Simulating Flow through Fractures in a Rock Mass Using Analog Material

Abstract

Understanding the mechanism of fluid flow through a rock mass (intact rock with discontinuities) is essential for safe and economical construction of the structures that are located in the hard or crystalline rocks. In these rocks, fluid flow occurs mainly through interconnected voids or fracture network, which in turn is governed by the flow properties of the fractures or the most prominent single fracture. However, simulating fluid flow through a fracture network, which is a conglomeration of several individual fractures, is quite intricate and difficult. Hence, focusing on characteristics of the fluid flow through a single fracture under varied confining stress becomes an excellent stepping stone. In addition, collection of the undisturbed rock samples from the deep locations and creation of the fracture(s) for laboratory testing is a cumbersome task. To overcome these limitations, a methodology to simulate flow of water through a fractured rock mass using an analog material, paraffin wax, imbibing a single fracture was developed and its details are presented in this paper. This methodology facilitates easy simulation of the flow through a fracture of certain aperture. Based on the study, it was demonstrated that the Reynolds number is quite sensitive to the fracture aperture and the base pressure, and there is a critical base pressure, beyond which transition in laminar to turbulent flow occurs. It is believed that such studies will be quite handy, useful, and economical for studying fluid flow through the rock mass.