The Terzaghi and Peck (1948) method was the first for predicting the settlementof footings on sand using standard penetration test blow counts (N values). Overthe following 26 years, various modifications to this basic method were suggested.Herein, an extensive database of 426 settlement case histories is used to assess themodel factors for this family of methods. The uncertainty of the model factors ischaracterized using the coefficient of variation. Considering the model factor as arandom variable, the common “log-normality” assumption is investigated critically.The impact of model uncertainty on the reliability of settlement estimations is discussed,and criteria are given to assess their accuracy and conservatism. For settlementprediction, the uncertainty from the model factor is most influential. The resultsindicate a low accuracy for all of the methods considered.
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