The behavior of quay walls and breakwaters, damaged in Kobe Port during the 1995 great Hanshin earthquake, were investigated for liquefaction susceptibility of their foundations. This investigation presents the results of laboratory tests and analysis to predict the possibility of liquefaction due to the earthquake.
　The grain size distribution of the masado, used for reclamation and replacement of port facilities in Kobe area, was not in the range of high of liquefaction, as recommended by the Japanese design code for construction of port & harbour facilitie. It was, however, found that the liquefaction resistance of the masado was less than 0.25, which is in the range of values for clean sands with possibility of liquefaction.
　Standard penetration tests (SPT) were conducted on replaced layers and reclaimed layers at nine selected port facilities in Kobe area to verify the occurence of liquefaction. It was found that the layers at every selected facility had possibility of liquefaction.
　The prediction of the occurrence of liquefaction by the cyclic triaxial test method was conducted on replaced layers and reclaimed layers for two quay walls in Port Island and Rokko Island, which damaged during the earthquake. The prediction resulted from the laboratory tests indicate that the layers at every spot had possibility of liquefaction. The liquefaction resistance factors (FL) obtained from the cyclic triaxial test were about 0.5 at the quay wall in Rokko Island and within the range of 0.2 to 0.5 at the quay wall in Port island. Thus, the liquefaction level, which caused the deformations, is believed be very high.
　A linear elastic finite element (FEM) analysis was conducted to predict the vertical and horizontal deformations of a Caisson-type quay wall after liquefaction based on the liquefaction resistance parameters obtained from the cyclic triaxial tests. The result showed the horizontal displacement of the bottom of the caisson to be 3m, and the vertical settlement of the ground surface hehind the caisson to be 3m. Although the analysis did not take the effect of inertia induced by the seismic load into consideration, the displacements predicted by the analysis was in good aggrement with the deformations observed in the field.