ABSTRACT
The resilient modulus (RM) has been used commonly to characterize the behavior of asphalt under repeated loading (Uzan 1985; Witczak & Uzan 1988; Huang 1993). It results essentially in a piecewise linear (elastic) approach to simulate the nonlinear behavior. Although it may be appropriate for computing displacements in pavements, it is not suitable for other important features such as plastic and creep deformations, volume change (dilation), stress path effects, microcracking leading to fracture and softening. It is often claimed that the RM approach is suitable for unbound materials such as soils. However, it is believed that the RM model cannot be suitable for the realistic behavior of soils because it cannot account for plastic and creep strains, volume change, stress path and softening aspects of the soil behavior. Plasticity, viscoelasticity, viscoplasticity, fractures and damage models have been proposed for specific behavior of materials (Lytton et al. 1993; Schapery 1990, 1999; Chelab et al. 2002, 2003; Tashman et al. 2004; Gibson et al. 2003; Gibson & Schwartz 2006). However, they may not be appropriate for the combined behavior involving elastic, irreversible (plastic) and creep, strains, microcracking leading to fracture, softening (damage), and healing, because each addresses only specific behavior, e.g., elastoplastic, viscoelastic, viscoplastic, sometimes with fracture and damage, which may not account for realistic discontinuities and combined behavior. The empirical, mechanisticempirical and mechanics approaches including DSC model and applications are presented by Desai (2002, 2007).
