软土地区深基坑预应力钢筋混凝土支撑对邻近地铁隧道变形影响分析

Influence of prestressed reinforced concrete struts in a deep excavation on deformation of the adjacent metro tunnel in the soft soil area

依托上海地区一邻近地铁的深基坑工程,通过基坑分区后大坑内预应力钢筋混凝土支撑的使用,解决了上海软土地区复杂地质条件下深基坑开挖对邻近地铁隧道结构变形影响较大的技术难题。第三至第五道支撑使用预应力钢筋混凝土,共设置89个伺服式千斤顶。监测结果表明,大坑内预应力钢筋混凝土支撑的使用,使中隔墙墙身侧向位移向坑外方向持续发展,未改变隧道水平位移、竖向位移及管径收敛沿轴线方向的变化趋势;在该支撑系统工作过程中,隧道水平位移变化量控制在0.5 mm内,竖向位移和管径收敛变化量控制在2~3 mm内。预应力钢筋混凝土支撑的使用成本增加有限。

Based on a deep excavation project near a metro tunnel in Shanghai,the technical problem that deep excavation has a great impact on deformation of the adjacent metro tunnel in Shanghai's soft soil area is solved by using the prestressed reinforced concrete strut in the largest excavated zone of the entire foundation excavation.Prestressed reinforced concrete struts were installed for the third to fifth layers of foundation bracing,and 89 servo jacks were installed in total.The monitoring results showed that the use of prestressed reinforced concrete struts makes the lateral displacement of the middle partition wall develop continuously towards the outside of the foundation pit.The variation of tunnel horizontal displacement,vertical displacement,and pipe diameter convergence along the axial direction is not changed.By using this support system,the variation of horizontal displacement of the tunnel is controlled within 0.5 mm,and the variations of vertical displacement and pipe diameter convergence are controlled within 2~3 mm.The total cost has not increased significantly after using prestressed reinforced concrete strut.