中文摘要：

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，将转折点对应的加栽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，高于该值时加栽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，此时即对应临界加栽速率．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．

英文摘要：

The change of loading rate will affect the mechanical behavior of media. Thus, uni- axial tests with coal samples under different loading rates are carried out. Results show that the strength of coal increases firstly and decreases later with the increase of loading rate, the loading rate corresponding to the turning point is named as ＂critical loading rate＂, below which the coal strength increases with the increase of loading rate, and above which the coal strength decreases with respect to loading rate. A ＂skeleton model＂ is established to explain these phe- nomena. It indicated that higher loading rates will reduce the fracture damage, while the infini- tesimal element will store more elastic energy which may lead to local failure. Thus, there must be an optimal loading rate at which the maximum strength appears, that is, the ＂critical loading rate＂. Based on this theory, techniques with lower unloading rates and uniformly weakening the media were proposed to ensure the safety of mining with high intensity.