大断面隧道软弱围岩约束混凝土高强控制机理研究

As a new kind of high-strength support technology, confined concrete is preliminarily applied to control the weak surrounding rock, which shows significant effect. However, the bearing characteristic and control mechanism of confined concrete are still indefinite. With the engineering background of typical large cross-section tunnel with weak surrounding, the contrast experiments of different support schemes will be carried out by model test in this project. By the experiments, the failure mechanism of surrounding rock can be studied, and the load model of weak surrounding rock will be built. Mechanical property test of confined concrete components and joints will also be carried out, to clarify the failure modes and mechanical properties, and establish the bearing strength criterion. Based on the stable mechanical model, considering the influence of initial imperfection to the confined concrete arch, the modified criterion of its in-plane stability and the modified critical load’s formula of its out-of-plane stability will be established. Based on these, a calculation method of bearing capacity for confined concrete arch can be formed, and a full-scale laboratory test will be carried out to validate it. Therefore, the high strength bearing mechanism of confined concrete arch support will be clarified, and its mechanics model could be built. Based on the studies above, coupled effect between weak surrounding rock and confined concrete arch will be analyzed, as much as high-strength control mechanism will be revealed, which could be verified and improved based on the field test. The research results of this project will provide theoretical basis and technical guidance for solving the problems to control the weak surrounding rock tunnels in large cross-section.

约束混凝土作为一种新型高强支护技术，在解决软弱围岩控制难题中得到初步应用，效果显著，但其承载特性及控制机制仍不明确。本项目拟以典型软弱围岩大断面隧道为工程背景，开展不同支护条件下模型对比试验，研究大断面隧道软弱围岩变形破坏机制，得到软弱围岩荷载作用模型。进行约束混凝土基本构件与节点构件力学性能试验，明确其破坏模式和力学特性，建立构件强度承载判据。基于初始缺陷影响下的拱架失稳力学分析模型，建立约束混凝土拱架平面内稳定承载修正判据和平面外稳定临界荷载修正计算公式。在此基础上，形成约束混凝土拱架承载能力计算方法，并通过拱架全比尺试验进行验证，明确约束混凝土拱架高强承载机制，构建约束混凝土支护力学模型。基于上述研究，进行大断面隧道软弱围岩-约束混凝土支护耦合作用分析，揭示约束混凝土高强控制机理，并进行现场验证和完善。研究成果可为解决隧道、矿山等大断面地下工程软弱围岩控制难题提供理论依据与技术指导。

本项目以大断面隧道-龙鼎隧道为工程背景，主要采用三维地质力学模型试验、约束混凝土基本构件及全比尺拱架试验、理论分析、数值计算和现场试验等相结合的研究方法，对大断面隧道软弱围岩-约束混凝土支护相互作用机理进行了系统研究。开展软弱围岩大断面隧道传统支护与高强支护条件下三维地质力学模型对比试验，结合理论分析和数值试验，明确大断面隧道软弱围岩变形破坏机制与荷载作用模型，得到大隧道软岩围岩高强承载机制。建立大断面隧道高强约束混凝土支护体系，开展轴压、纯弯和压弯作用下的约束混凝土基本构件以及节点构件室内力学性能试验，明确各构件破坏模式及力学特性。构建基本构件及节点构件的强度承载判据，建立基本构件及节点构件等效计算模型。开展装配式拱架配套装置力学性能试验，结合数值试验，研究各构件在施工及支护过程中的受力特征及最不利荷载组合，建立配套装置强度计算方法。建立约束混凝土拱架平面内与平面外失稳力学分析模型，推导轴压和弯曲双重效应下的拱架稳定临界荷载计算公式。建立地下工程拱架结构任意节数非等刚度计算模型，推导拱架内力计算公式，结合基本构件、节点构件强度承载判据及拱架稳定承载修正判据，形成约束混凝土拱架承载能力计算方法。开展传统支护拱架与约束混凝土拱架的全比尺室内对比试验，验证拱架承载能力计算方法的合理性，明确约束混凝土拱架高强承载机制，建立约束混凝土支护力学模型。基于围岩荷载作用模型与约束混凝土支护力学模型，系统开展不同围岩荷载及约束混凝土支护荷载条件下的计算分析，进行大断面隧道软弱围岩-约束混凝土支护耦合作用分析，揭示约束混凝土高强控制机理。基于上述研究成果，开展约束混凝土支护体系现场对比试验，建立定量评价指标，验证约束混凝土高强控制机理，优化约束混凝土支护体系。