Reserch on Strata Behaviors Features and Control Technology of Hard Roof Underground Goaf

In order to solve the problem of roof hanging distance too long underground goaf in coal mining face, the field observation, numerical simulation and exp erimental research method were used, the hard roof control technology was proposed based on analyzsis strata behaviors features of hard roof underground goaf in CO al mining face. The analysis results showed that the periodic weighting were 33、40 m of frist rock beam and second rock beam of coal mining face in No. 22 coal sea m. The dynamic coeficient was 1. 8 during first weighting, during the periodic weighting was 1. 42 ~ 1. 65. The UDEC2 Dnumerical simulation software was used to anal yze the roof migration situation of No.3213 ( 1) coal mining face and obtained the different hard roofs fracture condition between appeared, breakage form, dynamic pr essure characteristics and abscission layer hard roof underground goaf in coal mining face. By using deep hole blasting of forced caving technology could make the har d rock generated a lot of internal conduction fissure space, this technology could make the first weighting of first rock beam decrease 21. 1 m and the second rock bea m decrease of first rock beam 27. 2 m, effective prevention and control of the roof hanging distance too long was achieved.