三维盾构隧道开挖面极限支护压力的上限解

Three-dimensional Upper Bound Solution of Limit Support Pressure during Shield Tunnelling

为了研究掘进过程中盾构隧道开挖面附近土体的稳定性,假设土体为纯粘性土,且为理想弹塑性材料,服从摩尔-库仑屈服准则,参照矩形基础承载力问题的三维Hill机构,建立了盾构隧道开挖面土体处于主动、被动极限平衡状态下的破坏模式。从塑性极限分析上限法的基本原理出发,推导出三维盾构隧道开挖面极限支护压力上限解的计算公式。结合某算例,讨论了三维盾构隧道开挖面主动、被动极限支护压力上限解与平面应变上限解的关系,以及开挖面极限支护力与土体粘聚力、h/D的相互关系。研究结果表明:三维盾构隧道开挖面主动极限支护力要比平面应变上限解小,而被动极限支护力要比平面应变上限解大;随着粘聚力的增加,三维盾构隧道主动、被动极限支护力与平面应变上限解的差别也逐渐增大;盾构隧道开挖面主动、被动极限支护力的上限解均随h/D的增大而增大,且h/D越大,盾构隧道开挖面主动、被动极限支护力随土体粘聚力的变化速率也越快。

In order to research the stability of shield tunnel face during shield tunnelling,soil is regarded as pure clay,and obeying elastic-perfectly plastic Mohr-Coulomb yield criterion.According to three-dimensional Hill mechanism,which is used in the bearing capacity of rectangular foundation,the failure mode is established when shield tunnel face is in the active or passive limit equilibrium state.Based on the plastic upper-bound limit analysis,the three-dimensional upperbound solution of limit support pressure is obtained during shield tunnelling.Combined with an example,comparison between the three-dimensional upper-bound solution and plane strain upperbound solution is made for limit support pressure in shield tunnel face.The relationship between limit support pressure and soil cohesion is discussed,and the influence of the ratio between thickness of the overburden hand the diameter Dfor tunnel on the limit support pressure is studied.The results show：the three-dimensional active limit support pressure is smaller than the plane strain solution,the three-dimensional passive limit support pressure is larger,and the difference increases gradually with the soil cohesion increasing.The active and passive limit support pressure increases with the ratio between hand Dincreasing,and the larger the ratio is,the faster the change rate of limit support pressure with soil cohesion will be.