Particle mechanics modeling of creep behavior of rockfill materials under dry and wet conditions

Keywords: Rockfill creep Particle mechanics method Water weakening Wetting–drying cycles Particle breakage Abrasion a b s t r a c t Rockfill is an important construction material for infrastructure engineering, such as dams, railways and airport foundations, which display a long-term post-construction settlement. However, the main mechanisms for rockfill creep and weathering influence still remain poorly understood. Particle mechanics method is used to understand the rockfill creep process under dry and wet conditions. Different bond-aging models and wetting models that represent different degradation and weakening mechanisms are compared, in order to clarify the principle and secondary mechanisms for rockfill creep and weathering influence. The results show that rockfill aggregate breakage in terms of angularity abrasion is the main source for rockfill creep under dry state. Wetting can induce additional strain mainly due to the reduction of contact friction coefficient, i.e. lubrication, and the bond strength reduction just plays a secondary role in producing additional strain. The earlier the wetting occurs during rockfill creep, the more rapidly the rockfill becomes stable. The wetting–drying cycles can induce strain evolution in a 'stepped' way, which is in agreement with experimental observation. The practical implications from the modeling and the outstanding issues in this study are also discussed. Rockfill materials, which are coarse and mainly composed of quarry rock debris or crushed rock fragments, have been widely used in many infrastructure projects, such as dams, railways and airport foundations in mountain area. It is observed that creep settlement at these infrastructures continues for a long period after their construction [52,43]. The operability and safety of railways and airports impose tight limits for post-construction settlements of the supporting embankments. Significant post-construction settlements may affect the infrastructure's serviceability, or even induce engineering disaster. In addition to time-dependent strains under constant external loading, significant rockfill settlement can also be caused by other environmental factors, such as rainfall or flooding. There is therefore a pressing need to clearly understand the physical and chemical mechanisms responsible for rockfill creep under dry and wet conditions, in order to derive more comprehensive constitutive models, interpret safety monitoring records without misleading conclusions, make more reliable predictions of creep settlement and minimize maintenance costs during the infrastructure's working life. Over the years, many laboratory or in-situ experiments have been conducted to study the complex settlement behavior of rock-fill-type materials (Takei et al. among others). The results showed that rockfill creep, during which crushing …