Settlement of an Embankment Constructed on Marine Clay

Abstract

Construction of Highway 417, located in the Ottawa Valley region of south-eastern Ontario, commenced in 1969. At one of the structure crossings along this highway, namely the Anderson Road site, a 180–196 ft (55–60 m) thick stratum of sensitive compressible marine clay exists. The approach embankments, at this site, induced a level of stress in excess of the preconsolidation pressure of the clay. It was decided to surcharge the approaches in order to accelerate the time–rate of consolidation of the foundation clay and thus minimize postconstruction maintenance. Settlement observations have been made regularly since the placement of the fills. This paper describes the site, the applied loading, the settlements observed, and the results of laboratory tests. The recorded settlements, at various locations along the south approach, have been compared with settlements computed by methods in which different stress distribution theories and drainage assumptions were used. One method gave settlement results which were in close agreement with those observed.