Investigation of the microstructure damage and mechanical properties evolution of limestone subjected to high-pressure water

The water-weakening effect is one of the most important causes for changes the physical and mechanical characteristics of rock materials, triggering large deformations and failures in rock engineering. To investigate the degradation effect of high-pressure water on a rock material, this study performed laboratory tests on limestone specimens. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) were used to examine limestone subjected to different water pressures, and the results showed that with the water pressure increasing, the dissolution degree and porosity of a limestone specimen increased. Meanwhile, an infrared radiation thermal (IRT) imager was used during uniaxial loading to study the temperature evolution laws of the limestone materials under different water pressures. The phase development characteristics of the stress-strain curve were more obvious, and the average infrared radiation temperature (AIRT) rose in a fluctuating manner during different stages. The AIRT reached an extreme value suddenly before the peak stress and gradually returned to the room temperature after a structural failure. The strength and temperature differences for the specimens continuously decreased with water pressure increasing, with temperature decreases of 5.71%, 12.86%, 18.57%, 22.86% and 24.29% respectively under 2-10 MPa water pressure compared to 0 MPa. In addition, the IRT images intuitively reflected the spatial evolution process for the specimen temperature. There were high temperature anomalies on the IRT image before structural failure, which could be used as the omen of the limestone structure failure.