新建隧道下穿施工对既有上卧盾构隧道扰动影响规律研究

Study on the influence law of underpass construction of new tunnel on the disturbance of existing upper shield tunnel

针对新建盾构隧道下穿施工时,对既有上卧盾构隧道结构的扰动影响问题,应用非线性接触理论和多尺度混合建模技术,建立三维非连续精细化数值模型,重点分析隧道正交下穿施工扰动下,既有上卧盾构隧道管片与接头受力和变形规律。研究结果表明:新建隧道下穿施工诱发既有上卧盾构隧道整体下沉,表现为隧道结构竖向收敛波动和仰拱沉降显著;纵缝接头变形以张开为主,环缝接头变形以错台为主,且同一环中拱顶处变形最大;环缝接头应力集中明显,靠近交叉点处管片环缝的最大、最小应力均接近混凝土强度设计值,局部裂损风险高;受下部开挖影响,上卧盾构隧道环缝接头螺栓剪应力值增加显著。

To further understand the influence caused by construction of underline shield tunnel on the existing shield structure, a three-dimensional non-continuous refined numerical model was established by non-linear contact theory and multi-scale hybrid modeling technology. The emphases were put on the stress and deformation of segment and joint structures of existing tunnel, especially when the underline shield tunnel is passing through perpendicular to the existing one. The results show that under the construction of underline tunnel, integral sinking is observed in the existing one, which is characterized by fluctuant vertical convergence and significant settlement of inverted arch. Besides, the deformation of joints at longitudinal and circumferential seams of lining show significant opening and dislocation respectively, and the largest deformation is found in the vault. The stress concentration is obvious around the joints at circumferential seam of lining, where the maximum and minimum stress values almost reach to the design values of concrete strength nearthe intersection of two tunnels, resulting in high risk at local cracking. On the other hand, significantly increased shear stress of longitudinally connected bolt is detected during construction of underline shield tunnel.