岩石破坏前的损耗比及加卸载响应比特性研究

以多种岩石循环加卸载声发射试验为基础,针对岩石损耗比和加卸载响应比特性进行了研究,探索岩石在受载过程中的内部损伤演化和破坏前兆特性。结果表明,在循环加卸载下角岩等三种岩石损耗比变化特性一致:低应力水平阶段损耗比较大,呈明显下降趋势;中等应力水平阶段比值下降趋势较平缓;高等应力水平阶段比值趋于稳定,在0.08～0.10时,试样破坏。而钨钼矿等三种岩石加卸载响应比变化特性一致:低应力水平阶段卸载时几乎没有声发射,加卸载响应比较大;中等应力水平阶段卸载时声发射较活跃,比值下降至1左右;高等应力水平阶段卸载时声发射很活跃,当比值重新大于1时,试样破坏。试验结果都体现了岩石内部损伤从很小到稳定扩展再到不稳定扩展的过程。可见,损耗比和加卸载响应比的变化特性均可用于评价岩石损伤情况,也可用作岩石破坏预测的参考依据。

Study on the Characteristics of Loss Ratio and Loading-unloading Response Ratio before Rock Failure

On the basis of the acoustic emission for rock under cyclic loading and unloading,the characteristics for the loss ratio and loading-unloading response ratio of rocks is studied,and the evolution of the internal damage in the course of loading and the precursor characteristics of failure are explored.The results show that the variation characteristics of loss ratio of three kinds of rocks like hrnfelswere are consistent under loading and unloading conditions;The loss ratio is relatively large in the low stress level stage,and it shows a clear downward trend.After entering the medium stress level,the ratio decreases with a relatively fiat trend.In higher stress level,the ratio tends to be stable,and the specimen fails at 0.08～0.10.At the same time,the variation characteristics of loading-unloading response ratio of three kinds of rocks like tungsten and molybdenum ores are consistent.There were almost no acoustic emission at the unloading stage in the low stress level stage,and the loading-unloading response ratio were relatively large.Acoustic emission was more active at the unloading stage in the medium stress level,and the ratio dropped to about 1.In higher stress level,acoustic emission was very active at unloading stage,and the specimen failed when the ratio increased over 1 again.The results reflect the process of rock internal damage from small to steady expansion and then to unstable expansion.So the variation characteristics of loss ratio and loading-unloading response ration can be used to evaluate the damage of rock,and also can be used as a reference for prediction of rock failure.