Layered Grouting Reconstruction And Stability Control Of Roadway Fracture Coal And Rock Bearing Structure

Due to the development of primary fractures in the surrounding rock of the roadway,the surrounding rock of the roadway is broken after excavation,and it is difficult to form a stable bearing structure with conventional support.After support,the roadway still undergoes deformation and destruction.In response to this difficult problem,this paper takes the support of the coal roadway along the bottom of the thick seam ZF3806 working face in Shuiliandong Coal Mine,Binxian County,Shaanxi Province,as the engineering background and comprehensively uses research methods such as field investigation,laboratory mechanical experiments,theoretical analysis,physical similarity simulation experiments,numerical simulation,and engineering field tests to conduct in-depth research on the deformation and instability mechanisms of the roadway’s broken top coal,soft direct roof,and layered grouting to reconstruct the top bearing structure of the roadway.The main research results are as follows:(1)Drilling and coring were carried out on the surrounding rock of the mining roadway in ZF3806 working face,and indoor rock mechanics tests were conducted.The mechanical parameters of the top coal and roof strata were obtained.The analysis of their deformation and failure characteristics showed that the shallow coal body at the top of the roadway was highly fractured,and the deep roof strata developed fissures,resulting in difficulties in roadway support.(2)Using two geophysical exploration methods,channel wave detection and microseismic monitoring,the fracture zone of the roof of the stoping roadway in the ZF3806 working face of Shuiliandong Coal Mine was detected.The channel wave detection results show that there are six fracture areas around the roadway.The microseismic monitoring results show that this method can not only detect the crack and expansion of surrounding rock and guide roadway support,but also monitor the grouting support effect of the roadway roof surrounding rock.(3)The mechanical mechanism of grouting action on fractured coal and rock mass is analyzed,and the relationship between the shear strength of the fracture surface and the surface roughness is derived based on Barton’s formula.It is believed that the friction effect after the closure of the rock fracture can enhance the shear strength of the rock.Based on the maximum circumferential stress composite fracture criterion of fracture mechanics,the expression of the fracture stress field and displacement under the influence of the slurry adhesive force under biaxial unequal pressure conditions are derived,indicating that the adhesive force generated by the slurry condensate inhibits the initiation of cracks.(4)"Shallow bolt+deep cable" layered grouting is proposed to reconstruct the bearing structure of fractured coal and rock mass so as to form a composite beam bearing structure composed of a "shallow" bearing beam and a "deep" bearing beam,and a mechanical model of the fixed support beam of the composite beam bearing structure is established.The bending capacity of a single-layer bearing beam and the bending moment,deflection,and maximum normal stress of a superimposed beam bearing structure are analyzed.(5)Physical similarity simulation of layered grouting reinforcement for fractured coal and rock roadway roofs was carried out.The experimental results show that the top coal and the layered grouting reinforcement of the direct roof have a significant inhibitory effect on the deformation of the roadway and have no significant impact on the floor and both sides.At the same time,they can effectively improve the stress environment of the surrounding rock of the roadway,reduce the deformation and damage of the roof,improve the stability of the roadway roof,and exert the bearing capacity of the superimposed beam bearing structure at the top of the roadway.(6)The field test of layered grouting reinforcement support for the mining roadway in ZF3806 working face of Shuiliandong Coal Mine was carried out,and numerical simulation verification was conducted.The results showed that after using the layered grouting method of "shallow bolt + deep cable",the roadway roof subsidence and roof separation amount were significantly reduced,the roadway surrounding rock stability was significantly improved,the roadway integrity was good,and there was no deformation or damage under the original support scheme.The displacement and floor heave of both sides of the roadway are within a controllable range,ensuring safe mining while reducing the cost of later maintenance of the roadway.