单轴循环冲击下岩石的动力学特性及其损伤模型研究

利用改进的大直径SHPB试验装置，对花岗岩试件进行单轴循环冲击压缩试验，分析花岗岩在循环冲击载荷下的力学特性及能量吸收规律。通过基于Weibull分布的动态统计损伤模型计算岩石的累积损伤，结合试验曲线分析岩石累积损伤的演化规律。研究结果表明：随着冲击载荷循环作用次数的增加，变形模量变小，试件的屈服应变增大，峰值应力呈降低趋势。岩石的累积比能量吸收值随着冲击次数的增加而增大，且试件破坏前其值增加缓慢，试件破坏时其值急剧增大。基于Weibull分布的动态损伤本构模型的计算曲线与试验曲线具有较好的一致性，该模型能反映岩石的强度与应变、应变率的关系。累积损伤随着循环冲击次数的增加而增大，其增加速率由小变大，试件破坏前累积损伤的增加较为平缓，其主要增量由最后一次冲击破坏产生。

Dynamic characteristics and damage model for rock under uniaxial cyclic impact compressive loads

Experiments on dynamic mechanical performance of granite are carried out under uniaxial cyclic impact loads by using a modified large diameter split Hopkinson pressure bar (SHPB). The dynamic characteristics of the granite specimens and the laws of the energy absorption are analyzed. The cumulative damage of the granite specimens is calculated by use of the dynamic statistics damage model based on the Weibull random distribution. The laws of the cumulative damage of the granite specimens are also analyzed through the stress-strain curves. The results show that, in the cyclic impact compressive tests, with the increase of repeated action times of impact loads, the deformation modulus of granite decreases, the yield strain increases and the yield stress shows a decreasing trend. The value of cumulative specific energy increases with the increase of impact times, which increases slowly before the failure of the specimen and increases rapidly at its failure. The model curves and the test curves have good consistency, which shows that this model can reasonably reflect the relationship of the stress-strain and stress-strain rate. The value of cumulative damage increases with the increase of impact times, and its increasing rate changes from slowly to rapidly. Before the failure of the specimen, the cumulative damage increases smoothly, and the main increment occurs in the last impact when the specimen is broken.