Evolution mechanism of wave velocity and mechanical properties in coal samples under water-saturated and cyclic stress coupling effects
LI Jie
Abstract：In deep coal mining,the influence of hydro-mechanical coupling on coal mechanical properties is a critical factor indu-cing dynamic disasters.To reveal the damage evolution law of coal under water saturation and cyclic stress disturbance,this study systematically investigated the wave velocity,deformation,strength,and failure characteristics of natural coal samples(Group A),water-saturated coal samples(Group B),and cyclic stress-disturbed coal samples(Group C)through ultrasonic testing,conventional triaxial compression tests,and CT scanning.The results indicate that water saturation effect reduces acoustic wave scattering by filling pores,increasing the longitudinal wave velocity by 18.2%(Group B),however,the cyclic stress disturbance triggers the micro-fracture expansion and the"water-fracture coupling effect",resulting in a 4.44%decrease in the wave velocity of Group C com-pared with the natural group;hydro-mechanical coupling action significantly alters deformation mechanisms:water saturation shortens the compaction stage and weakens yield strength(reduced elastic modulus in Group B),whereas cyclic disturbance induces post-peak stress stepwise decline and residual strength enhancement,and its energy dissipation characteristics are similar to the mechanism of"self-supporting cracks";both water saturation and cyclic stress degrade coal strength,the peak strength of the satur-ated water group(decreased by 28.0%)and the cyclic disturbance group(decreased by 33.0%)was significantly lower than that of the natural group.However,the confining pressure sensitivity of the cyclic disturbance samples was the strongest(the strength in-creased by 174.8%with the confining pressure),indicating that the damaged coal body can restore part of its bearing capacity through confining pressure constraints;hydro-mechanical coupling action leads to different failure modes of coal body.The water-saturated coal samples were mainly subjected to shear failure,while the cyclically disturbed coal samples formed multi-directional fracture zones and lateral expansion.The accumulation of damage was dominated by the"water wedge effect"and fatigue crack propagation,and the shear-tensile combined failure intensified after confining pressure unloading.
Keywords：coal or rock dynamic disastercyclic stresswater saturationmechanical properties of coalstrength characteristicfail-ure characteristic
Publication Date：2025-07-20
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：9( 98-106 )