隧道穿越富水断层隔水岩体冲切剪切破坏研究

隧道在修建过程中不可避免会遇到富水断层等不良地质情况,极易引发突水突泥灾害,若能提前预测隔水岩体的最小安全厚度,则能有效避免灾害的发生。首先,以隧道穿越富水断层为背景,提出冲切剪切破坏模式的隔水岩体计算模型,得到最小安全厚度计算公式并进行影响因素分析;然后,采用FLAC3D软件建立三维数值模型,确定最小安全厚度的模拟解,并与理论解进行对比;最后,将计算公式应用于永莲隧道以验证其适用性。结果表明： 1）最小安全厚度随断层宽度、隧道半径、水头高度的增大而增大,随断层倾角、隔水岩体内摩擦角及黏聚力的增大而减小; 2）模拟解与理论解较为吻合,且模拟得到掌子面附近围岩的移动态势与理论模型假定的破坏体运动方向一致; 3）计算公式能较为准确地预测隧道穿越富水断层时的隔水岩体最小安全厚度。

Punching Shear Failure of Water ResistantRock Mass of Tunnel Crossing Water Rich Fault

During tunnel construction, it is inevitable toencounter bad geological conditions, e.g., water rich faults, which can causewater and mud inrush disasters. However, such disasters can be avoided if theminimum safe thickness of the water resistant rock masscan be predicted. Thus, in this paper, based on a tunnel crossing water rich fault, a calculation model for water resistantrock mass with punching shear failure mode is proposed, the calculation formulaof the minimum safe thickness is obtained, and influencing factors areanalyzed. A three dimensional numerical model isestablished using the FLAC3D software to determine the simulation solution forthe minimum safe thickness. Finally, the calculation formula is applied to theYonglian tunnel to verify its applicability. The results demonstrate thefollowing: (1) The minimum safety thickness increases with increasing faultwidth, tunnel radius, and water head height, and it decreases with increasingfault inclination, internal friction angle, and water resistantrock mass cohesion. (2) The simulated and theoretical solutions are in goodagreement, and the movement trend of surrounding rock near the tunnel face isconsistent with the movement direction of the damaged rock mass assumed by thetheoretical model. (3) The calculation formula can accurately predict theminimum safe thickness of a water resistant rock masswhen the tunnel passes through a water rich fault.