Acoustic emission characteristics and law of halite and thenardite under uniaxial cyclic loading and unloading are studied by using TYJ 600 rock mechanics testing system controlled by the microcomputer, electro-hydraulic servo control and SDAES digital acoustic emission instrument. The results show that acoustic emission count rate and energy rate are small for two kinds of samples in the initial state during uniaxial compression; in the elastic deformation stage, increase of AE counts is stable and little for halite and thenardite, respectively; in the plastic deformation stage, halite AE count rate and energy rate are linear growth with time increasing, thenardite AE count rate and energy rate increase rapidly; at the peak strength, halite and thenardite AE count rate and energy rate reach the maximum at the same time; after the peak strength, there are still AE counts and a few AE in the unloading period under cyclic loading and unloading. Before stress load to last unloading stress in the loading period, thenardite acoustic emission also exist, which is different from the typical "Kaiser Effect". Under monotonous and cyclic loading and unloading, halite and thenardite AE count rate and energy rate are consistent, either count rate or energy rate can be served as criteria of precursor of rock failure for these rocks.
Acoustic emission (AE) monitoring is a viable nondestructive method for detecting microfracturing prior to a macroscopic rock fracture (Zhao 2006). This phenomenon has been found by the Obert in the early 1930s, and acoustic emission technology is applied in monitoring the stability of rock mass and predicting the rock burst in mine (Li 2004). Since then, acoustic emission technology which is a kind of dynamic nondestructive testing means has been widely applied and developed in geotechnical engineering, earthquake monitoring and rocks' damage (Li 2004, Katsuyama 1996).
To study the acoustic emission characteristics and laws of the salt rock, extensive work had been done by many experts as follows.