针对深部矿井开采过程中岩体自稳能力差、动力灾害频发等问题, 采用自主研发的ZST−1500微机控制电液伺服煤岩动静组合自适应耦合试验系统, 开展了不同幅值与频率的砂岩单轴动载扰动试验, 分析了动载作用下砂岩动态力学响应规律与破坏特征。研究结果表明: (1)随动载幅值增加, 砂岩滞回环由“疏−密”向“疏−密−疏”变化, 依据动载循环期间试样塑性变形量, 将动载周期划分为对数上升阶段Ⅰ、匀速损伤阶段Ⅱ和指数加速阶段Ⅲ。(2)动载对试样强度的弱化作用存在阈值, 当动载水平为70%${sigma _{mathrm{c}}}$时, 诱发砂岩发生破坏的幅值阈值在17.5%~22.5%${sigma _{mathrm{c}}}$范围内, 低于阈值的动载作用不会造成砂岩失稳, 越过阈值后砂岩强度、破坏前动载持续时间与动载幅值及频率均成负相关。(3)动载幅值与频率对砂岩弱化作用机制存在差异, 动载幅值、频率均与动载单次循环平均塑性变形$ Delta {bar{varepsilon }}_{(text{i})} $成正相关, 但$ Delta {bar{varepsilon }}_{(text{i})} $对动载幅值更为敏感, 在阶段Ⅰ、Ⅱ内随幅值增大呈指数型增长。动载幅值主要通过提升塑性变形量来实现对砂岩的弱化作用; 而动载频率提升降低了动载循环间隔, 在砂岩内部形成小增量、短时、连续的损伤, 从而实现对砂岩的弱化作用。(4)砂岩AE信号累计能量与振铃计数率随动载幅值的增大呈指数型变化, 也随动载频率的增加同步增长。随着动载幅值增加, 砂岩微观裂隙起裂、扩展程度递增, 剪切裂纹占比增大; 随着动载频率增大, 砂岩拉伸裂纹占比增大。

For the poor self-stability of rock mass and frequent dynamic disasters in the process of deep mine mining, the uniaxial dynamic load disturbance test of sandstone with different amplitudes and frequencies were carried out using the self-developed ZST−1500 microcomputer controlled electro-hydraulic servo coal and rock dynamic and static combination adaptive coupling test system, and the dynamic mechanical response law and failure characteristics of sandstone under dynamic load were analyzed. The results show that with the increase of dynamic load amplitude, the hysteresis loop of sandstone changes from "sparse-dense" to "sparse-dense-sparse", and the dynamic load cycle is divided into logarithmic rising stage I, uniform damage stage II and exponential acceleration stage III according to the plastic deformation of the sample during the dynamic load cycle. There is a threshold for the weakening effect of dynamic load on the strength of the specimen when the dynamic load level is 70%${sigma _{mathrm{c}}}$. The amplitude threshold of failure is 17.5%~22.5%${sigma _{mathrm{c}}}$, and the dynamic load below the threshold value will not cause sandstone instability. The sandstone strength and the dynamic load duration before failure are negatively correlated with the dynamic load amplitude and frequency beyond the threshold value. The effect of dynamic load amplitude and frequency on the weakening mechanism of sandstone is different. Both the dynamic load amplitude and frequency are positively correlated with the average plastic deformation $ Delta {bar{varepsilon }}_{(text{i})} $ in every single cycle of dynamic load, but $ Delta {bar{varepsilon }}_{(text{i})} $ is more sensitive to the dynamic load amplitude and increases exponentially with the increase of the amplitude in the stages of I and II. The dynamic load amplitude weakens the sandstone mainly by increasing the plastic deformation, while the increase of frequency reduces the cyclic interval of dynamic load, and forms a small amount of continuous damage in sandstone in short time, thus weakening the sandstone. The cumulative energy and ringing count rate of sandstone AE signals increase exponentially with the increase of dynamic load amplitude, and also increases synchronously with the increase of dynamic load frequency. With the increase of dynamic load amplitude, the initiation and propagation degree of sandstone micro-cracks increase, and the proportion of shear cracks increases. Also, the proportion of sandstone tensile cracks increases with the increase of dynamic load frequency.