摘要

In finite element-based three-dimensional numerical simulation of direct current (DC) resistivity method, applying traditional mixed boundary condition cannot accomplish solving linear equations through recursion due to computation of stiffness coupling with source positions. Currently Neumann boundary condition or infinite element boundary condition is usually used instead. Although rapidly resolving, these two methods reduce the precision of numerical simulation. To realize recursive resolving rapidly and ensure simulation precision, an approximate boundary condition is proposed to implement both fast recursive resolving and precise simulation. The key ideas underlying the method are to separate boundary coefficient matrix coupled with source positions from stiffness matrix so as to make the resultant stiffness matrix independent of source positions. Production of boundary coefficient matrix and primary electric field vectors on the boundary is then transferred to the right hand of linear equations. In doing so only right-hand source items need to be computed when source positions are changed. Synthetic tests show that the numerical simulation precision applying the newly proposed boundary condition is superior to the one using mixed boundary condition in the case of horizontal topography. Also, in the case of rugged topography, the simulation results, compared with the application of neumann boundary, are much closer to those with mixed boundary condition.