With the increasing mining depth of deep mineral resources, the influence of high temperature on the fracture failure of surrounding rock with fissures becomes increasingly serious. To investigate the fracture mechanical properties and the evolutionary characteristics of fracture process of fissured rock experiencing initial temperature damage, the three-point bending experiment was conducted on the small sized granite samples with different initial damaging temperatures and prefabricated fissure lengths by applying a μTS mesoscopic testing system. Based on the digital image correlation methods, the evolution of fracture process zone of sample was revealed. Moreover, the macroscopic fracture failure of sample was predicted by the evolution of time-varying acoustic emission b-value. The results show that with the increase of initial damaging temperature and prefabricated fissure length, the peak load of granite sample has a decreasing trend and the fracture characteristics of sample experiencing initial temperature damage gradually transform from brittleness fracture to ductility fracture, resulting in a decrease in the fracture toughness of sample. The crack tip opening displacement, the critical opening displacement and the length of fracture process zone of sample all show an increasing trend. The time interval from the time when time-varying acoustic emission b-value continues to decline to the appearance moment of macroscopic cracks is selected as the warning time of fracture failure of sample, which can conclude that the warning time increases with increasing the initial damaging temperature and prefabricated fissure length, indicating an increase in ductility and a reduction in failure suddenness of sample.

中文翻译：

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考虑初始温度损伤和预制裂隙长度的花岗岩力学性能及断裂破坏演化实验研究

随着深层矿产资源开采深度的不断增加，高温对裂隙围岩破裂破坏的影响日益严重。为研究裂隙岩初始温度损伤的断裂力学特性及断裂过程演化特征，采用μTS细观测试方法，对不同初始损伤温度和预制裂隙长度的小尺寸花岗岩样品进行三点弯曲试验。系统。基于数字图像相关方法，揭示了样品断裂过程带的演化过程。此外，通过时变声发射b值的演变来预测样品的宏观断裂失效。结果表明，随着初始破坏温度和预制裂隙长度的增加，花岗岩试样的峰值载荷有减小的趋势，初始温度破坏试样的断裂特征逐渐从脆性断裂向延性断裂转变，导致花岗岩试样的断裂强度降低。样品的断裂韧性。样品的裂纹尖端张开位移、临界张开位移和断裂过程区长度均呈现增加趋势。选择从时变声发射b值持续下降到宏观裂纹出现时刻的时间间隔作为样品断裂失效的预警时间，可以看出预警时间随着初始损伤的增加而增加。温度和预制裂缝长度，表明样品的延展性增加和破坏突然性降低。