Study On Comprehensive Mechanized Mining Of Irregular Block And Evolution Law Of Water Flowing Fractures In Overburden

With the deepening of coal mining,the mineable coal reserves are decreasing.In order to improve the recovery rate of coal resources,it is urgent to recover the irregular block coal left at the initial stage of coal mining and extend the service life of the mine.In the recovery process,the overlying strata will produce water flowing fractured zone,which will not only threaten the safety of underground production,but also easily lead to the loss of water resources.In order to recover the irregular block of 4^-2 coal seam under the water body of Huixing coal mine in Northern Shaanxi,based on the mine engineering and hydrogeological conditions,the comprehensive mechanized mining technology of trapezoidal stope is developed by using the research methods of field investigation,theoretical calculation and numerical calculation,and the elastic thin plate mechanical model of overlying strata movement in trapezoidal stope is established,which reveals the development mechanism of overlying strata water flowing fractured zone,This paper studies the development law of water flowing fractured zone in overlying strata of working face,identifies the control factors of the height of water flowing fractured zone in trapezoidal stope,and puts forward the prediction model of the height of water flowing fractured zone under different control factors,so as to provide a theoretical basis for the safe and efficient mining of irregular blocks under water body.The main research results are as follows(1)This paper analyzes the reasons for the formation of irregular(trapezoidal)block in Huixing coal mine 4^-2 coal seam and its mining principles,and develops the comprehensive mechanized mining technology of trapezoidal stope.The key technologies are as follows:using fully mechanized excavators or continuous shearers supporting shuttle cars to cut and transport coal;When the scraper conveyor of the original production system is removed,the support of the working face is moved by the coal baffle,which can adapt to the change of the length of the working face,shorten the time of adding and removing the support of the working face,and ensure the safe and efficient recovery of irregular blocks.(2)The failure characteristics of overlying strata in trapezoidal stope are analyzed,and the mechanical model of elastic thin plate in trapezoidal stope is established.Based on the Kantorovich approximate variational method,the bending deflection function of overlying strata is analyzed,and the internal stress characteristics of trapezoidal thin plate are obtained.The calculation process of overlying strata breaking and water flowing cracks is given,By using MATLAB software,the split mining ratio of trapezoidal stope is 16.1.(3)The criterion of water flowing fractured zone in trapezoidal stope is determined,and the distribution characteristics of plastic zone at different time and position in trapezoidal stope are analyzed.The numerical calculation shows that the shape of water flowing fracture zone in the working face has changed from"left saddle shape","saddle shape"to"right saddle shape",and the fracture mining ratio is17.2.(4)This paper analyzes the controlling factors of the height of water flowing fractured zone,such as the slope of the inclined edge,the length of the bottom edge and the strike length of the trapezoidal stope,expounds the influence law of each factor on the height of the water flowing fractured zone,studies the temporal and spatial evolution characteristics of the shape of the water flowing fractured zone under the above controlling factors,and establishes the prediction model of the height of the water flowing fractured zone under the influence of multiple controlling factors of the trapezoidal stope,It can realize the protective exploitation of water resources in irregular trapezoidal block.There are 46 pictures,11 tables and 106 references in this thesis.