Analysis of compression failure and acoustic emission characteristics of limestone under permeability-stress coupling

In order to investigate the macro-mechanics behavior and acoustic emission characteristics of limestone with different osmotic pressures,the compression failure test,acoustic emission test and mercury injection test of limestone under different osmotic pressure conditions were carried out by permeability-stress coupling apparatus. The stress-strain curves,peak strengths,characteristic stresses,characteristics of failure and acoustic emission and degradation mecha-nism were analyzed. Results show that with the increase in osmotic water pressure,the compression phases and elastic phases of stress-strain curves are prolonged and shortened,respectively,and the peak strengths attenuate exponentially. The strength degradation coefficients,elastic modulus and deformation modulus all decrease linearly with the in-crease in osmotic water pressure,indicating the damage sensitivity of limestone is increased. Osmotic water pressures have no great influence on fracture forms and the splitting failure is dominant,the limestone fragment uniformity is ex-ponential with osmotic water pressure and peak strength. Due to the structural stability of limestone is weaken by the water-rock interaction,resulting in the early release of strain energy. Osmotic water (pressure) has the effect of disso-lution and crack on limestone,the pore volume per unit mass increases exponentially and the crack initiation stress de-creases linearly with the increase in osmotic water pressure.