抄録
A review of field liquefaction behavior during several recent earthquakes was made with emphasis on the Cone Penetration Test (CPT) qc-values and the grain size of the soils. The field correlation between the earthquake-induced cyclic stress ratio and normalized cone resistance indicates that fine-grained soils with a mean grain size of D50<0.25mm have greater resistance to liquefaction than do clean sands (D50≥O.25mm) having the same qc-values. On the basis of this finding, we have developed a liquefaction assessment method for soils using the CPT. The normalized critical value of the CPT, (qc1)cr' which separates liquefiable from nonliquefiable conditions, is defined as a function both of the cyclic stress ratio, and the mean grain size of a soil. A simple chart showing variation in the critical CPT value, (qc)cr' with depth was developed for various earthquake magnitudes, maximum surface accelerations and ground water levels. Our proposed CPT-based liquefaction assessment method was evaluated by data on the known performance of soils in the field.
