水压轴压共同作用下深部矿井岩石峰后力学效应研究

Rock dilates will happen in the successive failure process after the rock peak strengh, but the rock still has bearing capacity after failure, so the supporting in underground engineering usually takes advantage of this property. Actually, surrounding rock in most of the deep rock mass engineerings such as soft rock roadway is in the post-peak state, therefore, the research on character of rock post-peak has become a hotspot issue in rock mechanics field. According to shortage of research on character of rock post-peak under the action of water pressure and axial compression, with the help of the special experimental device, beased on experimental rock mechanics, utilizing the experimental means such as the mechanics-practial, mineral and microstructure analysis and acoustic emission monitoring and theoretical analysis, this program makes research mainly on the subjects as follows. The first, get the variation and influence factors of volume in the successive failure process when loading and unloading in the post-peak;the second, get the rheological characteristic and constitutive model of the strength degradation in the successive failure process when loading and unloading in the post-peak;The third, get the size effect of strength degradation and volume expansion n the successive failure process when loading and unloading in the post-peak. The research on these key and basic problems supports the essential theoretaical basis and technical support, has the foundational universality and prospective, complies with national major strategic needs for energy security.

岩石达到峰值强度后继续破碎过程中会发生体积膨胀，但仍具有一定的承载能力，地下工程中多利用岩石的该性质进行支护。实际上绝大多数深部岩土工程如软岩巷道的围岩是处于峰后应力状态条件下的,因此研究岩石峰后特性一直是岩石力学领域的一个重点。本项目针对水压轴压长期共同作用下岩石峰后力学特性研究的不足，借助于特制的实验装置，以实验岩石力学为基础，采用力学实验、矿物与微结构分析、声发射监测等实验手段和理论分析，重点研究水压轴压长期共同作用下及加卸载时，深部矿井煤或岩石：①峰后继续破碎过程中的扩容效应及其影响因素；②峰后继续破碎过程中强度衰减的流变特征与本构模型；③峰后继续破碎过程中强度衰减与体积膨胀的尺寸效应。通过这些关键性基础问题的研究，为深部岩体工程设计与施工提供关键理论与技术保障，具有基础性、普遍性和前瞻性，符合国家能源安全的重大战略需求。

项目以岩石峰后强度衰减特征为切入点，而割线模量峰值与材料的弹性极限或屈服极限有较为稳定的对应关系，又并将强度与变形的发展演化起点扩大至割线模量峰值处。为了证实割线模量峰值与弹性极限或屈服极限之间的对应关系，并为了排除材料非均质性的影响，借助于准均质金属材料，开展了高碳钢与低碳钢的拉伸和压缩试验，绘制了割线模量-应变曲线，分析了割线模量峰值与弹塑性变形的相关性；开展了砂岩的三轴压缩试验，并以割线模量的退化系数作为损伤变量，分析了割线模量与峰后强度和变形的累积演化特征，并分析了围压对损伤发展的影响；考虑边界条件对岩样破裂路径的影响，分析了粗砂岩理论破裂面与实际破裂面不一致的机理，并在莫尔-库仑准则下对比了不同破裂面上强度差异的机制；高强度混凝土高温爆裂概率随含水率的增大而增大，表明蒸汽压力是诱发爆裂的重要因素之一，该压力通过改变有效应力影响了强度。为定量研究蒸汽压力对强度的影响，本文基于莫尔-库仑准则和有效应力原理，推导了临界爆裂蒸汽压力的求解公式，并从数理角度证明了其严密性。最后基于对岩石峰后强度研究的思想，对EPS轻质混凝土这种性质介于软岩与硬土之间的材料的力学性能进行了研究，给出了科学合理标定其力学性能的建议，并起草制定了企业标准一部，联合企业申请的建设科技成果推广项目得到批复。