Effect of Cross-Anisotropy of Hot-Mix Asphalt Modulus on Falling Weight Deflections and Embedded Sensor Stress–Strain

In this study, the effects of cross-anisotropy on asphalt pavement responses are examined. A dynamic finite element model (FEM) was developed in ABAQUS to simulate pavement responses under falling weight deflectometer (FWD) and truck loads on a pavement section on I-40 at Mile Post 141 in New Mexico. This section was recently instrumented with strain gauges, moisture probes, and pressure cells. Pavement response (i.e., stress, strain, deflection) from the instrumented section is compared with the FEM-predicted values. Two combinations of cross-anisotropy are considered. The first combination considers cross-anisotropy of modulus in every layer of the pavement, and the second combination considers it only in the hot-mix asphalt layer. Time–deflection histories, stress, and strain are predicted from the FEM under FWD and truck loads. Results show that predicted deflections, stress, and strain are highly sensitive to cross-anisotropy. Predicted deflections, stress, and strain increase with a decrease in n-value, defined by the ratio of horizontal to vertical modulus of elasticity. Analyses are performed for two shapes of loading area: semicircle–rectangle and rectangle. Predicted stress and strain are shown to be larger for the rectangular shape of the loading area than for the semicircle–rectangle area. This study recommends including modulus anisotropy in FWD backcalculation and in pavement design.