富水弱胶结软岩地层锚固界面力学强度弱化特性及渐进失效机理研究

It is a common phenomenon that the bolt or cable presents poor boltability, low anchoring force and is prone to induce disasters in weakly cemented soft rock stratum under water-enriched condition. Nevertheless, the fundamental understanding of the weakening characteristics and progressive failure mechanism for anchorage interface in such stratum remains elusive, which is one of the key problems of stability control of roadway surrounding rock. Firstly, the anchorage interface unit shear test under water-enriched condition will be conducted. The local shear flowing law and the peak (or post) strength weakening characteristics in interface failure process, under varying water content of weakly cemented soft rock, will be revealed from the viewpoint of mesomechanics by using Digital Photogrammetry & Deformation Measurement Technique. Secondly, based on the elastoplastic damage theory, the critical strength criteria of interfacial failure, and the progressive damage evolution constitutive model will be proposed. The constitutive model, considering the interface characteristics of shear dilative hardening and softening, will be embedded in existing numerical software. Thirdly, considering the effects of different submerged environments, anchoring parameters and surrounding rock stress, the macroscopic anchorage failure simulation test and numerical test will be conducted, and a three-dimensional mechanical model of anchorage body will be constructed. Then the whole progressive failure process of anchorage interface will be analyzed, and the law of anchoring load transfer will be studied. By doing so, the interfacial progressive failure stress transfer mechanism will be discerned. Furthermore, the dynamic analysis method of anchoring force, the safe and rational suggested anchoring parameters, will be also proposed for bolt or cable under such condition. This research serves to provide theoretical basis for the design of anchoring support and control of disasters such as large deformation or collapse in weakly cemented soft rock stratum of western coal mining region in China.

富水弱胶结软岩地层锚杆（索）支护可锚性差、锚固力低且易失效致灾，锚固界面力学强度弱化特性及渐进失效机理仍不明确，是此类地层巷道围岩控制面临的关键科学问题之一。本项目首先开展富水条件锚固界面单元剪切试验，利用数字照相量测技术，从细观力学角度揭示不同含水率下弱胶结软岩锚固界面失效过程应变局部剪切流动规律及峰值（后）强度弱化特性；基于弹塑性损伤理论，提出界面失效临界强度判据，建立可描述界面剪胀硬化-软化特性的渐进损伤演化本构模型，并嵌入现有数值软件；考虑不同浸水环境、锚固参数及围岩应力影响，开展宏观锚固失效模拟试验与数值试验，构建锚固体三维力学模型，对锚固渐进失效过程进行全历程分析，研究锚固荷载传递规律，揭示界面渐进失效应力传递机理，提出此类条件锚杆（索）锚固力动态分析方法及安全合理锚固参数建议值。研究成果可为我国西部矿区弱胶结软岩地层锚固支护设计及大变形、塌方等灾害控制提供理论依据。

针对富水弱胶结软岩地层锚杆（索）构件普遍存在的可锚性差、锚固力低等现象，本项目聚焦此类地层锚固界面力学强度特性及渐进失效机理不明确这一关键科学问题，首先考虑弱胶结软岩的遇水泥化崩解及强度衰减特性，研发了弱胶结软岩相似模拟材料，并通过系列室内基本力学试验，建立了浸水时间、含水率及单轴抗压强度等强度参数之间的定量对应关系；构造了锚固界面单元体模型，系统开展了富水工况弱胶结软岩锚固界面单元体剪切试验，揭示了不同含水率下锚固界面失效过程的剪切变形规律及峰值（后）强度弱化特性；在此基础上，考虑胶结软岩地层锚固体设计参数、界面剪胀效应、围岩强度参数及围岩应力等因素影响，基于Mohr-Coulomb强度理论，提出了锚固体界面黏结强度的理论计算方法，提出了提高软弱地层锚固支护构件可锚性的建议措施；考虑界面峰前剪胀硬化及峰后强度跌落特性，提出了可描述弱胶结软岩地层锚固界面“弹性-剪胀硬化-脱粘”特性的渐进失效本构模型，并通过编写Fish语言将其嵌入FLAC-3D软件Interface单元中，实现了锚固界面黏结强度参数的动态修正及渐进失效过程的有效模拟；最后，基于锚固体荷载传递原理，提出了弱胶结软岩地层锚固体渐进失效的全历程分析方法，建立了任一阶段对应的锚固体轴力、界面剪应力及极限锚固力计算公式，揭示了弱胶结软岩地层锚固界面失效过程的应力传递机理。研究成果为我国西部矿区弱胶结软岩地层锚固支护设计及大变形、塌方等灾害控制提供了理论依据。