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A study on the use of selected ground
improvement target areas to achieve optimal
seismic resistance of quay walls
Akito Sone
NEWJEC Inc., Osaka, Osaka, Japan
Susum Iai
Department of Civil and Earth Resources Engineering - Kyoto University, Uji, Kyoto, Japan
ABSTRACT
The purpose of this study is to demonstrate that targetted ground improvement efforts can substantially improve the
overall earthquake-resistant performance of quay wall systems. Appropriate planning of soil improvement efforts is
considered key in performance-based design, particularly with respect to limited budgets available for seismic retrofit of
quay walls.
Two-dimensional effective stress analyses were carried out on selected quay walls known to be supported on potentially
liquefiable soils. A strain space multiple shear mechanism model was adopted for effective stress analyses. Quay walls
commonly used in Japan were selected for analysis, and these include simple gravity quay walls. In addition, verticalpile anchored and batter-pile anchored sheet pile quay walls were considered in the study.
Parametric study included varying ground improvement efforts and locations, varying density contrast of original and
improved ground, and varying intensities of the input earthquake shaking. The findings of the study confirmed that
targeting ground improvement efforts can be an effective approach to mitigate earthquake induced damage to quay wall
systems. The results of the analyses clarified the following findings on the appropriate spots for soil improvement to
mitigate the earthquake induced damage most effectively.
<The summary of the appropriate spots for soil improvement>
For gravity-type quay walls
- The back-fill, where the lateral earth pressure to the quay wall may be reduced by the soil improvement.
- The front side (water side) foundation ground of the quay wall, where the bearing capacity may be increased by the soil
improvement.
For sheet pile quay wall (both vertical anchorage type and batter anchorage type)
- The back-fill, where the lateral earth pressure to the quay wall may be reduced by the soil improvement.
- The front side (water side) foundation ground of sheet pile, results in enhanced soil resistance against the embedded
area of the sheet pile such that the sheet pile and anchor pile(s) deform as one unit and bending moments and
deformations are reduced.