Abstract:

Experiments on acoustic emission (AE) of coals with saturated water under triaxial stress were conducted, and the relationship between stress and strength under triaxial stress was analyzed on the rock mechanical experimental rig (GAW2000). The results reveal that the coals of different ranks always have variable AE characteristics. Normally, they were divided into three types. The results of triaxial experiments and AE analysis of watersaturated coals show that AE events were less active at the elastic stage, after that the AE become active; Experimental comparison between uniaxial and triaxial shows that the confining pressure will significantly change the strength of semianthracite coal at the compaction stage, while it is not obvious for anthracite coal. And the confining pressure is insignificant for other stages of coal deformation and failure process. AE ring counts and energy counts reveal that they can be applied to predicting the coming failure point. The frequency and amplitude of the ringing rate and energy rate have been greatly raised during approaching the destruction precursor for the semianthracite coal. When the stress reaches 90% of the yield stress, the ring counts and energy counts will remain unchanged. For anthracite coal, the destruction precursor will produce an obvious sharp increase in frequency or amplitude. Meanwhile, the results also reveal that AE characteristics have significant relationship with coal composition and coalification.

Key words: triaxial stress, saturated water, coals, acoustic emission