上软下硬地层盾构下穿既有隧道扰动变形研究

Research on disturbance deformation of shield tunneling beneath existing tunnels in soft-top and hard-bottom strata

针对上软下硬倾斜地层中,盾构下穿既有地铁时的管片变形控制问题,以武汉轨道交通7号线下穿既有2号线工程为背景,采用三维数值模拟方法和离散元软件3DEC建立地铁2号线管片模型,同时使用FLAC3D软件进行三维数值分析,探讨新建隧道与既有隧道间距、地层倾斜和注浆填充对既有地铁及周边地层的影响。分析结果表明:既有隧道沉降值受地层条件和隧道间距影响显著,尤其在新建盾构隧道与既有隧道距离较近时;既有地铁管片加固和新建隧道注浆填充对控制上软下硬地层条件下新建隧道近接下穿既有隧道的沉降变形具有显著效果。在新建盾构隧道施工前需对既有地铁管片的前期变形量进行准确分析,确保既有隧道安全,且加固和注浆填充措施对于类似工程的变形控制至关重要。

Aiming at the issue of segment deformation control in shield tunneling through existing subways within stratums that were soft on the top and hard on the bottom,taking the project of Wuhan Metro Line 7 tunneling under the existing Line 2 as the background,the three-dimensional numerical simulation methods and the discrete element software 3DEC to establish a model of the Line 2 segments was used.We carried out a 3D numerical analysis using FLAC3D software to investigate the distance between the new tunnel and the existing tunnel,the ground inclination and the effect of the grouted fill on the existing metro and surrounding strata.The analysis showed that the settlement of the existing tunnel was significantly affected by the stratum conditions and the distance between tunnels,especially when the newly constructed shield tunnel was close to the existing one.The reinforcement of the existing subway segments and grouting filling in the new tunnel significantly controled the settlement deformation when tunneling close under the existing subway in soft-top and hard-bottom conditions.The study emphasized the importance of accurately analyzing the pre-deformation of existing subway segments before the construction of new shield tunnels to ensure the safety of the existing tunnels,and the reinforcement and grouting filling measures were crucial for deformation control in similar projects.