对围岩-支护共同作用原理的讨论

Discussion on the Interaction of Surrounding Rock and Support

围岩-支护共同作用原理在地下工程支护设计以及安全评价中发挥着重要作用,基于该理论的收敛约束法也是目前国际上通用的支护设计方法。但共同作用原理未考虑地下工程先开挖后支护的特点,而是假定开挖与支护在同一瞬间完成。目前已有学者证明隧道开挖与支护分别符合塑性力学定义的加载和卸载条件,这表明开挖是发生塑性变形的过程,而支护是发生弹性变化的过程。对满足莫尔-库伦屈服准则的圆形隧道进行理论分析,结果表明:由支护产生的围岩位移增量与支护应力成正比,而传统的围岩特性曲线并不符合该规律。使用有限差分数值计算软件FLAC对圆形隧道的开挖与支护进行验证计算,得到支护后围岩位移增量与支护应力的关系符合弹性变形规律。因此,此前广为应用的围岩-支护相互作用原理中的围岩特性曲线在塑性力学理论范畴内并不正确。

The principle of the interaction between surrounding rock and support plays an important role in the support design and safety evaluation of underground engineering.The convergent constraint method based on this theory is also an international popular support design method.However,the principle of interaction does not consider the characteristics of underground engineering that excavation is first and supporting is second,but assumes that excavation and supporting are completed at the same instant.At present,scholars have proved that tunnel excavation and supporting meet the loading and unloading conditions defined by plastic mechanics,which shows that plastic deformations occur in excavation process,while elastic deformations occur in supporting process.The theoretical analysis of a circular tunnel satisfying the Mohr-Coulomb yield criterion shows that the displacement increment of the surrounding rock caused by the supporting is proportional to the supporting stress,while the traditional characteristic curve of the surrounding rock does not conform to the law.From the finite difference numerical calculation software FLAC to simulate the excavation and supporting of a circular tunnel.It shows that the displacement increment of the surrounding rock is proportional to the supporting stress in supporting process.This indicates an elastic law.Therefore,the characteristic curve of surrounding rock in the previously widely used principle of surrounding rock-support interaction is not correct in terms of plastic mechanics theory.