粒径及洞室形状对围岩应力、应变影响的模拟

Modeling of Stress and Strain in the Tunnel Surrounding Rock for Different Granular Radii and Tunnel Shapes

将岩石视为含孔隙的颗粒体材料,研究了粒径尺寸及洞室形状对洞室围岩中的最大、最小主应力及剪切应变增量的影响。研究发现,随着粒径尺寸的降低,呈圆环形的剪切应变增量的高值区圈数增加,其间距(与颗粒平均直径大致相同)降低;呈辐射状的最大主应力的正高值区(受拉区)范围减小。最小主应力的负高值区(受压区)与剪切应变增量的高值区呈现类似的规律,这两种高值区与压力拱的形态基本一致。洞室围岩中的最大主应力的值有正有负(径向受拉或受压),其正值主要位于洞室表面附近,这是由于这一位置高的最小主应力引起了颗粒之间的明显剪切错动;其余的正值位置较为分散,且其值较小。洞室围岩中的剪切应变增量、最小主应力及最大主应力的分布规律都受洞室形状的影响。在洞室表面的尖角位置,前两种量都较高,而最后一种量较低。最大主应力在洞室表面的直边界上向围岩中延伸的尺寸较大,这对于围岩的稳定有不利的影响。

Rock is treated as a kind of granular materials with pores. Distributions of the maximum, minimum principal stresses and shear strain increment in the tunnel surrounding rock are studied for different granular radii and tunnel shapes. It is found that the number of annular regions with higher shear strain increments in the vicinity of the tunnel is increased with decreasing granular radius. The spacing between them is decreased, which is approximately the averaged granular diameter. The extending depth of regions with higher maximum principal stresses is decreased with decreasing granular radius, which are in the radial direction. The annular regions with higher values of the mini- mum principal stress are similar to those of the shear strain increment, basically similar to the pressure arch patterns. The positive or negative maximum principal stress is possible in the tunnel surrounding rock. The positive maximum principal stress is mainly in the vicinity of the tunnel surface, which is due to the apparent movement between gran- ules caused by higher values of the minimum principal stress, while it is scattered and lower at other positions. Distri- butions of the shear strain increment, maximum and minimum principal stresses in the surrounding rock depend on tunnel shapes. At the positions closer to tunnel comers, the former two are higher, while the latter is lower. The maximum principal stress extends more deeply from the straighter tunnel surface, leading to a passive influence on the stability of the surrounding rock.