In the paper, an analysis of a system consisting of a retaining wall supported by a set of temporary supports carrying large inclined force resulting from earth pressure is presented. 2D analysis of the retaining wall is accompanied by the 3D analysis of the support, which prove to be the key issue of the design, as nonlinear load– displacement characteristic of the support influence substantially static of the supported wall. Both 2D and 3D finite element analysis were performed with use of Z_SOIL.PC advanced engineering software package [1].

The structural system of the support shown in Figure 24.1a, invented by the author, consists of:

• sheet piles destined to carry horizontal force component,
• pre-cast reinforced concrete slab for vertical one,
• connecting rods and beams.

Although the structure of the support remains simple and reusable (and, as a consequence, inexpensive), its analysis is not so straightforward. This is due to: immanent three-dimensionality of the problem (no way to deal with any reasonable 2D model), soil-structure interaction in the presence of frictional contact between soil and structural elements, non-linearity of the soil response under large stresses, elasto-plastic behaviour of the structural elements.

The description of the FE model used in evaluation of load-–displacement characteristics of the aforementioned support is given. In the model, shown in Figure 24.1b, only 1/2 of the structure is included, due to the symmetry versus vertical plane. In particular, the following issues are discussed in details:

• modeling of a soil media as an elasto-plastic continuum based on standard data, constitutive models and finite element formulation,
• identification and modelling of sheet piles as an elasto-plastic orthotropic shell,
• modeling of soil-structure interface between sheet pile and the soil,
• influence of support stiffness on the retention wall,
• modeling of non-linear spring, representing the support in the numerical model of the retaining wall as a set of parallel simple elasto-plastic truss elements,
• algorithmic strategy of the analysis.

Figure 24.1: Structural system of the support and its computational model.

The results cover load-displacement diagrams for different variants of the support. Also a comparison of results obtained for different material models based on the same data is given. Performance of the whole system was later controlled by the displacement measurements. These were compared with the numerical prediction showing acceptable agreement. Finally, some conclusions concerning feasibility of 3D finite analysis in engineering practice are given.

1

Z_SOIL.PC. Users manual, ZACE Services 1985-2002.

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