| Distribution characteristics and the effects changes of original rock stress influenced by mountain topography have an important influence to the coal seam group mining design, roof control etc.The key influencing factor of surrounding rock control and reasonable selection of support in the coal seam group mixed mining conditions is multiple interaction of coal seam mixed mining.That the research on characteristics of overlying strata breaking, influence characteristics of mining, distribution of formation stress field and fissure field evolution characteristics of overlying rock had an important significance for the safe and efficient mining of coal seam group mixed mining.Discrete element numerical calculation and similar material simulation experiment are used to research on this subject according to the mountain occurrence surface condition.Studies suggest that rock stratum under mountains can be divided into significantly effect area(distance to surface less than 100m), effect decreased area(distance to surface 100m~250m) and no effect area(distance to surface more than 250m). 3# coal seam depth is about 400 m which is outside of the influence of mountain.The presentation of the 3# and 9# coal mining pressure manifestation to show the characteristics of single seam mining pressure,which is because the overlying rock breaking instability and floor damage extent are not affected by adjacent coal seam mining.While, the 4# and 6# coal mining are respectively effected by the surrounding rock movement of the 3# and 9# coal mining.Fractal geometry theory was used to quantitatively descript the roof and floor damage degree after each coal seam mining of coal seam group mixed mining.Studies show that, the crack-production ratio increased with the increase of lower coal seam composite thickness after each coal seam mining, which impact by coal layers spacing; Seam thickness, coal layer spacing and the overlying rock lithology had affect the fractal dimension of seam roof fractured,and the fractal dimension of fracture increased with the increase of composite seam thickness;The 4 #, 6 # coal seam mining greatly influenced by near coal mining have got and it should strengthen the control of working face roof and floor by analyzed fractured fractal dimension after coal mining.Based on Songhe Coal Mine seam group occurrence conditions, the discrete element numerical studies show that working face roof support design can use conventional support design when 3 # 、9 # coal seam mining; that support design should focus on broken roof control when 4 # coal seam mining; that support design should focus on strengthen broken roof and floor control when 6 # coal seam mining.According to the surrounding rock stability,the overlying rock structural characteristics under conditions of coal seam group mixed mining and characteristics of the interaction between the stent and the surrounding rock,the mechanics model between the support and the surrounding rock of ascending mining and descending mining is established, and the method of support parameters is determined. ZY6400/16/34 type shield hydraulic is select to support the roof based on 3 # coal seam face behavior characteristics and support resistance determination method. ZY4800 / 09/21 type hydraulic is select to support the roof based on the fact that 4 #、6 #、9 # coal seam average thickness is between 1.2m~1.5m.By the face strata behavior regularity field measurement that in the process of 3# coal seam mining shows that the stent average resistance of the end cycle is 4446 KN,the average of time-weighted resistance is 3904 KN, which is agree well with theoretical calculations.The stent has a good adaptability to protect the 3 # coal seam safe mining. |
PDF Full Text Request