Experimental study on seepage characteristics of red sandstone under triaxial continuous loading

ZHANG Shun; LUO Feng; WANG Jintao; WANG Peng; WANG Tieji; HU Jiaqi; XU Zhenming; HUANG Zhengwen

doi:10.11799/ce202601020

Abstract：To investigate the coupling mechanism between stress and seepage fields in rocks under triaxial continuous loading,seepage characteristics of red sandstone specimens were tested under different pore water pressures.The mechanical response and seepage characteristics of red sandstone under fluid-solid coupling were analyzed.Particle flow numerical simulation coupled with the Fipy method was employed for experimental validation and meso-interpretation,to reveal the development and propagation of cracks as well as seepage evolution under fluid-solid coupling.The influence mechanism of effective confining pressure on volumetric strain,mesoscopic fracture,and seepage was elucidated.The results show that,based on crack volumetric strain,the complete stress-permeability coefficient-strain curve of red sandstone under pore water pressure can be divided into four stages.Under effective confining pressure,a reduction in effective confining pressure at the upper end of the rock specimen promotes force chain breakage and microcrack initiation,thereby increasing seepage velocity and flow.Simultaneously,this leads to stress concentration and localized crack development at the lower end,ultimately inducing macroscopic fracture.Pores and cracks serve as the main channels for seepage,which evolves due to the generation of new pores and cracks under stress.The heterogeneity in pore structure and crack distribution across different regions results in spatial variability of the permeability coefficient.During rock fracture,seepage channels transition from dispersed microscopic pore networks to concentrated macroscopic fracture surfaces,significantly enhancing permeability and forming a continuous and relatively stable seepage path along the fracture surface.