Research on Failure Law of Mining Floor under Close Distance Coal Seam Goaf
To study the influence of the upper coal goaf in close distance coal seams on the failure of the lower coal mining floor,taking the 8199 working face of Tashan Mine as an example,the failure depth of the working face floor is estimated through statistical formula and plastic mechanics formula;using bidirectional loading similarity simulation experiments to analyze the impact of roof with or without goaf on the floor failure;using the"specialized electrode cable direct current method"to observe the changes in the apparent resistivity of the floor during mining process on site,and obtain the maximum failure depth of the floor.The results show that the failure depth of the 8#coal floor is influenced by the combination of roof goaf and floor lithological association;the existence of the roof goaf reduces the initial stress of the floor during the mining of the 8#coal,weakens the degree of stress concentration,and reduces the step distance of direct roof collapse during the stoping process,which easily forms a"short masonry beam"structure.The periodical weighting of the roof is accompanied by the expansion of cracks of the floor;the measured maximum failure depth of the working face floor is 17.1 m.Compared with statistical formula and plastic mechanics formula,the predicted values are reduced by 11.4%and 7.8%,respectively.The plastic mechanics formula has better applicability.
close distance coal seamfloor failure depthsimilarity simulationdirect current method
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