Combined Test-Numerical Analysis Method for Unsaturated Soil Relative Permeability Coefficient

Abstract

The invention relates to an experiment-numerical analysis combined determination method for the relative permeability coefficient of unsaturated soil. The method comprises simple experiment tests and numerical analyses, the relative permeability coefficient equation of soil under unsaturated state is obtained via simple laboratory experiments and numerical optimization fitting analyses, therefore, the relative permeability coefficient of the unsaturated soil is obtained by calculation. The method is mainly suitable for cohesive soil with a small permeability coefficient. At the same time, the invention provides a numerical analysis procedure which comprises a basic analysis module and an optimization back analysis module, wherein the basic analysis module simulates the dehydration process of test specimens under the condition of a given boundary; the optimization back analysis module takes a determined dehydration mass-time curve as basic input to confirm two parameters Pr and m describing the changes of the relative permeability coefficient of the unsaturated soil along with saturation via an orthogonal optimization method in the numerical analyses. The method is simple in experiments, convenient to operate, wide in usable ranges and good in accuracy; the determined relative permeability coefficient equation can be directly applied to soil engineering structure analyses.

Description

1. Technical field [0001] The invention relates to a test-numerical analysis combined determination method for the relative permeability coefficient of unsaturated soil. 2. Background technology [0002] In civil engineering, such as roadbeds, clay core walls of earth-rock dams, all engineering and agricultural soils can be considered unsaturated soils: that is, gas and water coexist in soil pores. The mechanical properties and deformation properties of soil are controlled by both water content and pore water pressure. The relative permeability coefficient is an important parameter reflecting the migration of water in the pores of unsaturated soil. It plays an important role in the deformation of the subgrade, the seepage control of the clay core wall of the earth-rock dam, the construction of geotechnical engineering, and the study of the agricultural soil environment. How can it be correct and convenient? 1. Accurately measuring the variation of soil permeability coeffici...

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Problems solved by technology

Therefore, it is not easy to measure the relative permeability coefficient of soil in the laboratory or on the spot: it is usually necessary to use axial translation technology to control water pressure and air pressure at the same time, and high-quality water-permeable and air-tight ceramic plates are required. The test equipment requires high requirements and the test time is long. In addition, the results measured by the test are only for the relative permeability coefficient at several specific saturations, which need to be further expanded, and can only be used in geotechnical calculations through curve fitting

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