基于超声波与声发射特征的岩体动态损伤演化规律及门槛值研究

The determination of damage threshold of rock mass under dynamic load is the core issue of damage assessment and damage control for the engineering rock mass. Based on the ultrasonic characteristics that can be directly measured to evaluate the damage of engineering rock mass, combined with the acoustic emission monitoring and discrete element simulation, the project intends to systematically measure the stress-strain date, crack propagation, characteristics of ultrasonic wave and acoustic emission of rock and fractured rock mass under dynamic compression with different strain rate and confining pressure in order to obtain the following goals: 1. determine the dynamic mechanical and deformation properties of fractured rock mass, and the influence of mesoscopic crystal structure on the mechanical properties based on the crystal structure analysis of mesoscopic scale. 2. reveal the dynamic damage evolution mechanism, the characteristics of crack propagation and polymerization, and establish the relationship between the propagation of micro cracks and the stress-strain characteristics of rock mass. 3. clear the evolution of ultrasonic and acoustic emission characteristics during the rock failure process, and set up the correlation characterization between the propagation, polymerization characteristic of microcracks and the stress-strain, the ultrasonic and acoustic emission characteristics. 4. propose the dynamic damage model based on the ultrasonic characteristics, meanwhile, determine the dynamic damage evolution and the corresponding damage threshold characterized by ultrasonic characters of fractured rock mass under different strain rate and confining pressure. Finally, the regularity of damage threshold and its influencing factors will be explored, so as to provide theoretical and experimental basis for the meticulous evaluation and control of dynamic damage of engineering rock mass.

岩体动力损伤门槛值的确定是进行工程岩体损伤评价和损伤控制的核心问题。本项目基于工程岩体中超声波测试损伤的可行性，结合声发射测试和数值模拟，系统地测试岩石及裂隙岩体在不同应变速率和围压下的动力压缩试验过程中应力应变、裂纹扩展、超声波及声发射特征变化，结合材料细观晶体结构分析，确定岩体动态力学和变形特征及细观晶体结构分布对其影响规律，揭示岩体动态损伤演化机理及裂纹扩展、聚合特征，分析岩体动力损伤的细观裂纹扩展与岩体应力应变特征的联系。同时，明晰岩体破裂过程中超声波与声发射特征演化规律，建立岩体宏观应力应变特征、波速-波幅-频谱特征和声发射特征与细观裂纹扩展和聚合演进的关联性表征，提出基于工程可测试的声波特征的岩体动态损伤模型，确定不同应变速率、围压下裂隙岩体动态损伤演化规律和以声波特性表征的损伤门槛值，探索损伤门槛值的变化规律和影响因素，为工程岩体动态损伤精细化评价和控制提供理论和实验基础。

爆破作为核电工程基础开挖最主要的方式，伴随岩石爆破破碎过程，建基面保留岩体一定会产生不同程度的动力损伤，工程岩体损伤临界值的确定是进行损伤评价、划定损伤范围的前提，是基础爆破工程中岩体损伤控制的核心问题。本项目围绕岩体宏细观破裂表征及损伤临界值，以室内试验、理论分析和数值模拟方法为手段，结合主动超声波测试、被动声发射监测技术、高速摄像技术及DIC分析方法，系统地研究岩石及裂隙岩体压缩过程中应力应变、超声波及声发射特征随裂纹扩展的变化规律，建立了岩石/体微裂纹萌生扩展及贯通的宏细观表征方法，揭示了岩石及裂隙岩体损伤演化机理，分析了声波波速、波幅及频谱特征与细观裂纹扩展、聚合演进过程的关联性表征，建立了声发射特征与不同阶段微裂纹扩展及岩体宏观应力应变特征的对应关系，明确了岩体宏观应力应变特征、波速-波幅-频谱特征和声发射特征与细观裂纹扩展和聚合演进的关联性表征。基于宏观力学及变形特征、声波及声发射特征量化了岩体的损伤演化规律，结合多参量分析，明确岩体损伤临界值及其变化规律。本项目的研究成果为核电及类似工程基础爆破施工损伤评估及精细化控制控制提供了试验和理论基础。