Research On Synergistic Anchorage Technology Of Gob-Side Entry Retaining With Composite Roof

In the context of the continuous reduction of coal resources,the waste of coal resources caused by the traditional coal mining method coal pillar layout has become increasingly apparent,vigorously promote pillarless mining is imminent.However,in the actual production process,the supporting technology of gob-side entry retaining is not perfect,especially when the stratum conditions are more complicated.Various variable factors in the roadway seriously restrict the normal production of the mine.The technology of gob-side entry retaining with composite roof is particularly important for research and innovation.This paper studies and analyzes the stress distribution law and support parameters of the surrounding rock with the gob-side entry retaining with composite roof based on the principle of synergy and through a combination of field investigation,theoretical analysis,numerical simulation and engineering practice.The main conclusions are as follows:(1)Variation law of stress and displacement of gob-side entry retaining with composite roof show that: The composite roof of the roadway under the action of external forces is very easy to occur under the tensile damage perpendicular to the rock seam and shear damage along the level,resulting in the phenomenon of delamination,and then the occurrence of rock fragmentation and collapse phenomenon,and in the peak stress position of the coal gang will be damaged into the plastic state,the bearing capacity is significantly reduced,the stability of the surrounding rock is difficult to control,so the composite roof along the empty stay of the roadway requires strong support strength to meet the requirements of the stability of the surrounding rock.In this context,the collaborative anchoring theory of roadway surrounding rock provides a more advanced design method for the control of the surrounding rock of gob-side entry retaining with composite roof.(2)Numerical simulations of co-anchoring show that the vertical stress and cocrease in the anchor body increase with the increase of anchor preload;increasing the anchor length increases the compressive stress range in the anchor solid,increases the shallow vertical stress and co-crease,but the increase is decreasing,and the co-crease in the middle of the anchor rod decreases with the increase of anchor rod length.As the anchor rod spacing decreases,the shallow vertical stress and synergistic increment in the anchor solids increase,and the increase tends to increase.The vertical stress and synergistic increment in the anchor body increase with the increase of anchor cable preload;the increase of anchor cable length increases the compressive stress range and synergistic effect range,but the compressive stress and synergistic increment in the middle of the anchor solid are reduced;reducing the anchor cable spacing mainly increases the stress value and synergistic increment in the stress concentration area,and the smaller the spacing,the more obvious the lifting effect.The anchor rod and anchor cable have a coordinated relationship in terms of preload,length and spacing,and the synergistic anchorage effect of both can be fully developed when the above factors reach a coordinated relationship.(3)Based on a site study of 5921 haul road in Longfeng coal mine,it was concluded that insufficient preload on anchor rods and anchor cables in the original support scheme and the design of anchor rods and anchor cables in terms of length and inter-row distance based on experience were the main causes of severe deformation in the roadway.The results show that the anchor rods and anchor cables form a continuous and stable effective compressive stress zone in the tunnel rock under the synergistic action of the anchor rods and anchor cables,and that the bearing capacity of the rock body is significantly increased,while the overall stability of the anchoring system is greatly enhanced.The stresses and displacements of the tunnel rock were simulated,and the feasibility of using the co-anchoring technique to control the surrounding rock of gob-side entry retaining with composite roof was initially demonstrated.(4)Combined with the actual production conditions of 5921 transportation lane in Longfeng coal mine,the cooperative anchoring scheme was further designed,and the corresponding monitoring scheme was designed for the surface displacement,deep displacement and anchor rod-anchor cable force of the lane.The strong anchor rods,high preload anchor cables and steel belts in the cooperative anchoring scheme effectively control the separation phenomenon of the roadway roof,and the anchor rods and anchor cables axial force are all within a reasonable range,which basically meets the requirements of coal mine safety production,verifies the reasonableness and effectiveness of the selected support parameters,and further proves the feasibility and applicability of using the cooperative anchoring technique to control the surrounding rock of gob-side entry retaining with composite roof.This paper has 79 pictures,8 tables,and 82 references.