Title: Assessment of Linear and Nonlinear Subgrade Behavior Using FWD Deflection Ratios: Implications for Pavement Modelling
Authors: Eng. Catherine Mugai Dr. Kepha Abongo, Dr. Brian Jacks Odero
Volume: 10
Issue: 1
Pages: 6-9
Publication Date: 2026/01/28
Abstract:
Accurate modelling of pavement performance requires understanding the linearity or non-linearity of subgrade soil behaviour. This study assesses subgrade response under falling weight deflectometer (FWD) loading on 24 road sections in Kenya. Deflection ratios (DR) derived from FWD deflections at multiple geophone offsets were used to evaluate linear and nonlinear behaviour. Statistical analysis, including descriptive statistics, Pearson correlation, and ANOVA, were applied to explore relationships between DR and soil properties. Results indicate that fine-grained soils such as elastic silt (MH) and lean clay (CL) exhibit higher DR variability, suggesting nonlinear behaviour, while coarse-grained soils such as silty gravel (GM) and silt with sand (ML) demonstrate more linear response. These findings provide guidance for selecting appropriate pavement modelling techniques based on observed subgrade behaviour.