Research on the development law of roof fracture zone in fully mechanized top coal caving in Daping Colliery

In order to study the development rules of the water-conducting fracture zones in fully mechanized top coal caving in the Daping Coal Mine,ground drillin g and laboratory tests were used to detect the development height of the water-conducting fracture zones in the fully mechanized top coal caving face and the physical and mechanical characteristics of the impervious rock layers above the interface of the fracture zone.The measured results were compared with the measured data of t he fully mechanized caving fracture zone in the adjacent in Lu'an mining area.The results showed that the development height of the water-conducting fracture zone in t he fully mechanized sublevel caving was 105.53 ~ 112.62 m above the roof and the fracture-production ratio was 19.18 ~ 19.42.The height was basically proportional t 0 the mining thickness, and the empirical formula for calculating the crack zone height was obtained.Results of rock mechanics tests showed that all rock formations on t he top interface of the fracture zone had water absorption and softening,with a softening cofficient of 0.29 ~ 0.85,which was more favorable for inhibiting fracture dev elopment and expansion.Research results could be used to guide coal mining under the river and the roof water damage prevention in this mine.