Abstract Fractured crystalline rocks are widely regarded as suitable host formations for applications such as deep geological repositories for spent nuclear fuel. Fluid flow within these formations predominantly occurs through networks of fractures characterised by internal heterogeneity and multiple contact points, both of which are strongly influenced by in situ stress conditions. These stresses may vary due to processes occurring on a wide range of time scales, from excavation-induced stress redistribution to glacial loading. Understanding the coupled hydro-mechanical mechanisms that govern flow through individual fractures is therefore essential for developing reliable large-scale discrete fracture network models. This study uses a coupled hydro-mechanical experiment on a rock sample containing a natural single fracture to evaluate the applicability of the local cubic law and the effects of normal loading on flow. The fracture aperture field was determined by 3D scanning the opposing fracture surfaces after opening, with vertical alignment refined using pressure film data. A sensitivity analysis of 27 alignment cases incorporating translational uncertainties along the x -, y - and z -directions was conducted to evaluate their influence on flow behaviour under increasing normal load. Results indicate that flow is highly sensitive to surface alignment, and that the local cubic law overestimates flow by at least two orders of magnitude for all loading cases. Applying a constant correction factor to convert mechanical to hydraulic aperture based on the unloaded cases fails to reproduce experimental flow rates as loading increases. A new expression relating the correction factor to contact area evolution under loading achieves close agreement with experimental data across all cases.
Stock et al. (Thu,) studied this question.