Method and device for quickly determining permeability functions of unsaturated soil

Abstract

The invention discloses a method and a device for quickly determining permeability functions of unsaturated soil. The method comprises the following steps: carrying out discretization and inverse solving on a partial differential equation of a basic soil water movement equation Richards by applying a forward Euler method and a backward Euler method to obtain two permeability coefficient expressions of the unsaturated soil; then measuring a series of data that the volumetric water content theta t at detla z in a sample and tension ht change along the time through a constant water head one-dimensional vertical unsaturated infiltration test; substituting experimental data into obtained two expressions; combining calculation results of the two expressions to quickly and accurately obtain the permeability functions of the unsaturated soil. The experimental device comprises a sample cylinder body, a measuring system, a water supply system and a water collecting system; the water supply system is used for providing constant water head water source required by the test; the water collecting system is used for collecting and measuring water yield; the measuring system comprises a sensor for measuring the theta t and the tension ht and an automatic acquiring device for acquiring data; the sensor is buried at a fixed position delta z inside the sample cylinder.

Description

technical field [0001] The invention relates to the field of experimental measurement of unsaturated soil permeability coefficient, in particular to a method and device for quickly determining the permeability function of unsaturated soil. Background technique [0002] The functional relationship between the unsaturated permeability coefficient and the soil water content is called the permeability function. Most of the soil covered on the earth's surface is in an unsaturated state. With the decrease of saturation, the degree of reduction of the unsaturated permeability coefficient of the soil can produce changes of several or more orders of magnitude. Therefore, how to determine the unsaturated permeability coefficient of soil has become a key issue in the unsaturated seepage analysis of common slope engineering, foundation engineering, dam and other geotechnical engineering and pollutant migration. [0003] At present, the unsaturated permeability function of soil is mainl...

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Problems solved by technology

The test process of the transient section method is very complicated. It is necessary to control the flow boundary conditions and prevent any part of the sample from having an obvious wetting surface or saturation, and the time period is also long.

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