Numerical modelling on water retention and permeability of compacted GMZ bentonite under free‐swelling conditions

Abstract

SummaryIn this study, a solid–liquid–gas coupled equation was established to simulate water retention characteristics of highly compacted GMZ bentonite. Then, modelling results were compared with laboratory test results. Results indicate that GMZ bentonite has a strong moisture expansion (or a limit drying shrinkage) characteristic. The control equation can simulate the water absorption and deformation characteristics very well at high relative humidity (or low suction). Environmental scanning electron microscope (ESEM) observation reveals the course grain soil texture of the surface under low relative humidity (RH), while the surface of GMZ bentonite becomes smooth (more fine‐grained soil texture) as RH increases. Differences were found between the porosities calculated by macroexperiment results and microscopic observations with ESEM method. This is because only the interaggregate pores can be observed by ESEM photographs. Additionally, we find that the simulated effective porosities are close to the results calculated by microscopic tests, while the effective porosity is considered as the main flow channel of flow. Further, the intrinsic permeability, the effective water and gas permeability are calculated based on the proposed model. The modelling results coincide well with the laboratory experimental results and support the reliability of the proposed model.

Evolution of anisotropy with saturation and its implications for the elastoplastic responses of clay rocks

“…Many hydromechanical models in the unsaturated range have been developed to model porous media subjected to drying and wetting process 46–56 . Some of these models 57–59 extend the modified Cam‐Clay (MCC) model 60,61 or the Barcelona Basic Model (BBM) 62 to account for the mechanical behavior of partially saturated materials.…”

“…Many hydromechanical models in the unsaturated range have been developed to model porous media subjected to drying and wetting process. [46][47][48][49][50][51][52][53][54][55][56] Some of these models [57][58][59] extend the modified Cam-Clay (MCC) model 60,61 or the Barcelona Basic Model (BBM) 62 to account for the mechanical behavior of partially saturated materials. Various authors have further extended these plasticity models to account for the effects of evolving anisotropy.…”