A study on piezoelectric effect of Rock

从压缩和/或破裂岩石中发出的电磁（EM）信号已被研究多年。有些岩石含有许多压电材料，例如石英。因此，一些研究者认为压电效应是电磁信号产生的主要原因。在含大量石英的花岗岩块上进行了电磁信号发射实验。这块花岗岩是用锤子手工敲击的；无冲击锤或标准钢锤。实验结果表明，锤击过程中会发出电磁信号。第一阶段。观察到的电磁信号与贴在钢锤上的应变片测得的应变相似。同时，用电袍子在块体表面观察到电磁信号。每件电袍子都被放置在距离锤击点有一段距离的位置上。在本例中没有观察到时间滞后或延迟。观察到的电压的初级/峰值与到锤击点的距离成反比。通过实验，在各个方向上都观察到相同的结果。电磁信号的后半部分与声发射（AE）传感器观测到的弹性波相似。用声发射传感器观测到的弹性波信号与距锤击点的距离成比例地延迟。可以得出结论，电磁信号相对较大，可能用于民用或采矿目的。

Electromagnetic (EM) signal emitted from compressed and/or fractured rocks has been studied for many years. Some kinds of rocks contain many piezoelectric materials, for example, quartz. Therefore some researchers consider the piezoelectric effect as the dominant cause of the EM signals.An experiment was carried out in which EM signal was emitted from a block of granite which contains a lot of quartz. The block of granite was manually impacted with a hammer ; a shockless hammer or a standard steel hammer. As a result of the experiment, it was found that EM signal was emitted on hammering. The first phase of the. observed EM signal was similar to strain measured by strain gauge affixed on the steel hammer. EM signal was also observed simultaneously by the electric robes on the surface of the block. Each electric robe was located at position separated by a distance from the hammered point. No time lag or delay was observed in this case. The primary/peak value of the observed voltage was inversely proportional to the distance from the hammered point. The same results were observed in all directions through the experiments. The later part of the EM signal was similar to the elastic wave observed with an acoustic emission (AE) sensor. The elastic wave signal observed with the AE sensor was delayed in proportion to the distance from the hammered point. It can be concluded that the EM signal is relatively large and potentially used for civil or mining purposes.