高地应力洞室围岩应力释放时滞性特性及其工程效应控制研究

Under high and extremely high geo-stress condition, unloading damage of surrounding rock mass during cavern excavation develops from outward and shallow area to inner and deep area. It is essentially a continuous evolution process related to geo-stress release and damage rupture of surrounding rock mass caused by excavation. The key issue lies in the fact that the stress release of surrounding rock mass under high geo-stress condition takes on time-lag characteristic. .Based on engineering practices such as excavation of underground caverns and diversion tunnels for hydropower projects under high geo-stress condition, this project plans to propose a new concept called time-lag characterization of stress release, which is intended for rock mass excavation under high geo-stress condition. This concept reflects rock crystalline unloading friction effect and is used to describe the initial stress release and redistribution evolution process when excavating rock mass with high geo-stress. By means of theoretical research, test analysis of both specimen scale and project scale, and numerical simulation approaches, etc., this project plans to reveal unloading damage mechanism determined by time-lag characteristic of stress release of surrounding rock mass under high geo-stress condition, to establish analysis theory reflecting effects of time-lag characteristic of stress release, to propose constraining method against high geo-stress unloading damage of underground caverns. The proposed project is anticipated to provide insight into unloading damage mechanism of surrounding rock mass under high geo-stress condition, to develop safety assessment and control method for surrounding rock mass stability of caverns under high geo-stress condition. Therefore it is of theoretical significance and practical engineering value.

高至极高地应力条件下地下洞室开挖围岩卸荷损伤由表及里，由浅至深，实质是开挖后岩体地应力释放与围岩损伤破裂随时间推移不断演化的过程，其核心问题是高地应力洞室围岩应力释放具有时滞性特性。项目以高地应力水电工程地下厂房及引水隧洞等工程建设实践为依托，提出一种反应岩石晶体卸荷摩擦效应的高地应力岩体开挖应力释放时滞性特性概念，用以描述高应力岩体开挖初始应力释放调整演化过程。通过理论研究、试件尺度和工程尺度下的试验与分析，并结合数值模拟分析等途径，揭示由围岩应力释放时滞性特性控制的高地应力洞室围岩卸荷损伤机制，建立反映应力释放时滞性特性作用效应的分析理论，提出高地应力地下厂房卸荷损伤抑制方法。项目成果对深化高地应力条件洞室围岩卸荷损伤机制、发展高地应力条件洞室围岩稳定安全评价与控制方法具有重要的理论与工程实用价值。

高至极高地应力条件下地下洞室开挖围岩卸荷损伤由表及里，由浅至深，实质是开挖后岩体地应力释放与围岩损伤破裂随时间推移不断演化的过程，其核心问题是高地应力洞室围岩应力释放具有时滞性特性。项目以高地应力环境下，工程岩体应力释放过程问题为靶向，通过理论研究、多尺度岩体力学试验与分析，并结合数值模拟分析等途径，揭示由围岩应力释放时滞性特性控制的高地应力洞室围岩卸荷损伤机制。项目取得成果包括：开发了高应力与复杂岩体结构地应力测试技术及装备，并在工程白鹤滩水电站，锦屏1级水电站地应力测量中取得较好的应用；以国家标准工程岩体分级标准BQ法为基础，提出了含隐形节理玄武岩岩体质量评价问题新方法；开展了锦屏I级地下厂房大理岩、猴子岩地下厂房灰岩在高应力、加卸载复杂应力路径下的力学试验，在不同强度的岩石受应力及加载路径影响特性问题上取得了新的认识；以非连续变形分析（Discontinuous Deformation Analysis，DDA）作为细观数值试验平台，建立了基于混合高阶求解架构的伺服数值试验分析方法，并从细宏观层面研究了岩石应力应变全过程试验控制过程及变形破坏力学规律；开展了锦屏高应力条件下岩心饼裂特征调查分析，基于岩心饼裂拉破坏模式，提出了地应力估算公式；提出了深埋高储能岩体应力释放时滞特性测定系统及方法，并开展了原位大尺度试样应力释放时滞性现场观测，取得重要成果；以锦屏I级极高地应力条件下的工程建设为例，基于系统的监测资料分析，结合精细非线性数值模拟，对极高地应力条件地下厂房围岩应力时滞性特性影响机制与锚固支护受力特性进行了研究，在围岩变形破坏机制、卸荷松弛特征、时效破裂演化机制以及锚固结构受力特征与长期承载特性等方面进行了力学剖析与归纳总结。以上成果对深化高地应力条件洞室围岩卸荷损伤机制、发展高地应力条件洞室围岩稳定安全评价与控制方法具有重要的理论与工程实用价值。