盾构扩挖法建造地铁车站的桩-柱-预应力支撑体系参数研究

盾构扩挖法建造地铁车站的施工方案的一个技术关键是在拆除部分管片之前对隧道结构进行加固．综合国内外对于管片破除时的加固措施，提出一种新型的支撑体系：桩-柱-预应力支撑体系．通过有限元分析对支撑体系中钢索预应力施加的位置和大小进行了研究．结果表明：管片开口部位的上下位置均需要施加预应力；远离管片开口部位的对面管片腰部也需要施加预应力，大小约为开口部位的10％；隧道外侧施做排桩有利于控制管片的纵向变形；在不超过混凝土设计强度的情况下，预应力越大，对管片纵向的约束越强．

Parameter Research of Pile-Column-Prestressing Support System of Metro Station Constructed by Enlarging Shield Tunnels

Reinforcing the tunnel structures before segments are partly removed is a technical key of constructing metro station by enlarging shield tunnel combined with mining/open cut method. Based on the domestic and international reinforcing measures for removing the segments, a new support system is put forward, which is called Pile-Column-Prestressing Support System. The positions and values of prestressing forces exerted to the support system are studied with finite element analysis. These results indicate that prestressing force should be exerted at both the top and the foot of the segments peristome. Besides, prestressing force should also be exerted at the middle of segments opposite to the peristome, which is about 10 percent of the value at the peristome. Piles beside the shield tunnel are helpful to control longitudinal deformation of segments. The bigger the prestressing force is, the stronger the longitudinal restraint to the segments is, provided that design strength of concrete is not exceeded.