Study On Ore Pressure Manifestation Law And Stent-surrounding Rock Stability Of The Composite Roof Comprehensive Mining Face

Compared with the coal seam mining in general working face,the coal seam mining in composite roof fully mechanized mining face is different,The composite roof is composed of the roof of two or more layers of thin rock layers.The adjacent rock layers are very different in lithology and weak alternately.There are coal lines or weak interlayer between the rock layers,so the roof is prone to collapse,and the collapse is sudden,which increases the difficulty of support.Due to the lack of mastery of roof weighting law and surrounding rock control effect,safety accidents such as roof caving in front of support,serious coal wall spalling,false roof connection and collapse of support occur frequently.Therefore,it is very important to study the law of strata behavior and the stability of support-surrounding rock in composite roof face.In this paper,the 7₂42 fully mechanized coal mining face in Suntuan Coal Mine is taken as the research background,and the laws of surrounding rock activity and the interaction between support and surrounding rock during coal mining are studied.The main research conclusions are as follows:（1）The distribution law of stress and displacement of surrounding rock in compound roof stope is studied by numerical simulation.The simulation results show that with the increase of strata dip angle,the stress reduction area gradually develops from"arch"shape to"spoon"shape,and the advance abutment pressure of working face decreases with the increase of strata dip angle.With the continuous advancement of the working face,the stress distribution is asymmetric,the advance abutment pressure is increasing,and the displacement and subsidence of the roof are gradually increasing.（2）The FLAC^3Dnumerical calculation model of non-composite roof face is established and compared with composite roof face.It is concluded that with the increase of advancing distance,the stress release of composite roof face is larger,and the maximum difference of abutment pressure with the lower end of non-composite roof is 22.4%.In the process of coal seam mining,the displacement and subsidence in the middle of composite roof face is large,and the maximum displacement difference between composite roof face and non-composite roof face is about 8.2%.（3）By establishing the mechanical model of face roof failure,this paper studies the evolution law of face roof deflection of fully mechanized mining face with composite roof under different influencing factors,such as face distance,rock dip angle,elastic modulus and direct roof thickness.It is concluded that the maximum deflection point of the roof along the inclined direction of the working face is（a,3.529b/π）under the action of uneven load.The stress analysis of the directly roof,the basic roof fractured rock block and the support in the fully mechanized mining face with composite roof is carried out,and the supporting ability of the hydraulic support to the roof is studied in detail.（4）The 3DEC numerical calculation model is established to study the control effect of hydraulic support on the end face roof under the conditions of different control parameters,such as the distance from the end face,the working resistance of the support,the basic roof pressure and the thickness of the direct roof.The theoretical analysis results are verified,and it is concluded that controlling the distance between the end faces below 0.45m can effectively control the roof leakage and coal wall spalling;When the working resistance is greater than 6000k N,the damage degree of the end face roof and the front coal wall can be effectively reduced;The instability of the roof when the roof basically comes under pressure is stronger than that during the non-pressure period,which is mainly manifested in the degree of coal wall spalling in front,and there is little difference in the situation of roof falling in front of the frame.The roof caving height of the end face decreases with the increase of the thickness of the direct roof,and the greater the thickness,the better the control effect of the stope roof.（5）According to the on-site mine pressure measurement of 7₂42 working face,combined with the analysis of weighting time and advancing distance,the first weighting step and periodic weighting step are obtained.It is concluded that the weighting law of the working face is sequential,and the first weighting occurs at the upper and lower parts of the working face;With the continuous advancement of the working face,the weighting in the middle of the working face is the fastest,and the periodic weighting step is the smallest,followed by the upper measuring area and the tail;The average working resistance of hydraulic support is 29.51MPa,which is 72.33%of the rated working resistance.The distribution characteristics of working resistance of hydraulic support are analyzed,and it is concluded that ZY6800/14/28 hydraulic support can meet the roof control requirements of 7₂42 working face.Figure[54]Table[10]Reference[82]...