Structure Characteristic And Stability Analysis Method Of Rectangle Coal Roadway Roof And Engineering Validation

Roof is the key part of roadway stability.The current research of roof stability is mainly based on modelling and field monitering and lacks theoretical basis,which makes the bearing mechanism of roof unclear.Based on the analysis of predecessors' achievements and the boundary condition of roof,the roof was classificated into three types,which are thin roof under uniform load,thick roof under uniform load and composite roof under uniform load.Moreover,this dissertation established a mechanical model for each type of roof and derived the closed-form solution of internal force and sag of roof.The numerical simulation,experiment and engieneering practice were employed to validate the accuracy of the above analytic results,which are in good agreement.Main results are as follows:(1)The closed-form solution of stress distribution of plastic zone and elastic and the plastic width was derived.The numerical simulation was used to validate the accuracy,which are in good agreeement.(2)The closed-form solution of internal force and sag of thin roof was derived The numerical simulation was used to validate the accuracy,which are in good agreeement.There are two types of roof failure under uniform load.One is the failure of normal cross-section caused by the tensile stress,the other is the failure of oblique cross-section caused by the compressive and tensile stress.The research result of stability of thin roof was validated based on the engineering practice of 10209 air-return entry of Tashan coal mine and 1905 S entry of No.3 coal mine of Changcheng.(3)By treating the thick roof as deep flexural beam,the closed-form solution of internal force and sag of thick roof was derived The numerical simulation was used to validate the accuracy,which are in good agreement with the vertical stress of the whole rock and horizontal stress of shallow rock.Since the horizontal stress of deep rock has little effect on the analysis of roof stabiliyty,the error could be neglected.The failure part of roof is mainly in the shallow rock and arch stress system is formed in the deep rock.The research result of stability of thin roof was validated based on the engineering practice of 4101 entry of Changheng coal mine and 1513061 and 1513063 entry of Gushuyuan coal mine.(4)The closed-form solution of internal force and sag of composite roof was derived.The composite roof is usually less stable than thick roof.The first stratum of composited determined the stability of roadway.The caving of roof follows two conditions.One is the failure of coal-rock interface and the other is the failure of oblique cross-section.The shallow rock is in failure and the deep rock formed the arch stress system.The research result of stability of composite roof was validated based on the engineering practice of the mining entries of Shenzhou coal mine.(5)Based on the theory of compressive bar stability,the critical stress of roof stability is derived.The modelling of compressive bar stability by FLAC 3D is conducted.Moreover,the effect of the horizontal stress and the interfical properties on roof stability is studied.The internal force and sag of roof is derived under the vertical and horizontal bending.