近接工程施工对地铁盾构隧道结构的影响分析

ANALYSIS OF THE INFLUENCE OF ADJACENT CONSTRUCTION ON THE STRUCTURE OF METRO SHIELD TUNNEL

近接工程施工易对既有地铁隧道结构造成扰动,甚至导致结构失效。依托南宁市民族大道北侧山体公园路网完善工程,通过数值模拟方法分析了近接工程施工对地铁盾构隧道的影响。首先,构建了三维地层–结构模型,按照道路施工步序,预测施工引起的轨道交通1号线区间隧道的附加变形及附加内力;其次,采取二维荷载–结构模型,选取轨道交通结构典型截面进行内力分析及承载力验算,进而分析轨道交通结构的安全性。结果表明:土体施工主要引起下方隧道管片的竖向变形;土体开挖后,管片出现朝向卸载区域的变形;土体回填、道路平整后,管片变形略有减小;轨道交通结构安全性验算证明在正常施工条件下,隧道结构处于安全状态。

The construction of adjacent projects is prone to cause external loads and disturbances to existing structures,leading to premature structural failure.The impact analysis of the construction of adjacent projects on the metro shield tunnel was analyzed by numerical simulation method based on the improvement project of the road network of the Mountain Park on the north of the National Avenue in Nanning Province.The study first built a three-dimensional stratigraphic-structural model to predict the additional deformation and internal forces of the tunnel in Line 1 interval caused by the construction of adjacent project according to the road construction step sequence.Then,a two-dimensional load-structure model was established to carry out internal force analysis and bearing capacity verification based on the typical cross-section of the rail transit structure for the safety examination of the rail transit structure.The results indicate that the adjacent construction mainly causes verticaldeformation of the tunnel tube sheet below.After soil excavation,the tube sheet showed deformation toward the unloading area,while it slightly decreased after soil backfilling.Besides,the structural safety examination of the rail transit structure demonstrated that the tunnel structure is safe under normal construction conditions.