陡倾岩层隧道破坏机理及其稳定性研究

Study of the damage mechanism and stability of steeply dipping rock tunnels

倾斜层状岩体具有明显的各向异性,隧道修建过程中易产生大变形、塌方、初期支护破坏、二衬开裂等一系列问题。为深入研究隧道在层状岩层中的力学特性和破坏机理,以大岗山隧道为项目依托,借助数值模拟研究有、无支护状态下不同节理倾角对隧道稳定性的影响,并针对现有支护方案提出优化。结果表明:节理的存在使得隧道开挖后变形具有非对称性,无支护状态下,当节理倾角在30°~60°变化时,隧道洞周最大变形发生在右拱肩处,塑性区破坏前期以拉伸破坏为主,集中于右拱肩及左拱脚,随着节理角度增大,后期以剪切破坏为主;支护状态下,洞周变形得到有效改善,其中拱底隆起最为明显,但最大隆起量降至30 mm以内,围岩塑性区域减小,当节理角度为45°时,拱顶、拱底产生最大变形,随着节理角度的增大,左右两侧变形非对称性降低;布设局部加长锚杆,增加隧道仰拱厚度的优化方案能增强围岩稳定性,抑制围岩进入塑性状态,减小拱底隆起,增强隧道稳定性,减小节理岩层引起的潜在风险,为现场施工提供理论指导。

Inclined laminated rock masses exhibit significant anisotropy and are prone to large deformations,collapses,initial support damage,and second lining cracking during the construction of tunnels.In order to study the mechanical properties and damage mechanisms of tunnels in the laminated rock,the Dagangshan Tunnel was used as the basis for the project.With the aid of numerical simulations,the effect of different joint inclination angles on the stability of tunnels with and without support was investigated and optimization was proposed for the existing support scheme.The results show that the existence of joints makes the tunnel deformation after excavation is asymmetric,when the angle of joints varies from 30°to 60°in the unsupported state,the maximum deformation of the tunnel perimeter occurs at the right arch shoulder,and the plastic zone is broken mainly by tensile damage in the first stage,concentrated in the right arch shoulder and left arch foot,and shear damage in the later stage as the angle of joints increases;in the supported state,the deformation of the tunnel perimeter is effectively improved,among which the arch bottom uplift is the most obvious,but the maximum uplift drops to less than 30 mm.When the joint angle is 45°,the maximum deformation occurs at the top and bottom of the arch,and as the joint angle increases,the asymmetry of deformation decreases on the left and right sides.The optimized solution of placing locally lengthened anchors and increasing the thickness of the elevation arch can enhance the stability of the surrounding rock,restrain the surrounding rock from entering a plastic state,reduce the uplift of the arch base,enhance the stability of the tunnel,reduce the potential risks caused by the jointed rock formations and provide theoretical guidance for the construction on site.