浅埋软弱围岩隧道掌子面锚杆预加固参数分析

Analysis on the Parameters of Bolt Pre-reinforcement in the Face of Shallow Buried Soft Surrounding Rock Tunnel

大断面浅埋隧道在软弱围岩中全断面开挖时,隧道掌子面核心土处于短暂稳定或不稳定状态,处理不慎便会造成核心土的失稳,因此采用玻璃纤维锚杆对核心土进行预加固是有必要的。结合格鲁吉亚某隧道工程实例,采用新意法理念,运用FLAC3D有限差分软件,对浅埋软弱围岩隧道全断面开挖时掌子面玻璃纤维锚杆加固长度l(5个工况)和加固密度β(7个工况)进行优化分析,结果表明:随着l或β的增大,目标掌子面挤出位移和拱顶前方位移逐渐减小,目标掌子面拱顶前方应力逐渐趋于原始状态;当l>6 m或β>0.75时,掌子面锚杆对核心土的预加固效果不明显,综合工程的安全性和经济性,取l=8 m、β=0.75较为合理,为类似工程提供了一定的参考依据。

When a large section shallow buried tunnel is excavated in soft surrounding rock,the core soil in front of the face is often in a transient stable or unstable state.If the core soil in front of the tunnel face is not properly treated,it can cause instability of the core soil.Therefore,it is necessary to use glass fiber an⁃chor rods for pre-reinforcement of the core soil.Combined with a tunnel project in Georgia,adopting the con⁃cept of new Italian law,the reinforcement length l(5 working conditions)and reinforcement densityβ(7 working conditions)of bolts in the face of tunnel with full face excavation in shallow soft surrounding rock are optimized and analyzed with FLAC3D.The results indicate that as l orβincreases,the extrusion displace⁃ment of the target tunnel face and the displacement in front of the arch gradually decrease,and the stress in front of the arch gradually approaches the original state.When l>6 m orβ>0.75,the pre reinforcement ef⁃fect of the rock bolt on the core soil is not significant.Considering the safety and economy of the project,tak⁃ing l=8 m andβ=0.75 is relatively reasonable and provides a certain reference basis for similar projects.