Influence of irrigation method on the infiltration in loess: field study in the Loess Plateau

Abstract

a b s t r a c tIt is well known that loess soils are collapsible upon wetting, and subsidence or cracking or failure of structures induced by loess collapsing poses serious threat to human being. Wetting is the most important prerequisite for loess collapsing; however, how the irrigation water, both man-made and natural, infiltrates and flows in loess is not well known. For this reason, a field soaking test simulating flooding irrigation method and a rainfall infiltration test simulating dripping irrigation method were conducted in instrumented sites in the Loess Plateau. This paper presents the results from soil water meters to reveal the infiltration process in loess based on the soil water content variations. The results highlight the significance of the preferential flows when a large amount of water is irrigated to the soils (flooding irrigation). Owning to the presence of preferential paths, the water infiltrates from both shallower and greater depths to the intermediate depths, as a result, bell-shaped zone of wetting and saturated zone are developed in the soils. However, the influence of environmental factors is of dominance when the amount of irrigation water is very small (precipitation). The rain water, pore water, and water vapor transform from one to another depending on the rates of precipitation and evaporation as well as soil properties. For this reason, the maximum depth of the wetting front measured in a drought year was less than 3 m. The test results provide valuable information for interpreting the infiltration of water in loess with respect to varying irrigation method, soil heterogeneity, and environmental factors. However, such information is required for modeling the wetting-induced collapse of loess and analyzing the stability of structures built on loess.

Experimental study of loess disintegration characteristics

“…Loess disintegration aggravates slope erosion, destroying slope forms by cutting and forming gullies, cracks, and caves (Derbyshire, 2001;Zhuang et al, 2017). The Loess plateau has a particular sediment type that formed in the Quaternary period and is characterized by vertical joints, large pore structures, weak cementation, loose texture, and high calcium and soluble salt content (Gu et al, 2015;Wang et al, 2018aWang et al, , 2018bWang et al, , 2019aWang et al, , 2019b. These properties are conducive to loess disintegration in the form of fragmentation, disintegration and caving, after water infiltration.…”

Infiltration Law of Water in Undisturbed Loess and Backfill

“…Li et al [23] carried out the water immersion test in an unsaturated undisturbed loess slope and studied the formation of a transient saturated zone and the migration process of water in the loess; they also considered that the infiltration range of water in unsaturated loess was approximately elliptical. Wang et al [24], Huang et al [25], Yao et al [26], An et al [27], and Wang et al [28] also studied the law of water seepage movement and collapsibility in loess by a field immersion test.…”