Experimental of mechanical properties and gas flow of containing-gas coal under different unloading speeds of confining pressure

Based on self-developed "Triaxial Stress Thermal-hydrological-mechanical Coal Gas Permeameter", the experiment of the influence of different unloading speeds on mechanism and gas seepage features of containing gas coal is carried out, with the condition of initial confining pressure 6MPa and gas pressure 1.0MPa. It shows that: with the increasing of unloading speed of confining pressure, the time of coal maintaining at a stress plateau phase reduces, and it tends to 0, and the easier coal is to be fail After the start of unloading confining pressure, the time of coal maintaining in the stage of stress plateau showed a power function relation with unloading speed of confining pressure. In this study, the speed can be classified into three regions in text: the low speed region of unload confining pressure, the intermediate speed region and the high speed region. In the three speed regions, the confining pressure, when coal fails, is lowest in the low unloading speed of confining pressure, middle in the intermediate unloading speed region, and highest in the high unloading speed region. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of China Academy of Safety Science and Technology, China University of Mining and Technology(Beijing), McGill University and University of Wollongong.