巷道围岩分区破裂化(或分区破碎化、分区碎裂化)是指在深部开挖巷道时围岩交替呈现破裂区和未破裂区的现象,该现象与对围岩破坏的传统认识不同。正确认识不同强度围岩分区破裂化的发育程度,可为其治理及应用奠定基础。

巷道掘进会引起掘进工作面附近岩石涌向巷道,这将导致掘进工作面附近垂直于巷道轴线平面的应力状态并非平面应变,而是三维状态。

采用以FLAC^3D应变软化模型为基础发展的非均质应变软化模型(通过引入Weibull分布函数实现),研究了内摩擦角对逐步开挖拱形巷道围岩分区破裂化的影响,考察了围岩中剪切应变增量、最小主应力及最大主应力在巷道即将贯穿模型时的分布规律。

研究发现:①内摩擦角越小,围岩的破坏越严重,剪切带的发育越充分,分区破裂化越明显;② 并非围岩的破坏就会导致分区破裂化,围岩破坏到一定程度后,才会出现分区破裂化;③分区破裂化的机理为:在载荷及开挖作用下,在过巷道轴线的平面上,随机分布的缺陷发展成(共轭)剪切带,从而在垂直于巷道轴线的平面上,形成多个相间隔的圆环形的破坏区。

本文过巷道轴线平面上的结果与室内实验结果在定性上一致。根据本文的研究,在垂直于巷道轴线的不同平面上,分区破裂化不同,这意味着不必选择统一的巷道支护参数,例如,在分区破裂化显著的部位,延长锚杆的长度,反之则不然。

Zonal disintegration is a phenomenon that the alternated regions of fractured and relatively intact rock mas- ses appear in the surrounding rock at great depth,which is completely different from the traditional understanding on the failure characteristics of the tunnel surrounding rock. A full understanding on the development of zonal disinte- gration in different surrounding rock can provide a foundation for its control and application. Excavation of a tunnel will lead to motion of rocks in the vicinity of the working face toward the tunnel. Thus,the stress state of planes or- thogonal to the tunnel axis is not a plane strain state,but a three-dimensional state. Using the heterogeneous strain-softening model where the Weibull distribution function was introduced based on the strain-softening model in FLAC3D ,the effects of the internal frictional angle on the pattern of zonal disintegration were studied,and the distri- bution of the shear strain increment,minor principal stress and major principal stress were investigated when the tun- nel nearly intersected the numerical model where a U-shaped tunnel was progressively excavated. The following re- sults were found. The low internal frictional angle leads to the serious failure of the tunnel surrounding,a full devel- opment of shear bands,and an apparent zonal disintegration. Zonal disintegration appears after the tunnel surround- ing rock is subjected to a certain failure. The mechanism of the zonal disintegration can be summarized as follows: under stresses and excavation,at planes going through the tunnel axis,the randomly distributed defects develop into ( conjugated) shear bands,and at planes orthogonal to the tunnel axis,the isolated annular fracture zones can be formed. At planes going through the tunnel axis,the present results are qualitatively consistent with the previous ex- perimental results. According to the present research,at different planes orthogonal to the tunnel axis,zonal disinte- gration is different,which means that it is not necessary to choose the unified tunnel support parameters. For exam- ple,at some positions where zonal disintegration is obvious,the lengths of rock bolts should be extended,and vice versa.