【摘要】 隧道围岩失稳模式和稳定性判据一直是工程界争论的焦点,迄今没有科学合理的标准,常以洞周位移或塑性区经验值作为稳定性判定指标。洞周位移受围岩弹模、隧道形状等因素影响,而且不同部位变形值差异很大,很难找到统一标准;以塑性区作为稳定性判据优于以位移作为判据,围岩塑性化反映连续介质宏观塑性流动力学动态,而不能用于量化判定由优势结构面控制节理岩体破坏的隧道稳定性。文章结合细观节理形态和变化,通过UDEC离散元程序,研究节理岩体隧道失稳模式及量化的稳定性判定指标,探讨了细观结构机制和宏观力学行为关系。结果表明:(1)结构面极大地削弱岩体力学性质及其稳定性,结构面变形与强度性质对于隧道稳定性起着关键控制性作用;(2)节理岩体隧道扰动区可划分为脱落区、张开区和剪切滑移区,其中脱落区表征围岩失稳模式,张开区围岩处于脱落临界状态,即塌方潜在区域;(3)剪切滑移区是诱发围岩发生渐进性破坏主因,提出将剪切滑移区作为节理岩体隧道稳定性判定指标具有严格力学依据,可以定量化评价围岩稳定程度。最后,以在建兰渝铁路木寨岭隧道为例,对比了锚杆支护前后力学效应,验证了以剪切滑移区作为节理岩体隧道稳定性判定指标的可靠性、合理性和现实性。更多还原

【Abstract】 The instability model and criterion for the stability of tunnels in jointed rock masses have been a subject of debate,and no scientific and reasonable standard has been reached for the subject so far.The empirical value of the displacement around the tunnel and plastic zone is deemed the criterion for stability of surrounding rock;elastic modulus and the shape of a tunnel have a great influence on the displacement around the tunnel.Additionally,displacements around a tunnel are unequal at different positions.For these reasons,it is difficult to settle upon a unified criterion.The empirical value of the plastic zone is superior to the displacement around the tunnel when it comes to the stability criterion.The plastification of surrounding material reflects the plastic dynamic mechanics of continuous media,but it cannot be adopted to quantitatively evaluate the tunnel stability in a jointed rock mass in which failure is induced by a preferred structural plane.Therefore,combined with the shapes and changes of micro-joints,the instability mode and quantitative criterion for the stability of a tunnel are studied by means of UDEC,and the relationship of the mechanisms of micro-structure and macro-mechanical behavior is analyzed.The conclusions are as follows:(1) The structural plane greatly weakens the mechanic property of the rock mass and its stability.Deformation and the strength of the structural plane play the controlling role in tunnel stability;(2) In the jointed rock mass,the disturbance zone of the surrounding rock is divided into failure shape,open zone and shear and slip zone.The failure means the instability mode of the tunnel,and the open zone means that surrounding rock is under the shedding critical condition,which creates a potential landslide area;(3) The shear and slip zone is the main cause of progressive damage of rock masses,so the shear zone is proposed as the criterion for stability of a tunnel in a jointed rock mass.Based on its strict mechanical foundation,the stability of a rock mass can be evaluated quantitatively.Using the Muzhailing Tunnel of the Lanzhou-Chongqing Passenger Dedicated Line as an example,the mechanical effects of surrounding rock are investigated before and after the implementation of bolt support,which verified the reliability,rationality and feasibility of using the shear and slip zone as the criterion for stability of a tunnel in a jointed rock mass.更多还原