Assessing the reliability of the lightweight deflectometer test for compaction control in highway subbase layers through SPSS analysis

The condition of the highway base/subbase layers is critical for the durability and performance of the road pavement. Compaction control plays an important role in determining the ability of these layers to support traffic loads, their strength and stability. Various methods are used to evaluate the compaction rate of subbase layers; such as nuclear density gauge (NDG) and sand cone. These methods also have their own limitations and difficulties. While the NDG test is used to determine the compaction percentages, the lightweight deflectometer (LWD) test is used as a relatively more practical, portable and non-destructive method to measure the surface stiffness modulus (Emod). In this study, the possibility of using the surface stiffness modulus obtained by the LWD test in the subbase layer instead of each other is investigated by establishing a correlation between the compaction percentages determined by the NDG test. To investigate how well the LWD results are in line with established methods, only correlation and regression analysis of SPSS software are focused on. Correlation analysis helped us assess the strength and direction of the relationships between LWD modulus values and compaction percentages, while regression analysis provided insights into the predictive capability of LWD in estimating compaction outcomes. These methods helped evaluate the reliability and accuracy of LWD as a compaction control tool, providing a deeper understanding of the role of LWD in highway subbase layer assessment.