Application of arch shaped deep cement mixed walls for excavation support

R. Nishanthan, D.S. Liyanapathirana and C.J. Leo

Abstract

In this paper, a typical arrangement of compound DCM columns with bored piles at the toes for excavation support is investigated. The excavation is analysed considering the three-dimensional nature of the problem. A case study was modelled, where the wall design was carried out assuming a uniform lateral pressure distribution over the wall section in the horizontal plane. Both computed and measured deformations are similar and confirm that the wall design was conservative and hence the deformations are very small for this case. Also this study shows that it is too conservative to assume uniform pressure distributions for arch walls. An analytical computation presented in the paper shows that the flexural rigidity gained by an arch wall is substantially higher than that gained by a planar wall section between bored piles. Finally a parametric study was carried out varying the geometric parameters of the arch section (span and rise) to investigate the viability of DCM wall sections in supporting excavations. Results confirm that the even with a small curvature, tensile stress development within the wall sections can be completely eliminated.