隧道钢管混凝土复合支护结构承载特性研究

为研究钢管混凝土复合支护结构变形破坏特征及承载机制,考虑拱架-混凝土粘结滑移特性,在支护结构典型破坏模式的基础上,开展支护结构纯弯室内试验及精细化数值模拟研究,对试件在弯矩作用下的力学响应进行深入分析,明确拱架布设位置、喷射混凝土强度、钢筋网直径及保护层厚度等参数对结构承载性能的影响规律。结果表明,钢管混凝土无钢筋网试件（SRCS-FW）强度较低,混凝土迅速开裂后与拱架发生滑移破坏,钢管混凝土双层钢筋网试件（SRCS-FS）变形效果较好,呈现较好的后期承载特性;SRCS-FS试件临界滑移破坏强度较高,其极限弯矩比SRCS-FW试件极限弯矩高40.9%;构件弹性变形阶段拱架、钢筋网、混凝土三者协同作用效果明显,开裂阶段试件拉力主要由受拉侧钢筋网和拱架分担,压力由拱架和受压区混凝土分担;支护结构参数设计要综合分析其承载性能、经济性及工程经验和施工便利性。

A Study on the Bearing Characteristics of Composite Concrete-filled Steel Tube Support Structure in Tunnels;

To investigate the deformation and failure characteristics and bearing mechanism of composite concrete-filled steel tube support structure, pure bending indoor tests and refined numerical simulation are carried out for support structures, taking into account the arch frame-concrete bond-slip characteristics on the basis of typical failure mode of support structures. An in-depth analysis is conducted on the mechanical response of the specimens under the action of bending moment, so as to clarify the impact pattern of different parameters, such as arch frame installation position, shotcrete strength, steel mesh diameter and protective layer thickness, on the structural bearing capacity. The results show that the concrete-filled steel tube specimens without steel mesh (SRCS-FW) are weaker in strength, the concrete cracks rapidly and then slips with the arch frame, while the concrete-filled steel tube specimens with double-layer steel mesh (SRCS-FS) are better in terms of deformation effect and display better bearing characteristics later. Besides, the SRCS-FS specimen has a higher strength of critical slip failure and its ultimate bending moment is 40.9% higher than that of the SRCS-FW specimen. Furthermore, the synergistic effect of the arch frame, the steel mesh and the concrete is significant in the elastic deformation phase of the component. The tensile force of the specimen in the cracking phase is mainly shared by the tensile-side steel mesh and the arch frame, while the pressure is shared by the arch frame and the concrete under compression. It is suggested that the parameter design for the support structure should take into account its load-bearing performance, economy and engineering experience, and construction convenience. © 2023 Editorial By Modern Tunnelling Technology. All rights reserved.