公路隧道开挖应力变化及锚杆受力影响研究

Effects of Highway Tunnel Excavation on Stress Variation and the Force Applied on Anchor Bolts

文章基于S13等级公路1#隧道工程实例,采用数值模拟方法,分析了隧道在不同埋深、不同围岩等级、不同开挖方式情况下应力变化及锚杆支护内力变化等规律,并和实测数据进行了对比。研究结果表明:当隧道进行开挖时,隧道周围岩体初始应力被释放,岩体发生变形,原岩体应力重新分布,随着开挖面不断推进其应力会随之发生改变;隧道洞口开挖面以及隧道中段开挖面的拱顶A、拱腰B、拱底C处应力状态变化规律并不一致。不同开挖方式、不同围岩等级、不同埋深对锚杆内力的影响大小和区域也不相同,Ⅲ级围岩锚杆最大受力主要集中在拱顶及附近区域,Ⅳ、Ⅴ级围岩锚杆最大受力产生在拱脚左右两边;隧道埋深为60 m、100 m时,锚杆所受最大轴力在隧道拱底左右两侧;当隧道埋深增加到140 m时,锚杆最大轴力在拱顶左侧区域。研究成果可为相关隧道设计和施工提供参考,可使隧道初期支护以及二次衬砌选案更加合理。

Based on the 1# tunnel project on the S13 highway, the variation law of stress and internal foree in the anchor boh is analyzed by a numerical simulation method in respect to buried depths, rock mass grades, and excavation methods, and a comparison is made with the testing data. The results indicate that the initial stress of the rocks around the tunnel is released during tunnel excavation, resulting in rock mass deformation and stress redistribution, while the stress varies with the advancement of the excavation face. The variation rules of the stress state of the crown （A）, haunch （B）, and invert （C） at the tunnel portal and mid-section are ineonsistent. There are different effects on the internal force of the anchor bolts and tunnel areas based on different excavation methods, rock mass grades, and buried depths. The largest stress applied on the rock boh is mainly concentrated on the crown and the areas nearby for surrounding roek of grade III, while it is mainly concentrated on the two sides of＇ the arch springing for surrounding rock of grade IV or V. At a buried depth of 60 m or 100 m, the maximum axial force acting on the rock bolt occurs at the both sides of the tunnel invert, while it occurs at the left area of the tunnel crown at a buried depth increasing to 140 m. These research results provide a reference for the design and construction of similar tunnels, and encourage a more reasonable primary support and secondary lining.