Laboratory study of the possible division of fractures and conduits and the applicability of Cubic law in closed fractures

Abstract:

A new laboratory experimental method has been developed to obtain the hydraulic head loss of either the closed fractures or conduits whose surfaces are in contact. This method has been developed based on the balance of energy. It was found that the linearity between the hydraulic head loss and the flow velocity decreases with the aperture increases, based on which a possible division of fractures and conduits is proposed. The results of the division show that a closed flow structure with about less than 1.4635mm aperture can be defined as a fracture whilst a closed flow structure with more than 1.8375mm aperture can be defined as a conduit. The flow structure with an aperture of 1.6000mm is in the transitional area of fractures and conduits. In addition, the Cubic law cannot exactly describe the relationship between the hydraulic head loss and the velocity when applied to closed fractures in these investigations. The effects of deviations from the ideal conditions when applying the Cubic law cause an apparent reduction in hydraulic head loss and may be incorporated into the Cubic law by adding the effects of both the width of the fracture and the ratio of the width to the aperture.