A water retention model for deformable soils

Abstract

The paper presents an experimental study on water retention behaviour of two reconstituted soils, a silty clay (Speswhite kaolin) and a sandy clayey silt ( Barcelona silt) and two compacted soils, a silty clay ( Speswhite kaolin) and a silty sandy gravel (Adige river embankment). These soils were used with the aim of encompassing a wide range of soil types and soil fabrics. Specimens were subjected to drying and wetting 'hydraulic' paths by removing or adding water under zero total stress and to 'mechanical' wetting paths by compressing specimens at constant water content. To investigate a broad range of void ratios, the reconstituted sandy clayey silt was initially reconstituted from slurry by applying different consolidation vertical stresses, whereas the compacted Speswhite kaolin and Adige river embankment were compacted to a broad range of water contents and compaction energy. On the basis of the experimental data, a modification to the van Genuchten's model is proposed to account for the effect of void ratio on 'main drying' and 'main wetting' behaviour. The model is based on parameters having clear physical meaning and can properly describe water retention at medium and low degrees of saturation. It is formulated in such a way that effect of void ratio on 'scanning' behaviour can potentially be accounted for. The model applies to both the compacted and reconstituted soils investigated in this programme and describes water retention behaviour regardless of whether the degree of saturation is changed in a mechanical or hydraulic fashion

Soil-Water Characteristic Curve of Residual Soil from a Flysch Rock Mass

“…Many studies were conducted to assess the influence of different factors on the water retention properties of the soil in geotechnical engineering applications. Numerous investigations (e.g., [23][24][25][26]) noted that the void ratio, water content, and stress state of a soil have a strong influence on the SWCC. Standard laboratory equipment based on the axis translation technique, such as the pressure plate, volume extractor, suction-controlled oedometer, modified triaxial apparatuses, and standard tensiometers, are the most common devices used to control or measure matric suction.…”

Consequences on water retention properties of double-porosity features in a compacted silt

“…The water retention curve expressed in terms of water content or degree of saturation and suction is hysteretic, stress path dependent (void ratio) and depends on the pore network [1,10,16,18,19,21,23,25,27,28,31]. To properly describe its evolving water retention character, a multimodal retention model is proposed in the paper by considering a linear superposition of two subcurves of the van Genuchten [33] type.…”

Bridging Effective Stress and Soil Water Retention Equations in Deforming Unsaturated Porous Media: A Thermodynamic Approach

“…The air entry values in this approach were all determined directly from the available experimental data, and the slope of SWRC was considered to be almost the same under different net stress levels (consistent with the assumptions in the previous studies [see, e.g. Tarantino (2009)]. Therefore, the coupling parameter was the only parameter which was found from calibrating the proposed equation with the experimental data at zero net stress level.…”

“…One major characteristic of unsaturated soils is the soil water retention curve (SWRC), which specifies capillary pressure value associated with the water saturation degree. In recent years, experimental evidences have clearly shown that soil water retention curves are dependent on the stress level (Romero and Vaunat 2000;Karube and Kawai 2001;Gallipoli et al 2003b;Tarantino and Tombolato 2005;Nuth and Laloui 2008;Tarantino 2009;Uchaipichat 2010). Tarantino (2009) has considered the dependency of air entry value on stress level and has offered a SWRC equation for deformable media.…”

“…He considered zero residual saturation for simplicity. Consequently, his modified formulation of van Genuchten equation reads (Tarantino 2009):…”