Study On The Bearing Law And Adaptability Of Hydraulic Support In Three-soft Coal Seam With Large Mining Height

In addition to the three-soft characteristics of the coal seam in Huaibei mining area,most of the coal seams also have large thickness variations,large strike angles and dip angle,there are support drill bottoms,roof caving,coal wall fragments,poor support stability and other issues during mining of the working face.These problems are the major difficulties that are currently plaguing the exploitation of such coal seams in the Huaibei Mining Area.Taking the II883-1 working face of Luling Mine as the research background,the paper comprehensively uses field research,theoretical analysis,numerical simulation,field measurement and other research methods to systematically study the bearing rules and support adaptability in the working face.The main conclusions are as follows:(1)The average working resistance of the working face and the dynamic load of the support during pressure stepping and pressure during the first pressing step and cycle of the old top on the working face,the middle and the lower parts of the work surface are obtained by the field measurement data,the analysis shows that the support in the middle of the working face is larger and the pressure is more obvious.The statistical data of the support column shows that the initial support force of the face support is generally low,and the frequency of the central support work resistance greater than 30 MPa is far greater than that of the upper and lower supports.It also shows that the pressure in the middle of the face is strong;the load on the stent is “unbalanced”."The front and rear column work resistance difference is greater,the front column is significantly larger than the rear column.(2)In view of the unbalanced bearing of the face support and the bottom drilling caused by the loose floor,the hydraulic force analysis model of the face of the working face was established in conjunction with the measured site structural parameters of the support,and the support was covered when the support reached the rated working resistance.The rock pressure,the location of the action point and the concentrated force of the support base were used.Based on the theory of the plastic floor and Winkle elasticity theory,the distribution law of the specific pressure of the floor and the settlement of the floor were studied respectively.(3)The main factors affecting the loading of the soft coal floor are studied.Theoretical analysis shows that the depth of the support bottom has little effect on the critical plastic load of the bottom coal,and the most important influence factor of the critical plastic load is the cohesion of the bottom coal.Numerical simulation results shows: The tensile strength has little influence on the bearing capacity of the bottom coal.The increase of the elastic modulus of the bottom coal can increase the bearing capacity of the bottom plate.The cohesive force and internal friction angle of the bottom coal are the most critical factors affecting the bearing capacity of the bottom plate,the minimum cohesion and internal friction angles that meet the requirement of no damage to the bottom coal are obtained.(4)Simulation of soft coal floor compression resistance process,study of the soft coal floor bearing evolution law,obtained that the maximum depth of bottom coal failure occurs on both sides of the support base,in addition to a large plastic zone in the depth of the bottom coal,plastic zone spreads more in the shallow layer of the bottom coal to the surroundings.Means of mating the wood with the bottom of the artificial support in front of the support are proposed to ensure the smooth advancement of the support.At the same time,the optimal wood placement scheme is selected according to the mining conditions of the working face.(5)The numerical simulation method was used to study the effect of end face distance,supporting force,working resistance and the secondary retaining plate on the stability of the coal wall.It was found that the supporting force was improved,the work resistance of the support was ensured,and the secondary retaining plate was used can effectively alleviate the problem of wall ribspalling.At the same time,the resistance calculation of the support shows that the support can meet the pressure of the strata bearing the overburden.(6)Taking into account the joint impact of the working face to the pitch(tilting)mining angle and working face inclination angle,the stability of the support under free and working conditions were studied.At the same time,the cause of the bracket truss accident occurred during the mining of the working face was analyzed,and the corresponding technical measures for anti-slip and anti-slip of the bracket were proposed.