Comparison of DMT, CPT, SPT, and VS Based Liquefaction Assessment on Treasure Island During the Loma Prieta Earthquake

Investigations at Treasure Island involving CPT, DMT, SPT and Vs measurements provide arelatively rare opportunity to compare these methods in predicting liquefaction. All the in-situ techniques were relatively consistent in predicting liquefaction within a depth range of 3 to 7.5 m below the ground surface. The factors of safety predicted by the CPT and DMT were quite consistent except at shallow depths where the DMT gave higher values owing to the higher Ko in this zone. Analysis of the CSR and KD data points within the depth range from 3 to 7.5 m suggests that the liquefaction boundary curve is reasonable for sand but may be somewhat unconservative for silty sands. The factor of safety predicted by the Vs correlation was consistently lower than other methods owing to insensitivity to higher Ko values and higher silt content.