Deflection and failure of high-stiffness cantilever retaining wall embedded in soft rock

Abstract

In this study, a centrifuge modelling system has been developed, in which the loading process from design conditions to the ultimate failure conditions can be simulated on an embedded wall in soft rock at a constant centrifugal (50g) acceleration. Soft sand rock was artificially modelled by using a sand−cement−clay mixture. In-flight excavation and the lateral loading processes were simulated by means of draining water from the wall front and feeding water to the retained soil side, respectively. Two centrifuge model tests have been carried out to investigate the influence of embedment depth on the stability of large-stiffness cantilever walls having flexural rigidity equivalent to a 2·5 m steel tubular pile wall. The results observed reveal that the wall can stand in the design condition with relatively small embedment depth, and provides a reasonable safety margin against ultimate failure. The stiff cantilever walls move by rigid-body rotation about a pivot point under ultimate loads, and a small increment in the embedment depth – for example, 20% – can significantly increase the stability of the wall considered in this study. A compression failure of the embedded medium at the shallow wall front and a shear wedge failure at the wall back from the wall toe were observed.