Abstract
Resilient modulus ( M r ) of subgrade is a very important factor in the pavement design and evaluation process. Typically, this factor is evaluated using simple empirical (non–stress-dependent) relationships with CBR (California-bearing-ratio) values as defined by several agencies. However, with the current state of knowledge, it is evident that the response of typical unbound subgrade materials may be nonlinear and hence, a function of the state of stress. Because of this material's stress dependency, different pavement cross sections (due to change in layer thickness) and/or layer moduli will cause a change in the M r response of the subgrade material under given moisture-density conditions. Three approaches are presented in this paper to estimate the nonlinear resilient modulus response of fine grained soils to be used in the flexible design procedure from the American Association of State Highway and Transportation Officials (AASHTO). These approaches are based on stress-dependent Lotfi and Moossazadeh predictive equations for estimating nonlinear modulus of subgrade. A close comparison between the three approaches appears to be very encouraging in the characterization of nonlinear subgrade modulus.
Published Version
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