Influence of bedding structure on stress-induced elastic wave anisotropy in tight sandstones

作     者：Xiaying Li Xinglin Lei Qi Li Dianguo Chen Xiaying Li;Xinglin Lei;Qi Li;Dianguo Chen

作者机构：State Key Laboratory of Geomechanics and Geotechnical EngineeringInstitute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of SciencesBeijing100049China National Institute of Advanced Industrial Science and Technology(AIST)Tsukuba305-8567Japan Chongqing Dizhiyuan Geology and Engineering Testing Co.LtdChongqing401329China 

出 版 物：《Journal of Rock Mechanics and Geotechnical Engineering》 (岩石力学与岩土工程学报（英文版）)

年 卷 期：2021年第13卷第1期

页      面：98-113页

核心收录：

学科分类：08[工学] 080104[工学-工程力学] 0818[工学-地质资源与地质工程] 0815[工学-水利工程] 0813[工学-建筑学] 0814[工学-土木工程] 0801[工学-力学（可授工学、理学学位）] 

基　　金：The research was partially supported by the National Natural Science Foundation of China(Grant Nos.41902297,41872210) the Natural Science Foundation of Hubei Province(Grant No.2018CFB292) Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.Z017006). 

主　　题：Elastic wave anisotropy Stress-induced anisotropy Anisotropy reversal Bedding orientation Microstructure Tight sandstone 

摘      要：To understand the evolution of stress-induced elastic wave anisotropy,three triaxial experiments were performed on sandstone specimens with bedding orientations parallel,perpendicular,and oblique to the maximum principal stress.P-wave velocities along 64 different directions on each specimen were monitored frequently to understand the anisotropy change at various stress levels by fitting Thomsen’s anisotropy equation.The results show that the elastic wave anisotropy is very sensitive to mechanical loading.Under hydrostatic loading,the magnitude of anisotropy is reduced in all three specimens.However,under deviatoric stress loading,the evolution of anisotropic characteristics(magnitude and orientation of the symmetry axis)is bedding orientation dependent.Anisotropy reversal occurs in specimens with bedding normal/oblique to the maximum principal stress.P-wave anisotropyε0 is linearly related to volumetric strain Sv and dilatancy,indicating that stress-induced redistribution of microcracks has a significant effect on P-wave velocity anisotropy.The closure of initial cracks and pores aligned in the bedding direction contributes to the decrease of the anisotropy.However,opening of new cracks,aligned in the maximum principal direction,accounts for the increase of the anisotropy.The experimental results provide some insights into the microstructural behavior under loading and provide an experimental basis for seismic data interpretation and parameter selection in engineering applications.