Evolution of relative density and shear wave velocity in non-compacted embankment layers: Geological long-term monitoring

This study proposes a novel method for assessing the evolution of relative density and shear wave velocity that vary with depth and effective stress in non-compacted embankment layers. Embedded soil stiffness measurement devices were used to monitor the shear waves at each stage of filling at the test site, and comprehensive laboratory compaction tests were conducted using a floating ring oedometer cell to reproduce real field conditions with minimal friction. Assuming a constant soil unit weight γ with 7% water content, the effective stress σ’ is proportional to depth z (i.e., σ’ = γ·z). Field test results were compared with the shear wave velocity relationships determined in laboratory tests for four samples of differing relative density (30%, 50%, 70%, and 90%), indicating that the relative density at the bottom of the embankment varied between 15% and 48%. However, the constant soil unit weight applied in this study can underestimate the relative density of the embankment, causing a prediction error if the self-weight compaction of the embankment is not minute. Therefore, this study provides guidelines based on a physics-inspired and data-based approach and anticipates the relative density and shear wave velocity analyzed in the context of depth in non-compacted embankment layers. The physics-based data analyses suggested in this study can be used in first-order estimations to assess the relative density and shear wave velocity evolution in non-compacted embankment layers.