Research On The Strata Behavior Characteristics And Control Of Ultra Large Height Mining Face In Shendong Mining Area

The technology of once full height mining has been widely used in China due to its high resource recovery rate,high production efficiency,etc.It has been successfully mined 7.0m high-cutting working face.Based on the fact that there are abundant reserves of large-thick high-quality coal seams above 7m in Shendong Mining Area,increasing the mining height and achieving once full height is a relatively effective and economical way to extract this part of resources.The abundant rock formation control technology,mature coal mining technology and increasingly advanced equipment are the foundation for further breakthrough of 7.0m mining height.However,the overlying strata movement and damage law,the characteristics of coal wall damage,and the type of support for the ultra large height working face above 7 m are still unclear.Therefore,it is of great practical significance and theoretical value to study the characteristics and control of mine pressure in the ultra large height working face.This dissertation takes ultra large height working face as the engineering background.the characteristics and control of mine pressure was researched in depth through theoretical analysis,numerical simulation,similar material simulation,field measurement.According to statistical principles,the impact of depth,height and length of working face on the pressure step of the roof was analyzed,provided the data basis for the pressure step of the roof in ultra large height working face;the top plate to The mechanical model was established to calculate the pressure step of the roof.Based on the theory of key layers,the roof structure and movement law of the ultra large height working face were analyzed,and the influence on the pressure of working face of roof fracture characteristics was analyzed in depth.Based on the semi-plane theory of elastic mechanics,the mechanical model of the stress distribution of overlying strata was established to analyze transfer law of mining abutment pressure in overlying strata.On the basis of the law of stress variation in overlying strata,the characteristics of shear stress changes was further analyzed in depth.Then,according to the stress state at any point in the plane,the stress change law was analyzed.Based on the theory of maximum shear stress,a method for calculating the"three-belts" height of overburden based on the "shear stress variation characteristics" method was proposed.D-P-? theory is used to analyze the width of the limit equilibrium zone,considering the influence of the intermediate principal stress on the yield function in order to improve the reliability of calculation results.It was proposed to determine the depth of the coal wall from two angles of limit equilibrium width and regression analysis,and analyze the easy-to-unstable position of the coal wall,provided a basis for design for the stent of the hydraulic support and the rational application of technical measures to control the wall of the coal wall.Take the dual control of the roof and the coal wall as the entry point,the mechanical model of the interaction between the hydraulic support and the roof was established,and the calculation formula for the support strength of the hydraulic support was proposed.The dynamic load factor regression prediction model was established to achieve the purpose of scientific prediction,improving the reliability of the support strength results.The influence of the strength of different supports on the stability of the coal wall was analyzed from the angles of roof subsidence,horizontal displacement,etc.by FLAC3D,thus,the support strength of the hydraulic support was determined comprehensively.The research results have been verified in the first 8.0m the ultra large height working face-the 12511 working face in Bulianta,created a record of the highest daily output of 52,200 tons,the highest monthly production of 1.35 million tons,and the recovery rate has increased to over 98%.The successful mining of this working face lays a solid theoretical foundation for the safe and efficient production of 8.8m height working face,and provides valuable experience that can be learned.The dissertation has 80 figures,45 tables,and 151 references.