主应力方向对围岩稳定性的影响

Effect of principal stress orientation on stability of surrounding rock of tunnels

采用模型试验和数值模拟方法研究了在不同方向的主应力作用下,直墙拱形隧道的围岩损伤破坏规律,考虑了隧道内含有裂纹和不含裂纹两种情况,利用水泥砂浆制作了直墙拱形隧道模型,并利用有机玻璃光弹试验对无裂纹隧道的试验结果加以验证;数值模拟采用混凝土损伤塑性模型,计算出隧道周边各点的应力,而对于含有裂纹的隧道计算了裂纹尖端的无量纲应力强度因子YⅠ和YⅡ,与模型试验结果吻合较好。结果表明:对于无裂纹的隧道,当主应力方向与隧道垂直边墙的夹角?=45°左右时,隧道的抗压强度最低;对于带裂纹的隧道,当裂纹与垂直边墙的夹角?=130°时,裂纹尖端无量纲应力强度因子YⅡ最大,其隧道强度最低;对于含有裂纹且0?=130°的直墙拱形隧道,当主应力方向与隧道垂直边墙的夹角?较小时或在70°左右时,隧道的抗压强度最低。

In order to investigate the effect of principal stress orientation on the stability of the surrounding rock of tunnels, experimental and numerical studies are performed. Cement mortar models are applied, and two cases for the tunnel with and without cracks are considered. Photoelastic experiments are conducted to confirm the results of the cement mortar model tests. In the numerical simulation, the plastic damage of concrete damaged plasticity is adopted. The stresses at the points around the tunnel and the stress intensity factor of crack tips are calculated, and the results are in good agreement with the experimental ones. The results show that for the tunnel without cracks, when the angel of principal stress orientation and tunnel wall θ =45°, the compressive strength is the lowest; for the tunnel with a crack, when the angel of crack direction and tunnel wall β=130°, the stress intensity factor of crack tips is the largest, and the compressive strength is the lowest, and for the tunnel with β=130°, when θ was small or θ=70°, the lowest compressive strength occurs.