近距离煤层群围岩碎裂特征与裂隙分布关系

六家煤矿近距离煤层群裂隙网络发育，为了防止顶板及层内裂隙导水、邻空面瓦斯超限与煤体自然发火等隐患，基于分形理论，以巴西劈裂试验和现场窥视统计试验为研究手段，探讨了岩体碎裂尺度及均匀度对裂隙分形特征的影响。研究表明：劈裂块度分维值越接近2，则破裂后碎块尺度越均匀，表现为存在一条主裂隙将试样大致均分且裂隙面较平整；劈裂块度分维值与2相差越大，碎块尺度差距越悬殊，裂隙面越粗糙。劈裂块度分维值与裂隙分维值之间符合抛物线分布，劈裂块度分维值越接近2，则裂隙分维值越大，表明劈裂块体尺度越接近，岩层内裂隙条数越少、裂隙环越平整且与层面夹角越小；劈裂块度分维值与2相差越大，则裂隙分维值越小，表明劈裂块体尺度相差越悬殊，裂隙条数越多、裂隙面越粗糙且裂隙方位无规律。裂隙分布规律与劈裂碎块尺度大小无关，与碎块尺度均匀性密切相关。

Relationship between failure characteristics and fracture spacing of surrounding rock of short-distance coal seams group

The fracture network of short-distance coal seams group in Liujia Coal Mine is well developed.In order to prevent water conduction caused by fracture in roof and coal seams,gas exceeding the limit in the working face that near goaf,and spontaneous combustion,based on fractal theory,Brazilian splitting test and borehole peeping statistical test,the impact of fragmentation scale and evenness of rock mass on fracture fractal characteristics were investigated.The study shows that the fractal dimension D of split fragmentation is closer to 2,the fragmentation scale becomes more even after fracture.It shows that there is a main crack that roughly divides the sample and the fissure-plane is relatively flat.The fractal dimension D of split fragmentation shows greater difference with 2,the fragmentation scale becomes more uneven and the fissure-plane is rougher.The fractal dimension D of split fragmentation and the fractal dimension D of cracks are in accordance with parabolic distribution.The fractal dimension D of split fragmentation is closer to 2,the bigger the fractal dimension D of cracks.This shows that the fragmentation scale gets more even,the less the number of cracks in the rocks,the more smooth the crack ring and the smaller the angle between the crack ring and interface of rock stratum.The fractal dimension D of split fragmentation shows greater difference with 2,the smaller the fractal dimension D of cracks.This shows that the fragmentation scale gets more uneven,the more the number of cracks in the rocks,the more rough the fissure-plane and the more irregular the crack azimuth.Crack distribution has nothing to do with the splitting fragmentation scale size,but is closely related with the homogeneity of fragmentation scale.