砂岩四面卸载矿柱岩爆实验研究

Experimental study on pillar burst of sandstone under four-faces unloading conditions

为了探索工程现场矿柱岩爆灾害的特征及发生机制,采用立方体红砂岩开展真三轴四面卸载条件下矿柱岩爆实验和单轴压缩实验,获得岩石试样的破坏全过程、声发射特征、速度场特征、碎屑特征以及能量演化特征。结果表明:单轴压缩破坏和矿柱岩爆过程相似,但两者的破裂模式不同;卸载过程会使得损伤加剧,而且围压越高,由卸载引起的损伤越大;单轴压缩破坏的碎屑呈现块状和板状,而矿柱岩爆的碎屑为长条状;速度场呈现出先增加再降低的特征,在岩爆发生时刻达到峰值,且最大速度随着围压的增大而增大;矿柱岩爆声发射频谱分布范围不同,低围压时声发射频谱集中在300~350 kHz,高围压时声发射频谱集中在150~200 kHz;单轴压缩破坏声发射波形能量分布呈现复杂的多频率带特征,而矿柱岩爆的声发射波形能量分布呈现单一频率带特征,且不同频率带与裂纹类型存在较好的对应关系。

To explore the characteristics and mechanism of pillar burst at engineering sites,this paper uses cubic red sandstone to carry out pillar burst experiments under the condition of four-faces unloading and uniaxial compression conditions.The process of rock failure,acoustic emission(AE) characteristics,velocity field characteristics,debris characteristics and energy evolution characteristics were obtained.The results show that the failure process of uniaxial compression and pillar burst is similar,but the failure modes are different.The unloading process will aggravate the damage,and the higher the confining pressure,the greater the damage caused by unloading.The debris of uniaxial compression is massive and plate-shaped,while the debris of the pillar burst is long strips.The ejection velocity increases first and then decreases,reaching the peak at the moment of the burst,and the maximum velocity increases with the increase of the confining pressure.The distribution range of the AE spectrum is different,the spectrum is concentrated at 300–350 kHz when the confining pressure is low,and the spectrum is concentrated at 150–200 kHz when the confining pressure is high.The waveform energy of uniaxial compression distributes in complex multi-frequency bands,while the waveform energy of pillar burst distributes in single frequency band,and there is a good correspondence between different frequency bands and crack types.