Field Correlation of Soil Liquefaction with SPT and Grain Size

Two earthquakes of magnitudes 6.7 and 7.4 that occurred in 1978 off the Pacific coast of Miyagi Prefecture, Japan, provided field liquefaction data for a fairly wide range of peak ground surface acceleration from 100 to 290 gal. The range of SPT N-values was also fairly wide because special efforts were made to collect non-liquefaction data in addition to liquefaction data. Dynamic shear stress ratios adjusted for earthquake magnitudes and effective overburden pressures are plotted against N-values adjusted for effective overburden pressures. The field data are compared with two methods proposed recently, one by Seed and the other by Iwasaki et al, after a critical review of the methods and the SPT\u27s in the U.S. and Japan. The method by Seed tended to underestimate the resistance to liquefaction for small N-values, particularly for silty sands; whereas the method by Iwasaki et al tended to underestimate the resistance to liquefaction for large N-values

Liquefaction Potential Evaluation for the Messina Straits Crossing by Field and Laboratory Testing

The method adopted for the evaluation of the soil liquefaction potential in the Messina Straits, Italy, is presented and the results are discussed. The study was carried out for the design of three submerged floating tunnels linking Sicily to the Italian mainland. The method is based on a combined approach where field measurements are used to partly re-create the original soil fabric in the specimens for cyclic laboratory tests. The method is suitable for offshore investigations where recovery of truly undisturbed samples is hardly possible. The results show that in this way a much higher resistance to liquefaction is predicted than from conventional laboratory tests. The results of indirect methods based only on CPT records or shear wave velocity measurements in the field are presented first, and their limitations that led to the selection of an improved laboratory testing program are outlined