Characteristics Of "Load-Bearing And Permeable" Area Of Coal Pillar Dam In Underground Reservoir Of Coal Mine

The seepage performance of coal pillar dam are the key factors affecting the longterm stability of the dam.By using field investigation,theoretical analysis,laboratory test,numerical simulation research methods an effective evaluation model is established to predict its bearing-penetration characteristics and hidden safety hazards during service period.According to the strata control theory and salamon theoretical model,the three-dimensional stope stress environment of the coal pillar dam body was recon-structed based on FLAC3D numerical simulation platform.According to triaxial seepage test data from the similar strength properties of coal rock,we estabalished the the quantitative relationship between axial pressure,confining pressure,permeability and starting pressure gradient of coal and rock samples.The research show that:The influence of confining pressure on permeability of coal sample is obviously greater than axial pressure.When head pressure difference is less than or equal to 1MPa and lateral pressure is greater than or equal to 2.75MPa,no matter how the axial pressure changes,the unbroken coal samples was almost lose their water-passing capacity.The coal pillar dam with lower natural permeability and larger buried depth is easy to have greater water-proof area which increases along with the distribution range of high stress concentration on pillar.According to the evolution mechanism of permeability property of coal rock(block)at different scales during loading,the relation of partial permeability property of coal rock(block)at different scales,such as"indoor rock sample,intermediate scale rock mass and macro engineering rock mass",was put forward.The fluid-mechanical model coupled parameter transfer system was established according to the mechanism.Combined with three-dimensional stope stress environment and fluid-mechanical model coupling parameter transfer system,the seepage characteristics of coal pillar dam under mining disturbance of adjacent working face were predicted.The research show that:The conditions for the existence of irregular water-proof area are as follows:the natural permeability of coal sample is less than or equal to1×10^-14m²,the Poisson's ratio of coal sample is about 0.2,the buried depth of coal seam is greater than or equal to 440m,and the height of reservoir water level from the bottom of coal seam is less than or equal to 13m.The part of pillar which is disturbed seriously is easy to appear the top and bottom communication seepage channel.Low seepage threat exists at the side of roadway ahead of stopping mining line.There are 35 figures,4tables and 62 references in this paper.