Deterioration Mechanism and Constitutive Model of Coal Subjected to Drying-Wetting Cycles of Salty Mine Water

Abstract

Abstract The stability of coal pillar dams is influenced by cyclic fluctuations of salty water from underground reservoir. Subjected to long-term drying-wetting cycles in salty solution, the microstructure and surface topography of coal dams can be significantly changed which results in the deterioration of mechanical properties. To investigate the damage mechanism of coal subjected to cyclic drying-wetting in salty solution, the uniaxial compression test and microstructure test of prepared coal samples were conducted. The deterioration law of coal under the cyclic drying-wetting in salty solution with different concentrations was obtained. The results show that the unconfined compression strength and elastic modulus logarithmic decrease with cycle numbers in salty solutions with different concentrations. The higher the concentration of salty solution is, the deterioration of coal is more severe. After drying-wetting cycles in salty solution, the granular particles on the coal surface become powdered and the number of holes and cracks in coal increases. A damage constitutive model for coal subjected to drying-wetting cycles of mine water was developed based on experimental results. This model can well describe the deformation characteristics from the compaction stage to failure stage. The research results can provide guidance for the construction and safety operation of underground reservoir.