| The typical characteristics of coal seams in Shengdong coalfield are large reserves,generally shallow burial,thin bedrock,thick loose layer,fragile ecological environment on the surface,and most of them belong to shallow burial coal seams.Many years’ practical mining experience shows that the ground pressure of mining face with large mining height in shallow coal seam is severe,the dynamic load of mining face is obvious,and roof subsidence is easy to cause roof pressure disaster.Coal seam is buried shallowly,and highintensity mining is easy to damage the surface environment.Therefore,the study on the movement characteristics and weighting law of overlying strata in large mining height working face in shallow coal seam is beneficial to more reasonable support,high efficiency and green mining in shallow coal seam mining,and it is also of great significance to the normal operation of coal mine and the safety of employees.In view of the study on the movement characteristics and weighting law of overburden rock at large mining height face in shallow coal seam,this paper takes the mining of 42303 face in Wanli No.1 Coal Mine as the engineering background,carries out the research on the movement law and weighting law of overburden rock at large mining height face in shallow coal seam,and explores the movement law and weighting law of overburden rock at 42303 face with various research methods.Firstly,according to the geological conditions of shallow coal seam in 42303 large mining height working face,this paper establishes a physical similarity simulation model for this working face.Through the physical similarity simulation model,it simulates the movement law of overlying strata in the process of mining 240 m in the working face,and records the pressure change at every mining distance through a pressure sensor.Draw statistical tables to analyze overburden movement phenomenon and pressure change law.Then,according to the geological conditions of 42303 large mining height working face,a numerical simulation model is established by FLAC3 D software,and the simulati on results are generated to analyze the law of weighting and overlying strata subsidence in this working face.Finally,through the analysis of on-site investigation results,statistics and records of data such as support weighting,roof breaking and caving step,initial weighting and periodic weighting of working face are analyzed.Combined with physical similarity simulation and numerical simulation,the adaptability of the support and the rationality of the support scheme are verified.The main research results are as follows:(1)In 42303 large mining height working face,the first falling step of the direct roof is37 m,and the peak pressure of the working face support is 10212 k N;the first falling step of the main roof is 57 m,and the peak pressure of the working face is 12766 k N.After that,the average interval of periodic caving is 14 m,and finally it presents a trapezoidal structure with the height of caving zone of 22 m and the height of fracture zone of 169 m.The overlying strata in goaf presents a trapezoidal caving structure.As the working face moves forward,the influence range of the trapezoidal caving structure in overlying strata in goaf gradually increases.(2)The weighting strength of 42303 large mining height working face is the strongest in the middle,the second in the lower part and the weaker in the upper part.The measured results show that the initial pressure and periodic pressure of the basic roof are nonsimultaneous pressure along the direction of the working face,showing the characteristics of local pressure and pressure migration with the recommendation of the working face as a whole.(3)Through the checking calculation and actual measurement analysis of the support strength of the working face support,the ZY12000/26/55 D type shielding hydraulic su pport is overloaded and cannot fully meet the mining requirements of the working face,and a support with greater working resistance should be selected. |
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