A Semianalytical Solution for Transient Confined–Unconfined Flow with Non-Darcian Effect

Abstract

Pumping at a large rate can convert a confined flow to a confined–unconfined one in a confined aquifer. In this paper, a new semianalytical solution is proposed to investigate the mechanism of transient confined–unconfined flow under the non-Darcian condition in a fully penetrated confined aquifer. By using Izbash’s equation, a new linearization method was developed to approximate the nonlinear terms of the mathematical model of pumping-induced flow. The solution was derived by using the Laplace transform. The acceptability of the proposed solutions was verified by comparisons with numerical solutions by COMSOL Multiphysics and an analytical solution. The effects of the non-Darcian index, hydraulic conductivity, and the storativity ratio on developments of drawdown and the transient unconfined region were especially investigated. It is indicated that the non-Darcian index and the hydraulic conductivity have a positive effect on the drawdown in the confined region and a negative effect on that in the confined region, respectively. Otherwise, the drawdown simulation is negatively related to the storativity ratio. The result of this paper offers much-needed insights in the field of mine dewatering and the application of geological and hydrological conditions.