Reseach On Overlaying Strata Failure And Moving Character And Controlling Technology

In recent years,large mining height one pass cutting coal miningteachnologyhas been widely used in China’s major coal mining area because of its high efficiency,high yield and low cost advantages. Due to the theoretical study on the mining technology lags behind engineering practice, even in greatly improve the working face production potential at the same time, the working face of large mining heightshowed apressuredifference with theordinaryfully mechanized working face in strata behavior anddisaster. According to the specific conditions of occurrence of thick coal seam in Wang Zhuang coal mine,this paper studies on large mining with large mining height of surrounding rock control technology. With the use of field observations, the development of experimental equipment, laboratory experiments, numerical calculation and theoretical analysis of comprehensive research method,Systematically analyzed coal wall spalling mechanism、grouting prevent coal wall 、support-rock system、the calculation method of the rood load、coal mining teachnology optimization problem,We can obtain the following research results.(1)The main coal seam sampling, carried on the coal and rock mechanical parameters test.In order to obtain the mechanical parameters of the coal mine, and lay the foundation for the numerical analysis of surrounding rock stability, We collected and processed into standard coal of the 50*100 specimen and theuniaxial compressionand shear test in Wang Zhuang coal mine 8101. If the amount ofdeformationfailureof theaxialcompression testis less than five percent, it can show obvious brittle failure form. The compressive strength of small faults in 3# coal is only 4.2MPa, and the compressive strength of coal seam under normal storage conditions is about 12 MPa, therefore, in high intensity mining conditions, working face coal wall to expose the encounter fault prone torib spalling phenomenon.(2)Optimizing the size of work face and coal pillar. To increase the recovery rate of resource, limit analysis is used to get the stability condition of basic roof at some load and obtain the maximum length of work face. numerical and therotical analysis is used to get the stablility conditions of pillars. if certain range of elastic neuleus exists in pillar, then it can be stable and roadway need not be supported. According to the results of numerical analysis for coal strata of different forms of distribution above the load, and inversion in the pillar of the state, by the occurrence and layout of the working face under the condition of optional minimum size of coal pillar, finally from the biggest extent improve the reserve area, the recovery rate of coal resources.(3)Similar simulating experiments have applied to study of overlying rock breaking movement form in large cutting height working face.For the specific storage conditions of Wang Zhuang 3# coal seam, the similar simulating of two-dimensional plane stress have been laid. The overburden motion morphology and the main roof structure in the process of excavation can be acquired from the photos of HD camera. Due to the one time produced space increasing, caving zone and fractured zone are increasing and reached 20 m, 70 m respectivelyafter overlying rock breaking.According to the movement of the main roof form, the mechanical model is established to the breaking roof stability analysis of the first weighting and periodic weighting in workface, the structure of limit equilibrium position and buckling form are acquired by using principle of minimum potential energy, and finally we conclude that the buckling form of main roof breaking rock is main of slide instability and the reveal strength is improving when the workface is shown pressure because of the one time mining height multiplied in large cutting height workface.Combined with numerical calculation and the result of similar simulation, the reasonable parameters of workface is determined.(4)According to the slide instability characteristics of main roof in large cutting height workface, the working resistance of support can be determined with energy conservation principle. The reduce of gravitational potential energy can be all transformed into the energy of immediate roof and workface support absorption in the instability falling process of main roof breaking rock, the working resistance of support can be determined by support absorption energy. According to the characteristics of immediate roof, the different calculation formula of support working resistance can be determined, and analyzing the influence factors of support resistance under different condition. By using this method, the support selection of 8101 workface has been success.(5)The technology is passing through fault and prevention rib spalling in workface. The fault structure is weakened the coal rock mechanical parameters, and large scale joints greatly enhance the accident probability of the coal wall spalling near fault. The mechanism of coal wall spalling accident is analysis in fault structure by using limit analysis theorem, and acquired the main influence factors indifferent coal wall spalling situation combined with numerical analysis and laboratory experiments. The coal rock mechanical properties reducing、the roof pressure increasingand the flipperto provide the level of support force is mainly caused the coal wall spalling phenomenon in 8101 workface of fault structure. In view of the above conclusions, the technology of high resistance in the heavy equipment and low advancing speed are proposed. The coal wall grouting technology can not only increase the strength and integrity of coal, but also can play the role of anchor strengthening coal wall. The key of the coal wall grouting technology is layout grouting holes, the best layout scheme is the position of grouting hole consistent with the coal wall starting damage point. According to the results of laboratory grouting experiments, the prevention rib spallingcomprehensive technology of high grouting pressure and the lateral protecting network is proposed, and achieved good results, and to improve the operating rate of 8101 workface.(6)We can conclude the occurrence mechanism of crushing accident in workface retracement stage, according to the workface and roadway of retracement stage and the relative space of roof fracture line, the roof control measures in retracement stage have been proposed, such as the changes to the mining height, the advancing speed of workface and yield mining, and on this basis to optimize the fast moving technology of heavy equipment in large cutting height mining, and to improve the back moving efficiency of corollary equipment.