Seismic performance of SSPQ retaining wall—Centrifuge model tests and numerical evaluation

• Centrifuge model tests and numerical evaluations on the seismic performance of sheet pile retaining wall were carried out.
• Bending moment, deformation, acceleration of the retaining wall are discussed and compared.
• The retaining wall will deform largely under Level 2 earthquake. However, it will not collapse due to its flexibility.
• Fixed side boundary in the centrifuge has significant influence on the deformation of retaining wall and ground.
• The proposed numerical method can give a suitable seismic evaluation for the sheet pile retaining wall as a permanent structure.

As temporary structures, steel-sheet-pile-quay (SSPQ) retaining walls have been widely used to counteract excavation problems in Japan not only in urban areas, but also in mountainous areas. The most important features of retaining walls are that they are easy to install in any narrow space, they can be reused many times in different types of soil and, above all, they are strong enough to resist any kind of earth pressure. The shortcoming of retaining walls, however, is that the deformation of the structures may sometimes be rather large, which might become an obstacle for geotechnical engineers wanting to use them as permanent structures. In this paper, centrifuge model tests [1] on the seismic performance of SSPQ retaining walls are simulated systematically with a two-dimensional (2D) dynamic analysis using the finite element method (FEM). In the centrifuge model tests, an SSPQ retaining wall subjected to five consecutive seismic waves is considered. To analyze the influence of the soil density on the performance of the retaining wall and the ground, a middle dense Toyoura sand ground (Dr=60%) and a dense Toyoura sand ground (Dr=75%) are used. In the analysis, the seismic behavior of the SSPQ retaining wall and the surrounding ground are described separately by beam elements and a cyclic mobility model in which the stress-induced anisotropy, the density and the structure of the ground can be described in a unified way. In order to clarify the influence of the fixed boundary adopted in the centrifuge model vibration tests, an analysis in prototype scale, that completely corresponds to the conditions of the centrifuge model tests, and an analysis in full scale, that corresponds to the real ground conditions, are carried out. By comparing the calculated results with the results of the centrifuge model vibration tests, the anti-seismic capacity of the SSPQ retaining wall and the dynamic performance of the ground during earthquakes are discussed in detail. The accuracy of the evaluation method using FEM is also verified. The purpose of this study is to establish an evaluation approach for the seismic behavior of SSPQ retaining walls as permanent earth-balanced structures.

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