In Situ Assessment of Stiffness of a Road Sand Embankment

The subgrade and foundation of a pavement have an important role to play in the design and performance of pavements because failure of these layers will inevitably lead to total reconstruction of the pavement. One method of ensuring a stiff foundation is to specify a minimum surface stiffness as an end product requirement for the completed foundation. Belgian practice is to use the plate load test as a practical and quick method of measuring this surface stiffness. For the construction of the ramps of a road bridge, two sand embankments were put in place and compacted with rollers. Compaction of the sand base course was evaluated using this plate load test and showed satisfactory results. However for stability reasons it was necessary to assess the quality of the sand densification due to compaction at greater depth. So addditionally cone penetration tests and non-destructive seismic testing were used to evaluate stiffness profiles within the sand embankment. Both the CPT and SASW results showed good agreement. This paper focuses on the in situ assessment of the stiffness of the sand out of the PLT, CPT and SASW measurements. Correlations will be formulated between plate load moduli, dynamic shear moduli and point resistances for the compacted sand material. Finally the feasibility of the SASW method to determine the compaction quality at depth in a fast and economical way is discussed. For the covering abstract see ITRD E118503.