考虑不同前期时效荷载影响的裂隙硬岩流变特性研究

Generally, the construction of large scale rock engineering is a long-term process, which is easily affected by different factors. Thus, the rock masses will experience various multi-stage, time-dependent load (i.e. previous time-dependent load) before completion, which has an important influence on the mechanical properties of rock mass under the final stress. However, the study of rock mass rheological mechanics are currently carried out under the condition of single constant load and full action, without considering the influence of the previous time-dependent load. Based on the study of rock mass structure and surrounding rock stress in typical engineering, the object is to perform a series of rheological experiments on the fracture hard rock under the action of different previous time-dependent loads. Through the comparative analysis on the deformation, strength and crack propagation pattern of specimens, the rules of influence of different stress states, duration time and stress paths of previous time-dependent load on the mechanical properties of rock mass under the final stress are investigated. Then combined with energy principle, damage and fracture mechanics theory, the quantitative relationship between the damage of rock mass and the previous time-dependent load is established, the roak mass crack aging model under the influence of previous time-dependent load is analyzed. Furthermore, based on the rheological mechanics, the full stage rheological constitutive model, which considering the influence of previous time-dependent load is proposed. Finally, by means of numerical calculation and geomechanical analysis, the full stage rheological constitutive model are applied to the stability evaluation of the aging deformation of typical engineering. The research results provide theoretical basis for the aging stability evaluation and safety control of the hard rock mass engineering.

大型岩体工程工期一般较长且易受各类因素影响，岩体在竣工前会经历多级长短不一的时效荷载（即前期时效荷载）作用，对其在最终应力下的力学特性产生重要影响。而目前岩体流变力学研究均是在单一恒定荷载且充分作用的前提下开展，没有考虑前期时效荷载的影响。课题拟在典型工程岩体结构和围岩应力变化研究的基础上，开展一系列前期时效荷载作用的裂隙硬岩流变试验，通过对岩体变形、强度及裂纹扩展模式等的分析，研究不同应力水平、持荷时间和应力路径的前期时效荷载对岩体在最终应力下流变特性的影响规律。并结合能量原理、损伤和断裂力学理论，揭示前期时效荷载作用与岩体损伤的量化关系，建立前期时效荷载影响的岩体裂纹时效扩展模型，最终利用流变力学知识提出考虑前期时效荷载影响的裂隙硬岩流变全阶段本构模型。通过数值计算并结合监测及地质力学分析，将研究成果运用于典型工程时效变形稳定性评价。为硬质岩体工程时效稳定评价和安全性控制提供理论依据。

大型岩体工程工期一般较长且易受各类因素影响，岩体在竣工前会经历多级长短不一的时效荷载（即前期时效荷载）作用，对其在最终应力下的力学特性产生重要影响。本项目在对典型工程岩体结构特征、应力、时效变形和局部破坏特征进行分析的基础上，采用室内试验、理论和数值模拟等相结合的方法，较系统地对裂隙岩体的特征应力、不同特征应力区间下裂隙岩体蠕变变形和破坏规律以及典型工程局部破坏机理进行了分析。重要的研究成果包括：1）除施工期产生的前期时效荷载，运营期的渗水压力也可看成时效荷载的作用；2）裂隙岩体闭合应力、起裂应力和扩容应力随裂隙角度的变化规律与峰值应力随角度的变化规律基本一致，各特征强度与对应峰值强度的比值随角度和裂隙组合形式变化不大，基本保持在一定的范围。但围压对各特征强度与对应峰值强度的比值有影响，随着围压的增大，起裂应力和扩容应力间的距离越来越小，且越来越靠近峰值强度；3）基于裂纹起裂强度和峰值强度以及扩展破坏模式随角度变化的特点，提出了一种压剪条件下裂隙岩体裂纹起裂破坏准则，该准则认为控制张拉型裂纹萌生的I型应力强度因子应包含法向压应力和切向应力的共同作用；4）当前期时效荷载小于起裂应力时，岩体不会产生时效损伤；而当前期时效荷载大于起裂应力时岩体则会产生时效损伤并最终导致裂纹贯通破坏。基于此，建立了裂隙岩体蠕变损伤本构模型，指出岩体蠕变损伤模型的建立应由宏观裂纹产生的初始损伤和在不同特征应力阶段产生的时效损伤两部分组成，然后可通过损伤力学相关原理建立完整岩石和裂隙岩体间的相关关系。研究成果可为硬质岩体工程时效稳定评价和安全性控制提供理论依据。