This report describes an investigation of the settlement and stability of a road embankment constructed on compressible alluvium along the route of a new by-pass (A1035) near Tickton in Yorkshire. To assess the feasibility of using earthworks in place of more-costly viaducts which had been proposed in the areas of poor subsoil adjoining the river hull, a 90m length of an approach embankment to the bridge was constructed in advance of the main contract. A full-scale investigation carried out on this length enabled the problems of settlement and stability to be more closely examined. A range of instruments was installed to measure the pressures and deformations occurring in the subsoil. Observations of the settlement and porewater-pressure dissipation during construction showed that the rate of consolidation was considerably in excess of predictions based on conventional laboratory tests and this enabled the embankment to be successfully completed within a 9-month period. Satisfactory estimates of both the rate and magnitude of settlement were obtained from a multi-layer method of analysis using coefficients of consolidation determined from in-situ measurements of permeability. Stability charts based on an effective-stress method of analysis and using the measured porewater pressures provided a convenient procedure for site control. (Author/publisher)
Abstract