单轴循环冲击下弱风化花岗岩的损伤演化

为研究爆破应力波作用下弱风化花岗岩的力学特性和损伤演化机理，利用直径50 mm的改进分离式Hopkinson压杆装置，开展以不同速度对花岗岩进行单次和等速循环冲击下的实验研究。研究结果表明:单次冲击中，用能量法确定的损伤阈值，可用于循环冲击实验中；不同应变率下弱风化岩石裂纹扩展阶段存在应力松弛平台，且随应变率升高而愈发明显，峰值应力与应变率呈正相关。等速循环冲击中，最大应力、应变与冲击速度呈正相关，与岩样累积冲击总次数呈负相关；损伤演化具有3个阶段呈倒S形，由其构建的双参数损伤演化模型拟合效果理想，且具有物理意义；利用模型中的参数α和β可计算中值点处的损伤度和相对循环次数，且与冲击速度正相关；不同损伤变量计算的损伤演化模型不同，合理定义损伤变量是必要的。

Damage evolution of weakly-weathered granite under uniaxial cyclic impact

In order to study the mechanical properties and damage evolution mechanism of weakly-weathered granite under blasting stress wave, single and constant-velocity cyclic impact tests on the granite specimens at different velocities were carried out using a modified split Hopkinson pressure bar (SHPB) with the diameter of 50 mm. The results show that the damage threshold determined by the energy method in single-impact tests can be used in the cyclic-impact tests. The stress relaxation platform exists in the crack propagation stage of the weakly-weathered granite at different strain rates, and it becomes more obvious with the increase of strain rate. The peak stress is positively correlated with strain rate. In the cyclic impact, the maximum stress and strain are positively correlated with the impact velocity, and negatively correlated with the total number of cumulative impacts; the damage evolution can be divided into three stages taking on an inverted-S shape, and a damage evolution model with two parameters is established by it. The fitting effect of the model is ideal and has physical significance; the damage degree at the median point and the relative number of cycles can be calculated by using the parameters α and β in the model, are positively correlated with the impact velocity. The damage evolution models described by different damage variables are different, so it is necessary to define the damage variables reasonably.