| The hydraulic characteristics of unsaturated soils include soil-water characteristic curves and permeability functions.The soil-water characteristic curves represent the change in matrix suction with water content(including volume water content,mass water content,saturation,etc.);the permeability function indicates It is the relationship between unsaturated soil permeability coefficient and soil water content,water inflow time or matrix suction.The soil-water characteristic curve and unsaturated permeability coefficient are important for the analysis of engineering disasters caused by natural disasters such as slope instability and dam break,and loess wet subsidence and swelling soil expansion.Therefore,accurately obtaining the hydraulic characteristics of unsaturated soils is of great value in solving the above natural disasters and actual engineering problems.The method commonly used in the laboratory to test the soil-water characteristic curve is the pressure plate method,but this method is limited by the air intake value of the clay plate,and the test range cannot exceed 1 500 k Pa.After drying the soil,the moisture content of different sections is obtained,which makes the test soil column very tall,which not only increases the test time and cost,but also destroys the integrity of the soil column.Since the soil resistivity can well reflect the change of the water content in the soil,the soil resistivity test is introduced into the experimental study of the soil-water characteristics of unsaturated soils.The test device for the soilwater characteristic curve and the permeability of unsaturated soils The coefficient test container is improved,and the soil-water characteristic curve test system based on the resistivity method and the unsaturated soil permeability coefficient test system based on the resistivity method are integrated.According to the above systems,the soil-water characteristic curves and unsaturated soil permeability coefficients of different soil properties are tested to verify the broad applicability and accuracy of the test system.Provide theoretical and technical support for actual engineering.The following are the main contents and research results of this article.(1)A soil water characteristic curve test device and unsaturated soil permeability coefficient test container based on resistivity method were developed.The influence of different probe types on the test in soil-water characteristic curve test was analyzed.(2)The resistivity and volumetric water content of three different soil properties are calibrated.The calibration test is the basis for calculating the volumetric water content in the soil-water characteristic curve based on the resistivity method.(3)The soil water characteristic curve obtained based on the resistivity method is compared with the soil water characteristic curve obtained by the pressure plate method.According to the comparison results,it can be known that the device for measuring the soil-water characteristic curve based on the resistivity method is not limited by the air intake value of the clay plate,which can greatly increase the test range.(4)According to the permeability test based on the resistivity method,the change curve of the resistivity of each section of the soil column with the infiltration time is obtained,and then the change curve of the volumetric water content of the section of the soil column with the infiltration time is obtained.The curve composed of the volumetric moisture content of each section is the volumetric moisture content profile,and the unsaturated soil permeability coefficient of the selected soil sample can be calculated based on the volumetric moisture content profile and the VG model fitting equation for the soil-water characteristic curve.(5)The prediction model of unsaturated soil permeability coefficient is compared with the measured permeability coefficient of unsaturated map to verify the wide applicability of resistivity method in testing unsaturated permeability coefficient. |
PDF Full Text Request