Yield-power-law fluid propagation in water-saturated fracture networks with application to rock grouting

Abstract

Cement grouting is widely applied in rock tunneling and underground construction to reduce groundwater inflow and increase the tightness of rock masses. The rock grouting process involves complex non-Newtonian grouts propagation in fracture networks. In this study, a two-phase flow model extended for yield-power-law fluid (e.g., cement grout) propagation in water-saturated fracture networks is presented. The effective transmissivity is scaled from analytical solutions for single-phase yield-power-law fluids flow between a pair of smooth parallel plates. This extended two-phase flow model for fracture networks is verified based on a unique set of experimental data. The full experiment dataset is presented in this work for the first time. Impacts of rheological parameters and time-dependent rheological properties of injected yield-power-law fluids on propagation processes are investigated through numerical simulations. A measure referred to as the propagation volume fraction is defined as an indicator of the propagation process. The results generally show that the rheological properties significantly affect the evolution of the propagation volume fraction. The propagation rate reduces with increased yield stress, consistency index and flow index. The two-phase flow of yield-power-law fluid propagation in a heterogeneous fracture network is also simulated, showing that the heterogeneity of fracture apertures may significantly affect the propagation process. For the heterogeneous case, with two-point distribution of apertures, the propagation volume fraction can be represented by using the harmonic mean aperture. Since the yield-power-law constitutive model covers a wide range of non-Newtonian fluids, the results presented in this work can be used for studying non-Newtonian fluid propagation in a variety of homogeneous or heterogeneous fracture networks, which can be used for rock grouting design.