3-D finite element modelling of slurry trenching

The movement due to trenching for the construction of diaphragm wall has to be considered when there are nearby structures. Such trenches are often constructed in panels of length 3m to 6m with width ranging from 0.6m to 1.2m. The problem is 3-dimensional and a 2-dimensional plane strain analysis will yield grossly conservative results. Axisymmetric analysis has been used to simulate the trenching process, but this may still be inadequate. In this paper, 3-dimensional finite element analyses were conducted to analyse the trenching process. The results were calibrated against a reported field study at a site which contained a thick marine clay layer. Data including lateral deflection, pore pressure and surface settlement allow a careful evaluation of the movement in the ground adjacent to the trench. The results suggest that 3- dimensional analysis can capture the reported data reasonably well. The results from 3-dimensional analyses will also be compared with that from axisymmetric analyses.