Most civil engineering construction requires an estimate be made of the deformation of the foundation material under the applied working loads. Predictions often rely on a number of simplifying assumptions, either inherent in the theories used or specific to the particular problem. As a general rule, relatively good predictions of field settlement can be obtained using the conventional approaches, however, on occasion, these yield unsatisfactory results.
The East-West Arterial Road was designed and constructed by the Queensland Department of Transport and comprises embankments to a maximum height of 5. 5 m over soft estuarine clay deposits ranging up to 15 m thick. Field settlement has exceeded design predictions in both magnitude and duration. This thesis endeavours to explain the discrepancy. A review has been made of the theories used to estimate settlement, and the associated assumptions and limitations. A comprehensive laboratory testing program has been carried out to evaluate the geotechnical properties of the soft clay at the site, particularly their consolidation characteristics. A comparison was subsequently made with the original design parameters adopted, and back-analysed values from field monitoring data.
The findings of the research reveal an anomaly with the original design parameters, in addition to the occurrence of large undrained plastic deformations. The phenomenon of creep occurring simultaneously with primary consolidation, was also identified as a possible contribution to the discrepancy.