The Occurrence Characteristics of Thin Bedrock and the Numerical Simulation of Overburden Failure Law Induced by Mining

摘要

Firstly, the occurrence characteristics of thin bedrock, water type, Shanxi formation coal seam sections and hydrogeological features were analyzed in research coal field. The elevation contour of the bedrock surface was made from the borehole data by Sufer software. Based on the geological and mining conditions, using discrete element numerical simulation, the overburden failure law and characteristics of strata pressure behaviors were studied under thin bedrock during coal mining. The results indicated that under the conditions of thin bedrock, the fracture length of old roof pressure decreased, the distribution range of abutment stress ahead of the working face was 15m, the peak point of abutment pressure in front of working face was in the range of 5-15m, smaller than working face of thick bedrock, but the strata pressure behaviors of the working face were clear. The development heights of caving zone and water flowing fractured zone of difference thickness of coal seam were calculated. The concept of thick unconsolidated layer and thin bedrock was defined, that was the overburden thickness less than the development height of water flowing fractured zone, meanwhile, the thickness of upper unconsolidated layer more than 100m. The influence degree of coal layer safety mining was assessed. The appropriate measures on prevention and cure of water were submitted purposefully, which has been confirmed by the field tests and assured that no water-intrusion hazard or sand rush would occur.