Both caisson-type and sheet pile-type quay walls faced extensive damage during the 1995 earthquake in Kobe. Seaward displacement of the sheet pile quay walls due to lateral spreading of the liquefied backfill soil reached to several meters. As a result, neighboring pile foundations faced relatively large translations and inclinations. In order to realistically model liquefaction and lateral spreading of saturated sand deposits behind sheet piles and the consequent deformation and translation of neighboring pile foundations, the largest laminar box in the world (12m × 3.5m × 6m) was employed and a series of shake table tests were conducted at National Research Institute for Earth Science and Disaster Prevention in Japan (NIED). In these nearly full-scale tests, a group of four concrete piles were modeled behind steel sheet piles. Piles in the ground were extensively instrumented with strain gauges to measure distribution of moment during lateral spreading. This allowed computing the loading condition, as well as conducting damage and performance assessments. Other instrumentations including pore water pressure transducers and accelerometers were installed in various depths and locations. Displacements of the laminar box, top cap and top of the sheet pile were also measured by means of displacement transducers. The test results revealed that after a few cycles of loading and unloading, pore water pressure in saturated and relatively loose backfill increased and the consequent loss of effective stress resulted in lateral spread of the liquefied sand. The tendency towards minimal potential energy in the liquefied soil caused deformation in the sheet pile and resulted in bending moments and lateral deformation of the piles. It was also intended to model post liquefaction behavior of the liquefied sand as observed during real earthquakes, particularly during the 1964 Niigata earthquake. The delayed lateral displacement of the sheet pile started a few minutes after the end of the input shake. The clear evidence of pore water redistribution and second phase of lateral movement was observed. This paper reports the investigation on liquefaction and post liquefaction phenomena which occurred during the experiment, and presents the discussion on the experimental results.
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