Study On The Law Of Moisture Migration In Unsaturated Subgrade Soil Under Electroosmosis

The moisture condition of the subgrade has a profound influence on the service performance and life of the subgrade.Under the periodic freezing and thawing cycle,the water redistribution will occur in the road subgrade of the seasonal frozen soil area and form the stagnant water layer.The existence of the stagnant layer will cause the Subgrade Frost Heave and the thawing disease,and seriously reduce the strength of the subgrade;the electroosmosis is often used in the drainage and consolidation of the high water cut and low permeability soft soil.The flow field drives the pore water to flow out of the cathode.Due to the large electrical conductivity of soil,larger pore flow can be formed under the driving of lower electric potential gradient.The purpose of this paper is to apply electroosmotic drainage to the subgrade drainage in the frozen area.Therefore,the feasibility and drainage characteristics of electroosmotic drainage in unsaturated soil with large dry density and low water content need to be explored.In this paper,a laboratory unit test was carried out to study the variation of water content,electric potential and resistivity in the electroosmotic drainage process of unsaturated soil,based on the unsaturated soil hydraulic clay as the research object,and the influence factors of water content,electric potential and resistivity were studied in the electroosmotic drainage process of unsaturated soil.The relationship between the permeability coefficient and water content found the relation between the electrical permeability coefficient and water content of unsaturated soil,and then established the seepage flow equation of the unsaturated soil by electroosmosis,and realized the numerical reproduction of the electroosmotic drainage process of unsaturated soil.The main research contents and achievements of the paper are as follows:The electroosmosis and drainage test system of unsaturated soil was developed.A one-dimensional electroosmotic drainage test system of unsaturated soil with high pressure and low water content is designed,which includes specimen forming device,saturation device,electroosmosis device,humidity acquisition device,voltage acquisition device,current acquisition device,and the distribution of volume and potential in the volume of real time acquisition and recording unit.The variation of water content,voltage,current and resistivity during the process of unsaturated seepage drainage was studied.The effects of voltage,dry density and electrode materials on the electroosmotic drainage of unsaturated soil were analyzed.A coupled model of electric field and unsaturated water is established,and the law of water movement in unsaturated soil under electroosmosis is analyzed.Based on the Richard seepage equation of unsaturated soil and the linear superposition of the electric osmosis rate and the hydraulic permeation rate in the electroosmosis theory,the coupling model of the electric field water field of unsaturated soil is established by considering the nonlinear changes of the electric osmosis coefficient,hydraulic permeability coefficient and electrical conductivity of unsaturated soil,and the model is compared with the experimental results.The rationality and effectiveness of the type.The influence of different parameters on the results of the model is further analyzed by using the electric field unsaturated water coupling model.The saturated hydraulic permeability coefficient,the saturated permeability coefficient,the VG model aperture coefficient and the intake state coefficient,the parameters of the unsaturated electrical permeability coefficient model,the electrical conductivity parameter and the effective working voltage model in the model are transformed by the control variable method.The variation of the volume water content of the soil layers under different parameters is compared by comparing the different parameters.The influence of various parameters on the coupling model is analyzed,which lays a theoretical foundation for further exploration of the design method of the electroosmosis and drainage of unsaturated soil.