Coupled forward of seepage field and current fields based on the element-free Galerkin method

Jointly solving the seepage and current fields is essential for determining the precise distribution of seepage in earth-rock dams and assessing its severity. In an effort to tackle the issues of insufficient fitting of seepage-electric relation and resolution loss in the hydrological-geophysical method, this paper addresses the sensitivity of electrical parameters to hydrological state variables and develops the coupled seepage-current forward modeling based on the Element-Free Galerkin Method (EFGM). On the one hand, the coupled model is constructed using the empirical formula for rock-physical relationships and the results of hydrological state variables; on the other hand, the sliding least squares method is employed to construct the shape function, and the penalty function is used to calculate the boundary conditions to solve the of over-dependence problem on grids in the coupled model construction and improve the seepage-electric fitting accuracy. The correlation response of the seepage field and current field was conducted separately through numerical simulations, the analysis focused on the current field and seepage path in the earth-rock dam, and compared the anomalous response characteristics of each component to the different accessory structural bodies of the earth-rock dam. The correlation response results indicate that the correlation response of seepage and electric field in the saturated zone is in good agreement. Whereas, due to the specificity of unsaturated seepage, the petrophysical properties of an unsaturated zone vary with saturation, porosity and other factors. It consequently led to a different distribution of physical parameters in the unsaturated zone from that in the saturated zone, causing differences in the correlation response of seepage and current field in the unsaturated zone. The coupling potential and current density distribution in the unsaturated zone are in good agreement with the seepage distribution. The results of the coupled seepage-current fields are considered significant in both theoretical and practical terms for constructing a hydrological-geophysical coupling inversion using model constraints.