Shear failure investigation of unbound pavement layers under accelerated heavy aircraft loading: case study

Airport pavements are designed to sustain aircraft-induced stresses while maintaining adequate serviceability. To enhance pavement design procedures, the Federal Aviation Administration (FAA) utilises the National Airport Pavement Test Facility (NAPTF) to perform full-scale tests of airfield pavements under representative tire loads. Due to higher tire loads and pressures, unbound layers may experience shear failure and excessive permanent deformation. In this study, a new methodology is proposed to estimate the shear strength parameters of unbound materials by extrapolating resilient modulus test data until failure by adopting the hyperbolic stress-strain constitutive soil model. Using those shear strength parameters of unbound pavement layers of the NAPTF Construction Cycle 3 (CC3), a comprehensive simulation was performed using a modified version of SuperPACK (Super Heavy Load Pavement Analysis PACKage), developed based on the Federal Highway Administration (FHWA) Analysis Methodology for superheavy load (SHL). Pavement behaviour and performance were investigated for four FAA flexible pavement configurations tested mainly to study the role of different subbase thicknesses. It was found that modified SuperPACK was able to reasonably predict the shear failure mechanism in the different unbound layers existing in CC3.