Study On Three-dimensional Saturated And Unsaturated Seepage Mechanism Based On RBF

Groundwater seepage is one of the most important indicators in the field of hydraulic engineering.In Fujian Province,the groundwater reserves are abundant due to special geological structure and climatic reasons.Therefore,during the construction process,it often confronts the phenomenon of seepage failure caused by groundwater.It is of great theoretical value and engineering significance to study the variation trend of seepage field in saturated and unsaturated soils.Based on the project of ’Fujian Natural Science Foundation of China’,this paper uses the theory of groundwater seepage,derives the control equations of saturated and unsaturated soil seepage,and the groundwater seepage model is established.By using the meshless method’Multiquadric Radial Basis Function Collocation Method(MQRBF)’to discrete spatial domain,and the euler implicit method is applied to the discrete time domain.Through numerical simulation,the pore water pressure distribution law in different time and depth of soil is obtained,effectively solves the numerical ill conditioned problem of traditional numerical method in simulating soil percolation.The research contents and related results are as follows:(1)Based on literature research,I summaries the basic theory of saturated-unsaturated soil seepage.According to the law of conservation of flow and energy,the governing equation of soil seepage in saturated layer-generalized Richard equation is deduced.Combining with the Gardner(GR)model in the soil water characteristic curve,and overcoming the highly nonlinear of the seepage material and equation parameters in unsaturated soil,I derives the control equation of seepage flow in unsaturated layer-the linearized Richard equation.(2)The mathematical model of amoeba with irregular boundaries is given,and it is proved that MQRBF has some advantages in solving partial differential equations.I discretes the governing equations and boundary conditions of groundwater seepage and establishes a two-dimensional and three-dimensional numerical model of groundwater seepage.The seepage algebraic equations of saturated soil andunsaturated soil are obtained respectively,and the steady-state and transient flow field of soil flow field is described.(3)For the seepage problem of saturated layer,the single connected,double connected,multiply connected and interbedded soils are analyzed.By comparing the similarities and differences of each case,the trend of pore water pressure is summarized.For the seepage problem of unsaturated layer,the numerical simulation results are compared with the analytical solutions by Fred T.Tracy and finite difference results proposed,and then the head distribution of three-dimensional seepage field is simulated.Compared with the traditional numerical method,MQRBF can well solve the dynamic difference of wetting peaks in the infiltration of surface flow.When the permeability of soil varies greatly.the mesh will not undergo torsion and deformation,and no singular matrix will be generated.The numerical results can be well converged.