| The roof of coal group 1 in 230106 working face of Xinji No.2 mine is mainly thick-bedded sandstone,and the goaf roof is difficult to fall off normally.There are dangers such as large overhanging roof,sudden collapse and roof protration and gas accumulation,which seriously affect the efficient and safe mining of coal seam.Therefore,with 230106 working face as the actual engineering background and huge thick hard sandstone roof as the main research object,this paper carried out the research on advanced deep-hole blasting weakening technology through the combination of field investigation,laboratory test,theoretical analysis,similarity simulation,numerical simulation and field practice,etc.The main results are as follows:(1)Through field investigation and research,the geological data of 230106 working face are obtained,and the roof is confirmed to be a thick hard sandstone roof.Through the indoor rock mechanical parameter test,the relevant mechanical parameters of 1 upper coal roof and floor are obtained,which provides data support for the subsequent similar simulation and numerical simulation.(2)For the huge thick hard sandstone roof,the Saint-Venant principle is no longer applicable.Based on the semi-inverse solution condition in the shear formula of material mechanics,the mechanical model of the roof’s initial breaking is established,and the mathematical expression of the roof’s initial pressing is obtained.Combined with the identification and numerical calculation of the key layer,the initial pressing step is obtained as 53.8 m.When the basic roof is broken for the first time,the roof is changed from a fixed beam at both ends to a cantilever beam,and the mechanical model of the periodic failure of the roof is established.The periodic pressure step is25 m.Through the discrimination of goaf developing conditions,combined with230106 working face mining height and roof thickness,the initial determination of the roof height of 25 m.(3)By building a similar simulation physical test platform,simulation and comparative analysis of the roof caving step before and after the roof weakening,the stress evolution law of the surrounding rock of the stope and the movement and subsidence law of the overlying rock can be obtained: Under normal mining conditions,the initial caving step of the roof is 60 m,the peak vertical stress of the stope surrounding rock is 24.88 MPa,and the maximum subsidence of the roof overburden is4.15 m.After the advanced weakening of the roof,the initial caving step of the roof is45 m,which decreases by 25% compared with before.The peak vertical stress of the stope surrounding rock is 25.08 MPa,and the maximum subsidence of the roof is 4.58 m,which increases by 10%.By using the infrared thermal imager to monitor the roof caving characteristics,it is found that: before the roof weakening,when the basic roof is pressed for the first time,the roof caving height is 38 m,and the front and rear caving angles are respectively 62° and 56°.After the roof is weakened,when the basic roof is pressed for the first time,the roof caving height is 35 m,and the front and back caving angles are 75° and 66° respectively.(4)In the numerical simulation,the stress field,displacement field and elastic-plastic zone deformation before and after the roof weakening are compared.The results show that: before and after the roof weakening,the stress of the stope surrounding rock decreases first,then increases to the peak of the advanced abutment pressure with the advance of the working face,then decreases,and finally tends to be stable.The roof subsidence and span also increase with the advance of the working face.The maximum subsidence before and after the roof weakening is 4.29 m and 4.59 m,respectively,which increases by 7%.Before and after the roof weakening,the elastic-plastic zone of the stope surrounding rock expands with the advance of the working face and develops to the depth continuously,and the elastic-plastic zone after the roof weakening is obviously greater than that before the roof weakening.(5)On the basis of the research of the first five chapters,combined with the actual site environment,finally determined the advanced deep hole pre-split blasting technology scheme,and successful practice;According to the analysis of rock pressure observation data,the surface displacement of roadway decreased by 60% from 452 mm to 180 mm.The axial force of bolt decreases obviously.The pressing step distance of the working face is reduced from 53.8 m to 30.5 m,with a decrease of 43%.This shows that the pressure relief effect is obvious,improves the stability of roadway surrounding rock,and ensures the safe and efficient stoping of working face.Figure [68] Table [10] Reference [87]... |
PDF Full Text Request