Abstract
At present, there are only a few existing models that can be used to predict the relative permeability of unsaturated soil under deformations, and the calculation process is relatively complex. In order to fit the measured value of the relative permeability coefficient of unsaturated soil before deformation, this work employs the simplified unified model of the relative permeability coefficient of unsaturated soil, and it obtains the index λ before deformation of the soil. In addition, the value of index λ remains unchanged before and after deformation. Based on the actual measured value of the soil–water characteristic curve before deformation, the air-entry value prediction model is used to predict the air-entry value of soil with different initial void ratios. The relative permeability coefficient of unsaturated soil is then conveniently predicted using the graphical method in combination with the simplified unified model. The method is validated by using the test data of silt loam, sandy loam, and unconsoildated sand. The results show that the predicted results are consistent with the measured values. The prediction method in this paper is simple and overcomes the limitations associated with the determination of the index λ. It expands the application range of the unsaturated relative permeability coefficient model while improving the accuracy of predictions.
Highlights
Accepted: 29 September 2021At present, there are many studies on the mechanical properties and hydraulic properties of soil [1,2,3]
This paper suggested that, in order to predict the unsaturated permeability coefficient under deformation conditions, the unsaturated permeability coefficient of the soil should be measured first, and the λ value obtained by fitting the experimental data of the unsaturated relative coefficient and air-entry value prior to deformation
The deformation of soil will cause changes in the pore ratio, pore size distribution, unsaturated relative permeability coefficient and the matrix suction at the maximum and pore shape of soil, for example, large pores will be compressed into small pores [24]
Summary
Accepted: 29 September 2021At present, there are many studies on the mechanical properties and hydraulic properties of soil [1,2,3]. Accurate prediction of permeability coefficient is an important prerequisite for studying soil water conservancy characteristics, and it plays an important role in the impact of groundwater on buildings, slope instability caused by rainfall, seepage and diffusion of pollutants in landfills, and seepage prevention of soil dams. Water and air occupy the pore volume in the soil, so its permeability coefficient is affected by saturation, even in the near-saturated state (suction range is 0~1 kPa). A small change in suction can cause a great influence in the permeability coefficient [7]. This renders the task of measuring the permeability of unsaturated soil difficult to achieve. It is crucial to propose a method to predict the unsaturated permeability coefficient.
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