Research on development law of repeated mining overburden fractures in close inclined multiple coal seams

DONG Xufeng; GAO Weifu; ZHU Haifeng; SUN Wenbin; CAO Yining; CHEN Houcheng

doi:10.13347/j.cnki.mkaq.20241284

Abstract：In the field of roof water hazard prevention and control,the evolution height of water conducting fissure zone is one of the important parameters of water hazard prevention.In order to study the evolution law of repeated mining induced water fracture zone in close inclined coal seam,the 1505 working face of a mine was taken as the research object by theoretical analysis,numerical simu-lation and field measurement.Based on the geological conditions of the working face and the fracture characteristics of overlying rock,the mechanical model of the overlying rock composite beam is established,and the theoretical prediction formula of the water-induced fracture zone is deduced according to the model and the mine pressure control theory;using FLAC3D numerical simulation software,a numerical model was established,which was influenced by four factors:cumulative mining height,slope length of work-ing face,tensile strength of overlying strata and mining depth of working face.The relation curves of the water-conducting fracture zone and each factor were analyzed,and the rationality of the theoretical prediction formula was verified.The rationality of the theor-etical prediction formula is further verified according to the measured values in the field.The results show that the height of the re-peated mining water-conducting fracture zone is 48.5 m,and the height of the repeated mining water-conducting fracture zone shows a trend of"rapid growth-steady growth-gradually stable".The three factors of cumulative mining height,oblique length of working face and mining depth are positively correlated with the development height of water-conducting fracture zone,while the tensile strength of overlying strata is negatively correlated with the development height of water-conducting fracture zone.The theoretical prediction formula calculated the development height of the repeated mining induced water fracture zone as 47.6 m,the field meas-ured value as 47.23 m,the empirical formula calculated as 45.6 m,the theoretical calculation results are closer to the measured value.The prediction formula can be used as the basis for calculating the evolution height of the repetitive mining water-conducting frac-ture zone in close coal seam,and provide a certain reference for predicting the development height of the repetitive mining water-conducting fracture zone in similar geological conditions.