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. © 2020, Editorial Staff of EXPLOSION AND SHOCK WAVES. All right reserved.