盾构隧道下穿城市高架桥桩基预加固方案研究

Study on Pre-reinforcement Schemes for a Shield Tunnel Passing under the Pile Foundation of an Urban Viaduct

文章以某区间盾构隧道下穿既有城市高架桥工程为依托,对盾构施工前城市高架桥桩基的预加固方案进行了系统分析,提出了4种加固方案,分别是袖阀管注浆预加固方案、隔离桩预加固方案、袖阀管注浆+隔离桩预加固方案和袖阀管注浆+隔离桩+新增桩基预加固方案;并详细介绍了每种预加固方案的设计思路,最后对4种预加固方案进行了三维精细化数值模拟计算。结果表明,单独设置袖阀管注浆的预加固方案和单独设置隔离桩的预加固方案的加固效果有限;同时设置袖阀管注浆和隔离桩的预加固方案能很好地控制桩基的水平位移、竖向沉降及墩台的差异沉降,加固效果较好;而额外再增设桩基的预加固方案,对沉降控制的贡献有限,性价比较低。

In this paper,the pre-reinforcement schemes for the pile foundations of an urban viaduct before shield construction are systematically analyzed on the basis of a shield-driven running tunnel passing under the existing urban viaduct,and four reinforcement schemes are put forward:namely the pre-reinforcement scheme with sleeve valve grouting pipes,the pre-reinforcement scheme with isolation piles,the pre-reinforcement scheme with sleeve valve grouting pipes+isolation piles,and the pre-reinforcement scheme with sleeve valve grouting pipes+isolation piles+additional pile foundations.Then,the design idea of each pre-reinforcement scheme is introduced in detail and the refined three-dimensional numerical simulation calculation is performed for four pre-reinforcement schemes.The results show that the pre-reinforcement scheme with sleeve valve grouting pipes alone and that with isolation piles alone have limited effect;the pre-reinforcement scheme with sleeve valve grouting pipes and isolation piles can desirably control the horizontal displacement,vertical settlement and differential settlement of piers and abutments,with good reinforcement effect;the pre-reinforcement scheme with additional pile foundations has limited contribution to settlement control,and so with a low cost performance.