Deformation and failure characteristics and support technology of deep roadway with composite roof

In view of problems of deep roadway with composite roof, such as easily roof falling, large deformation and difficult support, taking 53182 roadway of Chengzhuang Coal Mine of Jincheng Blue Flame Coal Industry Co., Ltd. as research object, deformation and failure characteristics of deep roadway with composite roof were analyzed. It is found that roof deformation is dominated by shallow separation layer, which mainly occurs at interface of different rock strata. Shear deformation of bolts in top corner and two sides of roof occurs mainly at coal-rock interface, and shear deformation of bolts in the middle of roof is relatively large at weakly cemented strata and interface between anchor section and free section. Roof strata experiences processes of original rock state during initial excavation of roadway, and stable state, critical instability state and instability state after roadway excavation. The numerical simulation results show that with the increase of bolt preload, plastic zone range and vertical displacement of roof decrease obviously, which indicate bolt has better inhibiting effect on roof separation and subsidence. High prestressed bolt plays an active support role and greatly improves self-bearing capacity of surrounding rock. Support countermeasures of deep roadway with composite roof with high prestressed long and short anchor cables combined with steel mesh and W steel strip were put forward, which could greatly improve support stiffness of composite roof, form constraints on roof subsidence and separation, and enhance overall stability of composite roof strata. The engineering practice shows that high prestressed support effectively controls separation and subsidence of composite roof. Shallow separation value is controlled within 30 mm, deep separation value is controlled within 10 mm, two sides displacement is controlled within 80 mm, and roof subsidence is controlled within 43 mm. The above values indicate stability and integrity of surrounding rock.