Mechanism of water inrush from the tunnel face induced by fault and its application

Abstract

The limit equilibrium method, slice method and elastic mechanics method are adopted to investigate the mechanism of water inrush from the tunnel face induced by fault. Semi-analytical expressions of the minimum safety thickness of the rock resisting water inrush are derived. The safety thickness calculation method is applied to the actual tunnel engineering, and the accuracy of the proposed method is verified by comparing with the actual excavation results. On this basis, the minimum safety thickness affected by karst water pressure, fault dip, vertical force, width and shear strength indexes of the fault fracture zone are further analyzed and discussed. The results show that: 1) The minimum safety thickness increases with karst water pressure; 2) As the fault dip increases, the minimum safety thickness first increases and then decreases, and water inrush from the tunnel face is prone to occurring when the fault dip is between 45° and 60°; 3) The minimum safety thickness linearly increases with the width of fault fracture zone; 4) The minimum safety thickness linearly decreases with the increase of shear strength of the fault fracture zone; 5) The minimum safety thickness increases with vertical force on the fault fracture zone. The research results provide a new idea for calculation methods and theoretical research of water inrush in karst tunnel, which has certain reference significance and application value for similar projects.

摘要

本文采用极限平衡法、条分法和弹性力学方法研究了断层作用下隧道掌子面突水力学机理, 推导了防突层最小安全厚度的半解析表达式。将防突层安全厚度预测方法应用到齐岳山隧道实际工程案例中, 通过对比实际开挖结果, 验证了所提新方法的准确性和有效性。在以上案例研究的基础上, 进一步分析和讨论岩溶水压力、断层倾角、破碎带宽度和破碎带抗剪强度指标对防突层最小安全厚度的影响, 结果表明:1)防突层最小安全厚度随着岩溶水压力的增加而逐渐增加;2)随着断层倾角的增大, 防突层最小安全厚度呈先增大后减小的趋势, 且当断层倾角在45°∼60°之间时, 隧道掌子面易发生突水;3)随着破碎带宽度的增加, 防突层最小安全厚度呈线性增大趋势;4)随着破碎带抗剪强度的增大, 防突层最小安全厚度呈线性减小趋势;5)随着破碎带垂直压力的增大, 防突层最小安全厚度增大。研究结果为隧道突水计算方法与理论研究提供了一种新的思路, 对类似工程具有一定的借鉴意义与应用价值。