Study On The Characteristics Of Earth Slope With Sudden Change Of Water Level In Front Of Slope

The slope instability near rivers and reservoirs is usually caused by the sudden change of water level in front of the slope. In order to realize the failure mechanics of landslide, it is meaningful to research the effects of sudden change of water level in front of the slope on the characteristics of soil slope. The study has great practical significance to control landslide disaster and to develop a reasonable dewatering program for excavation project. Using GEO-SLOPE software, the seepage characteristics was studieded on the basis of seepage-stress imperfectly coupled method and unsteady saturated-unsaturated theory. The effects on stress and deformation characteristics of the slope are also analyzed.Firstly, neglecting rainfall infiltration and evaporation for the slope, for horizontal impermeable layer with infinite lateral extension, one-dimensional Boussinesq Equation was sloved to obtain the distribution function of phreatic line and flow velocity of groundwater analytically. The expression was got by using partially linearization. Change of the phreatic line in the upper layer of a double-layered ground with was also researched.Secondly, a numerical model of unsaturated seepage theory was built and the method of obtaining the seepage parameters was introduced. The thesis paid close attention to the isochrone of pore water pressure in the slope. The effect of water level change in front of slope would gradually decrease from the slope surface to beyond. It was deduced that during the sudden change of water level and a period after the water level becoming stable, lag effect was more obvious beyond the slope surface. It was found the seepage lag effect was more obvious when the saturated hydraulic conductivity was smaller.Thirdly, based on the seepage-stress imperfectly coupled method by using the GEO-SLOPE software, the effect of sudden change of water level to the physical properties and deformation characteristics of slope soil were calculated when the temporary seepage field was obtained. And it could be found that multiple factors affected the slope when the water level before the slope changed suddenly. In the initial stage of the water level changing, the seepage force played a vital role to the slope deformation, but its duration was short. The deformation of slope was almost the same with seepage lag effect caused by sudden change of water level in front of slope. The saturated hydraulic conductivity played a role to slope deformation. When the saturated hydraulic conductivity was greater, the slope deformation developed more rapidly. The saturated hydraulic conductivity played fewer roles to the ultimate settlement.Finally, for the engineering cases of subgrade reinforcement in west Zhejiang area, the stability of subgrade joined with retaining wall was studied taking change of valley water table into account. Based on the monitoring results of Three Gorges Reservoir, the deformation of Xietan Landslide under water level change of Three Gorges Reservoir was analyzed by using the numerical method. It shows that the numerical results using seepage-stress imperfectly coupled method of unsteady saturated-unsaturated theory give a good simulation of the effect of water level change on Xietan Landslide.