Darcian Seepage through a Parallelogrammic Ramp: Toth’s Model Revisited

Fully saturated, 2-D steady seepage in a homogeneous, isotropic, parallelogrammic ramp is studied using the methods of complex analysis (a conformal mapping and integral representation of mixed boundary-value problem). A porous medium flow is induced by an overland free-surface flow with the latter determining the "shearing" pressure (hydraulic head) of the former through a boundary condition along one side of the polygon serving as a conjugation line. For a uniform overland flow, the stream function along the conjugation line has a single maximum corresponding to the Toth hinge line. The inflow rate into the ramp is divided into a part exfiltrating through the toe and through a toe-adjacent segment of the conjugation boundary. A wavy free surface is shown to generate a more complex seepage topology.