| With the high intensity and large-scale mining of coal,the annual consumption of coal roadway gradually increases,and the current situation that the driving speed is far behind the mining speed makes the mining relationship unprecedented tense.As one of the main working procedures of coal roadway driving,the reasonable selection of its parameters is an important prerequisite to ensure the safety of driving construction and improve the driving speed of the coal roadway with compound roof.In the process of fully mechanized excavation of coal roadway,if the lag distance of support is too large,roof caving in the empty roof will occur easily.If the distance is too small,it will increase the number of drifting cycles,and then reduce the driving speed.In addition,the insufficient strength of the permanent support is easy to cause accidents,and improving the strength of the support will often increase the support time,reduce the operating rate of comprehensive excavation equipment,and then limit the improvement of the driving speed.Therefore,how to design reasonable support parameters and construction process,on the premise of ensuring construction safety,to maximize the speed of comprehensive excavation of coal roadway,has become an urgent problem to be solved in the production process of coal mine.In this thesis,the 53122 return airway of Zhaozhuang Mine is taken as the engineering background,the methods used include field research,theoretical analysis,numerical simulation and field engineering tests,systematic research the restricting factors of the speed of comprehensive excavation in the coal roadway with compound roof,geomechanical characteristics of surrounding rock of coal roadway,gradual evolution law and influencing factors of the stability of the composite roof in the fully mechanized coal roadway,deformation and failure mechanism of composite roof in empty area and support area.This paper reveals the stability mechanism of the composite roof in the empty and support area of the fully mechanized coal roadway,and then puts forward the safety control technology of composite roof in the fully mechanized coal roadway,and carries out the comprehensive excavation practice in the composite roof coal roadway.The main results are as follows:(1)Based on the factor analysis of the questionnaire on the restrictive factors of the comprehensive excavation speed of the coal roadway with compound roof in Zhaozhuang Mine,the restrictive factors of the comprehensive excavation speed of the coal roadway with compound roof are obtained.The factors that affect the speed of comprehensive excavation of the coal roadway with compound roof in Zhaozhuang Mine mainly include five aspects: factors of surrounding rock's safety control technology,engineering geological environment factor,driving equipment factor,staff quality factor and construction management factor.(2)The gradual evolution law and influencing factors of the stability of composite roof in the process of fully mechanized excavation of coal roadway are analyzed,and the stability mechanism of composite roof in different space areas of fully mechanized coal roadway is revealed.The stress,deformation and plastic failure of the composite roof in the fully mechanized coal roadway are gradually evolving along the axial direction and the depth direction of the roof.Especially in the shallow strata of the roof in the empty and support area in the fully mechanized coal roadway,the stress is reduce significantly,the bearing capacity is sharply reduce,and the deformation is gradually increased.The influence of surrounding rock conditions,driving parameters and roadway support on the stability of composite roof in the support and empty area of fully mechanized driving coal roadway shows that,the subsidence of the roof in the goaf and support area increases with the increase of the buried depth and the side pressure coefficient.The subsidence of the roof in the empty roof area and the supporting area decreases nonlinearly with the increase of the thickness of the strata.The subsidence of the roof in the empty and support area increases with the increase of the driving width of the coal roadway,and the increase shows a nonlinear decreasing feature.The subsidence of the roof in the empty roof area and the supporting area decreases with the increase of the comprehensive excavation speed.The subsidence of the roof in the empty roof area and the supporting area increases with the increase of the driving cycle distance.The subsidence of the roof in the empty roof area and the support area increases with the increase of the lag distance of support.The roof in the empty roof area is more sensitive to the lag distance of support than that in the support area,and the vertical maximum displacement and its position are closely related to the lag distance of support.The influence of support strength on the roof of support area is obviously higher than that on the roof of empty roof area.(3)Constructed the mechanical model of the composite roof in the empty area and the supporting area,analyzed the deformation and failure characteristics and the influencing factors of the stability of the composite roof in the empty area and the supporting area,the deformation and failure mechanism of the composite roof in the empty roof area and the supporting area is further revealed.Established the mechanical model of composite roof with one side simply supported and three sides fixed,and the deflection and stress formula of composite roof at any point in the empty area is solved by the theory of elasticity.Under the combined action of horizontal stress and deadweight of rock strata,the composite roof in the empty area takes the lead in deflection and subsidence,resulting in interlayer separation and shear dislocation.With the further increase of deflection,the lower surface of the roof in the empty area produces large tensile stress,and the surrounding edges produce large shear force.When the tensile stress or shear stress exceeds the ultimate strength of the roof rock strata,the roof will occur Instability.According to the stress value of the lower surface of the roof in the empty,according to the tensile stress failure criterion,it is determined that the empty-support distance of the fully mechanized coal roadway in Zhaozhuang Mine is not more than 4.64 m.The empty-support distance decreases with the increase of the roadway's width and the overlying load,and increases with the increase of the thickness of the roof strata in the empty.Established the mechanical model of elastic foundation beam for anchorage composite roof in support area of fully mechanized coal roadway,obtained the basic characteristics of the deflection distribution of the roof in the support area.The influences of the depth of burial,the vertical stress concentration coefficient,the elastic modulus of the roof strata,the elastic modulus of coal rib coal,the thickness of the coal rib foundation and the roadway driving width on the bending deformation of the roof in the support area are systematically studied.Under the combined action of overburden pressure,deadweight and high-horizontal stress,the anchored composite roof in support area produces bending deformation,the continuity and integrity of the anchored rock beam of the composite roof are destroyed by the interlayer separation and shear dislocation,and it will lose stability under the combined action of tensile stress and shear stress.(4)Puts forward the coupling support technology of "beam-arch" bearing structure with prestressed bolt and anchor cable as the main body of support and its step-by-step support technology to composite roof.Analyzed the reasons for the influence of surrounding rock prevention and control measures on the speed of fully mechanized excavation of coal roadway:(1)No clarified the stability mechanism of the empty roof for the fully mechanized coal mining face,prevented the roof instability of the roof in the empty blindly by shortening the empty-support distance,so that the number of driving cycles increases,roadheader advancing and retreating more frequently.(2)No-intensive study the spatial evolution law of the composite roof stability and the mechanism of the deformation and instability of the anchored roof,in order to make the roof stable,the one-time and high strength of support is emphasized during the excavation,which results in a long time-consuming supporting process and a low starting rate of the roadheader.(3)Due to the frequent cross transposition between the roadheader and the hydraulic anchor rod drill and the limit of the number of drill trucks allowed to support at the same time,the driving cycle operation time is prolonged.(4)The control of the engineering geological environment is not refined enough,the driving working faces of all the mining roadways in the whole mine adopt the same driving(empty-support distance,circulation step distance)and supporting(row distance between anchor cables,supporting process)parameters,but fail to make dynamic adjustment according to the change of the engineering geological environment in real time.On this basis,puts forward the safety control idea of the composite roof for the fast and comprehensive excavation of coal roadway.After the prestressed anchor is installed in the composite roof,it can not only play the role of "pin" of the anchor,but also increase the friction between the layers,so as to enhance the shear resistance of the composite roof.After the pre-stressed bolt reinforcement and support,the compressive stress formed in a certain anchorage range improves the stress state of the roof,the strength of the roof is greatly improved,and the bearing capacity is significantly enhanced.The anchor cable can not only connect the deep stable rock stratum with the composite beam bearing structure formed by the shallow bolt support,forming a roof composite bearing structure with larger thickness and stronger bearing capacity,It can also increase the shear impedance between the strata,effectively control the roof separation,enhance the continuity of the composite roof strata.With the increase of pre-tightening force of anchor cable and bolt,the superposition degree of medium pressure stress of composite roof increases gradually,which is helpful to form a bearing structure with greater rigidity of roof.With the decrease of the spacing of anchor cable and anchor bolt,the superposition degree of support stress field will gradually increase.However,the range of bearing structure will be reduced even though the stiffness of bearing structure becomes larger when the spacing is too small.With the increase of the length of the anchor cable,the medium pressure stress range of the roof is increasing along the height direction of the roof,while the effective support stress is decreasing.The formation of the balanced arch of the natural bearing structure of the compound roof of the coal roadway makes the strata with insufficient self stability capacity in the arch become the key point of the roof stability control.At the same time,because the composite roof of coal roadway has the engineering characteristics of gradual caving layer by layer,the key to maintain the stability of the composite roof is to enhance the self-stable ability of the strata in the arch and fully mobilize the bearing capacity of the natural bearing structure to make its interaction.Based on this,puts forward the coupling support technology of "beam-arch" bearing structure with prestressed bolt and anchor cable as the main body of support.Meanwhile,based on the significant spatial effect of the excavation face of the comprehensive excavation of coal roadway,and the full use of the self-bearing ability of the surrounding rock,puts forward the step support technology of fast comprehensive excavation in coal roadway.(5)Based on the "beam-arch" bearing structure coupling support technology of composite roof and the step-by-step support technology of the fully mechanized coal roadway,selected the typical coal roadway as the test roadway,and the field test of comprehensive excavation of composite roof coal roadway is carried out,which has achieved good application results.Combined with the comprehensive excavation construction conditions of Zhaozhuang Mine and the engineering geological conditions of 53122 return airway,give full play to the supporting characteristics of prestressed bolt and anchor cable,and take the construction of "beam-arch" bearing structure of coal roadway composite roof as the starting point.The scheme of timely safety support and lagging stability support was formulated,optimized the comprehensive excavation process and construction organization management.The test results show that while the surrounding rock of the coal roadway remains stable,the comprehensive excavation speed increases from9.6m/d to 12 m /d,with an increase rate of 25%. 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