Contaminant Transport in Fissured Soils by Three-Dimensional Boundary Elements

Abstract

A boundary element method for the solution of contaminant transport equations in three-dimensional (3D) fissured soils with non-equilibrium exchange is proposed. Fast transport is assumed to take place through a network of fissures which can be one-dimensional, two-dimensional or 3D space. Soil-matrix blocks act as storage sites for the contaminant, combining with sorption in the fissures, to increase retardation. The 3D boundary element method is formulated in the Laplace domain, where equations are linearized with respect to time, and the need for time stepping is hence removed. Solution is inverted back into time domain using a numerical technique. The numerical solution is validated and the scope of the method is illustrated by applying it to the study of cylindrical, rectangular, and spherical waste repositories in a fissured clay. The effects on contamination patterns of various fissure configurations as well as the shapes, dimensions, and number of repositories are assessed.