连拱隧道复合式中墙偏转机制及其预防措施

Research on Deflection Mechanism of Compound Middle Wall of Double-arched Tunnel and Preventive Measures

基于连拱隧道支护体系结构特点与现场实况,建立连拱隧道开挖模型,模拟连拱隧道施工过程。通过添加接触单元,模拟主洞初次衬砌与围岩间的相对滑动,研究造成中墙偏转的力学机制、偏转发生的阶段、偏转发展趋势及其对隧道稳定性的影响。基于对中墙偏转机制的研究,提出采用设置中墙侧锁脚锚杆的方式预防中墙偏转,并通过对比分析的方式验证预防措施的有效性。结果表明:中墙的偏转发生在先行洞施做初次衬砌后,并随着后行洞的开挖有加重趋势。中墙的偏转对于隧道的整体稳定性极为不利。增设中墙侧锁脚锚杆能有效防止中墙偏转,控制中墙顶部位移,保障隧道整体稳定性。

Based on structural features of supporting system of double-arched tunnel and in-situ conditions,the model of excavation of double-arched tunnel is built to simulate the construction process of tunnel.By adding contacting units,the relative sliding between surrounding rock and initial lining of main tunnel is simulated,and the deflection mechanism of middle wall,the phase when deflection occurs,the tendency of deflection and how the deflection affects the stability of tunnel are studied.Based on the research on the deflection mechanism of middle wall,the idea that the bolts could be set between the foot of initial lining and the surrounding rock above the middle wall is proposed.By contrast and analysis,this kind of preventive measure is proved to be effective.The conclusions as follows:the deflection of middle wall occurs after the construction of initial lining of the former main tunnel,and becomes more and more serious along the excavation of latter main tunnel.The deflection of middle wall is extremely unfavorable to the stability of tunnel.The settlement of bolts between the foot of initial lining and the surrounding rock could effectively prevent the deflection of middle wall,control the displacement of the head of middle wall and protect the stability of tunnel.