Soil-water characteristic curve and permeability function for unsaturated cracked soil

Abstract

Cracks are widely present in natural and engineered soils. As water infiltration into a cracked soil often starts from unsaturated conditions, the soil-water characteristic curve (SWCC) and permeability function for the cracked soil are required when conducting seepage analysis. This paper presents a method to predict the SWCC and permeability function for cracked soil considering crack volume changes during drying–wetting processes. The cracked soil is viewed as an overlapping continuum of a crack network system and a soil matrix system. The pore-size distributions for the two pore systems at a particular state can be determined and used to estimate the SWCCs and permeability functions. The estimated SWCCs and permeability functions for the two pore systems can be combined to give the SWCC and the permeability function for the cracked soil at that state. Then, the SWCC and permeability function for the cracked soil at different states along a crack development path can be obtained and combined to give the SWCC or permeability function for the cracked soil considering crack volume changes. Examples are presented to illustrate the prediction of the SWCCs and permeability functions for a cracked soil along five crack development paths.

Hydro-mechanical coupling effect on surficial layer stability of unsaturated expansive soil slopes

“…It is well known that the shape of SWCC is strongly related to the pore size distribution of the soils [25,23]. The bimodal nature of SWCC is possible for soils with a dual porosity structure such as the compacted coarse colluvial soils and the gap-graded soils [34,37,36,41,51]. The presence of cracks in expansive soils can lead to a dual porosity structure, including the macro-pores (i.e.…”

“…the intra-aggregate pores) resulting in a bimodal SWCC. For the purpose of numerical simulation of unsaturated hydraulic properties of cracked soils, some attempts were recently made to predict the bimodal SWCC equations [67] as well as corresponding bimodal hydraulic conductivity functions [34]. Alternative way to generate the continuous SWCC is to fit the measured data using spline function.…”

“…The unimodal SWCC for intact Regina clay used herein (see Fig. 5) is obtained from the bimodal SWCC for cracked surficial soil layer according to the superposition technique suggested by some researchers [26,34] for establishment of the bimodal SWCC. The AEV of unimodal SWCC of intact Regina clay is equal to the second AEV of bimodal SWCC of fissured Regina clay (i.e.…”

“…6 for the intact soil layer, which has a low saturated hydraulic conductivity of 3.456 Â 10 À6 -m/day. There is limited information about the measured hydraulic conductivity function of cracked Regina clay; however, some recent research [24,34] suggested that the hydraulic conductivity function of the cracked soil also exhibited a bimodal trend. The saturated hydraulic conductivity of such soil is reported to increase by one or more orders of magnitude compared to that of corresponding intact soils.…”

Limit analysis of slopes with cracks: Comparisons of results

“…The potential causes of cracks in slopes can be grouped into four categories: tension (Spencer, 1968;Chowdhury and Zhang, 1991;Wen and Aydin, 2005), weathering (Christaras, 1997;Ayalew et al, 2005), desiccation (Konrad and Ayad, 1997;Rayhani et al, 2008;Tang et al, 2010) and drying-wetting cycles (Rasa et al, 2009;Li et al, 2011).…”