturated layered loess and backfill remolded loess. The results of the in situ immersion test show that the vertical seepage velocity of water was very fast, and the infiltration depth was close to 25 m after 9 days of water storage, and at the interface of the new loess, the paleosol, and the old loess, the water infiltration line appeared to be refracted. Finally, the vertical and horizontal penetrations of water in the loess are analyzed, and the range of water immersion and saturation are determined. Through the rain test and water storage test of a loess-filled surface, the relationship between the moisture content and depth of the backfill loess before and after rainfall and storage is obtained. The results of rain period test show that the water infiltrated into the loess about 3 m after 25 days of rainfall. A further 90 days storage test shows that the final infiltration depth of water was about 7 m.
Highlights
The permeability characteristics of soil have been studied for a long time
We based the extent of water infiltration on the change of water content in loess in the boreholes, in combination with the monitoring results of the moisture meters to determine the range of water immersion
The following conclusions were drawn: Infiltration rate of undisturbed loess was very fast and water would always infiltrate in the in situ water immersion test, after 9 days of water storage, the infiltration depth of water was close to
Summary
The permeability characteristics of soil have been studied for a long time. The related permeability models for calculation are established, such as Van Genuchten model, Fredlund–Xing model, etc. Wang et al [24], Huang et al [25], Yao et al [26], An et al [27], and Wang et al [28] studied the law of water seepage movement and collapsibility in loess by a field immersion test. Researching water seepage in soil horizons, Gvirtzman et al [29] conducted two large-scale outdoor experiments to study the permeability characteristics of unsaturated loess—the loess deposit was composed of alternating silt and sandy clay loess deposits. Gao et al [31] studied the soil–water characteristic curves of remolded clay under different compaction work and different compacted moisture content by using a conventional pressure plate instrument; the permeability coefficient of the saturated soil was measured by the variable head method. It is necessary to study the permeability of water in loess
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