MODEL TEST AND NUMERICAL SIMULATION OF OVERBURDEN FAI-LURE PROCESS IN MULTI-COAL SEAM MINING

Firstly,the Shanxi formation coal seam sections and hydrogeological features were analysed.Based on characteristic of the associated mining of multi-coal seams and the engineering geological characteristics of overburden,the mining impact pattern of multi-coal seam mining and the dynamic fracture mechanism of overburden were characterized.A comprehensive research method combining engineering geological mechanical model test and finite element numerical simulation was applied.The related strata movement parameters,stress distribution and influence area of multi-coal seam mining were obtained as follows: strike boundary angle=62°,full extraction coefficient=0.95,the greatest subsidence angle=82°,horizontal movement factor=0.39,and deviation of inflection point /mining deep=0.12.The stress distribution of multi-coal seam mining was analysed.The stress concentrated locations at the roof,bottom and surround rocks were determined.The maximum stress concentrations were on the coal wall lines.The bottom stresses tended to transfer into the coal pillar.The development height of caving zone and water flowing fractured zone of multi-coal seam mining were calculated.They were 32 m and 81.5m respectively.The assess of influence degree of coal layer safety mining was that,for the area of influence of height of crack belt reached to the belt of weathering,which didn't form the transfixion,and it penetrated the clay layer partially,there existed the possibility of sand boil when stoping.Some measures for mine water prevention and control should be used.The method of small work face,mining separate layers,mining thickness below the local strictly limit should be adopted.The results were confirmed with the field tests and assured that no geologic hazard would occur.