Grain size and time effect on the deformation of rockfill dams: a case study on the Shuibuya CFRD

Abstract

The mechanical behaviour of coarse, granular geomaterials critically depends on their grain size distributions. In the settlement analysis of rockfill dams, however, the stress–strain curves obtained from specimens with reduced gradations are often used to approximate the behaviour of prototype rockfills. Accumulated evidence has shown that such practice can underestimate the settlement of concrete face rockfill dams (CFRDs), leading to unexpected damage of the concrete slabs and excessive leakage of the dam. In this paper, the recently developed rate-dependent breakage mechanics theory and breakage-energy scaling law is applied for the settlement analysis of the Shuibuya CFRD. The model is first calibrated using triaxial data from reduced specimens and then the parameters are extrapolated to represent prototype rockfills. The constitutive equations are implemented in a finite-element package and later applied to full-scale simulations of the dam, covering its construction, impoundment and operation phases. The predicted settlement profiles agree reasonably well with the data measured from the internal displacement gauges, thus corroborating the predictive capability of the new methodology. Finally, it is shown that neglecting the scaling and creep effect in the constitutive behaviour of rockfills will underestimate the maximum settlement of the dam by 14% and 18%, respectively.