This lesson illustrates the use of PLAXIS for the analysis of submerged construction of an excavation. Most of the program features that were used in the previous chapter will be utilised here again. In addition, some new features will be used, such as the use of interfaces and anchor elements, the generation of water pressures and the use of multiple calculation phases. The new features will be described in full detail, whereas the features that were treated in the previous lesson will be described in less detail. Therefore it is suggested that the previous lesson should be completed before attempting this exercise.

This tutorial concerns the construction of an excavation close to a river. The excavation is carried out in order to construct a tunnel by the installation of prefabricated tunnel segments. The excavation is 30 m wide and the final depth is 20 m. It extends in longitudinal direction for a large distance, so that a plane strain model is applicable. The sides of the excavation are supported by 30 m long diaphragm walls, which are braced by horizontal struts at an interval of 5.0 m.