Experimental investigation of the effect of change in control modes on the post-failure behavior of coal and coal measures rock

This paper presents post-failure tests on rock and coal specimens obtained from various coal mines in West Virginia and Hiawatha. Berea sandstone was used for comparing post-failure behavior of coal measures rock. Two feedback-control modes: axial strain control and lateral strain control modes were used to study the post-failure behaviors of the rock and coal specimens. The results obtained from the experiments show that coal measure rocks show significant change in post-failure behavior when the control modes were changed from axial strain to lateral strain. It was found that when the lateral strain control mode was used, in the post-failure region, coal measures rock exhibited class II behavior. Also coal specimen under lateral strain control showed class II behavior. However, it was observed that when the same coal specimens are tested under confining pressure, the class II behavior is replaced by Class I behavior.

► Post-failure behavior of coal and coal measures rock was obtained using lateral strain control.
► Coal measures rock show class I and Class II behavior.
► Coal specimens show class II behavior using lateral strain control.
► Under confining pressure coal specimens show class I behavior.