Three-dimensional elastoplastic constitutive modeling of green sandstone within ductile domain

Abstract

During deep underground engineering construction, rocks transition into ductile domain under the influence of high three-dimensional geostress. Therefore, this study proposed a three-dimensional elastoplastic constitutive model incorporating Lode angle dependence within ductile domain. Besides, this study conducts a series of experiments on green sandstone within ductile domain, including hydrostatic compression test and true-triaxial test adopting constant Lode angle loading path. Based on the strength and plastic deformation characteristics of rock within ductile domain, both yield function and potential function are expressed as the product of elliptical equation and deviatoric plane. Both yield function and potential function incorporate parameters that evolve with the plastic internal variable. This enables the yield surface and plastic potential surface to evolve in the deviatoric and meridian planes, providing a more accurate depiction of the stress state and plastic flow direction during hardening. The comparison between proposed model and experimental data of green sandstone validates its applicability and accuracy. A comparison between the associated (yield surface) and non-associated (plastic potential surface) flow rules indicates that the plastic shear strain predicted by the associated flow rule is smaller than that predicted by the non-associated flow rule. To demonstrate the significance of Lode angle dependence in the potential function, a comparison is made between potential functions with and without Lode angle dependence. The comparison results indicate that the potential function without Lode angle dependence overestimates the intermediate principal strain under true-triaxial stress state. The parameter sensitivity analysis reveals that the intermediate principal strain is mainly controlled by deviatoric parameter within potential function. This study provides a theoretical foundation for upcoming numerical simulations of underground engineering within the ductile domain.