Extension of the Boussinesq’s equation to reflect the actual changes in vertical stresses in geomaterials using LWD loading

This study evaluates soil stress distribution during LWD testing and refines Boussinesq's equation to better reflect actual vertical stress changes considering material properties. It examines the effects of soil type, moisture content, plate size and applied stresses on LWD's influence depth. Vertical stress sensor arrays in two geomaterials: large-scale in-situ tests and field material characterisation support the analysis. Notably, the suggested equation achieves significant error reduction compared to the original Boussinesq equation. For clayey soil, the results showed that the influence depth aligns with Boussinesq's theoretical predictions at about twice the LWD plate diameter. However, measured stress distribution in the field diverges from Boussinesq's equation for granular base material. Discrepancies stem from factors like particle interlocking, compaction energy and local moisture content. Significantly, measured stresses surpass Boussinesq's calculated values. To address these discrepancies, a modified Boussinesq-based model incorporates local water content and field density, significantly improving vertical stress prediction accuracy. This adjustment reduces errors by 69.5% for clayey soil and 94.4% for granular material, highlighting the importance of material-specific properties in modelling vertical-induced stresses, particularly for LWD-induced stresses. These findings enhance material behaviour prediction under dynamic loads, reinforcing mechanistic-empirical pavement design and enabling resilient, economical road infrastructure.