On the reliability assessment of a controlled dyke failure

A reliability-based analysis framework, accounting for uncertainty arising from the spatial variability of soil properties, has been validated for the controlled, well-instrumented slope failure of an historic dyke in the Netherlands. Using soil property statistics derived from the results of laboratory and cone penetration test (CPT) data for the different soil layers at the site, the dyke was analysed for the initial (i.e. operating) conditions, as well as for the later stage of the test leading up to failure. The computed probabilities of failure and back-figured factors of safety were consistent with the point at which failure occurred in the test, as was the range of possible failure mechanisms. The uncertainty in the stability assessment was reduced by considering the spatial nature of the soil variability, and by conditioning analyses to CPT measurement data. It is shown that the reliability-based approach enables more informed stability assessments that could make the difference between a dyke being assessed as safe or requiring costly improvement.