Understanding water inrush hazard of weak geological structure in deep mine engineering: A seepage-induced erosion model considering tortuosity

Abstract

Tortuosity is an important parameter to understand the formation mechanism of water-conducted pathways in deep mine engineering. In this study, a numerical method was proposed to calculate the tortuosity of fractured fault rocks. Convergence tests show that the simulation method has high accuracy. The evolution of tortuosity is consistent with previous studies: it can be divided into four stages, i. e., rearrangement of rock particles, particle migration, continued seepage, and steady water flow. There is an exponential relationship between tortuosity and porosity of fractured rock mass. A new concept (porous tortuosity index) was proposed in this study, which can reflect the spatial distribution of particles and particle size distribution of the fractured rocks and is not affected by the flow behavior of water. In addition, the seepage erosion model considering the tortuosity of the fractured rock mass can improve the calculation accuracy of permeability, non-Darcy coefficient and Forchheimer coefficient, which is fundamental for the prediction of water inrush in weak geological structures.

摘要

迂曲度是揭示深部采矿工程导水通道形成机制的一个重要参数。该研究提出了一种断层破碎岩 体迂曲度的数值计算方法,收敛性测试结果表明该方法具有较高的精度。通过该方法获得的迂曲度演 变特征与前人研究结果一致:迂曲度演变呈现四个阶段,即岩石颗粒重新排列阶段、颗粒冲蚀阶段、 持续渗流阶段和稳定渗流阶段。破碎岩体的迂曲度与孔隙率之间呈指数关系。提出了破碎岩体孔隙迂 曲度指标的新概念,该指标可反映破碎岩石颗粒的空间分布与粒径分布特征,且不受水流行为的影 响。构建了考虑破碎岩体迂曲度的渗流冲蚀模型,提高了渗透率、非Darcy 因子和Forchheimer 系数的 计算精度,为软弱地质构造突水灾害预测提供了理论基础。