深部软弱地层TBM围岩力学行为试验研究

为揭示TBM深部软弱围岩变形破坏力学特性,开展了反映深埋隧道TBM机械开挖卸荷本质——高初始围压下缓慢准静态卸荷这一卸荷特征的砂质泥岩三轴卸围压试验,研究结果表明:缓慢卸荷条件下的岩石峰前应力-应变曲线接近于常规三轴压缩峰前应力-应变曲线,卸荷屈服阶段产生损伤扩容,侧向变形加速增长,从体积压缩开始转向扩容;应力达到峰值强度后,岩石首先发生1~2级脆性跌落,随着围压继续缓慢卸荷,岩石沿一条斜率较小的近似斜直线发生伴随有多级次生微破裂的线性应变软化;岩石变形全过程由弹性变形段、峰前卸荷损伤扩容段、峰后脆性跌落段、含有多级微破裂的线性应变软化段以及残余强度阶段组成;岩石缓慢卸荷发生宏观张剪复合破坏,并伴有轴向劈裂裂纹,破裂断面为由许多劈裂裂纹相互贯通形成具有一定宽度的剪切带,剪切带内劈裂的岩片在轴向挤压力和沿破裂面的剪切力共同作用下被挤压和摩擦成许多细颗粒和岩粉。

Experimental research on the mechanical behavior of deep soft-surrounding rock tunneling by TBM

In order to understand the deformation and failure characteristics of deep soft ground under the condition of TBM mechanical excavation，a sandy mudstone triaxial unloading test was carried out which simulated the natural unloading characteristics of TBM excavation，a smooth quasi-static confining pressure unloading process with high initial confining pressure.The results show that：The pre-peak stress-strain curve under the condition of smooth quasi-static unloading confining pressure is close to the condition of conventional triaxial compression test：At the unloading yield stage，the specimens show damage dilatation，the lateral deformation curve accelerates its growth，resulting in the volumetric strain turning from compression into dilatation：Beyond the peak strength，initially the specimens show once or twice modest brittle drop，then the rock samples have linear strain softening along a small slope approximation oblique line with the continuous slowly unloading confining pressure，which is accompanied by multistage micro fractures：The complete deformation process is composed of elastic deformation，unloading damage dilatancy，post-peak brittleness drop，linear strain softening deformation containing multistage micro fractures and residual stress period：The specimens show a macroscopic shear composite failure accompanied by axial splitting cracks during the process of smooth unloading failure，and the fracture surface is a shear zone with a certain width which is formed by a lot of split cracks inter-permeation，and the shear zone is squeezed and rubbed into fine particles and powder as a result of the interaction of axial extrusion and the shear stress along shear plane.