ILLI-PAVE-BASED RESPONSE ALGORITHMS FOR DESIGN OF CONVENTIONAL FLEXIBLE PAVEMENTS

Abstract

In a mechanistic design procedure a structural model is used to predict pavement responses (stresses, strains, displacements). The ILLI-PAVE structural model considers nonlinear, stress-dependent resilient modulus material models and failure criteria for granular materials and fine-grained soils. The computational techniques of the ILLI-PAVE computer program are too costly, complex, and cumbersome to be used for routine design. To incorporate ILLI-PAVE structural model concepts into a mechanistic design concept, simplified analysis algorithms that reliably predict ILLI-PAVE response solutions for typical flexible pavements are needed. ILLI-PAVE-based design algorithms for conventional flexible pavements asphalt concrete (AC) surface plus granular base and subbase are presented for AC radial strain, surface deflection, subgrade deviator stress, subgrade deviator stress ratio, subgrade vertical strain, and subgrade deflection. Pertinent design algorithm inputs are AC thickness, AC modulus, granular layer thickness, and subgrade resilient modulus (E sub Ri). Additional algorithms relating AC radial strain and subgrade deviator stress ratio and surface deflection are also presented. The algorithms are sufficiently accurate for inclusion in mechanistic design procedures.