软岩隧道拉锚结构数值分析与支护机理研究

Numerical Analysis and Support Mechanism of Bolt-Steel Strip Structure in Soft Rock Tunnel

为研究拉锚结构在软岩公路隧道的支护效果并推进其应用发展,针对两台阶法开挖的Ⅴ级围岩公路隧道,使用FLAC3D进行数值分析。根据拉锚结构构件连接方式,提出拉锚结构模拟方法并建立模型,对4种不同支护方法的隧道围岩位移、应力和支护结构受力特性进行了对比分析,总结拉锚支护的结构受力特性和支护机理。结果表明:拉锚支护在改善围岩应力状态、减少隧道位移和发挥支护结构效用3个方面均最优;拉锚支护能够明显改善拱腰处应力状态和变形情况;拉锚支护的锚杆所受轴力大于传统支护,其轴力大小分布从杆尾到杆端越来越大;拉锚支护的横向钢带在各点的应力均大于钢拱架,尤其在拱腰处。

In order to study the supporting effect of the bolt-steel strip structure in the soft rock highway tunnel and to promote its application development,the FLAC3D was used for numerical analysis of the V-class surrounding rock highway tunnel excavated by the two-step method.According to the connection method of the structural members of the anchor,the simulation method of bolt-steel strip structure was proposed and the model was established.The displacement and stress of surrounding rock and the mechanical characteristics of supporting structure of four kinds of different supporting methods were compared and analyzed.The mechanical characteristics and supporting mechanism of the structure of the tension anchor support were summarized.The results show that the bolt-steel strip support is the best way to improve the stress state of the surrounding rock,reduce the displacement of the tunnel,and play the effectiveness of the supporting structure.The bolt-steel strip support can significantly improve the stress state and deformation of the bow waist;the axial force of the anchor bolt of bolt-steel strip support is greater than that of the conventional support,and the axial force distribution is getting larger and larger from the tail to the head of anchor bolt.The stress of the transverse steel strip of the tension anchor support at each point is greater than that of the steel arch frame,especially at the arch waist.