考虑σ_(2)及围岩—支护结构相互作用的隧道力学模型

A Mechanical Model for the Tunnel by Consideringσ_(2) and the Interaction between the Surrounding Rock and Support Structure

目前的隧道力学模型未能同时考虑中间主应力σ_(2)及围岩—支护结构相互作用对围岩塑性区等隧道力学特性的影响。为此,首先采用岩石统一强度理论替代目前常用的Mohr-Coulomb(M-C)强度准则以考虑σ_(2)对隧道围岩塑性区的影响。其次,针对Kastner方法未能很好地考虑支护前隧道围岩初始弹性位移及围岩—支护结构相互作用的不足,在其基础上,结合圆形隧道实际施工特点,提出了能够同时考虑σ_(2)、隧道围岩初始弹性位移及围岩—支护结构相互作用的圆形隧道力学模型。最后,通过算例研究了σ_(2)、隧道围岩初始弹性位移、原始地应力、支护结构刚度和岩石内摩擦角等对围岩塑性区、隧道洞壁位移和支护力的影响规律。研究结果表明:σ_(2)的影响不可忽略;一定的隧道围岩初始弹性位移可以减少支护应力,但会导致围岩塑性区和隧道洞壁位移的增加;支护结构刚度的增加可以有效减小围岩塑性区及隧道洞壁位移,但会增加支护结构应力;初始地应力的增加将增大围岩塑性区、隧道洞壁位移及支护结构应力;随着岩石内摩擦角的增加,围岩塑性区、隧道洞壁位移及支护结构应力均减小。最后,通过工程实例对模型的合理性进行了验证。

The existing mechanical models for the tunnel do not take into consideration the co-effect of the intermediate principal stressσ_(2)and the interaction between the surrounding rock and support structure on the tunnel mechanical behavior such as the surrounding rock plastic zone.Therefore,the unified strength theory for the rock is adopted to replace Mohr-Coulomb(M-C)one to consider the effect ofσ_(2)on the plastic zone of the surrounding rock.Secondly,for the shortcomings of Kastner’s method that the initial elastic displacement of the tunnel surrounding rock before the support structure is applied and the interaction between the surrounding rock and the support structure are not considered,the mechanical model for the circular tunnel,which can consider the effect ofσ_(2),initial elastic displacement of the tunnel surrounding rock before the support structure is applied and the interaction between the surrounding rock and the support structure,is proposed.Finally,the effect ofσ_(2),initial elastic displacement of the tunnel surrounding rock before the support structure,the initial ground stress,the stiffness of the support structure and the rock internal friction angle on the surrounding rock plastic zone,the displacement of the tunnel inner wall and the support stress is studied.The results show that the effect ofσ_(2)cannot be neglected.A certain value of the initial elastic displacement of the tunnel surrounding rock can reduce the support stress,while when it will lead to the increase in the surrounding rock plastic zone and displacement of the tunnel inner wall.The increase in the stiffness of the support structure can effectively reduce the surrounding rock plastic zone,displacement of the tunnel inner wall and the support stress.With increasing the rock internal friction angle,the surrounding rock plastic zone,displacement of the tunnel inner wall and the support stress all decrease.Finally,the validity of the proposed model is verified with the practical engineering.