Microstructure evolution in anisotropic tight sandstones under hydrostatic loading and unloading processes  

作　　者：Xiaying Li Haimeng Shen Qi Li 

机构地区：[1]State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan,430071,China [2]University of Chinese Academy of Sciences,Beijing,100049,China

出　　处：《Journal of Rock Mechanics and Geotechnical Engineering》2025年第3期1528-1538,共11页岩石力学与岩土工程学报(英文)

基　　金：supported by the National Natural Science Foundation of China(Grant No.U2244215);the Knowledge Innovation Program of Wuhan-Basic Research(Grant No.2022010801010159);the Major Project of Inner Mongolia Science and Technology(Grant No.2021ZD0034).

摘　　要：Preexisting cracks inside tight sandstones are one of the most important properties for controlling the mechanical and seepage behaviors.During the cyclic loading process,the rock generally exhibits obvious memorability and irreversible plastic deformation,even in the linear elastic stage.The assessment of the evolution of preexisting cracks under hydrostatic pressure loading and unloading processes is helpful in understanding the mechanism of plastic deformation.In this study,ultrasonic measurements were conducted on two tight sandstone specimens with different bedding orientations subjected to hydrostatic loading and unloading processes.The P-wave velocity was characterized by a similar response with the volumetric strain to the hydrostatic pressure and showed different strain sensitivities at different loading and unloading stages.A numerical model based on the discrete element method(DEM)was proposed to quantitatively clarify the evolution of the crack distribution under different hydrostatic pressures.The numerical model was verified by comparing the evolution of the measured P-wave velocities on two anisotropic specimens.The irreversible plastic deformation that occurred during the hydrostatic unloading stage was mainly due to the permanent closure of plastic-controlled cracks.The closure and reopening of cracks with a small aspect ratio account for the major microstructure evolution during the hydrostatic loading and unloading processes.Such evolution of microcracks is highly dependent on the stress path.The anisotropy of the crack distribution plays an important role in the magnitude and strain sensitivity of the P-wave velocity under stress conditions.The study can provide insight into the microstructure evolution during cyclic loading and unloading processes.

关 键 词：Plastic deformation P-wave velocity Discrete element method(DEM) Cyclic loading and unloading Crack evolution 

分 类 号：TG1[金属学及工艺—金属学]