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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 study the stability of soils near the excavated surface of shield tunnel during tunneling, assuming that the soil is purely clayey soil and is an ideal elastoplastic material, the three-dimensional Hill mechanism obeys the Mohr-Coulomb yield criterion and the rectangular foundation bearing capacity problem , Established a failure mode of shield tunnel excavation surface soil under active and passive limit equilibrium conditions. Based on the basic principle of the upper limit method of plastic limit analysis, the formula for calculating the upper limit solution pressure of the limit excavation face of three-dimensional shield tunnel is deduced. In this paper, the relationship between the upper and lower solutions of the upper and lower limit solutions of the active and passive support of three-dimensional shield tunneling surface are discussed in combination with an example. The relationship between the ultimate support force of excavation face and the cohesion of soil, h / D Interrelationship. The results show that the active limit support force of excavation face of 3D shield tunnel is smaller than the upper limit of plane strain solution, while the passive limit support force is larger than the upper limit of plane strain. With the increase of cohesion, The difference between the active and passive limit support forces and the upper limit solution of plane strain also increases gradually. The upper limit solution of active and passive limit support forces for shield tunneling surface increases with the increase of h / D, and h / The larger the D, the more active the shield tunnel excavation face, the faster the passive limit support force changes with the cohesion of the soil.