基于二次受力的隧道套拱加固损伤衬砌模型试验

Model Test of Cracked Tunnel Lining Reinforced with Umbrella Arch Based on Secondary Loading

松动荷载引起损伤衬砌失稳是不良地层隧道运营期间关键的科学问题。针对此问题,研制了双车道公路隧道带缝衬砌套拱加固模型试验加载装置,可对衬砌结构任意位置施加松动荷载,在损伤衬砌受力同时进行套拱加固,解决了衬砌加固二次受力的"瓶颈"问题;开展1∶10模型试验,研究了松动荷载作用下损伤衬砌套拱加固补强效果,对比变形特性、力学响应及破坏模式。结果表明:衬砌结构刚度随荷载增加而退化,套拱加固有效修复受损衬砌,整体结构刚度明显增大,损伤严重衬砌经套拱加固后承载力仍可提高1倍;原衬砌结构破坏位置为拱顶、拱肩和边墙;套拱加固带缝衬砌构件关键控制截面为拱顶和墙脚,拱顶易发生大偏心压弯破坏,建议加强拱顶纵向配筋,提高抗拉承载力;墙脚出现斜裂缝,属于压剪破坏,应增设墙脚箍筋,以提高抗剪承载力。

Instability of cracked lining induced by loosing loading has been a critical scientific problem during operation period for tunnel. The loading device for a two-lane highway tunnel model tests was manufactured. The device could impose load on any position of lining. It can reinforce cracked lining when it is under mechanical condition. It solves the ‘bottleneck'problem of secondary loading of reinforcement of cracking lining. The 1∶ 10 model tests were carried out to investigate strengthening effect by umbrella arch under loosing loading,such as deformation characteristic,mechanical response and failure mode. The stiffness of lining declines with loading increasing. The reinforcement with umbrella arch can repair cracked lining effectively,and increase its stiffness. It can make the bearing capacity of seriously cracked lining double. The original lining damages at arch,spandrel and wall. The critical controlled sections of umbrella arch are arch and wall-footing. Compressive-bent damage of large eccentricity takes place at arch. Heavy reinforcements are suggested for arch to improve tensile strength. Diagonal crack and compressive-shear appear at wall-footing. So stirrup of wall-footing should be supplemented to update ultimate shearing bearing capacity.