Research on roof disaster mechanism and prevention under soft water-enriched roof in Yonglong Coalfield

Supports crushing and water inrush disasters are frequent occurrence at Huanglong Jurassic Coalfield in Northwest China. Taking four fully mechanized working faces as engineering background,this study presents the results of monitoring and theory investigation of overburden breaking,strata movements,roof weighting,water inrush from separated fractured spaces,and finally,puts forward prevention measures for above disasters. The results show that the breaking characteristic of key strata is critical to the roof weighting and separation water disasters. The large breaking span and thickness of compound key strata generally cause large periodical roof weighting followed by abnormal strata behaviors during working face advances,which causes bed separated fractures to be generated under the Luo he Group. Subjected to dual effects of water pressure and continuous recharge from aquifer,water in separation breaks through aquiclude and rushes into working face.Based on above viewpoints,early warning system is established,which consists of large periodical roof weighting,abnormal high level warning of support resistance,rapid decline of water table and abnormal strata behaviors. Furthermore,a prevention system for roof and water disasters is established,which consists of predictions for potential disaster locations,top-coal drawing method optimization,and working face managements. The outcomes have contributed to the prevention of water inrush disasters at several panels. This study provides a new methodology and a set of engineering principles for the coal mines with similar geological conditions.