Study On Scale Effect Of Surrounding Rock Control In Fully Mechanized Face With Large Mining Height

Aiming at a series of surrounding rock control problems commonly existing in large mining height working face in China,such as coal wall slice,roof leakage and support collapse,this thesis selected 10 representative large mining height working face with different occurrence conditions as the object,and studied the large mining height working face because of its long face from the angle of surrounding rock control by means of laboratory test,numerical simulation,field observation and theoretieal analysis.Various scale effects caused by changes in mining height,coal seam dip,burial depth,structure,physical and mechanical properties of coal and rock.The results of this thesis are as follows:In the direction of mining height,it is considered that the strength of coal body decreases logarithmically with the increase of mining height.The peak strength obtained by SHPB can reflect the stability of coal body more accurately than that obtained by uniaxial compressive strength.The mechanism of slice side is studied from the angle of stress change and energy dissipation.It is considered that the unloading range of maximum horizontal principal stress and residual energy of coal body are in positive phase with the damage of coal wall.By establishing the deflection function of key strata,the stress distribution characteristics of the area affected by the advance support pressure under different mining heights are obtained.Through the simulation and inversion of the energy field in front of the coal wall,the corresponding relationship between the damage and energy release of the coal wall at different mining heights is obtained.In the direction of working face length,based on the difference of rock pressure appearances,the scale effects of working face length or dip direction under four conditions of shallow seaxn,deep mining,large dip seam and pseudo-dip mining are obtained respectively.For shallow coal seam,the key of surrounding rock control is to ensure the matching of support strength and advancing speed.The transmission efficiency of loose layer load is defined as a time factor,and the quantitative analysis of coupling effect between advancing speed and working face length is realized.In deep mining,it is eonsidered that the distribution of roof pressure is typical "double peak" or "multi-peak" with the increase of working face length,the key strata of old roof are characterized by regional breakage in the length direction of working face,and the relationship between large periodic weighting and gas exceeding limit in working face is consistent.In the aspect of mirung with large dip angle,it is considered that there is "critical length" in the working face with large dip angle.The working face is divided into filling section,collapsible buckling section and slip section along the inclination,and the method for determining the support strength of the working face with large dip angle is further obtained.In the aspect of pseudo-inclined mining,it is considered that the relationship between the dip angle of coal seam and the applicable pseudo-inclined angle of working face is exponential curve.The bigger the dip angle of coal seam is,the smaller the proportion of the applied pseudo-inclined angle is.The pseudo-inclined angle of working face has its applicable range.For multi-factor and multi-scale coupling coal seam conditions,an evaluation model of mining intensity based on the theory of entropy value is established.The problem of orderly division of adjacent intervals of evaluation indexes of mining conditions and occurrence conditions is effectively solved by using attribute recognition method,and the horizontal comparison of mining intensity of high mining height working face with different occurrence conditions is realized.In the aspect of roof disaster monitoring and early warning,this thesis studies and establishes the support position recognition model,inverts the load characteristics of the support before the catastrophe through the change of the position,puts forward the early warning index system and method based on the support position recognition,develops the early warming software and hardware system,and carries on the successful test in the field.The research results of this thesis have been successfully applied in the mining of high mining height working face with 8310,8303 and 8103 different occurrence conditions in No.1 Coal Mine of Yangquan Coal Group.