中低应变率加载条件下花岗岩尺寸效应的能量特征研究

Research on energy characteristics of size effect of granite under low/intermediate strain rates

能量相互转化过程的综合作用导致了岩石破坏,而其破坏的根本原因是岩石中储存的应变能的释放。对中低应变率加载条件下岩石尺寸效应能量特征的研究结果表明:花岗岩破坏时吸收的总能量U、弹性应变能U^e以及损伤应变能U^d均随试件尺寸的增长而降低;岩石强度与岩石中储存的能量有关,尤其与弹性储能有关,即弹性应变能愈高,岩石强度越大;试件长度由50mm变为125mm时,弹性储能逐渐降低,岩石破坏形态从劈裂破坏变为剪切破坏,大尺寸时局部化变形明显。能量是不同应变率加载条件下岩石破坏细微观及宏观特征存在差异的内在动力;亦是导致岩石强度存在尺寸效应的本质动因。

The fracture of rock is the results of a comprehensive role in the process of energy conversion, and the release of the strain energy stored is the essence of rock abrupt failure. The energy characteristics of rock size effect under low / intermediate strain rates have been studied. It is found that the total energy U, the elastic energy Ue and the damage energy Ud at failure decrease with the increasing sample size. Rock strength is related to the stored energy, especially to the stored elastic energy, namely the more the elastic energy, the higher the strength. The stored elastic energy reduces gradually with the specimen length changing from 50 mm to 125 mm. Splitting is the main fracture mode for the short specimens while the shearing fracture mode dominates the longer specimens with evident strain localization. Energy is the inherent impetus which leads to differences of failure in micro, meso and macroscopic characteristics under different strain rates, which is also the intrinsic motivation of the size effect of rock strength.