铁路标准断面隧道节理倾角效应研究

Study on the Effect of Joint Dip Angle of Railway Tunnel with Standard Section

以郑万铁路黄家沟隧道标准断面为研究对象,对不同产状岩质隧道进行稳定性分析,研究围岩力学响应、变形特性以及锚杆力学特征,阐明不同于传统松散介质的层状岩质隧道失稳模式及锚杆支护要点。结果表明:节理面极大削弱了岩体稳定性,开挖会引起沿层理面滑动,导致明显地质偏压。隧道开挖使得层间节理首先被破坏,节理离层区不是发生在最大主应力方向上,而是发生在节理垂直方向。水平层状或倾角较小时,顶部和仰拱节理之间产生离层区,易引起岩层弯折破坏;随着倾角增大,顺弱势节理面滑动趋势增大,破坏主要取决于节理面强度和层状节理之间滑移;当倾角为75°~90°时,破坏主要为边墙岩块弯曲压溃;竖向节理时,中间垂直土体挟持作用减弱,易剪切破坏失稳引起冒顶坍方趋势。从群锚效应来看,锚杆与滑移面夹角大于23°时,锚杆支护效果发挥较为明显的效果。

Taking the standard section of Huangjiagou Tunnel of Zhengwan Railway as the research object,this paper analyzed the stability of rock tunnels with different occurrence,studied the mechanical response,deformation characteristics and bolt mechanical characteristics of surrounding rock,and expounded the instability mode and bolt support key points of layered rock tunnels which were different from the traditional loose medium.The results show that the joint plane weakens the stability of rock mass greatly,and the excavation will cause sliding along the bedding plane,resulting in obvious geological bias.The tunnel excavation causes the first failure of the interlayer joints.The separation zone of the joints does not occur in the direction of the maximum principal stress,but in the vertical direction of the joints.When the horizontal or dip angle is small,there is a separation zone between the top and the invert joint,which is easy to cause the bending failure of the rock stratum;with the dip angle increasing,the sliding trend along the weak joint surface increases,and the failure mainly depends on the strength of the joint surface and the sliding between the layered joints;when the dip angle is 75°~90°,the failure is mainly caused by the bending collapse of the side wall rock mass;when the vertical joint,the middle vertical soil mass is held up with weakening,it is easy to shear failure and instability,resulting in the tendency of roof caving.From the point of view of group anchor effect,when the angle between anchor bolt and slip surface is greater than 23°,the effect of anchor bolt support is more obvious.