Study On The Overlying Strata Breakage And The Working Resistance Of Support In The Condition Of Thick And Hard Roof Hosting Directly Over The Coal Seam

According to the occurrence of the thick and hard roof (thickness, integrity, hardness), and the characteristics of mining pressure and support force, in this paper,compositive research techniques including of theoretical analysis, numerical simulation and in-situ measurement are carried out to investigate the overlying strata breakage and the working resistance of support in the condition of thick and hard roof. The result show that:(1) The incremental load of the thick and hard roof, before initial fracture, can be fitted the Function of the three parameter Weibull distribution, and through the analysis of mathematics and mechanics, the theoretical solutions of first breaking interval that the thick and hard roof is are given in face.(2) Difference of mining height and speed will lead to difference of first and periodic breaking interval of the thick and hard roof and the working resistance of support before and after fracturing its corresponding stage. The numerical simulation shows that the greater mining height, the smaller the first and periodic breaking interval of the thick and hard roof, the greater height of fractured, the obvious mine pressure behavior, the greater the working resistance of support; With the increasing mining rate, the degree of both the initial and peoriodical pressure will enlarge, the number of periodic breaking will be a trend of decrease at the working face, the step of periodic breaking will be a trend of increase, each pressure step will be also increases.(3)To establish a reasonable caving step distance calculation model on thick and hard roof at the working face, and to present the theoretical solution of the maximum caving step distance, and also to combine with Huainan in thick and hard roof working face, and conclusions in numerical simulation, to put forward a more reasonable caving method and step of1602(3) conventional working face in Panji No.1coal mine, and to study on characteristics of strata behavior in the working face after caving.The results provide important references and theoretical basises on the mining of safety and thick and hard roof control in the condition of thick and hard roof hosting directly over the coal seam.