中洞法连拱隧道施工稳定性分析及优化

Stability Analysis and Optimization of Double-arch Tunnel Constructed by Center Drift Method

针对中洞法连拱隧道暗挖施工的稳定性问题,依托广州大道中站工程实例,综合分析了开挖过程拱顶沉降、底部变形、洞周收敛、初支结构应力、中隔墙应力以及地表沉降等指标的动态响应特征,总结了不同工艺参数下隧道变形规律,结果表明:拱顶沉降最大值和最大沉降速率以及底部隆起最大值均在后行洞,而先行洞洞周收敛值最大,为1.59 mm;侧洞靠近中洞上台阶支护结构受拉而远离中洞上台阶受压;中隔墙中部主要承受压应力,而顶纵梁和底纵梁则同时承受拉应力和压应力;地表沉降最大值位于隧道中心,为7.20 mm,隧道施工影响区域半径约为25 m;隧道稳定性随中洞上下台阶错距及侧洞相邻台阶错距的增大而减弱,随侧洞拉开距离增大而增强。

Aiming at the stability of the excavation of the double-arch tunnel with the center drift method,relying on the Guangzhou Avenue middle station project,the dynamic response characteristics of the arch settlement,bottom deformation,tunnel convergence,initial support structure and partition wall stress,and surface settlement during the excavation process were comprehensively analyzed,and the deformation law of tunnel under different technological parameters was summarized.The results show that the maximum settlement and settlement rate of the vault,and the maximum bottom uplift are in the posterior tunnel,while the convergence value of the prior tunnel is the largest at 1.59 mm.The supporting structure of the upper step close to the middle hole is under tension,while that of the upper step far from the middle hole is under pressure.The middle part of the partition wall is subjected to compressive stress,while the top and bottom longitudinal beam bear both tensile stress and compressive stress.The maximum ground settlement is located in the center of the tunnel,which is 7.20 mm,and the radius of the affected area of tunnel construction is about 25 m.The stability of the tunnel decreases with the increase of the distance between the upper and lower steps of the middle hole and the adjacent steps of the side hole,and it increases with the increase of the distance between the side holes.