Measuring and simulating moisture uptake in a fractured porous medium

Water uptake in fractured brick samples is monitored with X-ray radiography. This technique can measure both the moisture profiles in the matrix and the height of the waterfront in the fracture during the experiment. It was found that the waterfront in the fracture could quickly reach the opposite side of the specimen, resulting in an extra water source for the surrounding matrix over the total height of the sample. For smaller fracture apertures, however, the waterfront in the fracture stagnates and moisture profiles in the matrix run ahead of the waterfront in the fracture. To simulate the experiments, a numerical model for unsaturated moisture transport in fractured porous media is developed. The model combines a discrete fracture model for moisture flow in a variable aperture fracture with a finite element model for unsaturated flow in the porous matrix. To achieve a stable numerical solution, movable nodes, following the moisture front in the fracture, are introduced on the boundary of the finite element mesh. The numerical results of height of rise in the fracture as well as of moisture profiles in the matrix show to be in good agreement with the measurements. The paper ends with a parameter analysis, investigating the effects of fracture aperture and matrix properties on the unsaturated moisture flow in fractured porous media.