Research On The Generation And Evolution Of Seepage Deformation In Levee

Seepage deformation and other problems related with seepage are the main cause of danger in levee during the flood period. In order to evaluate the safety of the levee, predict the form and location of the failure and suggest the the scientific instruction to reinforce the dyke, it is of great theoretical and practical importance to research the course of seepage deformation in the levee foundation during the flood period.Infact, the course of the seepage deformation in the levee foundation is just the course of"soil in water"turing into"water in soil". In the"piping area"where the seepage deformation generated, the expressions of Darcy's law will not be applicable, but the Navier-Stokes equations in hydrodynamics will be more suitable. In this thesis, on the base of laboratory simulation of seepage deformation in levee foundation, the theoretics of the generation and evolution of seepage deformation was setted up based on the coupled seepage-pipingflow analysis. And the numerical simulation of the seepage deformation was carried out by means of element-free method based on the above theoretics. The main researching resultes and creative works are summarized in three aspects:Firstly, the laws and the mechanisms of generation and evolution of seepage deformation in levee foundation are studied by means of laboration simulaton. The new technique of taking color sand as tracers was used to study the moving condition of the sand blow the clay layer, and it was really effective. The seepage deformation controlling mechanism of the cut-off walls was studied, and the controlling effects of the cut-off walls in different locations were also discussed.Secondly, the essential effecting factors of seepage deformation in levee foundation were studied based on the laboratory simulating result. The theories in hydrodynamics and sediment dynamics are used to analyse the course of seepage deformation. The thorey and the estimation system of seepage deformation evolution was setted up and improved. Thirdly, the technique of carrying out the coupled seepage-pipeflow analysis by elemwent-free method was setted up for the first time. Using the predominance of the elemwent-free method that its nodes are independent of its mesh, the boundary between the seepage area and the pipingflow area can be moved automaticly; and using the character of the elemwent-free method that its nodes can be moved, added or deleted freely, the nodes destiny in the some parts can be increased. After integrated the above theorems and researching results, the element-free method program named"Freeseepde"was built to simulate the course of seepage deformation, and the numerical validation contraposing the laboratory simulation result was carried out.Finaly, a typical levee of the Yangtze River was choosen to be simulated. Some common phenomenas in the seepage deformation course were described in the numerical method, and the seepage deformation controlling effects of the cut-off walls was evaluated. The computing result shows that the theory system of seepage deformation in this thesis is reasonable and effectual.