Characteristic values of soil properties in Dutch codes of practice : theoretical backgrounds and assumptions

Soil properties usually show significant uncertainty due to a combination of spatial variability, limited availability of measurements and other sources of uncertainty. Most modern design codes are based on Load and Resistance Factor Design. In these codes, uncertainties in soil properties are covered by design values of geotechnical parameters, which are a combination of characteristic values, often defined as cautious estimates of properties affecting the limit state, and partial factors. Characteristic values of geotechnical parameters are determined either based on engineering judgement or on a stochastic/statistical basis, of which the latter is subject of this paper. This report elaborates on the theoretical backgrounds and the practical assumptions made for the derivation of characteristic values based on a statistical basis. The methods were initially derived for Dutch flood defenses but are generically applicable to geotechnical design and assessment.