Back to Search Start Over

Reducing shear strength uncertainties in clays by multivariate correlations

Authors :
Ching, Jianye
Phoon, Kok-Kwang
Chen, Yi-Chu
Source :
Canadian Geotechnical Journal. January 1, 2010, Vol. 47 Issue 1, p16, 18 p.
Publication Year :
2010

Abstract

Quantifications Of uncertainties in soil shear strengths, including undrained shear strength of clay, are essential for geotechnical reliability-based design. In particular, how to reduce the uncertainties in undrained shear strengths based on all available information by correlation is a practical research subject, given the considerable cost of a typical site investigation. Although it is simple to reduce the uncertainties by correlation when the information is one dimensional (or univariate), it is quite challenging to reduce the uncertainties by using multivariate information through multiple correlations. This study proposes a systematic way of achieving multivariate correlations on undrained shear strengths. A set of simplified equations are obtained through Bayesian analysis for the purpose of reducing uncertainties: the inputs to the equations are the results of in situ or laboratory tests and the outputs are the updated mean values and coefficients of variation (c.o.v.s) of the undrained shear strengths. Two case studies are used to demonstrate the consistency of the proposed simplified equations. Results show that uncertainties in undrained shear strengths can be effectively reduced by incorporating multivariate information. Given that reliability-based design can justify more economical design with reduced uncertainties, the proposed equations essentially link the value of more and better tests directly to final design savings. Key words: uncertainty, undrained shear strength, in situ test, correlation. Bayesian analysis. La quantification des incertitudes dans les resistances au cisaillement des sols, incluant la resistance an cisaillement de l'argile, est essentielle pour la conception geotechnique basee sur la fiabilite. Un sujet de recherche pratique concerne les facons de reduire les incertitudes dans les resistances au cisaillement non drainees, basees sur toutes les informations disponibles par correlation, considerant le cout eleve d'une etude typique sur un site. Malgre le fait qu'il soil simple de reduire les incertitudes par correlation lorsque l'information est unidimensionnelle (ou univariee), il est neanmoins plus difficile de reduire les incertitudes a partir de donnees multivariees a correlation multiples. Cette etude propose une methode systematique pour obtenir des correlations multivariees sur des resistances au cisaillement non drainees. Une serie d'equations simplifies sont obtenues a 1'aide d'une analyse Bayesienne dans le but de reduire les incertitudes : les resultats d'essais in situ ou en laboratoire servent d'intrants pour les equations, les sortants etant les moyennes des valeurs et des coefficients de variation (c.o.v.s) pour les resistances au cisaillement non drainees. Deux etudes de cas sont presentees afin de demontrer la coherence des equations simplifies proposees. Les resultats montrent que les incertitudes dans les resistances au cisaillement non drainees peuvent effeclivement etre reduites en integrant des informations multivariees. Etant donne que la conception basee sur la fiabilite pent justifier des conceptions plus economiques avec des incertitudes reduites, les equations proposees font le lien direct entre la valeur d'essais meilleurs el plus nombreux et les economies a la conception finale. Mots-cles : incertitude, resistance au cisaillement non drainee, essai in situ, correlation, analyse Bayesienne. [Traduit par la Redaction]<br />Introduction Uncertainties are commonly encountered in geotechnical engineering. Possible sources of these uncertainties may include inherent variabilities, measurement errors, modeling (or transformation) uncertainties, etc. More economical geotechnical designs can be [...]

Details

Language :
English
ISSN :
00083674
Volume :
47
Issue :
1
Database :
Gale General OneFile
Journal :
Canadian Geotechnical Journal
Publication Type :
Academic Journal
Accession number :
edsgcl.219009282
Full Text :
https://doi.org/10.1139/T09-074