Comparative experimental studies of acoustic emission characteristics of sandstone and mudstone under the impacts of cyclic loading and unloading

In this article, the acoustic emission tests of uniaxial cyclic load imposed on or released from the sandstone and mudstone were carried out. The deformation and failure characteristics and the law governing the acoustic emission activity were studied. The results of the study show that (I) the variation of acoustic emission events of sandstone and mudstone is law governed and is in agreement with the tendency of stress and strain curve development. (2) The acoustic emission activity of mudstone is most active before peak stress, while sandstone is at peak stress. For the sandstone, when the number of acoustic emission events is the most active, the corresponding acoustic emission energy is not the largest. However, the peak value of acoustic emission events and the peak energy of the mudstone coincide, and the acoustic emission events get to the most intense due to the peak energy. (3) The acoustic emission activity is more severe when a load is imposed on or released from the rock. Compared to loading, the rock damage caused by unloading is even greater. (4) The acoustic emission event at the splitting point is more concentrated. The line of acoustic emission point is basically consistent with the shape of the split.