盾构隧道平行转叠线施工地表沉降特征及控制技术

Study on Surface Settlement Characteristics and Control Technology of Shield Tunnel Parallel to Overlap Construction

叠线隧道施工过程中,由于上下线的相互影响,对地层的扰动相比于普通隧道更加剧烈。结合郑州地铁3号线二太区间超小净距叠线盾构隧道工程,基于现场大量实测数据,对2条盾构隧道由平行转到叠线施工所引起的地表沉降进行了分析,得出了全过程的地表沉降特征:平行段左右线开挖对地表的最大沉降影响较小,叠加效应主要体现在地表沉降的横向范围;进入过渡段之后,由于地层、埋深变化和下线隧道开挖时的扰动,上线隧道开挖时引起的地表沉降逐渐增大;隧道开挖进入叠线段时,由于2条隧道间距逐渐减小,下线隧道开挖之后对上线隧道开挖的影响逐渐增大,又因为上线地层变为砂层,导致地表沉降达到26.63 mm,后采用二次补浆措施才得以控制。最后提出地表沉降控制措施。

The disturbance to the soil is more severe than the ordinary tunnel in the construction of the overlapped tunnel,due to the mutual influence of the upper and lower lines.A case study is conducted on the tunnel between Taikang Road station to Erqi Square station of Zhengzhou Metro Line No.3.Based on many fields measured data,the surface settlement caused by the construction of two shield tunnels from parallel to overlapped is analyzed,and the surface settlement characteristics of the whole process are obtained.The parallel excavation has little influence on the maximum settlement value of the surface,and the superposition effect is mainly reflected in the lateral range of the surface settlement.After entering the transition section the surface settlement caused by the excavation of the upper tunnel gradually increases due to the change of soil,depth and the disturbance during the excavation of the lower tunnel.When the tunnel excavation enters the overlapping section,due to the gradual decrease of the spacing between the two tunnels,the influence of the excavation of the lower tunnel on the excavation of the upper tunnel gradually increases after the excavation of the lower tunnel,and the upper soil becomes sand layer,resulting in surface settlement of 26.63 mm,and the secondary grouting measures are adopted.Finally,technical measures for surface subsidence control are presented to control the settlement.