软弱围岩隧道锁脚微型桩支护结构研究

Research on the Supporting Structure with Feet-locked Micro-pile in Weak Surrounding Rock Tunnel

针对软弱围岩隧道施工过程中存在的支护变形、围岩坍塌等问题,提出一种锁脚微型桩支护结构。运用理论分析手段,阐述了锁脚微型桩的承载作用和注浆加固作用,改善了软弱围岩和支护结构的应力状态,充分发挥了初期支护的承载作用,抑制了隧道变形。依托其古顶隧道,采用现场试验的手段,分别对围岩压力、钢拱架应力、拱顶下沉和周边收敛变化特征与规律进行研究。研究结果表明:隧道开挖对拱顶和左右拱腰位置影响较大,其围岩压力分布值最大;同等软弱围岩地质条件下施作锁脚微型桩支护结构,隧道钢拱架应力增大了20%~40%,隧道拱顶下沉和周边收敛量减小约30%~40%左右。施作锁脚微型桩支护结构可提高围岩稳定性,增加支护刚度,减小围岩变形,使得初期支护效果得到提升。

To solve the problems of supporting deformation and collapse of surrounding rock during the construction of weak surrounding rock tunnels, a kind of supporting structure with feet-locked micro-pile is proposed. The bearing function and grouting reinforcement function of the feet-locked micro-pile are elaborated by using theoretical analysis which can improve the stress state of the weak surrounding rock and the supporting structure,give full play to the bearing function of the initial supporting,and restrain the deformation of surrounding rock.Relying on the Qiguding Tunnel project,the characteristics and laws of surrounding rock pressure,steel arch stress,vault settlement and peripheral convergence are analyzed by means of field test.The research results show that tunnel excavation has a greater impact on the position of the arch crown and hance where the surrounding rock pressure is the largest.Under the same weak geological conditions of the surrounding rock,the stress of the steel arch frame increases by 20%~40%,and the vault settlement and the peripheral convergence are reduced by about 30%~40% when the feet-locked micro-pile supporting structure is used.The construction of the feet-locked micro-pile supporting structure can improve the stability of the surrounding rock,increase the support rigidity,reduce the deformation of the surrounding rock,and improve the initial support effect.