A nonlinear normal consolidation line for bentonite in e-logp space

Abstract

Investigation on compression behavior of bentonite is an important issue for designing the artificial barriers in a geological repository for nuclear waste disposal. However, significantly different from that of non-expansive clays, normal consolidation line of bentonite may be nonlinear in e-lnp plane. Obviously, the linear equation of normal consolidation line in conventional constitutive models could not describe nonlinear compression behavior of bentonite. In this work, compression tests were carried out on GMZ01 bentonite slurry and compacted specimens with suction-control (0, 1, 4.2, 9, 38 and 113 MPa). The mechanisms of nonlinear normal consolidation line for saturated and unsaturated bentonite were analyzed, respectively. According to the test results, an elastoplastic constitutive model framework with nonlinear normal consolidation line for describing compression behavior of bentonite was proposed. In which, a unified equation of normal consolidation line for saturated bentonite specimen related to water content was proposed. Meanwhile, a critical saturation curve was defined in a s-p space to describe the transformation from unsaturated to saturated states during the compression process of unsaturated bentonite specimens. Based on the critical saturation curve, a nonlinear equation of normal consolidation line for unsaturated bentonite was proposed. Finally, the compression test results for bentonite slurry and compacted specimens were simulated by the model newly proposed. Validation shows that good agreements are reached between the simulated results and experimental ones. Obviously, the nonlinear equation of normal consolidation line proposed in this paper could be used in development of constitutive models for describing nonlinear compression behavior of bentonite.