Simplified material model for analysis of asphalt core in embankment dams

Abstract

Asphalt concrete exhibits time- and temperature-dependent viscoelastoplastic behavior which is difficult to model and implement in practical dam design analyses. The main goal of the paper is to develop a simplified material model for the various types of loading conditions experienced by an asphalt core in an embankment dam. The types of loading conditions are simulated by conducting long-term triaxial creep tests with stepwise loading corresponding to the slow construction of the asphalt core and dam embankment; unloading-reloading cycles corresponding to seasonal reservoir fluctuations, and dynamic cyclic tests corresponding to earthquake loading. The results of the long-term triaxial creep tests show that creep strains accumulate until a “creep-stable state” is reached when virtually no further creep is occurring at that level of sustained deviator stress and temperature, and a corresponding “creep-stable stress-strain modulus” is defined. Based on the test results, a simplified material model expressed in terms of deviator stress is proposed and formulated analytically with a plastic yield boundary (PYB). The unloading-reloading and dynamic behavior was found to be almost linearly elastic, and the unloading-reloading modulus and dynamic secant modulus to be in the order of 20 and 40 times the creep-stable modulus, respectively. The proposed simplified material model and equivalent secant moduli may be used in finite element analyses of the asphalt core and its interaction with adjacent gravel and rockfill zones in the dam.