Abstract: To determine the failure characteristics of weak overburden by layered fully-mechanized top coal caving mining, numerical calculation, micro seismic monitoring and transient electromagnetic methods were used in 55003 panel in Laohutai mine to analyze failure height of overburden strata and the relationship between the failure height of overburden and extraction thickness. The results show that the failure height of overburden is linearly related to the extraction thickness under the condition of weak overburden in Fushun mining area, and the failure height of overburden is 8.4 times of extraction thickness. The failure height of overburden with weak layers is smaller than hard overburden in extremely thick coal seam mining. The overburden fracture is mainly controlled by rock structure including oil shale and green shale, and also influenced by F7 fault and F7-1 fault.

Key words: extremely thick coal seam, weak overburden, layered fully-mechanized top coal caving, failure height