Search

Through the systematic analysis of the upward slicing filling technology in extra thick coal seam，the special thick seam “single layered” and “multi-layered” elastic foundation beam model were built，which provides a judgment on the instability conditions of the roof under the calculation of roof deflection curve with corresponding mechanical analysis and the first roof strength theory. According to the specific conditions of Gonggeyingzi Coal Mine，the calculated results show that the maximum subsidence of the roof in single layered is 86 mm，and the maximum tensile stress is 0.77 MPa. With the gradual mining of different layers，they both have an increase，and reach their maximum of 549 mm and 2.25 MPa after all layers have been excavated. During the mining process，the roof has a good stability and the engineering test results are consistent with the calculation results. [ABSTRACT FROM AUTHOR]

In order to solve the water inrush problems induced by mining under water bearing strata, this paper proposes the method of water protection based on solid backfill mining. Meanwhile, the fundamental principle of this method is introduced and the evolution characteristics of water-conducting fracture in solid backfill mining are analyzed. Moreover, the calculation model of critical compression ratio is established according to the predicting formula of the height of water-conducting fracture zone in solid backfill mining and the coal mining regulations and coal pillar design affected by buildings, water bodies, railways and main roadway. Then, the compression ratio of coal seam induced by mining under water bearing strata is designed, which is used for the layout of solid backfill mining panel. The engineering application results in CT101 backfill mining panel show that the average measured value of mass ratio is 1.32, which is bigger than theoretical design value and the height of water-conducting fracture zone is about 10.0 meters, indicating that this method effectively reduces the height of water-conducting fracture zone and can achieve the goal of safe mining under water bearing strata. [ABSTRACT FROM AUTHOR]