Investigation into water retention behaviour of deformable soils

Abstract

Abstract:The paper presents an experimental and modelling approach for the soil-water retention behaviour of two deformable soils. The objective is to investigate the physical mechanisms that govern the soil-water retention properties and to propose a constitutive framework for the soil-water retention curve accounting for the initial state of compaction and deformability of soils. A granular soil and a clayey soil were subjected to drying over a wide range of suctions so that the residual state of saturation could be attained. Different initial densities were tested for each material. The soil-water retention curves (SWRCs) obtained are synthesized and compared in terms of water content, void ratio, and degree of saturation, and are expressed as a function of the total suction. The studies enable assessment of the effect of the past and present soil deformation on the shape of the curves. The void ratio exerts a clear influence on the air-entry value, revealing that the breakthrough of air into the pores of the soil is more arduous in denser states. In the plane of water content versus suction, the experimental results highlight the fact that from a certain value of suction, the retention curves corresponding to different densities of the same soil are convergent. The observed features of behaviour are conceptualized into a modelling framework expressing the evolution of the degree of saturation as a function of suction. The proposed retention model makes use of the theory of elastoplasticity and can thus be generalized into a hysteretic model applicable to drying-wetting cycles. The calibration of the model requires the experimental retention data for two initial void ratios. The prediction of tests for further ranges of void ratios proves to be accurate, which supports the adequacy of formulated concepts.Key words: soil-water retention curve, unsaturated soils, deformable media, constitutive modelling. Mots-clés : courbe de rétention d'eau du sol, sols non saturés, médium déformable, modèle constitutif.

Capillary water retention curve and shear strength of unsaturated soils

“…Specifically, volume swelling results in a decrease of saturation and volume shrinkage an increase of saturation; namely, dS r cap /dV ≤ 0. This phenomenon has also been widely observed from suction-controlled compressionswelling tests and interpreted by a number of other researchers in the literature as well (Vanapalli et al 1999;Gallipoli et al 2003;Sun et al 2007;Tarantino 2009;Masin 2010;Salager et al 2011).…”

Hydromechanical behaviour of a volcanic ash

“…The reduction in pore volume seems to have shifted the retention curve of the material (the points B and C do not match the reference retention curve in Fig. 3); in other words, the void ratio reduction is responsible for a higher retention capacity of the material in terms of degree of saturation for a given suction (Salager et al, 2013). The wetting path C-D (suction from 40 kPa to 0 kPa) induced a significant increase of the degree of saturation, which approached 90%.…”

Estudo do comportamento microestrutural de solos tropicais compactados

“…Esse comportamento tem sido observado em diversos trabalhos (Romero, 1999;Zhou e Yu, 2004;Salager et al 2007;Romero et al 2011;Salager et al 2013). …”