Study On Surrounding Rock Control Technology Of Hard Roof Pre-cut Goaf Roadway In Yunjialing Mine

It is easy to have large overhanging roof area and long caving step in roadway along goaf with hard roof,and long cantilever beam will lead to large roadway deformation and coal pillar failure.Based on the cloud drive thick hard limestone ridge9 coal roadway driving along goaf engineering as the background,the theoretical analysis,laboratory rock mechanics test,the physical analog simulation,state and FLAC^3Dnumerical simulation combined with comprehensive methods,such as the industrial experiment,carried out in the lane pre-splitting cut unloading,extremely narrow coal pillar along goaf roadway control research,obtained results are as follows:（1）Through the rock mechanics test,the uniaxial compressive strength of the limestone of Yunjialing No.9 coal seam roof is 81.895MPa,the Brazilian splitting tensile strength is 7.83175MPa,and the triaxial compression test strength is 114.34MPa.Obtained the characteristics of hard and strong integrity of the roof of No.9 coal ash rock.（2）Revealed the mechanism of pre cutting and pressure relief along goaf excavation in the adjacent roadway:the upper section is pre cracked and cut along the groove,and a cutting seam is formed along the mining direction on the edge of the coal pillar,cutting off the horizontal connection between rock block A and rock block B.The load on Block B will not generate force on Block A,and the degree of stress concentration in Block A will be greatly reduced.At the same time,after cutting the roof,after the excavation of the next section along the goaf roadway,the A rock block above the roadway forms a short cantilever beam structure,and the overlying rock structure along the goaf roadway changes from an arc-shaped triangular plate structure to a short cantilever beam structure.（3）Through UDEC analysis of different angles and heights of pre-splitting roof cutting pressure relief along goaf excavation parameters,the optimal parameters for roof cutting pressure relief were obtained.The optimal cutting angle is 10°,and the sliding force of the rocks on both sides of the cutting seam is greater than the friction force.The rocks slide rapidly along the cutting seam,reducing the length of the suspended roof structure,and reducing the load borne by the roadway and coal pillars.The optimal top cutting height is 11m,and the cut rock fully fills the goaf.The goaf rocks,coal pillars,and tunnels form an effective bearing structure to provide support for the overlying strata,achieving the goal of active roof pressure relief.（4）Using FLAC3D numerical simulation technology,numerical simulation models were established for conventional and pre cut goaf driving roadways.The differences in deformation,stress field evolution,and plastic zone distribution of surrounding rock in different mining stages of the two methods were compared and analyzed,revealing the technical feasibility of pre cut roof pressure relief goaf driving near the roadway.（5）Based on the geological conditions of the 19101 and 19103 working faces in Yunjialing Coal Mine,a blasting top cutting and pressure relief plan was designed for the 19101 haulage roadway.After using the technology of pre splitting top cutting and pressure relief along the goaf,Yunjialing effectively controlled the deformation of the surrounding rock of the 19101 haulage roadway,leaving the 19103 auxiliary roadway in a low stress environment.The width of the coal pillar decreased from 20-30m to 2m,and the deformation of the top plate,coal pillar side,solid coal side,and bottom plate of the 19103 auxiliary roadway after roof cutting was reduced by 73%,78%,75%,and62%compared to the corresponding positions of the 19101 auxiliary roadway top.