导水夹泥断裂破碎岩内在结构与渗透性

Internal Structural Characteristics and Permeability of Kata-rocks in Geological Structures Filled with Water and Mud

造成深长隧道开挖过程中涌突水危害的主要灾害源为导水夹泥构造。研究断裂破碎岩体内在结构特征与不同构造单元渗透特性可以在一定程度上规避工程施工过程中事故的发生。以甘肃典型导水夹泥断裂带为背景,针对典型断裂破碎岩样进行XRD矿物分析、SEM岩体裂隙内在结构表征、不同构造单元原位压水试验及室内典型破碎岩体渗透试验,分析导水夹泥断裂破碎岩矿物成分、内在结构及渗透系数。研究结果表明:岩样裂隙内的充填物随次生矿物比升高,渗透系数增大;断层核部渗透系数较破碎带与完整花岗岩体大,断层核部粒径浅部比深部大,岩体浅部变质程度比深部破碎,有效孔隙度核部深部比浅部大,比表面积值核部也比影响损伤带及母岩大;横向上,断层核部裂隙密集带具有较高渗透性,随着裂隙密度的降低渗透系数明显降低,且距断层核部越远,渗透系数越低;纵向上,断层带不同构造单元的岩体,其渗透系数由小到大的分布规律为断层泥(<10^(-9) m·s^(-1))、碎砾、角砾岩(10^(-5)～10^(-7) m·s^(-1))、碎裂岩(10^(-4)～10^(-7) m·s^(-1)),完整围岩部分(<10^(-9) m·s^(-1))渗透系数又变小。研究结果可为隧道涌突水防治提供理论与工程指导。

Geological structures filled with water and mud are the main causes of water inrush during excavations of deep-long tunnels. Research on the internal structural characteristics of fractured rock masses and the permeability of different tectonic units can help avoid accidents during the construction of tunnels. To study the internal structural characteristics and the permeability coefficient of a typical rock mass, a series of experiments were carried out in a typical slot of a fractured core in Gansu province. These tests included a detailed characterization of the recognition of fracture, X-ray diffraction（XRD） for mineral analysis of typical fractured rock, SEM-ED for characterization of the inner structure of the rock fracture, permeability tests in different tectonic units, and indoor permeability tests of typical broken rock mass. We also calculated the mineral composition, inner structure, and permeability coefficient of the fractured rock. The results of microcosmic tests show that the infiltration coefficient increases as secondary mineral content increases, and the percolation coefficient of the fault nucleus is lower than that of the fault. The permeability coefficient of the upper surface is larger than that at greater depth, because the particle size at the fault core is larger than that at depth. The rock mass shows a higher degree of shallow metamorphism on the surface. The effective porosity at the fault core is larger than that at depth. The ratio of the surface area of the core is larger than the damage belt and the surrounding rock. Pressure water tests conducted in the field and indoor penetration tests of typical samples show that the fault core has a high permeability coefficient with a high crack density of about 2×10～（-6） m·s^-1 in horizon. The permeability coefficient reduces as the distance from the fault increases because of the reduction in fracture density. Vertically, the fault zone rock mass can be classified into different tectonic units according to the distribution of the permeability coefficient. The permeability coefficient of fault gouge is low（10^-9 m·s^-1）, while that of debris and breccia（10^-5-10^-7 m·s^-1） and cataclastic rock（10^-4-10^-7 m·s^-1） varies over a wider range. The permeability coefficient（10^-9 m·s^-1） reduces in the undamaged surrounding rock. These results can provide the theoretical and engineering basis for the prevention and control of disasters in tunnels.