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An estimation method for earthquake-induced pore water pressure and the postearthquake settlement of soft clay was developed by focusing on its Atterberg's limits and the direction of cyclic shearing. To clarify the fundamental characteristics of clays with different Atterberg's limits under multi-directional cyclic shear, normally consolidated specimens of Kaolinite clay, Tokyo bay clay and Kitakyushu clay were subjected to cyclic simple shear under the undrained condition with various cyclic shear directions and shear strain amplitudes, followed by the dissipation of cyclic shear-induced pore water pressure. The effects of undrained cyclic shear on the pore water pressure accumulation and postcyclic settlement were observed, and relationships with Atterberg's limits were then investigated. In conclusion, the pore water pressure accumulation and post-cyclic settlement induced by multi-directional cyclic shear increase considerably to a higher level compared with those generated by the uni-directional one and such a tendency is evident for clays with a wide range of Atterberg's limits. Comparisons of the results indicate that the soil with higher plasticity index shows the lower pore water pressure accumulation and post-cyclic settlement, irrespective of number of strain cycles and shear strain amplitude. Based on these results, a model for earthquake-induced pore water pressure and postearthquake settlement was developed by incorporating the Atterberg's limits as a function of experimental constants and the practical applicability was confirmed.

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In order to introduce the performance-based design framework into the design of quay walls, it is necessary to stipulate the allowable displacements of the quay walls as one of the performance requirements. This paper aims at presenting the allowable displacement for gravity type and sheet pile type quay walls against the level-one earthquake ground motion. We conducted series of earthquake response analyses by using the level-one earthquake ground motion obtained by the earthquake hazard analysis and evaluated the displacements of the quay walls for each structural type. We proposed the average displacements as the allowable displacements of the quay walls.

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Some existing pile-supported wharves need to be repaired because of the insufficient countermeasures against corrosion. However, total amount of budget to be spent for maintaining the civil engineering works is reducing year by year. Therefore, it is very important to obtain the optimal repair strategy of the deteriorating structures. In this study, we discuss the optimal repair strategy of the existing pile supported wharf from the viewpoint of minimizing the expected total cost, which is defined as the multiplication of the failure probability and the repair cost. We conducted the reliability analyses and evaluated the failure probability of the pile-supported wharf in accordance with the repair strategy.