空间特征对盾构下穿既有隧道响应规律

Response law of spatial characteristics for underpass shield to existing tunnels

盾构隧道下穿施工对既有隧道沉降变形影响显著,两者的相对空间位置对既有隧道的沉降变形影响更为明显。以昆明地铁5号线叠交隧道为背景,利用自行加工的试验平台,开展不同隧道埋深、竖向净距、水平间距3种空间特征参数对既有隧道沉降变形的影响室内缩尺试验,探究不同盾构下穿空间位置在不同影响水平下既有隧道变形影响规律,开展正交试验,得到各参数对既有隧道与地表的影响显著度。结果表明:各空间特征参数对既有隧道沉降变形影响的敏感性顺序为竖向净距、水平间距及隧道埋深;随着隧道埋深的增大,地表沉降值不断减小,既有隧道沉降值不断增大;随着竖向净距与水平间距的增大,地表与既有隧道沉降值都不断减小。隧道埋深与既有隧道沉降值呈正相关,竖向净距、水平间距与既有隧道沉降值呈负相关。提出盾构下穿空间位置最佳组合方案为隧道埋深1.5D(D为隧道外径)、竖向净距0.5D,水平间距2.0D的组合。研究成果可为新建隧道盾构下穿既有隧道的沉降控制提供参考。

The shield tunnel undercrossing construction has a significant impact on the settlement deformation of the existing tunnel,and the relative spatial position of the two has a more significant impact on the settlement deformation of the existing tunnel.The overlapping tunnel of Kunming Metro Line 5 was taken as the research background,and the laboratory scale test of the influence of three spatial location parameters,i.e.,different tunnel burial depth,vertical clearance and horizontal spacing,on the settlement and deformation of the existing tunnel was carried out,using the self-developed test platform.The influence law of existing tunnel deformation at different spatial locations and different influence levels was explored.Meanwhile,orthogonal tests were complemented for different spatial locations,and the influence significance of each parameter on the existing tunnel and the ground surface was obtained.The results show that the order of sensitivity of each spatial index to the settlement deformation of the existing tunnel is vertical clearance,horizontal spacing and tunnel burial depth.With the increase of tunnelling depth,the surface settlement value decreases continuously,and the existing tunnel settlement value increases continuously.With the increase of vertical clearance and horizontal spacing,the settlement value of the ground surface and the existing tunnel decreases continuously.The buried depth of the tunnel is positively with the settlement value of the existing tunnel,while the vertical clearance and horizontal spacing are negatively correlated with the settlement value of the existing tunnel.It is proposed that the best combination scheme for the spatial position of the shield tunneling is the combination of 1.5D tunnel burial depth(D is the outer diameter of the tunnel),0.5D vertical clearance and 2.0D horizontal spacing.The research results can ensure the smooth construction of new tunnels and the operation safety of the existing tunnels,which provides a reference and guidance for similar tunnel engineering problems.