1.2 Scope of Study

To allow for a more realistic study of real excavation, props are installed in the centrifuge models to be tested to simulate a typical "top-down" excavation where basement slabs are constructed first as the excavation proceeds.

As this is the first time such tests were conducted, two series of tests were carried out. In the first series, the behaviour at limiting equilibrium is investigated. This series helps to establish the necessary experience for the next series as well as to produce data for verification of conventional stability analysis.

In the second series, the behaviour before failure is investigated. This series was conducted to produce data for a better understanding of the behaviour of a realistic excavation. The excavation rate and level are carefully controlled to ensure compatibility with actual field practise. Typical finite element analyses, similar to those done by consultants in practice, were carried out to availability of controlled data allows for a more accurate evaluation. However, as will be explained later on, problems still persist.