平面交叉隧道围岩及初期支护结构稳定性研究

Study on Stability of Surrounding Rock and Primary Support Structure of Grade Cross Tunnel

随着国民经济的不断增长和交通基础设施的不断完善,相邻隧道在修建时间和空间上不可避免地形成了一定的穿越关系,从而产生了平面交叉和立体交叉,其中平面交叉是交叉隧道的常见结构形式。平面交叉隧道的开挖和支护流程更加复杂,交叉区域围岩和初期支护结构的稳定性值得引起重视。基于Midas GTS NX有限元软件及现场实测数据,首先利用反演分析法完成了隧道三维模型参数的标定,获取了1组可真实表征围岩应力应变特性的模型参数,建立了可模拟施工工序的交叉隧道三维有限元模型,计算获取了开挖和支护过程中交叉区域围岩和初期支护结构的变形及应力演化规律。进一步地,将变形和应力作为考察指标,对交叉区域围岩的拱顶、仰拱、边墙、初期支护结构、系统锚杆等关键施工部分的稳定性进行了评估。结果表明:主洞和支洞相交处的4个拐角及主洞边墙是交叉区域变形和应力的集中区,施工过程中应针对这些区域采取相应的补强措施以确保结构的稳定性;设计文件中给出的系统锚杆的布局不够合理,使得整个系统锚杆的受力不够均匀,局部发生了应力集中现象,可能导致个别锚杆失效,建议将隧道拱部的锚杆数量减少,将主洞边墙处的锚杆数量增加,以规避施工风险。

With the continuous growth of national economy and the continuous improvement of traffic infrastructure, adjacent tunnels inevitably form certain crossing relationship in construction time and space, resulting in grade crossing and grade separation. Among them, grade crossing is a common structural form of cross tunnel. The excavation and support process of grade crossing tunnel is more complex, and the stability of surrounding rock and primary support structure in the crossing area deserves attention. Based on MIDAS GTS NX finite element software and field measured data, first, the parameters of the tunnel 3 D model are calibrated by using the inverse analysis method, a set of model parameters that can truly characterize the stress-strain characteristics of surrounding rock are obtained, a 3 D finite element model of cross tunnel that can simulate the construction process is established, and the deformation and stress evolution rules of surrounding rock and primary support structure in the crossing area during excavation and support are calculated and obtained. Furthermore, taking the deformation and stress as the inspection indicators, the stabilities of the vault, inverted arch, side wall, primary support structure, system anchor and other key construction parts of the surrounding rock in the crossing area are evaluated. The result shows that(1) the 4 corners at the intersection of the main tunnel and the branch tunnel and the side wall of the main tunnel are the concentration areas of deformation and stress in the cross area, and the corresponding reinforcement measures shall be taken for these areas to ensure the stability of the structure during construction;(2) the layout of the system anchor bolts given in the design document is unreasonable, as a result, the stresses on the anchor bolts of the entire system are not uniform enough, and stress concentration occurs locally, which may lead to failure of individual anchor bolt, it is suggested to reduce the number of anchor bolts at the arch of the tunnel and increase the number of anchor bolts at the side wall of the main tunnel to avoid construction risks.