软土地区浅埋偏压小净距隧道空间效应研究

Study on spatial effects Shallow bias in soft soil tunnel of the small spacing

通过对本构破坏准则的探讨,选取Mohr-Coulomb等面积圆屈服理论作为模型的破坏准则,将岩体的c、φ值进行修正,使其更适合于软土地区浅埋偏压的小净距隧道,进而建立有限元三维弹塑性数值模型,对米家寨隧道空间效应进行模拟,研究软土体中浅埋偏压小净距隧道施工过程中开挖面的空间约束作用,并对其双线隧道开挖面的合理间距作出分析.以米家寨隧道为例,开挖面对纵向20m以内围岩具有一定的空间约束作用、30m以内围岩具显著的空间约束作用且塑性应变较大,左右线隧道开挖面纵向合理间距应控制在30m左右,通过Matlab计算机编程和再进行工地现场的监测,分析数据证实了所得结论的正确性,为实际的工程提供了理论依据.

The equivalent area circle yield theory such as Mohr-Coulomb was selected to do a model of the damage criteria by discussing the constitutive damage criteria.Meanwhile the rock of c,φ values was rectified to be more suitable for shallow soft soil area of small interval tunnel bias.Then the 3-D elastic-plastic finite element numerical model was created.It could simulate the spatial effect of Mijiazhai tunnel to study the space restraints of the cutting surface about shallow bias of soft soil in the process of tunnel construction,and the surface spacing of two-lane tunnel excavation was analyzed to be reasonable.Take Mijiazhai tunnel as an example,the excavation face has certain space restraints within on 20m vertical rock face,a significant role of space constraints and large plastic strain within 30m,and the excavation face is controlled to be a reasonable distance within 30m for left and right vertical line of tunnel.The conclusions are analyzed to confirm the correctness by Matlab programming and on-site testing,which provides a theoretical basis for actual projects.