Advancements in lightweight deflectometer testing and strain modeling for subgrade evaluation

Abstract

This study investigates the modeling and prediction of permanent strains in subgrade soil using repeated lightweight deflectometer (LWD) testing. The research focuses on understanding the relationship between applied stress, recoverable strain, water content, and accumulated permanent strains, specifically in silty sand subgrade soils. In-situ LWD tests were conducted at different stress levels (50, 100, and 200 kPa) and water contents (8%, 10%, and 15%) to measure both permanent and recoverable deformations. A developed model, designed to predict permanent strains utilizing recoverable strains in road materials under various conditions, was compared with LWD results and evaluated for accuracy. While discrepancies were observed at higher water contents and certain stress levels using this model, the regression models demonstrated strong predictive capabilities, with R² values exceeding 0.91 for most testing conditions. This study underscores the potential of in-situ repeated LWD testing as a reliable tool for assessing subgrade behavior for pavement design.