5. Conclusion
A programme of large-scale instrumented shallow foundation field tests investigating the undrained and consolidated undrained load-settlement response and ultimate capacity under vertical centric loading has been carried out at the Australian National Field Testing Facility (NFTF) for soft soils. Site works and activities in preparing the tests are presented along with load- and timesettlement observations to failure. The load-settlement response, ultimate capacity and failure mode of the two unconsolidated undrained tests agreed well with each other providing confidence in the construction and testing procedures and the uniformity of the site over the area of the tests. The successful consolidated undrained (CU) test indicated an increase in bearing capacity due to the preload and consolidation phase, which was well predicted by a critical state based framework. The load-settlement response and ultimate limit state of the unconsolidated undrained tests (UU) were shown to be well predicted by numerical analysis using a simple elastic perfectly plastic constitutive model. Comparison of the observed and predicted load-settlement response were the subject of an international prediction exercise, the results of which are presented in a companion paper in this special issue.
The programme of field tests presented in this paper adds to a sparse database of large-scale shallow foundation tests on soft clay on sites with extensive site characterisation. Such studies provide an essential benchmark for assessing techniques and methods for deriving stiffness and strength parameters, available constitutive models and available prediction methods for shallow foundation response. Field testing provides an invaluable and convincing means of assessing analytical and numerical methods of predicting shallow foundation response.
