Investigation of Parameter Uncertainties Inherent to the Geotechnical Design of Bank Revetments at Inland Waterways

This paper describes the effects of uncertainty inherent to the choice of hydraulic load and soil parameters on the geotechnical revetment design. As for the practitioner, the effect of uncertainties on the required armour layer thickness is studied. Uncertainties inherent to revetment design mainly result from the load and resistance parameters employed in the design. At present, design loads are obtained from empirical equations and worst-case ‘design vessel passages’. Characteristic soil parameters are defined on the basis of a limited number of field and laboratory tests. Thus, uncertainties arise with regard to the choice of characteristic values. In order to investigate the effects of parameter uncertainty on the revetment design, distributions and correlations of loads are assessed using vessel passages observed in the field. In ensuing uncertainty analyses it is found that at present available data does not allow approximating loads by means of probability functions, whereas for the soil parameters the results indicate that the minima of the soil parameters govern the design. However, it is also found that when considering more than one soil parameter as random variable, a less conservative design can be achieved as with the individual minima. As a conclusion, recommendations regarding parameter choice and design procedure are provided.