Impact of cross-anisotropy on embedded sensor stress-strain and pavement damage

The effects of cross-anisotropy on asphalt pavement responses and damage are investigated in this study. As a part of this investigation, a dynamic Finite Element Model (FEM) of a pavement section at interstate I-40 (Mile Post 141) in New Mexico is developed in ABAQUS. This section has recently been instrumented with strain gauges, moisture probes and pressure cells. The dynamic FEM has been simulated to determine pavement responses under Falling Weight Deflectometer (FWD) and truckload. Pavement response (i.e. stress, strain and deflection) from the instrumented section are then compared to the FEM predicted values. To study the effect, a total of five combinations of cross-anisotropy are considered. The first combination considers cross-anisotropy of modulus in every layers of the pavement. The rest of the combinations considers it in each of the individual layers such as surface (Hot Mix Asphalt (HMA)), base (Granular aggregate), sub-base (PPC) and subgrade (Fine soil), respectively. Time-deflection histories, stress and strain are predicted from the FEM under FWD and truckload. Results show that predicted deflections, stress and strain are highly sensitive to HMA and all layer cross-anisotropy. In these cases, predicted deflections, stress and strain increase with a decrease in n-value, defined by the ratio of horizontal to vertical modulus of elasticity. The effect of cross-anisotropy in base, sub-base and subgrade is not as significant as the former two cases. Pavement damage is also determined using the tensile strain at the bottom of surface (HMA) layer. It is observed that damage increases with decrease in n-value. This effect is pronounced in HMA and all layer cross-anisotropy among the five combinations of cross-anisotropy. Finally, it is recommended to include this effect in the mechanistic analysis to improve the pavement design and evaluation.