Experimental investigation on multiscale damage characteristics of plagioclase amphibolite under water immersion

Abstract

Water immersion significantly influences the mechanical characteristics of rock materials, with the degradation of these properties often leading to engineering hazards. Understanding the micro mechanism of rock-water interaction is crucial when evaluating the mechanical behavior of a rock mass. A series of multiscale tests were conducted to investigate the micro and macro behaviors of Plagioclase amphibolite, sourced from Gansu, China, under water immersion conditions. The results indicated that the micro particles transitioned from a flake-dispersed structure in a dry state to floc clusters after 20 days of immersion. The surface micro morphology was analyzed using a laser scanning machine, revealing a transformation from a smooth state to roughness, attributed to the emergence and swelling of numerous micro humps. The evolution of parameters such as the standard deviation of the height distribution (Sq), profile area ratio(Sdr), and the root mean square of the first derivative of surface (Sdq) demonstrated that the rock expanded uniformly, with the micro grains swelling to varying degrees. NMR-based porosity testing suggested an exponential increase in damage, leading to the interconnectedness of newly formed micro-pores with neighboring ones due to water immersion. Ultimately, the water-induced porosity doubled compared to the original porosity. Additionally, the axial swelling rate exhibited a corresponding increase in tandem with the growth in porosity, with an average value of 0.141 %. Finally, linear functions were established between uniaxial compressive strength, elastic modulus, and axial swelling rate. These findings offer a comprehensive understanding of the multiscale evolution characteristics of Plagioclase amphibolite under water intrusion.