对轴对称荷载作用圆巷围岩理想弹塑性分析解的讨论

Discussion on the Perfect Elastoplastic Analysis of Circular Tunnel Under Axisymmetric Load

对轴对称荷载作用圆巷围岩理想弹塑性分析解——Kastner解适用于软岩和小变形情况,若用于非软岩和大变形情况,从Kastner方程会导得:不论巷道围岩塑性变形多大,巷道周边切应力恒等于岩体峰值强度;围岩所承受的地应力可以随围岩塑性区半径增大而持续增大,随巷道周边位移增大而持续增大;此外,Kastner解中切应力分布曲线在围岩弹、塑性区交界处有尖峰向上的应力集中.采用符合岩石实际的弹性、非线性硬化和软化光滑连接的应力-应变关系得到的巷道围岩分析解,可以弥补以上三点不足,恰当地反映巷道临界深度和巷道围岩自承地应力极限问题;所绘出的切应力分布曲线在围岩弹、塑性区交界处光滑连接,因而有更广的适用性和精确性,对巷、隧道围岩大变形支护设计有参考作用.

The Kastner Solutions-the elastoplastic analysis solutions of circular tunnel under axisymmetric load,are applicable to soft rock and small deformation only.Being applied to Non-softening rock and large deformation,the following conclusions could be deduced from the Kastner equations： The shear stress surrounding the circular tunnel always equals to the peak strength of rock mass no matter how big the plastic deformation of surrounding rock is;the geostatic stress of surrounding rock increases with the growth of the radius of plastic zone and displacement of surrounding rock;in addition,there is upward stress concentration at the junction of elastic and plastic zones on the distribution curve of shear stress.The analysis solutions of circular tunnel based on the stress-strain relationship which is smoothly connected by elastic,nonlinear hardening and softening sections,can resolve the three shortcomings above-mentioned,and correctly reflect the problem of the critical depth and the stress limit the surrounding rock suffers.The given distribution curves of shear stress connect smoothly at the junction of elastic and plastic zones,which have more extensive applicability and particularity and provide important reference for the support design of large deformation tunnels.