The cracked characteristic of occlude type of coal-bed crack under controlling hydraulic pressure in strata stress field

The control parameters of strata stress field in pre cracked top hard coal bed are researched using water fracturing under controlling of strata stress field, and the relationship between water seepage, expanding in occlude type of top coal crack and strata stress value is analyzed in this condition. According to the energy principle, the physical criterion expression in the condition of water injecting in coal mass is founded first. And then the method of determining surface energy of coal mass is presented. Finally, the applying effects of the choice of controlling parameters using water to crack and improving the rate of recovery are illustrated using some living examples.