Settlement behaviour of a fill on soft clay assessed by field and laboratory tests

A methodology is presented for evaluating past and future settlements of an area where fill was placed over soft clay some time before the site development – a situation frequently encountered in engineering practice. The proposed approach integrates field and laboratory tests to assess the consolidation stage and estimate settlement development over time. The case study addresses a fill constructed to raise the grade of an area of the campus of the Federal University of Rio de Janeiro, Brazil, which was subsequently developed as a Technological Park. The company leasing the land for a 50-year period required an assessment of the magnitude and rate of settlements expected during the lease term. The testing programme was designed to be cost- and time-effective while still providing results with reasonable accuracy. The consolidation stage was evaluated using in situ pore-pressure measurements obtained with a small-diameter piezometric probe, while the clay consolidation properties were determined from laboratory tests. Established consolidation theories were used to estimate settlement development over time, considering both primary and secondary consolidation.