脆性岩石蠕变裂纹成核宏细观力学机理研究

脆性岩石内部细观裂纹扩展、贯通及成核影响下的脆性蠕变行为, 对深部地下工程围岩微震及岩爆事件评价有着重要意义. 然而, 目前能够解释裂纹成核损伤突变影响下, 脆性岩石完整蠕变宏细观力学机理模型的研究很少. 本文基于脆性岩石亚临界裂纹扩展模型、裂纹-应变-声发射事件相关的损伤模型及裂纹成核损伤时间演化路径函数, 提出了一种脆性岩石裂纹成核损伤突变影响下的蠕变宏细观力学模型. 裂纹成核损伤时间演化路径函数通过岩石内部裂纹成核损伤突变大小$\Delta D_{CN}$及相邻裂纹成核损伤时间差$\Delta t$进行定义, 该函数可以结合岩石声发射监测试验数据定义的岩石损伤数据确定. 通过与试验结果对比分析验证模型的合理性. 并讨论了裂纹成核损伤大小、相邻裂纹成核损伤时间间隔、及裂纹成核数量对脆性岩蠕变裂纹长度、裂纹速率、轴向应变及应变率的影响. 该结果对于更加合理、经济、高效的深部地下工程施工及设计提供了一定的理论支持. 

A STUDY ON MICRO-MACRO MECHANISMS OF CRACK NUCLEATION DURING CREEP IN BRITTLE ROCKS

The creep behaviours influenced by the growth, coalescence and nucleation of microcracks in brittle rocks have an essential meaning for evaluating the microseismicity and rock bursts of the surrounding rocks in deep underground engineering. However, the micro-macro mechanisms of the damage catastrophe from the crack nucleation effect on the total creep behaviour of brittle rocks are rarely studied. In this study, based on the subcritical crack growth model, the damage model relating to the crack, strain and acoustic emission events, and the function of the damage path influenced by crack nucleation, a micro-macro model is proposed to explain the effect of crack nucleation on creep of brittle rocks. The function of the damage path influenced by crack nucleation is defined by the parameters of the size of damage catastrophe (i.e., $\Delta D_{CN}$) and the time difference (i.e., $\Delta t$) between the adjacent crack nucleations. The damage and time parameters in this proposed function of the damage path can be determined by the use of the experimental data of acoustic missions. The rationality of this proposed micro-macro model is verified by comparing the experimental results. The effects of the damage catastrophe size from crack nucleation, the happened time of crack nucleation, and the number of crack nucleation on the crack length, crack velocity, axial strain, and axial strain rate are discussed during creep of brittle rocks. The suggested model provides a certain theoretical help for the more reasonable, economical, and efficient construction of deep underground engineering.