Design of gravity quaywalls via nonlinear analysis of soil-quay ineraction

Abstract
There are several quay types parallel to the shore line such as the walls constructed by piles, sheetpiles or gravity walls. Among these types of structures, the gravity quaywalls are widely used because of their simplicity of structure and ease of construction. Usually, it is the best alternative particularly in the locations with acceptable soil strengths. Weight of the blocks provide the stability of the quaywall against overturning and sliding and therefore, their dimensions are determined based on the applied loads on the quay structure. The most important load is the soil pressure that increases the lateral loads acting on the quaywall particularly during an earthquake condition. For design, the soil pressure usually converts into a static load by utilizing the seismic coefficient method. Analytical equations such as the Mononobe-Okabe formula are usually employed to calculate the applied soil pressure. However, some researchers believe that these analytical formula do not appropriately express the real behavior of the soil, and therefore, they can not be used for a proper design. There are, actually, some simplified assumptions in calculating the applied soil pressure those decrease the accuracy of the commonly used methods for quaywall design. The main assumptions are neglecting the nonlinear behavior of the soil and neglecting the flexibility of quay blocks. Due to the importance of the soil pressure in the quaywall design, these assumptions are investigated numerically in this study by making use of two well known FLAC and ANSYS softwares. For this purpose, the quaywall of Shahid Beheshti port is selected as a case study and the soil pressure around this quaywall is calculated by modeling the nonlinear behavior of the soil via using the Mohr-Coulomb constitutive model. In addition, the effect of the block rigidity on redistribution of the soil pressure beneath the quay structure is studied by a 3-D modeling of the lowest block located on linear springs (representing the supporting soil). To study the importance of each above mentioned assumption individually, two seperated models are utilized separately. According to the results, the pressure distribution under the quay wall is more uniform in the case of employing the nonlinearity of the soil. The total pressure is, however, less than the total calculated pressure by analytical formula that shows the Mononobe-Okabe formula are not accurate, but its results are overestimated for the studied problem. In addition, results show that the simplified methods can not be used for design of the lowest block because the value and the location of the maximum moment along this block changes due to its rigidity. As a result, neglecting the block deformations what is done in simplified methods is not acceptable for design purposes. It should be noted that the lowest block is so important is providing the global stability of the quaywall because its failure can lead to a total failure of the quaywall. On the other hand, all blocks are supported on this block and consequently, its repair would be too difficult even in the case of any small failure.

Keywords

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Modares Civil Engineering journal
Volume 17, Issue 3
September and October 2017
Pages 9-20