Experimental Evaluation and Stress–Fractional Modeling of the State-Dependent Behavior of Rockfill

Abstract

As one of the main filled materials of the Lianghekou (LHK) rockfill dam, the strength and deformation characteristics of LHK rockfill is of great interest for hydraulic and geotechnical engineers. Correct interpretation of the state-dependent behavior of LHK rockfill is necessary for the design, construction, and operation of the dam. Therefore, a series of large-scale triaxial tests on LHK rockfill with different initial states were carried out in this study, where the state-dependent strength and deformation behaviors of LHK rockfill were investigated. It was found that both the phase transformation state and peak state of LHK rockfill are dependent on the material state. To capture such state-dependent behavior, two elastoplastic models (i.e., α1-model and α2-model) based on different stress–fractional concepts were developed and compared. It was found that the fractional order (α1) in α1-model exhibits insignificant dependence on the material state of LHK rockfill, whereas the fractional order (α2) in α2-model is dependent on the material state. As the fractional order determines the plastic flow direction of rockfill, it should be identified carefully, otherwise, an overestimation or underestimation of the critical-state stress may occur when using α2-model. Further validation against the large-scale triaxial data of LHK rockfill shows that without using additional plastic potentials, the two models can reasonably reproduce the state-dependent behavior of LHK rockfill. A slightly better performance on simulating the stress–strain response is observed when using α1-model, whereas α2-model works better when simulating the stress–dilatancy response.