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加载速率变化会对介质力学行为产生影响,选用煤进行不同加载速率单轴力学试验.结果表明:对于煤,其强度随加载速率增加表现出先升高后降低的现象,将转折点对应的加载速率称为临界加载速率,低于该值时,煤样强度随加载速率增加而增大,高于该值时加载速率增加强度反而降低.建立“骨架”模型对该现象进行解释,分析表明:较快的加载速率可减少裂隙损伤有利于承载,但同时微元体承载部分将储存更多的弹性能出现局部破坏不利于承载.故必然存在“最优”加载速率使强度出现最大值,此时即对应临界加载速率.以此为基础,提出现场条件下低卸载速率配合均匀弱化介质的手段保证高强度生产的安全.
The change of loading rate will have an impact on the mechanical behavior of the medium, and coal is selected for uniaxial mechanical tests with different loading rates.The results show that the intensity of coal increases firstly and then decreases with the increase of loading rate, and the loading rate corresponding to the turning point Is the critical loading rate, and below which the strength of the coal sample increases with the loading rate, and above which the loading strength increases but the strength decreases but the “skeleton” model is established to explain this phenomenon. The analysis shows that: A faster loading rate can reduce the damage of the fractures, which is advantageous to the bearing, but at the same time, the local damage caused by the storage of more elastic bodies in the bearing part of the micro-bodies is not conducive to the bearing. , This time corresponds to the critical loading rate.On the basis of this, the low unloading rate and uniform weakening medium under field conditions are proposed to ensure the safety of high-intensity production.