| The stability control of roadway surrounding rock is the premise of mine safety production.The stress environment of composite layered roof is particularly complex under the condition of deep mining,and the failure of supporting body is serious.In this paper,the 33082 mining roadway in The Sanpan area of Zhaozhuang coal industry is taken as the research object,and the structural characteristics and separation failure mechanism of composite layered roof are studied by means of laboratory test,theoretical analysis,numerical simulation and field measurement,and the failure mechanism of anchor cable fracture of composite layered roof is revealed.The multi-level zoning control technology for the collaborative support of composite layered roof with long anchor cable,short anchor cable and high strength anchor rod is proposed.The main conclusions are as follows:(1)There are 6～8 m thick composite mudstone strata in the roof of roadway,and the adhesion degree between the roof layers is low,the joints and cracks are well developed,and the stratification characteristics are significant;The stress distribution of bedding plane is not uniform,and the surrounding rock has poor tensile,shear and compressive capacity and weak bearing capacity,which has the structural characteristics and mechanical properties of composite layered roof.(2)The anchor cable is broken in oblique splitting form,mainly in the weak mudstone roof of 1～2 m.This is because the weak composite roof is prone to shallow layer bending separation and deep layer dislocation separation,resulting in a large shear force on the anchor cable,that is,the shear failure of the weak rock mass to the steel strand of large stiffness.(3)The anchor cable shape variable increases with the increase of the thickness of the weak composite laminated roof and the development of cracks and joints.Increasing the pretightening force can improve the stiffness of the weak composite rock layer.Adjusting the installation Angle can control the anchor cable to the shear stress peak point of each layer,improve the shear resistance of the anchor cable and reduce the breaking of the anchor cable.(4)The surrounding rock of roadway is divided into stable region,sub-stable region and non-stable region,and the multi-level zoning control technology of composite layered roof long anchor cable-short anchor cable-high strength extended bolt collaborative support is proposed.The long anchor cable support of 6.4 m is selected in the stable region,and the short anchor cable support of 3.0 m is selected in the sub-stable region.3.4m high strength extension bolt support was selected in unstable area.(5)Engineering verification was carried out in the test section of 33082 roadway.The subsidence of roadway roof stabilized at 240 mm after 90 days,and the bolt and cable were subjected to uniform forces and the failure rate was greatly reduced.The multi-level zoning control technology realized the stability control of composite layered roof. |
