A region in Mihama-ward, Chiba, Japan was developed using hydraulic fill techniques during the 1960s. Soil types vary from plastic clays to nearly clean sands reflecting the depositional environment related to the hydraulic fill discharge process. Clays are soft and sands have low relative density; groundwater throughout the area is relatively shallow (< 2 m). During the M9.0 Tohoku-Oki earthquake, the area was subjected to shaking of modest amplitude and long duration (peak horizontal accelerations of 0.2g to 0.35g and 100-180 sec, respectively). Post-earthquake observations show highly variable field performance, from non-ground failure to massive liquefaction. The intensity of shaking was clearly sufficient to trigger liquefaction of loose sandy materials. Hence, the key factor distinguishing the variable field performance in the region is liquefaction susceptibility. In this study, we describe this case history based on the information available to date focusing on (1) hydraulic fill placement operations, (2) results of post-event reconnaissance, (3) ground motions from the M9.0 Tohoku-Oki earthquake, and (4) results of geotechnical site characterization relevant to liquefaction susceptibility assessment.
Case study of liquefaction susceptibility from field performance of hydraulic fills
Zimmaro P.;
2018-01-01
Abstract
A region in Mihama-ward, Chiba, Japan was developed using hydraulic fill techniques during the 1960s. Soil types vary from plastic clays to nearly clean sands reflecting the depositional environment related to the hydraulic fill discharge process. Clays are soft and sands have low relative density; groundwater throughout the area is relatively shallow (< 2 m). During the M9.0 Tohoku-Oki earthquake, the area was subjected to shaking of modest amplitude and long duration (peak horizontal accelerations of 0.2g to 0.35g and 100-180 sec, respectively). Post-earthquake observations show highly variable field performance, from non-ground failure to massive liquefaction. The intensity of shaking was clearly sufficient to trigger liquefaction of loose sandy materials. Hence, the key factor distinguishing the variable field performance in the region is liquefaction susceptibility. In this study, we describe this case history based on the information available to date focusing on (1) hydraulic fill placement operations, (2) results of post-event reconnaissance, (3) ground motions from the M9.0 Tohoku-Oki earthquake, and (4) results of geotechnical site characterization relevant to liquefaction susceptibility assessment.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
