Study On The Mechanism Of Water Level Changes And Rainfall Induced Bank Slope Instability

The change of transient seepage field caused by the changes of reservoir water level and rainfall is the main factor for the destabilization failure of bank slope.By studying the changes of the seepage field of the reservoir bank slope under the action of reservoir water level changes and rainfall to revealed that the influence of rainfall and reservoir water level changes on slope stability is very important for predicting landslide hazard and avoiding loss of life and property.In this paper,the meshless method 'Multiquadric Radial Basis Function Collocation Method(MQ RBFCM)' is applied to solve the saturated-unsaturated seepage governing equation-Richards equation for calculating and analyzing the change of seepage field on the bank slope under the action of the changes of reservoir water level and rainfall.The mechanism of bank slope instability was studied by analyzing the effect of water level drop and rainfall on bank slope stability combined with rigid body limit equilibrium theory.The main contents and results in this paper are as follows:(1)Based on literature research,the basic principles of saturated-unsaturated seepage are summarized;The generalized Richards equation deduced according to mass conservation and flow conservation law and the unsaturated Richards equation linearized by Gardner's soil-water characteristic curve model.They are combined into the saturated-linearized unsaturated seepage governing equation.(2)Deducing the process of solving saturated-unsaturated seepage problem by MQ RBFCM:discreting the seepage problem governing equation and the boundary condition in the form of the radial basis function of the multivariate quadratic equation;Establishing the algebraic equations for the saturated-unsaturated seepage problem by foring discrete points to satisfy the governing equations and the boundary conditions.Simultaneouing Equations for solving transient and steady seepage.(3)Compiling the program of the process of solving saturated-unsaturated seepage problem by MQ RBFCM with Matlab language,to solve the problem of free surface of steady seepage,free surface of unsteady seepage and rainfall infiltration of one-dimensional infinite slope.The calculated results are in good agreement with the previous experimental results,analytical solutions and other numerical simulations.It is found that the MQ RBFCM can reduce the computational cost effectively,and the global non-polynomial interpolation of MQ RBFCM is more accurate than the local low-order polynomial interpolation of the traditional numerical methods.(4)Compiling the MQ RBFCM seepage analysis program with Matlab language,to calculate the steady state and transient seepage field of the bank slope under the action of reservoir water level changes and rainfall.Combining the rigid equilibrium theory,using the STAB program analysis the variation law of slope safety factor and the critical slip surface of the bank slope at each time,and discussing the failure mechanism of the bank slope.