Research On Deformation Mechanism And Control Of Fully Mechanized Caving Roadway In Thick Coal Seam

China's thick coal seam reserves are very rich,and its comprehensive utilization of high-yield,high-efficiency and safety will be one of the main technologies for thick coal seam mining in China in the future,and it will be rapidly developed and popularized.The mine pressure in the fully mechanized caving mining roadway in thick coal seams is severe,the two gangs and the top and bottom plates are moving closer,and the failure of the supporting structure is accompanied by serious damage to production safety and production efficiency.Based on the deformation and failure of the mining roadway in the 18103 fully mechanized caving face in Wangjialing Coal Mine,this paper studies the deformation mechanism and control technology of the fully mechanized caving mining roadway in thick coal seam through three main approaches:on-site monitoring,theoretical analysis and numerical simulation.Through the on-site investigation of the large deformation roadway under the influence of mining and the mine pressure monitoring such as roadway convergence,roof separation and support pressure,the deformation and failure characteristics of the surrounding rock and supporting structure of the mining roadway are mastered.It is indicated that the deformation of the roadway mainly occurs.In the area from 50 m in front of the working surface to 200 m behind the working surface,it is concentrated in the rear 20?150 m section;the working face is pressed to the pressure,which tends to be in the middle of the big end,and the basic top period is inferred.The pressing step is 16?21 m,and the number of basic top fractured rock beams is 3?4.Based on the theory of transfer rock beam,combined with the law of mine pressure appearance of 18103 fully mechanized caving face in Wangjialing Mine,the theoretical analysis of the movement law and mechanical structure of overlying strata in the stope and roadway is carried out.The direct top thickness calculation formula is derived,and the direct top "multi-layer cantilever" structure of the working face is proposed.The calculation formula of the "cantilever"length of each layer is derived,the lateral bearing pressure distribution formula is revised,and the overburden rock layer is calculated.The height of the falling belt,the fissure zone,and the parameters such as the fracture interval of the rock beam are used to establish the mechanical model of the overlying strata structure.The FLAC3D numerical simulation software is used to simulate the variation of the stress field,displacement field and plastic zone of the mining roadway affected by mining and terrain.The results show that the mining roadway is affected by the mining action and the main stress direction of the surrounding rock is promoted with the working face.Deflection,the plastic zone produces asymmetry expansion,the displacement is asymmetrically distributed;the additional stress superposition caused by the terrain of the mining roadway causes the overall deformation of the roadway to be "downhill" to be larger than that of the "uphill".By analyzing the variation law of stress field and displacement field in mining roadway,the deformation mechanism of fully mechanized caving mining roadway is revealed:the supporting pressure around the roadway is increased due to mining,and the stress is inclined,resulting in asymmetric expansion of plastic zone and asymmetric roadway.The deformation,together with the additional stress field superposition caused by the terrain,further aggravates the asymmetry of the deformation.Under the combined action of various factors,it eventually leads to the large deformation phenomenon of the roadway.According to the deformation mechanism of the roadway,the control scheme was designed from three aspects:coal pillar,topping pressure relief and support.The parameters were optimized by FLAC3D numerical simulation software.The results show that with the coal pillar width decreasing,the roadway circumference The stress and plastic zone distribution of the rock gradually deviate from the axis of the roadway,and the stress concentration factor gradually increases.It is more suitable to obtain the coal pillar width of 30 m after comprehensive consideration;with the increase of the cutting height,the stress concentration zone of the coal pillar on the left side of the roadway Gradually moving upwards,and the peak stress is gradually reduced,the plastic zone of the surrounding rock gradually tends to be symmetrically distributed,and the convergence values of the two groups are gradually approaching.It is more suitable to obtain the height of the cutting top at 24 m.The uniform arrangement of the support scheme is designed and The non-uniform support scheme for the key support of weak parts has been numerically simulated and compared,which shows that the deformation of the roadway with non-uniform support scheme is smaller and the support effect is better.