Multivariate probabilistic assessment of a regional database in Copenhagen

Abstract

Extensive research has been carried out to establish empirical equations between two geotechnical properties and in spite of the increase in correlation studies, a construction of a multivariate distribution function of more than two parameters is still rare. The objective of this study is to investigate the possibility of constructing two multivariate distribution functions, each consisting of 5 geotechnical parameters based on a) triaxial and soil classification tests and b) oedometer and soil classification tests in stiff over-consolidated clay till from Copenhagen. For this purpose, laboratory measurements from twenty-six sites in Copenhagen are utilized and two multivariate databases are constructed. The correlations among the ratio of deviatoric and mean effective stresses (q/p´), over-consolidation ratio (OCR), secant modulus at reference stress 100 kPa (E50ref), initial void ratio (eo) and liquid limit (LL) are investigated in multivariate model A, while multivariate model B demonstrates the correlations among oedometer modulus at 100 kPa reference stress (Eoed(ur)ref), over-consolidation ratio (OCR), permeability change index (Ck), initial void ratio (eo) and liquid limit (LL). The Nataf transformation model is used for the construction of the multivariate distributions, which are then used to simulate the correlations between geotechnical properties by generating artificial samples. Finally, the artificial samples are compared with the original database for an initial validation of the model. The constructed multivariate models obtained as a result of this study can act as prior for Bayesian updating in multivariate distribution functions when additional geotechnical tests are carried out.

Keywords

• multivariate distribution
• nataf transformation
• regional database
• copenhagen clay till