Research On Movement And Erosion Characteristics Of Seepage Water In The Loess

The structural heterogeneity of current loess is the result of continuous infiltration ofseepage water during the eras of geological history. Research on the movement characteristicsof seepage water in the loess and its erosion destruction to the soil structure, and use theresults for the utilization of groundwater, study on mechanism of groundwater erosion,prevention and control of groundwater pollution, which is very necessary.Therefore, we take homogeneous loess for cases, seepage tank as the main devices,indoor test as the main research methods, study on the relationship between movementcharacteristics of seepage water in the loess and the soil structural parameters mp, to explorethe relationship between destruction and reforge process of microstructure of loess andmovement characteristics of the seepage water. The main conclusions are as follows:(1) For simulating the original state accumulation of loess, the longitudinal velocity ofseepage water have obvious linear relationship with the horizontal velocity of seepage water,and the longitudinal velocity of seepage water is faster than he horizontal velocity of seepagewater. Thus, we can infer that, under the long-term effects, the soil longitudinal channel willbecome more developed as the preferred channel of seepage water, while the horizontalchannel develops relatively slow, which can explain the present situation of loess that thevertical joints, while horizontal fracture strike is different that it is difficult to form adominated flow direction.(2) Compared with multipoint water supply, the wetting front shape curve of seepagewater under single point water supply turn into a long elliptical sphere more quickly. Thelongitudinal and horizontal velocity after saline seepage water pass through the soil is fasterthan that of seepage water to a certain extent, because of the enhanced effect due to adsorption,adhesion influence between particles.(3) Use fractal dimension D to characterize complexity and nonsmooth of the wettingfront shape curve, we find that the fractal dimension D gradually increase in a overall trend asthe time pass. Draw the relationship curve of fractal dimension D and vertical, horizontalvelocity ratio, it turns out that, quadratic polynomial curve can fit well.(4) Use structural parameters mpto characterize the destruction of the soil structure after the migration and disturbance of the seepage water, it turns out that, with the seepage watergradually downward movement, the seepage water has a more and more strong effect on thestructure destruction, collapse, remodeling of the loess soil.(5) Through observation, the upward suction permeability curve of ground waterfluctuates slightly, presents basically a straight linear water level. When the seepage wettingfront contact with underground water, it is a point contact, then the wet point shrinkage,collapse, and expanded to around quickly. As a theoretical basis, we boldly put forward, thesoil near the contact point could rapidly collapse when the seepage water get contact withphreatic surface, which lead to the original cave erosion, also we draw the cave erosion modeldue to the contact of seepage water and phreatic surface.(6) Based on previous research results, we established the loess transfusion destructionmodel based on relationship between structure parameters mp, seepage time, longitudinalseepage velocity with the soil depth distance. After further deduce, we conclude the equationof structure parameters mp, which make it possible that using migration movement parametersof seepage to represent the structure destruction, collapse, remodeling of the loess soil afterseepage water pass through, has a certain significance.