高应力硬岩硐室板裂致灾机制及其风险控制支护方法

The phenomenon of the slabbing failure caused by the excavation of the highly stressed hard rock cavern is an important disaster origin for the deep underground hard rock engineering. At present, the slabbing disaster-causing mechanism is not disclosed explicitly, and the attention of the development for the support method is particularly paid to the qualitative analysis. The central theme of the project is, with the aid of the large-scale true-triaxial high-stress load-bearing experimental system, to implement the model test that aims at mimicking the progressive failure process of the hard rock cavern during the excavation in the highly stressed environment. During the whole process, the excavation is monitored for the initiation, propagation, perforation till the instability disaster-causing, and the distributive configuration and range are then obtained for the slabbing failure. In combination with the experimental results, the facture mechanics, the damage mechanics, the energy principle and the catastrophe theory are used together to reveal the slabbing disaster-causing mechanism pertinent to some critical issues like the strain-stress relationship of the surrounding rock, the requirement of the crack initiation, the requirement and criterion of the energy for crack propagation, and the catastrophe instability model resulting from the slabbing failure. The obtained slabbing disaster-causing mechanism is programmed and integrated with the numerical analysis software, thus extending the performance of the software. By carrying out the three-dimensional numerical simulation, the slabbing failure evolution process is mimicked in response to the excavation for the highly stressed hard rock cavern. On this basis, the support method for the risk control is established by employing the reliability theory, in view of the limiting level of the instability risk for the surrounding hard rock under slabbing failure. The results of this project can be used for the reference in theory and the support in the technique, which aims at solving some critical problems related to the slabbing failure, and effectively holding back as well as preventing the associated disaster triggered by the slabbing failure for the highly stressed hard rock cavern.

高应力硬岩硐室开挖导致围岩板裂破坏是深部地下硬岩工程的重大灾害源之一。目前，高应力硬岩硐室板裂致灾机制尚不明晰，且相应的支护方法主要偏重定性分析。本项目基于大尺寸真三维高应力加载试验系统，开展模拟硬岩硐室在高应力环境下开挖渐进破坏过程的模型试验，监测开挖造成围岩板裂的起裂、扩展、贯通至失稳致灾全过程，获得板裂破坏的分布形态及范围；结合试验结果，综合运用断裂力学、损伤力学、能量原理及突变理论深入研究围岩板裂的应力应变关系、板裂起裂条件、板裂形成的能量判别准则及突变失稳模式等核心问题，深刻揭示板裂致灾机制；将该机制植入数值模拟软件，扩充其功能，通过三维数值分析，模拟高应力硬岩硐室开挖板裂破坏演化过程；在此基础上，考虑围岩板裂破坏模式下的失稳风险控制水平，运用可靠性理论建立其风险控制支护方法。研究成果将为解决高应力硬岩硐室板裂破坏的关键性问题、遏制及防治由其引发的工程灾害提供理论依据与技术支持。

随着矿山开发领域浅部资源逐渐减少甚至枯竭，在当前资源需求量不断增加和开采数量日益增大的新形势下，国内外矿山已相继进入深部开采状态。由于与各类矿山密切相关的深部硬岩硐室赋存于高地应力环境中，围岩对工程开挖响应表现出与浅部地应力条件下完全不同的力学行为，其重要形式之一为板裂破坏。本项目从室内模型试验入手，通过数值模拟与理论分析，对高应力硬岩硐室板裂致灾机制及其支护方法开展了深入研究。首先，从高应力硬岩硐室的实际受力状态出发，基于大型真三维高应力加载试验系统，揭示了围岩的不同工程岩性因素（红砂岩、大理岩和花岗岩三类硬岩为主要代表）与开挖截面的不同几何形状因素（依照实际工程中常见的直墙拱城门洞形（高跨比>1）、直墙拱马蹄形（高跨比<1）和曲墙拱形）导致围岩板裂破坏分布范围和形态的影响机制；其次，针对硬质围岩变形过程中的应力应变关系，利用统计损伤理论，并基于不同强度准则与不同分布函数形式表征微元强度的相互组合，建立了准静态高应力下反映软硬化转变特征的硬岩本构模型和考虑不同应变率影响的硬岩动态本构模型；然后，利用断裂力学并结合能量原理与突变理论探讨了板裂裂纹的起裂、扩展、贯通及形成岩板后的失稳机制；在此基础上，通过对PFC离散元的二次开发，对照模型试验的不同工况分别开展了二维和三维数值分析，模拟了板裂渐进演化的全过程；最后，考虑板裂破坏模式下的失稳风险水平，围绕围岩不确定性参数信息量掌握程度的不同情形，依次建立了概率条件下基于逆可靠度的风险控制支护方法（参数信息量足够充分）、非概率条件下分别基于区间不确定性的风险控制支护方法（参数信息量不足）与基于Info-Gap嵌套凸集不确定性的风险控制支护方法（参数信息量严重缺乏）。本项目研究成果为高应力硬岩硐室开挖过程中有效遏制及防治因板裂破坏诱发的相关工程灾害，提供了可选用的围岩稳定性控制理论及与之相适应的支护处治技术。