单轴压缩下煤岩声发射及分形特征研究

Study of Acoustic Emission and Fractal Characteristics of Coal Rock under Uniaxial Compression

为了研究煤岩在单轴压缩下的声发射及分形特征,利用RMT-150C型岩石力学伺服试验系统和CDAE-1型声发射检测仪对砂岩、砂质泥岩和戊组煤试样进行了实验研究。对砂岩、砂质泥岩和戊组煤的力学特性、声发射计数和累计计数以及声发射序列的分形特征进行了对比研究。研究结果表明:煤岩全应力-应变过程可分为四个阶段:初始压密阶段、准弹性阶段、塑性变形破坏阶段和残余变形阶段。初始压密阶段,声发射计数都比较低,累计计数增加的趋势特别缓慢;准弹性阶段,声发射计数有所增加,累计计数变化趋势相对较快;塑性变形破坏阶段,声发射计数都出现了跳跃式上升,声发射累计计数都出现了激增现象,但是砂岩的特别明显;残余变形阶段,声发射计数水平比较低,累计计数基本不增加了。煤岩破坏过程中声发射序列都具有分形特征,分形维值在煤岩破坏前会出现突降现象,可以作为预测煤岩动力灾害的前兆。

In order to study the acoustic emission and fractal characteristics of coal rock under uniaxial compression, an experimental study was carried out to investigate the acoustic emission and fractal characteristics of sandstone, sandy mudstone and group Wu coal samples by using RMT-150C rock mechanics test system and CDAE-1 acoustic emission instrument. A contrast study was carried out on mechanical properties, acoustic emission count, cu- mulative count and acoustic emission sequence fractal characteristics of sandstone, sandy mudstone and group Wu coal sample. The results show that the complete stress-strain process of coal and rock was divided into four stages ： initial consolidation phase, quasi elastic stage, plastic deformation stage and residual deformation stage. In the initial consolidation phase, the acoustic emission count is small and the trend of cumulative count increase is very slow. In quasi elastic stage, the acoustic emission is increased, and increasing trend of cumulative count is fast. In plastic de- formation stage, the jumping up phenomenon of the acoustic emission count appears and surge phenomenon appears for the cumulative count and for the sandstone, it is particularly evident. In the residual deformation stage, the acoustic emission count is very small, and cumulative count did not increase. Acoustic emission sequence have fractal characteristics in the process of the coal rock failure. It can serve as precursors to forecast coal rock dynamic disaster based on that the fractal dimension value will have dump phenomenon in the process of coal rock failure.