Capturing a Layer Response during the Curing of Stabilized Earthwork Using a Multiple Sensor Lightweight Deflectometer

Abstract

The lightweight deflectometer (LWD) is a portable device that measures surface deflections and applied force, from which dynamic stiffness and elastic modulus can be estimated. The inclusion of radial offset sensors with LWD testing, referred to here as multiple sensor LWD testing, stemmed from the well-established falling weight deflectometer (FWD) testing method. However, little research exists in the literature addressing LWD use on stabilized or lightly bound layers with multiple sensors, or exploring the applicability of backcalculating/isolating layer moduli from multiple sensor LWD tests. To this end, over 200 multiple sensor LWD tests on stabilized base materials were performed at five sites and rigorously analyzed to determine if the test could capture growth in stabilized base stiffness while the underlying subgrade layer remained unchanged. Deflection results demonstrate that the LWD test is capable of detecting changes in the stiffness of the stabilized base material during curing as illustrated by the decreasing magnitude in center deflections. Furthermore, radial offset deflections measuring 60 cm from the plate center remained constant during curing, providing valuable information about the subgrade support. The findings made directly from the deflections were confirmed via an analytical backcalculation using Boussinesq’s equations and Odemark’s method of equivalent thickness. The use of multiple sensor LWD testing allows for a richer interpretation of earthwork behavior than the traditional center deflection LWD results.