On the Differing Role of Contact Obstacles on Variably Saturated Flow in Vertical and Horizontal Fractures

A series of flow visualization experiments is developed in order to observe the different role that contact obstacles have on variably saturated flow in a vertical fracture compared to a horizontal fracture. The model fractures consist of a single rough-walled quartzite fracture wall mismatched with a second transparent smooth replica wall. Results drawn from this research show that contact obstacles result in longer flow paths of between 4 and 14%, with longer flow paths observed in horizontal fractures. Furthermore, contact obstacles result in different unsaturated flow mechanisms when present in vertical compared to horizontal fractures under low flow rates. Contact obstacles enhance the variably saturated flow process in vertical fractures, but act as choke points in horizontal fractures.