软岩巷道钢管混凝土拱架支护失效演化与耦合抑止机理研究

Concrete filled steel tubular (CFST) arch support technology shows significant practical value, but the development of its support theory is lagging behind. The study on the failure deterioration and coupling restraint mechanism of CFST arch support in soft rock roadway, is the key to put forward an reasonable supporting design method and ensure the long-term stability of the roadway. Firstly, considering the section strength and global stability, the full size mechanics experiments of CFST arch, and compression bending tests of basic components in CFST arch are carried out. Based on the test results, the deformation instability mechanism of the CFST arch under surrounding rock pressure of soft rock roadway is revealed, the failure criterion is established and the bearing capacity calculation theory is improved. Secondly, based on the secondary development of FLAC3D, the precise simulation methods for the bearing capacity and failure behavior of the CFST arch and interaction between the supporting members and surrounding rock are studied. And combined with bolt element correction and surrounding rock rheological constitutive model implantation, a fine simulation platform for CFST arch support system in soft rock roadway is built. Thirdly, by using this platform, progressive failure mechanism of CFST arch support system in soft rock roadway is studied, and the dynamic coordinating restraint mechanism to the rheology deterioration by the supporting members is revealed, as well as the influence of stiffness, strength and supporting time on the final control effect of surrounding rock is clearly defined. Finally, the CFST arch coupling support design method is put forward, and then verified and improved by field test. The achievement from this project has great scientific significance to the establishment of CFST arch support theory system in soft rock roadway.

钢管混凝土拱架支护对软岩巷道实践价值显著，但缺乏系统理论支撑，支护体系的失效演化与耦合抑止机理研究，是实现巷道长期稳定的关键科学问题。本项目首先考虑拱架截面强度和整体稳定性，开展拱架全尺寸力学试验与基本构件压弯试验研究，揭示围岩压力作用下钢管混凝土拱架的变形失稳机制，建立失效判据，改进承载力计算理论；基于FLAC3D二次开发，研究拱架力学行为、各支护构件之间及与围岩相互作用的精确模拟方法，结合锚杆单元修正和围岩流变模型引入，构建软岩巷道钢管混凝土拱架支护体系精细化数值模拟平台；采用该平台研究软岩巷道支护体系的渐进失效机理，探究耦合支护体系各构件对承载结构流变劣化的协调抑止机理，揭示支护构件刚度、强度、支护时机等参数对围岩最终控制效果的影响规律；提出钢管混凝土拱架耦合支护设计方法，并进行现场验证和完善。研究成果将促进软岩巷道钢管混凝土拱架支护理论体系的完善和发展，具有重要理论和实践意义。

随着我国深地战略的逐步落地实施，越来越多的巷道、隧道等地下工程面临支护难题。钢管混凝土拱架是近年来快速发展的一种新型高强支护形式，但目前支护理论研究欠缺。本项目通过室内试验、数值模拟等手段开展了系统研究，主要工作及关键成果如下。.（1）开展了压弯试验28件，大偏心和纯弯曲试件失效是由于套管口应力集中导致的；套管节点使试件承载能力降低5.9%。开展了150个压弯数值试验，混凝土强度、套管长度是影响承载力的主要因素。揭示了拱架承载失效机理，最危险截面达到压弯承载极限发生强度破坏，拱架整体呈现极值点失稳破坏。开展了拱架承载行为数值试验，提出了拱架承载力计算方法，计算误差不超过4%。.（2）基于FLAC3D开发了软岩巷道拱架-锚杆联合支护精细化数值模拟平台，包括3项技术改进：基于Cable单元修正的锚杆破断行为模块；基于Beam单元修正的拱架屈服失效行为模块；基于Link连接修正的拱架-围岩相互作用行为模块。案例分析显示，模拟平台能够较为准确模拟现场实际，尤其在拱架和锚杆的承载、失效行为及其支护效应方面。.（3）采用构建的数值模拟平台，考虑巷道断面形式、地应力等级、侧压力系数、架锚支护参数组合等参量，实施了数值试验方案33个，研究了软岩巷道锚杆-拱架联合支护渐进失稳特征及失效机理。直墙半圆形巷帮内挤变形、拱架-围岩分离、锚杆破断失效是巷道渐进失效的重要环节。提出了软岩巷道锚杆-拱架联合支护设计优化建议9条，并开展了现场试验分析。.项目成果在TUST等发表SCI论文4篇，在《土木工程学报》等发表EI论文3篇。2篇论文被SCI源刊录用待刊，2篇第一作者论文获F5000论文证书，授权发明专利6项，协助培养硕博士6名；超额完成预期量化考核指标。项目成果可改善目前钢管混凝土拱架支护设计主要依靠经验的局面，开发的数值模拟技术提供了工程层面进行支护精细化模拟的有效手段。随着国家深地战略进一步推进，项目成果将深地围岩支护领域发挥直接作用。