Preloading of granular soils caused by deep vibratory compaction (Part 1)

An important objective of deep vibratory compaction is to reduce settlement. The compaction effect can be monitored by cone penetrometer (CPT) and dilatometer (DMT) tests. Both methods can be used to determine changes in horizontal stresses. Relationships between changes in horizontal stresses and overconsolidation ratio have been proposed in the literature.The results of DMT investigations in a calibration chamber have been re-analyzed in part 1 of the paper and show good agreement with existing empirical correlations based on CPT. An increase in horizontal stress implies that the soil has been preloaded. In part 2 of the paper five case histories were re-analyzed, where CPT and DMT investigations were reported before and after treatment. In spite of the variable soil conditions and different compaction methods, deep vibratory compaction resulted in all cases in a marked increase of horizontal stresses. This increase implies that the treated soil deposit has been preloaded, an effect which should be considered in settlement analyses.