Analysis on characteristics of overlying rock caving and fissure conductive water in top-coal caving working face at three soft coal seam

With the specimens obtained from the Dananhu Coal Mine,according to the comprehensive analysis and de- termination of engineering geological conditions and the physical and mechanics parameters of coal-rock in three soft coal seam from Dananhu No. 1 coal mine,a physical simulation model experiment has been built to analyze the moving law of surrounding-rock and the disturbed height of overburden stratum in the fully-mechanized top-coal caving work- ing face. The relationship between the measured resistance of field support and the position and water volume of overly- ing rock fissure conductive water is explored. The results show that the roof caving zone height at 1303 working face is 20 m,both the heights of fissure conductive water obtained by the observation of surface crack extension height on the model and revealed by 3D borehole TV synthetic borehole profile are 98 m,which is consistent with the empirical for- mula. The advance-disturbance scope expands with the increase of mining area,and eventually tends to be stable. The 1303 working face is divided into two parts of the pressure concentration(No. 1 area and No. 2 area). The volume and position of fissure conductive water are related to support pressure change,the position of overlying rock fissure con- ductive water has bigger chance in the middle and lower part of working face(No. 2 area). The authors suggest the o- verlying aquifer and gob water in the 1303 working face should be drained in advance,meanwhile,strengthen the de- tection of two pressure concentration areas,especially the No. 2 area. The roof failure and volume changes of water- drawing should be paid more attention,giving the immediate strata behavior warning and prediction of fissure conduc- tive water position and volume.