交通隧道高强约束混凝土拱架性能研究与应用

在交通隧道，尤其是大断面交通隧道建设过程中常面临开挖扰动剧烈，围岩控制困难，传统支护强度不足，易出现支护构件破断、拱架屈曲失稳、拱顶冒落掉块等问题。约束混凝土拱架是一种高强、高刚、稳定性好的新型支护形式，能够满足此类隧道的围岩控制要求。目前针对交通隧道约束混凝土拱架的研究均为单榀小比尺试验，无法模拟现场拱架之间的协同承载，试验结果与现场拱架真实受力和变形情况存在较大差别。基于此，研发了交通隧道支护结构大型力学试验系统，开展了组合工字钢拱架、组合约束混凝土拱架与单榀约束混凝土拱架的大比尺力学性能对比试验，研究了拱架的变形破坏机制与整体承载性能。试验结果表明：①工字钢拱架整体呈现“拱顶弯曲，拱腰弯扭，拱架变扁平”的变形形态，变形破坏严重。2类约束混凝土拱架的节点位置在加载后期出现大变形或破坏，单榀拱架拱顶出现平面内弯曲，整体变形较为明显，组合拱架除节点处焊缝撕裂外，加载结束时整体未出现较大变形。②组合约束混凝土拱架的刚度和承载能力分别是组合工字钢拱架的2.51倍和2.63倍，是单榀约束混凝土拱架的4.18倍和2.78倍，组合约束混凝土拱架稳定性能和承载能力较高。③试验拱架均呈现出拱顶、拱底外侧受压，拱腰外侧受拉的受力特性，拱顶位置应力的增长速率较快，拱腰位置由于向外变形受限，易发生平面外失稳，拱顶和拱腰是拱架的关键受力位置。在上述研究的基础上，提出了约束混凝土支护体系在交通隧道中应用的工程建议，研究成果可为该类支护体系的设计和后期研究提供依据。

Research and Application of High Strength Confined Concrete Arch in Traffic Tunnel

There are several challenges in the construction of traffic tunnels, such as intense excavation disturbance, weak surrounding rock control, and insufficient strength of traditional support forms, particularly in large cross-section traffic tunnels. Issues such as support components breaking, arch buckling and instability, and vault fall-block are common. The confined concrete arch is a new type of support form with high strength, high rigidity, and good stability, which can meet the requirements of surrounding rock control in traffic tunnels. At present, research on confined concrete arches is mostly small-scale single-piece tests, which cannot simulate the cooperative bearing between the field arches. The test results are quite different from the actual force and deformation of the field arch. Based on such situations, a large-scale mechanical test system for support structures in traffic tunnels was developed to perform a comparative test. A combined I-steel arch, combined confined concrete arch, and single confined concrete arch were used as research objects to study the deformation and failure mechanism and overall bearing capacity of these types of arches. The test results show that:① the I-steel arch presents the overall deformation pattern of vault flexural buckling, hance flexural-torsional buckling, and flattening of the arch. Thus, failure was considerable in this type of arch. The two types of confined concrete arches undergo large deformation or failure at the joints in the late loading stage. Outplane instability of the single arch occurs at the vault. The overall deformation was considerable. The combined arch did not exhibit large deformation except joint weld tearing at the end of loading; ② the rigidity and bearing capacity of the combined confined concrete arch are 2.51 times and 2.63 times that of the combined I-steel arch, and 4.18 times and 2.78 times that of the single confined concrete arch, respectively. The combined confined concrete arch has good stability and high bearing capacity; ③ all types of arch analyzed are under compression on the outside of the vault and bottom, and under tension on the outside of the hance. The stress growth rate at the vault is faster, and out-plane instability easily occurs at hance owing to the limited outward deformation, such that those positions are the key parts of the arch. Based on the research conclusions, this paper presents some engineering suggestions for the application of confined concrete support systems in traffic tunnels, and the research results can provide the basis for the design and future research of support systems.