盾构隧道施工对在建明挖公路隧道变形的影响

Influence of Shield Tunnel Construction on Deformation of Open-cut Highway Tunnel under Construction

近年来,新出现了明挖公路隧道与城市地铁盾构隧道同期施工的工程案例。明挖公路隧道断面尺寸通常较大,盾构隧道与明挖公路隧道同期施工相互影响显著,直接威胁邻近明挖公路隧道结构的安全和正常使用。基于深圳市某盾构区间隧道邻接明挖公路隧道开挖的实际工程,利用FLAC3D进行数值仿真分析,研究盾构隧道不同位置施工对在建明挖隧道的围护结构及周边土体变形影响。结果表明:地表沉降值随着盾构隧道埋深及距离围护结构水平间距的增加逐渐减小,其减小速率及地表沉降槽的形态在不同工况有着较大差异;地表沉降槽呈现出单峰和双峰的特征,与双线盾构隧道的间距密切相关,当双线隧道近距离施工时引起的地表沉降呈W型,而当双线隧道远距离施工时引起的地表沉降呈U型;在建明挖隧道围护结构水平位移受盾构隧道埋深及距离围护结构水平间距影响较大,围护结构整体朝向明挖隧道内侧偏移,其最大峰值出现在不同埋深处;当盾构隧道埋深确定时,规划设计时应尽量使得盾构隧道距离在建明挖隧道围护结构水平间距大于2倍明挖隧道埋深值,建议后续研究选取适当的变形控制标准,提出盾构隧道邻侧施工对在建明挖隧道变形影响区划分,从而在同类工程施工前对可产生的影响进行科学评估。

In recent years,the new cases of open-cut highway tunnel constructed with shield tunnel in urban subway have occurred.The cross-sectional size of open-cut highway tunnel is usually large,and the simultaneous construction of shield tunnel and open-cut highway tunnel has significant influence on each other,which directly threatens the safety and normal use of adjacent open-cut highway tunnel structure.Based on the actual project of the excavation of a shield interval tunnel adjacent to an open-cut highway tunnel in Shenzhen,by using FLAC3 D for numerical simulation analysis,the influence of shield tunnel construction at different positions on the enclosure structure and surrounding soil deformation of open-cut tunnel under construction is studied.The result shows that(1) The surface settlement decrease as the buried depth of the shield tunnel and the horizontal space between the shield tunnel and the enclosure structure increase,the decreasing rate and the shape of the surface settlement trough are different under different working conditions.(2) The surface settlement trough displays single-peak or double-peak characteristics,which is closely related to the space between the twin shield tunnels.The ground settlement caused by the close construction of the twin tunnels is W shape,while the ground settlement caused by the long-distance construction of the twin tunnels is U shape.(3) The horizontal displacement of the enclosure structure of the open-cut tunnel under construction is greatly affected by the buried depth of the shield tunnel and the horizontal spacing between the shield tunnel and the enclosure structure.The enclosure structure as a whole shifts toward the inner side of the open-cut tunnel,and the maximum peak value appears at different buried depths.(4) When the buried depth of the shield tunnel is determined,The planning and design should try to make the horizontal spacing between the shield tunnel and the open-cut tunnel enclosure structure under construction greater than twice the buried depth of the open-cut tunnel.It is suggested that the appropriate deformation control standard should be adopted during the successive research.It is proposed to divide the influence area of construction of adjacent shield tunnel on the deformation of open-cut tunnel under construction,so as to scientifically evaluate the possible influence before the construction of similar projects.