U型钢柔性拱架承载能力及稳定性的试验研究

Experimental Study on Carrying Capacity and Stability of Flexible U-Steel Support

随着国内外高地应力软岩大变形隧道施工案例的增多,高地应力大变形隧道中的拱架承载能力分析受到了越来越多的关注。通过设计U29型钢柔性拱架室内加载试验,研究了在不同拱架直径工况下卡缆螺栓预紧力、拱架直径变化以及偏载对拱架承载能力及稳定性的影响,为U型钢柔性拱架的设计提供参考。试验结果表明:相同径向收缩量下,直径较小的拱架曲率变化较快,更易发生接头快速缩动所导致的卸压。随着拱架直径增大,让压变形阶段中的卸压现象将减少;在保证拱架接头平稳有效缩动的前提下,提高螺栓预紧力有利于充分发挥拱架承载能力;拱架单段型钢过长易导致阻滑,从而降低拱架实际承载力;拱架的极限承载能力随直径增大而逐渐减小,破坏形式主要表现为整体结构变形和侧向扭曲失稳;拱架在偏载作用下,相邻接头缩动量的较大差异易导致拱架发生整体变形及侧向失稳。在工程施工中应对拱架受偏载处进行针对性补强,以降低失稳风险。

With the increase of softrock tunnels in construction cases with high ground stress and large deformation at home and abroad,the analysis of arch carrying capacity in high ground stress and large deformation tunnels has received more and more attention.Through the laboratory model test,the impact of pre-tension of clamp,the change of the arch diameter and eccentric load on the carrying capacity and stability of the flexible U29-steel support are studied,thus to provide reference for the design of flexible U-steel support.The results show that under the same radial shrinkage,the curvature of the arch with a smaller diameter changes faster,and the pressure relief caused by the rapid shrinkage of the joints is more likely to occur,as the diameter of the arch is increased,the pressure relief phenomenon will be reduced during the yielding deformation stage;On the premise of ensuring the smooth and effective contraction of the joints,increasing the pre-tension of clamp is conducive to giving full play to the arch carrying capacity;The excessive length of single section steel of the arch will easily lead to slip resistance,thereby reducing the actual carrying capacity of the arch;The carrying capacity of the arch gradually decreases with the increase in diameter,and the failure forms are mainly manifested as the overall structural deformation and lateral torsion instability;Under the eccentric load,the large difference in the shrinkage between adjacent overlap joints tend to bring the overall arch deformation and lateral instability.So in the construction of the project,the targeted reinforcement measures should be taken to reduce the risk of arch instability.