富水砂层盾构隧道开挖面主动破坏极限支护力研究

On the Limit Support Force on a Working Face under Active Failure: Case Study of a Shield-Driven Tunnel in a Water-Rich Sandy Stratum

文章基于长沙市南湖路湘江公路隧道工程,结合河漫滩地层特点,分析迎坡条件下富水砂层盾构隧道开挖面主动破坏极限支护力。通过运用极限平衡法,将支护力求解以变分学观点来描述,将问题转化为带多维约束的函数极值问题,并考虑隧道纵坡坡度及超孔隙水压力对极限支护力的影响,对隧道极限支护力计算公式提出了修正。分析结果表明:超孔隙水压力对主动破坏极限支护力有较大影响,隧道掘进进入砂层时,应适当提高掌子面支护压力。

Using the construction of a river-crossing highway tunnel on Nanhu Road in the city of Changsha as an example, and based on the characteristics of the flood plain, this paper analyzes the limit support force on the work-ing face under active failure that occurred when the shield excavated the front slope section in a water-rich sandy stratum. Specifically, by using the limit equilibrium method, the problem is converted to a functional extreme-value one with multi-dimension constraints, i.e., the support force solution is studied from the perspective of variation cal- culus, and the formula of the limit support force is modified by considering the influences of the longitudinal gradi- ent and excessive pore water pressure of the tunnel. The results show that the support force applied on the working face should be increased properly when tunnelling in a sandy stratum due to the great effects of the excessive pore water pressure.