Centrifuge modelling of supported excavations using an improved in-flight excavation tool

A modified tool for simulating the entire process of supported excavation in centrifuge modelling was developed based on a Cambridge type of excavating system. Utilizing the modified tool, a series of centrifuge tests of braced excavations in sand and clay soils were performed to investigate the impacts of staged excavation on the characteristics of retaining wall displacement and ground settlement. The experimental results show that before the struts were installed, the movement of the retaining wall follows a cantilever movement pattern, in which wall rotates about a fixed point near the toe and the maximum wall deflection occurs at the wall crest. For the strut installation process of a multi-strutted excavation, the wall deformation pattern changes to a concave profile. The maximum wall displacement in a multi-strutted excavation in sand is located slightly above the bottom of the excavation; while it is slightly below the bottom of the excavation in clay. The differences between the deformation pattern for multi-strutted excavations in sand and clay are clarified using the profiles of the ground settlement versus distance from the wall. The ground settlement follows a spandrel profile for excavation in sand; while for clay, the ground settlement follows a concave profile. The results from this study can provide useful references for predictions of excavation-induced deformations and understanding the associated deformation mechanisms.