ANALYTIC MODELING OF IMPERMEABLE AND RESISTANT BARRIERS

Superpositioned analytic functions are used to efficiently and accurat ely model ground-water flow fields containing thin barriers such as sl urry walls and sheet-pile walls. Barriers are modeled as a series of s traight-line segments strung together to create irregularly shaped ope n or closed boundaries with zero thickness. The complex analytic funct ions employed provide perfect continuity of flow across the boundary w hile approximating normal flux boundary conditions along the boundary. Along an impermeable boundary the normal flux is specified as zero, a nd along a resistant (leaky) barrier the normal flux is proportional t o a specified resistance parameter and the potential difference across the boundary. solution of a given flow problem requires solving a sys tem of equations with one equation per boundary corner. These equation s are linear for impermeable boundaries and for resistant boundaries i n confined aquifers or single-strata unconfined aquifers. In other cas es, the boundary condition equations associated with resistant barrier s can be nonlinear and a new technique for iterative solution is emplo yed. Implementation of these techniques in a computer program is teste d and it is demonstrated by modeling various configurations of flow fu nneled into a gap between two barriers.