Fracture/matrix interaction in a fracture of finite extent

Abstract

The behavior of a wetting front invading a fracture in an unsaturated, porous matrix is of some importance for understanding infiltration and recharge processes, contaminant transport, and similar topics. Previous investigators have examined this problem, and a number of models have been published in the literature. It is, however, difficult to observe processes inside a fracture, particularly in a field setting. Many models of fracture flow and fracture/matrix interaction therefore lack an observable quantity and instead rely on comparisons with numerical simulations to test the validity of the theoretical constructs. Here a method is proposed that avoids this difficulty by analyzing flow in a finite fracture or fracture network. The fracture is considered finite because, after some interval of injecting water to the fracture at a constant rate, the wetting front reaches the far end of the fracture and exits at a point where it can be monitored. The discharge from the fracture constitutes an observable quantity and allows comparison with field or laboratory data. A curve matching procedure is described by which parameters characterizing the fracture/matrix system may be estimated, and the method is demonstrated using output from a numerical simulation, data from a laboratory experiment, and data from two field tests. Copyright 2010 by the American Geophysical Union.