Mechanism Of Concealed Structure Activation By Karst Water Inrush Due To Deep Coal Mining In Northern China Coalfield

The "deep" of coal exploitation not only refers to the buried depth,but also is a kind of stratum state controlled by geostress,temperature,and chemical field.Karst water inrush caused by concealed structure(faults,collapse columns and structural fractures)is a major threat to deep coal mining in Northern China Coalfield.The characteristics and attributes,activation mechanism,and prevention of deep concealed structure are the significant scientific problems to be solved urgently at present.In this study,based on the physical simulation of underlying coal/rock mechanics properties and pore/fracture permeability during mining,numerical simulation of concealed structure evolution during coal mining,concealed structure activation monitoring,and combined with deep concealed structure detection and grouting reconstruction engineering practice in Northern China Coalfield,several innovative achievements have been reached on concealed structure activation: 1)The structural fracture zone was classified into the concealed structure for the first time,and the characteristics of karst water inrush caused by the concealed structure activation in deep coal mining in Northern China Coalfield were clarified.2)The increase of fracture porosity of the underlying tight sandstone was higher than that of coal and mudstone.The post-peak permeability of tight sandstone was 28 times of its initial permeability.The post-peak permeability was not only controlled by the development of pores and fractures,but also related to the macroscopic fracture mode of rock.3)The activation of concealed structure leads to stress concentration and rupture of the underlying strata,but the influence degree is related to the position of concealed structure.4)The mining fracture-fault-fracture activation,mining fracture-collapse column-fracture activation and mining fracture-collapse column-fault-fracture activation models were established.The activation mechanism of concealed structure is the combination of the tensile stress of the underlying strata caused by coal mining,the weak mechanical strength of concealed structure,and the karstic water pressure.The research results provide a theoretical and technical basis for the mechanism and prevention of karst water inrush in deep lower Taiyuan Formation coal mining in Northern China Coalfield.There are 85 figures,15 tables and 186 references in this thesis.