Evaluating Nonlinearity on Granular Materials and Soils Through the Use of Deflection Techniques

Abstract

The nonlinear behavior of soils and granular materials is widely known. Its proper evaluation is essential for the accurate determination of the stiffness of pavement layers and their structural evaluation. If this phenomenon is not considered appropriately, it can lead to significant errors in estimating the pavement responses. As part of the investigation of accelerated tests on full-scale pavements by the National Laboratory of Materials and Structural Models of the University of Costa Rica, four instrumented pavement sections were built and evaluated using a Heavy Vehicle Simulator. The wheel load was used at an average speed of 10 km/h, with various loading levels, at an average temperature of 23 °C and with a lateral wandering of 10 cm. The deflection profile of each pavement was studied by means of Multi-Depth Deflectometer sensors (MDDs), the Road Surface Deflectometer (RSD), and; the Falling Weight Deflectometer (FWD). This paper summarizes a comparison among the differences in the deflection basin measurements, and the related estimated moduli. Additionally, the pavement response modeling was performed by means of Multi-layer Elastic (MLE), Finite Element (FE) and Linear Visco-Elastic (LVE) methods. The objective of this study was to compare the results of different deflection measuring methods and their correspondent backcalculated moduli. The analysis showed similar results in the deflection curves and hence, back-calculated moduli obtained by the MDDs and the RSD. Both devices captured, as expected, nonlinear behavior of the granular materials as well as the subgrade. The FWD was not able to report such behavior.