隧道掘进面接近地质界面时围岩的应力特征研究

隧道开挖地层中往往呈现出明显的地质变异性,如软硬岩层的不均匀分布等,使隧道开挖后的力学行为十分复杂.本文采用FLAC3D初步分析了隧道掘进面接近地质界面时围岩的应力状态,并探讨侧向应力、纵向应力、断面形式对围岩应力的影响规律.分析结果表明:当隧道由硬岩往软岩或由软岩往硬岩向地质界面掘进时,掘进面前方围岩均有应力集中现象.隧道无论由硬岩往软岩还是由软岩往硬岩掘进至地质界面时,掘进面前方边墙位置围岩径向应力均随侧向应力的增大而增大,掘进面前方拱顶和边墙位置围岩纵向应力均随纵向应力的增大而增大.马蹄彤隧道开挖至硬岩与软岩的地质界面时,掘进面后方边墙位置围岩应力均小于圆形隧道相应位置的围岩应力.

A study of the stress of surrounding rock when tunnel excavation approaches the geological interface

Geological variability,such as irregular distribution of soft and hard ground,often obviously occurs in tunnel excavation grounds.As a result,the stress behavior of the tunnel after excavation will be very complex.The stress of surrounding rock is analyzed with FLAC3D when tunnel excavation aproaches the geological interface.The influencing factors such as in-situ stress,cavern shape are also studied in this paper.The calculation results show that there will be stress concentration in surrounding rock ahead the excavating face when excavation is from hard rock to soft rock or from soft rock to hard rock.The radial stress of surrounding rock of side wall ahead the excavating face will increase with increasing lateral stress,and the longitudinal stress of surrounding rock of the crown and side wall ahead the excavating face will increase with increasing longitudinal stress.The stress of surrounding rock of side wall of hoof-like tunnel behind the excavating face is smaller than that of circular tunnel.