Theoretical model and its experimental verification on nonlinear flow through a rough fracture of silty mudstone under low water head

Abstract

An important method to study the seepage characteristics of rock fractures is using nonlinear flow models. However, existing nonlinear flow models are unable to describe the flow law of water-soil particles mixture through the rough fractures of soft rock because the rheological properties of the fluid are rarely considered. In this study, a novel nonlinear flow model (WST model) for water-soil particles mixture through rough fracture of silty mudstone under low water head was proposed based on local viscous pressure drops and local pressure drops. To verify the accuracy of the model, saturated seepage experiments were carried out on five silty mudstone samples with a rough fracture under low water head. The results demonstrate that compared with the MT model (a nonlinear flow model for fluid flowing though rough rock fracture at a low velocity), the WST model is preferable to fit experimental data, showing better precision in describing nonlinear flow through rough fracture of silty mudstone under low water head conditions. Furthermore, the WST model is particularly applicable when the average height of the surface of all fracture units relative to the datum plane is less than 0.62 mm and the Reynolds number is less than 620. In addition, the disordered movement of soil particles under the combined action of inertia and water head is the main reason for the nonlinear flow of water–solid particles mixture in the silty mudstone fracture.