双护盾TBM在软弱地层中的掘进模式选择

 双护盾岩石掘进机(TBM)采用双护盾模式掘进时，支撑靴的支撑压力常会造成围岩的破坏进而引发其他事故，针对青海“引大济湟”工程中双护盾TBM在软弱地层中掘进模式的选择问题，提出模拟双护盾TBM掘进过程的三维有限元模型，分析支撑压力作用下围岩的破坏机制及不同地应力分布情况下支撑压力对软弱围岩的影响。分析结果表明，支撑压力作用下围岩的破坏形式主要为剪切破坏和拉裂破坏。在浅埋自重应力场下，当侧向压力系数l＜1时，支撑压力一般会使软弱围岩的塑性区有较大程度的扩展，且在隧洞埋深较小时还可能造成大面积拉裂区的出现；其次，对支撑压力导致塑性区扩展的围岩临界强度的分析表明：在自重应力场下应采用单护盾模式或掘进参数降低的双护盾掘进模式掘进。在埋深较大且地应力侧向压力系数l≥1时，支撑压力对围岩的影响相对有限，一般不会导致新塑性区的产生，但可能造成旧塑性区的进一步破坏，此时，可谨慎地采用双护盾模式掘进。

SELECTION OF ADVANCING MODE OF DOUBLE-SHIELDED TBM IN WEAK ROCK MASSES

To investigate the selection of the advancing mode of the double-shielded tunnel boring machines(TBM) in the weak rock masses of “Datong River-Huangshui River”Water Transfer Project，a three-dimensional finite element model is established to simulate the advancing of the double-shield TBM. The failure mechanisms of the weak rock mass under the gripper pads and the interaction between the weak rock masses and gripper pads are investigated. It shows that the gripper pads pressure will cause the shearing and tension failure of the weak rock mass. When the in-situ stress is mainly caused by the gravity and the lateral pressure with coefficient l＜1，the gripper pads pressure will probably cause the failure zone extend and large extent tensile failure zone appear. In addition，the critical strength of the weak rock masses is proposed when the pressure extends the failure zones. Under this condition，the single shield advancing mode and the double-shield advancing mode with lower parameters should be adopted. In the deeper depth with the lateral pressure coefficient l≥1，the gripper pads pressure will have limited influences on the surrounding rock masses and even can not cause the failure zone extend，but，the failure zone may be damaged further. In this case，the primary double-shield advancing mode should be adopted when the residual strength of the weak rock masses is high.