盾构隧道下穿地下过街通道安全控制案例研究

Case Study on Safety Control of Underground Street Passages During the Excavation of Shield Tunnels beneath

为解决新建盾构隧道近距离下穿矩形顶管法修建的地下过街通道变形控制的工程难题,以呼和浩特地铁盾构区间隧道下穿“井”字型地下过街通道为依托,通过数值模拟预测地下过街通道变形规律,据此提出安全控制方案,通过现场监测结果验证加固方案的合理性。结果表明:地下过街通道横断面沉降槽呈非对称的“W”形,最大沉降部位出现在左线隧道的正上方,是变形控制的重点区域;地下过街通道错台量最大的部位是先建盾构正上方的管节接缝处,最大错台量为2.7 mm;在盾构下穿期间,通过合理控制掘进参数和及时二次注浆加固的措施能够满足变形控制的要求。

To solve the problem of controlling the excessive deformation of the existing underground street passages excavated by the rectangular pipe jacking method due to the adjacent shield tunnels construction beneath, based on the shield tunnels constructed beneath a well-type underground street passage in Hohhot Subway, the numerical simulation was firstly performed to investigate the deformation of the existing underground street passages, hereby the appropriate scheme for controlling the structural safety was proposed. Finally, in-site monitoring was applied to verify the reasonability of the construction scheme. The results indicate that the settlement trough of the cross-section settlement trough of underground crossing channel displays an asymmetrical “W” shape. The maximum settlement is located above the left tunnel, which is the most important area for controlling the deformation. The maximum dislocation of the duct piece is located at the passage above the new-built shield tunnel, and the maximum dislocation is about 2.7 mm. During the shield beneath construction, the requirement for controlling deformation can be ensured by adjusting the shield driving parameters and performing secondary grouting in time.