穿越上软下硬复合地层交界面的双线盾构隧道开挖稳定性分析

Excavation Stability Analysis of Double Line Shield Tunnel Crossing the Interface of Upper Soft & Lower Hard Composite Stratum

随着城市隧道数量的增加、分布范围的扩大,穿越复杂地层条件已是城市盾构隧道在设计与施工中难以避免的问题。广州地区大范围分布砂层与岩层上软下硬复合地层,盾构隧道穿越时面临较大的复杂性和不确定性。以广州轨道交通L8北延伸段石—亭区间隧道工程为例,采用AQAQUS通用有限元平台建立盾构双线隧道开挖的2D数值计算模型,分析隧道穿越砂-灰岩交界面引起的地层变形规律、隧道衬砌受力及变形特征。结果表明,在砂-灰岩交界面处双线盾构隧道开挖造成衬砌的不均匀变形,应力的分布随着交界面位置的变化而发生规律性的改变。为穿越砂-灰岩交界面盾构隧道的设计与施工提供借鉴和参考。

With the increase of the number of urban tunnels&the expansion of the distribution range,crossing complex stratum conditions has become an unavoidable problem in the design and construction of urban shield tunnels.The soft&hard composite strata above the sand layer&rock stratum are widely distributed in Guangzhou.Shield tunnel crossing is faced with great complexity&uncertainty.Taking the Shi-Ting section tunnel project of north extension section of Guangzhou rail transit L8 as an example,the 2D numerical calculation model of shield double track tunnel excavation is established by using AQAQUS general finite element platform,and the formation deformation law,stress&deformation characteristics of tunnel lining caused by tunnel crossing the sand-limestone interface are analyzed.The results show that the excavation of double line shield tunnel at the sand-limestone interface causes uneven deformation of the lining,and the stress distribution changes regularly with the change of the interface position.It provides reference for the design and construction of shield tunnel passing through sand-limestone interface.