大变形隧道钢拱架自适应节点轴压性能研究

针对挤压型软岩隧道大变形问题，基于能量释放的让压支护理念，发明了一种适用于软岩大变形隧道的自适应钢拱架节点；该节点通过滑移实现让压，能够显著降低围岩压力，充分发挥支护材料的性能。通过理论计算与室内试验，研究了自适应节点的轴向承载特性，证实了自适应节点的可行性和让压性能，并总结了自适应节点工作的4个阶段：弹性变形阶段、恒阻滑移阶段、压实阶段和塑性变形阶段。建立了考虑自适应节点细部构造的三维精细化模型，并基于理论解析和试验结果进行了对比分析。研究结果表明：自适应节点能够在保持恒定滑移阻力的同时产生较大变形，对比传统钢架连接节点具有较高的可压缩性；自适应节点的滑移阻力随螺栓扭矩的增大而增大，螺栓扭矩在70，80，90，100 N·m时，理论值、模拟值和试验值吻合较好。对比分析设置自适应节点的钢拱架和传统钢拱架的支护效果可知：在相同收敛变形时，设置自适应节点可使钢拱架的内力显著降低，但在节点处出现了应力集中；设置自适应节点可使钢拱架的极限收敛变形提升10倍左右，能够更好地适应隧道大变形。新型自适应节点取材方便、构造简单，可以为高地应力区软岩公路隧道大变形支护技术研究提供新的思路，但其与围岩的相互作用还未探明，要在实际工程中应用还有待进一步的研究。

Axial Compression Behavior of Adaptive Steel Arch Joint for Large-deformation Tunnels

To address the large-deformation problem of tunnels in squeezing rock, a new adaptive steel arch joint was proposed for large-deformation tunnels based on the concept of consuming energy for yielding support. The adaptive joint yields through the sliding of the joint, which can significantly reduce the surrounding rock pressure and take advantage of the performance of supporting materials. The axial load-bearing behavior of the adaptive joint was studied by means of theoretical calculations and experiments, and the feasibility and yielding performance of the adaptive joint were verified. The mechanical response of an adaptive joint can be divided into four stages: the elastic stage, constant resistance stage, compaction stage, and plastic stage. A 3D refined model of the adaptive joint was established. A comparative analysis with and without an adaptive joint was examined through theoretical analysis and experimental results. The results show that the adaptive joint can maintain a constant resistance, bear a large deformation, and have high compressibility and good flexibility. The sliding resistance of the adaptive joint increases with an increase in the bolt torque. For bolt torques of 70, 80, 90, and 100 N·m, the numerical simulation results agree well with the theoretical and experimental results. The supporting effects of the adaptive joint and traditional steel arch were compared. The results show that, when the adaptive joint is set, the internal force of the steel arch is significantly lower than without the adaptive joint under the same convergence, but there is a stress concentration at the joint. The limit convergence of the steel arch with the adaptive joint reaches approximately 10 times that of the traditional steel arch, thus it can better resist large deformation. The new adaptive joint can easily obtain materials and is simple in structure. It provides new ideas for the research of large-deformation support technology for soft rock highway tunnels in high-ground-stress areas. However, the interaction between the adaptive joint and surrounding rock has not yet been proved, and further study is required for its application in actual engineering.