Abstract
The lack of understanding of plastic hardening (softening) laws, especially under anisotropic stress con-ditions, results in inappropriate geotechnical management. Most of the yielding envelopes do not con-sider the effect of intermediate principal stress and the influence of Lode's angle. In addition, the application of plastic flow rules regarding yielding surfaces compromises the softening of rock internal friction as well as the influence of Lode's angle on the plastic potential. Moreover, the ductility to brittle-ness transition in the intermediate principal stress direction still requires a theoretical foundation. In this study, based on poly-axial testing results of Yunnan sandstone, we adopted a failure criterion with the intermediate principal stress proposed by Menétrey and Willam. The proposed new failure envelope was applied to capture the plastic evolution of rock samples. A plastic hardening-softening model is con-structed, based on the framework of the plastic theory. The softening envelope is modified to better pre-sent the stress drop and considers the deterioration of rock internal friction in the post-peak stage of poly-axial loading. The differential of plastic potential according to the principal stresses is also modified, considering the rotation of Lode's angle in the poly-axial loading tests. The model results were compared with laboratory testing results, which showed great consistency across 9 different loading tests (5 under triaxial stress and 4 under poly-axial stress with 22 stress-strain curves in total). The induced brittleness by the intermediate principal stress is also well captured by the proposed model.
基金项目
State Key Laboratory Cultivation Base for Gas Geology and Gas Control(Henan Polytechnic University,China)(WS2020A01)
NETL
NSTL
维普
万方数据