为确定管幕、玻璃纤维锚杆及MJS等综合支护措施对于软弱围岩大断面双连拱隧道“三导洞”法施工开挖加固的可行性,以苏州长江路南延工程为依托,利用有限元分析软件建立多种加固工况下全过程开挖数值模型,分析模拟开挖过程位移曲线并现场实测数据比对,验证模型的合理性。根据研究结果进一步提出软弱围岩大断面双连拱隧道施工开挖位移变形控制技术。结果表明:(1) 不同支护工况下,隧道洞口同一测点地表位移沉降由大至小顺序为无支护措施>单一管幕支护措施>管幕和MJS协作支护措施>管幕与MJS及玻璃纤维锚杆综合支护措施;(2) 连拱隧道三导洞法施工,围岩变形以竖向沉降为主,水平收敛较小;(3)在无支护工况下,后行洞开挖对先行洞造成扰动,导致先行洞支护结构变形较后行洞大;(4)在综合支护措施工况下,左右线隧道围岩的竖向位移整体对称,后行洞对先行洞围岩影响小,围岩变形控制好;(5) 在双线连拱隧道施工中,拱顶最大沉降均出现于主洞顶部围岩,施工到接近该区域时,需重点加强对主洞上部围岩监测工作。

In order to reasonably determine the feasibility and specific effect of comprehensive support measures such as pipe curtain, fiberglass anchors and MJS on the excavation reinforcement of the triple pilot tunnels method for the construction of double-arch tunnels with large cross-section in weak surrounding rocks, the South Extension of Changjiang Road Project in Suzhou is taken as a basis, and a large-scale 3D finite element analysis software is used to set up the whole process of excavation numerical model for a wide range of reinforcing conditions. Numerical model of excavation is established by using large-scale 3D finite element analysis software under various reinforcement working conditions, and the displacement curve of the simulated excavation process is compared with the measured data in the field to verify the reasonableness of the model, and the displacement and deformation control technology of the excavation of the tunnel construction of the large-section double-arch tunnel with large weak surrounding rock is further proposed based on the results of the study. The results show that: (1) Under different support conditions, the surface displacement and settlement at the same measurement point of the tunnel portal are, in descending order, no support measure, single pipe curtain support measure, pipe curtain and MJS collaborative support measure, pipe curtain and MJS and fiberglass anchor integrated support measure. (2) The three-guide method construction of the continuous arch tunnel, the surrounding rock deformation is dominated by vertical settlement, and the horizontal convergence is smaller. (3) Under the condition of no support, the excavation of the trailing tunnel causes disturbance to the leading tunnel, resulting in larger deformation of the support structure of the leading tunnel than that of the trailing tunnel. (4) Under the condition of comprehensive support measures, the vertical displacement of the surrounding rock of the left and right tunnels is symmetrical as a whole, and the impact of the trailing tunnel on the surrounding rock of the leading tunnel is small, and the deformation of the surrounding rock is well controlled. (5) In the construction of the two-lane connecting-arch tunnel, the maximum arch settlement occurs in the peripheral rock of the top of the main tunnel, and the monitoring of the peripheral rock of the top of the main tunnel needs to be strengthened when the construction is close to this area.