Abstract
The hydraulic characterization of mixed compacted soils is helpful for the design of earthworks subjected to drying–wetting cycles. When the mixed soil is well-graded and made of both coarse and fine fractions, its matric suction may also be due to the short-range adsorption phenomena, as for the soil investigated in this research work. A silty–clayey sand was created by a mixing procedure and experimentally investigated at two different scales. Physical modeling of an infiltration process was performed, allowing an inverse numerical analysis to infer the water retention and the hydraulic conductivity functions of the soil, whereas element testing on soil specimens allowed direct determination of the same equations. In the article, problems related to the employed suction measurement techniques have been pointed out and discussed. By this two-scale combined strategy, features of the soil hydraulic behavior, such as the wetting collapse, the shrinkage during drying, and the loop of hysteresis, were also determined.
Highlights
IntroductionThe hydraulic characterization of mixed compacted soils is relevant to the design of earthworks subjected to imbibition–evaporation cycles (e.g., dams and embankments), since the changes in the suction profiles within the soil affect its stress–strain response and, work safety and serviceability
The tests have revealed that measuring the matric suction of this kind of soil by using mini-tensiometers is not enough to obtain reliable values when the water content is low, because the short-range component of the matric suction seems not detectable by this sensor
Measurements with filter paper tests have helped the definition of the soil retention properties and the loop of hysteresis over a wide suction range, making the inverse numerical analysis of the infiltration process more successful
Summary
The hydraulic characterization of mixed compacted soils is relevant to the design of earthworks subjected to imbibition–evaporation cycles (e.g., dams and embankments), since the changes in the suction profiles within the soil affect its stress–strain response and, work safety and serviceability. A physical infiltration process [4] through a large soil volume has been performed, and an inverse numerical analysis of such boundary value problems has revealed the hydraulic equations of the porous medium, i.e., both the water retention, WRC, and hydraulic conductivity, and k(s) functions [5,6]. At the element volume scale, the soil retention properties have been investigated through laboratory testing on soil specimens At both scales, the initially dry soil was subjected to a wetting path, followed. It is worth noting that the van Genuchten model assumes that the volumetric water to 100% (θ0 = θs , where θs is the volumetric water content at saturation) This is an ideal content, θ0,that at which matric suction is zero, a degree of saturation equal toat behavior is intermediate between thatcorresponds of swelling to soils recovering full saturation negative pressures that of soils needing positive pore pressures fully.
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