密贴运营地铁隧道两侧基坑合理开挖步序研究

Study on Reasonable Excavation Step of Closely Foundation Excavation on Both Sides of Existing Metro Tunnel

在建广州地铁12号线赤岗站被既有8号线隧道贯穿,既有线两侧车站基坑与隧道密贴,且施工期间隧道不停运,基坑开挖对既有运营隧道影响显著。由于实际因素,两侧基坑开挖不同步,对基坑及隧道变形影响未知。因此,通过数值计算方法,探究密贴既有运营地铁隧道两侧基坑不同步开挖对基坑及隧道变形的影响,提出合理开挖步序。结果表明:随着一侧基坑领先开挖步差的增大,该侧邻近隧道的围护结构开挖过程中的最大侧移有所增大,隧道向该侧侧移量增大;隧道上方地表沉降呈“W”形;合理步差以隧道水平位移为主要控制指标,在两侧同时开挖或1号基坑领先1~2步时施工均未超过预警值,是较为合理的开挖步差。

Chigang Station of Guangzhou Metro Line 12 is penetrated by the existing tunnel of Line 8.The foundation excavation of the stations on both sides of the existing line are closely attached to the tunnel,and the tunnel is not out of service during the construction.The excavation has a significant impact on the existing operating tunnel.Due to the actual factors,the excavation of both sides of the foundation excavation is not synchronized,and the influence on the deformation of the foundation excavation and tunnel is unknown.Therefore,through the numerical calculation method,the influence of unsynchronous excavation on the foundation excavation and the tunnel deformation of the excavation on both sides of the closely attached metro tunnel is explored,and the reasonable excavation step sequence is proposed.The results show that with the increase of the leading excavation step of one side of the foundation excavation,the maximum lateral displacement of the surrounding tunnel during the excavation process increases,and the lateral displacement of the tunnel to this side increases.The surface subsidence above the tunnel is W shaped.The reasonable step difference takes the horizontal displacement of the tunnel as the main control index,and the construction does not exceed the warning value when the two sides are excavated at the same time or the No.1 foundation excavation is one or two steps ahead,so it is a reasonable step difference.