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http://dx.doi.org/10.9720/kseg.2012.22.1.015

A Case Study on Quantifying Uncertainties of Geotechnical Random Variables  

Han, Sang-Hyun (Department of Civil Engineering, Seoil College)
Yea, Geu-Guwen (Technology Research Office, Sambu Construction Co., Ltd.)
Kim, Hong-Yeon (Technology Research Office, Sambu Construction Co., Ltd.)
Publication Information
The Journal of Engineering Geology / v.22, no.1, 2012 , pp. 15-25 More about this Journal
Abstract
Probabilistic design methods have been used as a design standard in Korea and abroad for achieving reasonable design by considering the statistical uncertainties of soil properties. In this study, the following techniques for reflecting geotechnical uncertainty are analyzed: quantification of the uncertainties of geotechnical random variables, and consideration of economic feasibility in design by minimizing the uncertainties related to the number of samples. To quantify the uncertainties, the techniques were applied to soil properties obtained from samples collected and tested in the field. The results showed an underestimation of the standard deviation by the 3-sigma approach in comparison with calculations using data from the samples. This finding indicates that economical design is possible in terms of probability. However, when compared with the Bayesian approach, which does not consider the number of samples, variability in the 3-sigma approach is underestimated for some variables. This finding also indicates a safety issue, whereas the number of samples based on the Bayesian approach showed the lowest variance. The variance of the probability density function showed a marked decrease with increasing number of samples, to converge at a certain level when the number exceeds 25. Of note, the estimation of values is more reliable for random variables having low variability, such as soil unit weight, and can be obtained with a small number of samples.
Keywords
Probability density function; Random variable; 3-sigma approach Bayesian approach; Standard deviation;
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