| Coal seam mining in fold structure area is prone to complex dynamic hazards of roof,which has great influence on coal mine safety production.In this thesis,taking the fold structure area of Yangdong Coal Mine as an example,the fold distribution characteristics of Yangdong Coal Mine were statistically analyzed,and the causes and basic types of folds were analyzed.Then,the stress distribution characteristics of fold area were explored,and the numerical simulation of fold was built by FLAC3 D,and the stress energy evolution and roof failure law of mining in fold structure area were systematically studied.At the same time,based on the mechanics of materials and elasticity,the mechanical model of roof sudden instability is established,and the mechanical mechanism of roof sudden instability in different fold areas is discussed.The numerical model of large fold structure is established by Rhino and FLAC,and the mining stress energy distribution and roof failure characteristics of macro stope are analyzed.The main conclusions are as follows:(1)Different parts of the fold have different stress distributions;According to the stress state of each part of the fold,it can be divided into five areas,and the stress distribution characteristics of each area are different,which leads to different disasters easily caused by coal seam mining in each area.(2)The results of numerical simulation show that: the closer to the anticline shaft,the smaller the advance abutment pressure is,while the vertical stress increases slightly when the mining is far away from the anticline shaft,and the vertical stress increases when the distance is closer to the anticline shaft;At the same time,with the increase of mining area,the arch stress reduction area formed by the roof of the working face also continues to expand;The energy accumulation and release degree of syncline is the highest,and the influence range is the largest,followed by fold wing and anticline is the smallest.In the mining process of working face from anticline shaft,fold wing and syncline shaft,the scope of plastic zone gradually expands;According to the dynamic load response of working face roadway after roof dynamic load,the roadway side is the most affected by dynamic load.For the stress fluctuation effect caused by dynamic load,the syncline axis has the greatest influence,the folded wing is the second,and the anticline axis is the smallest.(3)The stress distribution in each region of the fold structure area and the mechanism of sudden roof instability are analyzed theoretically.The results show that the horizontal stress of the anticline axis increases with the initial length of the fold,while the vertical stress decreases.The influence law of horizontal stress distribution in syncline is opposite to that in anticline.The horizontal stress and vertical stress in the wing region are symmetrical about the vertical coordinate axis.(4)Rhino and FLAC are used to build the numerical model of large-scale fold structure,and the stress energy distribution and roof failure characteristics of the working face in macro stope are analyzed.It is found that a certain range of stress concentration areas are formed in the shaft areas of syncline and anticline after the working face is mined.With the mining of the working face,the high stress concentration areas gradually shift to the vicinity of the shaft areas of syncline,and the plastic areas of anticline are about 60 m in roof and 30m;in floor.When mining in inclined shaft,the damage range of plastic zone of roof and floor rapidly expanded to130 m and 40 m.The plastic zone formed by mining in No.8472 working face of Yangdong Coal Mine is about 40 m in roof and 30 m in floor,which is consistent with the field measurement results. |
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