准脆性岩石的三维细观损伤统计与宏观灾变破坏模型研究

The catastrophic failure of quasi-brittle rocks is closely related to natural disasters such as shallow earthquakes (such as 5.12 Wenchuan earthquake), collapses and engineering disasters such as rock bursts. In view of the disastrous and unexpected nature of catastrophic damage, how to reveal its triggering mechanism and put forward corresponding theoretical model is a difficult problem to be solved urgently in engineering and scientific circles. Based on the self-organizing critical theory, this project takes the evolution of meso-structure and catastrophic critical point in the process of loading and failure of quasi-brittle rocks as the main line. Firstly, the accurate catastrophic critical point is obtained by analyzing the acoustic and stress-deformation response of rock samples under loading. Secondly, based on NMR imaging technology, topographic meso-structure of rock samples is used to study the evolution of critical fixed point and three-dimensional micro-structure. Finally, based on maximum likelihood superposition and self-organizing criticality theory, a theoretical model for macro-catastrophic failure of quasi-brittle rocks is established. The research results are of great theoretical significance to clarify the catastrophic failure characteristics of quasi-brittle rocks and reveal their physical and mechanical mechanisms, and have important guiding significance for disaster prevention and mitigation of natural disasters and geotechnical accidents.

准脆性岩石的灾变破坏与浅源地震（如5.12汶川地震）、崩塌等自然灾害，以及岩爆等工程灾害紧密相关。鉴于灾变破坏的灾害性与突发性，如何揭示其触发机理并提出相应的理论模型是工程界和科学界亟待解决的难题。本项目依据自组织临界理论，以准脆性岩石加载破坏过程中细观结构及灾变临界点演化为研究主线，首先通过分析加载中岩样的声学与应力变形响应量，获得准确的灾变临界点值；其次，基于核磁共振成像技术，拓扑化岩样细观结构，研究临界固定点演化与三维细观结构损伤关系；最后，基于最大似然叠加和自组织临界理论建立准脆性岩石宏观灾变破坏理论模型。研究成果对阐明准脆性岩石的灾变破坏特征及揭示其物理力学机制具有重要的理论意义，对自然灾害和岩土工程突发事故的防灾减灾研究具有重要的指导意义。

本项目将雪崩动力学临界理论应用在了准脆性岩石材料的失稳破裂中，并采用声发射监测技术获取由外部力学作用引起的损伤信号。以声发射信号为研究对象，采用最大似然估计获得临界固定点值，研究岩石灾变破坏雪崩效应的地震统计经验规律。结合实验室尺度“地震”与真实地震参数分布关联特征，验证统计分布的无尺度特征及普适性，最后对时间关联性进行检验。以煤和砂岩的复合岩体作为研究对象，并以声发射绝对能量作为信息载体，探究两种不同介质的临界固定点相互作用机理。验证不同式样尺度下的幂律无尺度特性；并探究复合岩破坏的最大似然曲线分布特征，揭示了临界指数叠加效应作用机理。针对准脆性岩石加载破坏过程中细观结构及灾变临界点演化，研究了基于声发射及核磁共振的干湿循环对泥质砂岩微观结构劣化特性影响研究；和基于声发射的热损伤对花岗岩微观裂化特征研究。实验结果表明，由雪崩临界指数反映的损伤程度与岩石力学参数，核磁共振参数及核磁共振成像呈现相关，并存在对应的函数关系。声发射能量概率密度分布能够反应材料破坏的细观机理，并提出了三类基于声发射能量最大似然临界指数分布的岩石灾变破坏理论模型：a.纯幂律分布；b.临界指数的叠加效应；c.临界指数的阻尼效应。

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