超声波振动下不同应力条件对岩石强度影响的试验

振动有助于碎岩,以往关于振动碎岩机理的研究大多在低频率段展开。为填补超高频率段下振动碎岩机理的空白,采用单轴动静组合加载模式,开展了超声波振动下不同应力条件对岩石强度影响的试验研究,其中超声波振动频率为20kHz,预压范围为100～500N。研究结果表明:当预压小于200N时,岩石内部应力状态无法满足强度准则,岩石强度下降不明显;当预压大于等于200N时,岩石强度随振动时间的增加而逐渐降低且存在最优预压力值(400N)使得岩石强度最低。缩短振动频率与岩石固有频率的差值有利于提高超声波振动碎岩效率。

Experiment on Effect of Different Stress Conditions on Rock Strength Under Ultrasonic Vibration

Vibration contributes to crushing of rocks. Research on the mechanism of vibrating rock is usually carried out in the low frequency range. In order to fill in the gap of the mechanism of rock crushing by vibration of ultra-high frequency section, an experimental study on the effect of ultrasonic vibration on rock strength under different stress conditions was conducted based on static and dynamic loading models, under the condition that the ultrasonic vibration frequency was 20 kHz, and the preloading range was 100-500 N. It is demonstrated that the rock strength remained unchanged basically when the preloading was less than 200 N. The reason is that the internal stress state of rock did not meet the strength criterion. When the preloading was more than 200 N, the rock strength increased with vibration duration, and there is an optimal preloading value (400 N) to minimize the rock strength. The efficiency of ultrasonic vibration rock crushing can be improved by narrowing the difference between the vibration frequency and the natural frequency of the rock.