Abstract

In many instances, a compressible layer is placed above rigid culverts when installed under embankments with heights in excess of 12 m. These types of installations are classified as induced trench culverts and the designs are based on Marston-Spangler Theory. Even though this approach has been used since about 1930, serious concerns about the assumptions made in the theory, and some recent serviceability related problems have led to the deletion of this approach from the American Concrete Pipe Association Handbook. As this method of construction has been successfully used in the Province of New Brunswick, a research program was undertaken to understand the complex soil structure interactions in such installations. Two prototype structures were instrumented and monitored and the field data were compared with the Marston-Spangler design approach and results of numerical analysis. A program of centrifuge modelling was undertaken to study the effect of various parameters such as the thickness, width and the location of compressible layer on the load transfer. The results of centrifuge modelling were supplemented with numerical analysis to obtain complete pressure distribution on rigid culverts. It is concluded that Marston-Spangler method does not capture the true load transfer behaviour and revised pressure distributions should be used for such installations.