Empirical correlations provide valuable information in early design stages, and they help tovalidate or discard single values from site investigations.This paper presents a multivariate database from commercial projects consisting of evaluated shear strengths obtained from direct simple shear tests and fall cone tests (which are calibrated to the field vane test), including index tests. The multivariate databaseis used to investigate the performance of common transformation models and to test the recommended correction for fall cone tests. It is found that the measured normalised shear strength evaluated from direct simple shear tests and fall cone tests is correlated to the liquid limit and that the results conform to Swedish and Norwegian recommendations. However, the scatter is large, more for fall cone tests than for direct simple shear tests, which is thought to depend mainly on sample disturbance. It can however be concluded that the trend of normalised shear strengths increases with increasing plasticity.

Lack of harmonisation between reliability-based design and the partial factor method in Eurocode 7 (EN 1997-1:2004) is preventing the widespread introduction of a risk-based concept in geotechnical design. This paper discusses how uncertainties are managed according to EN 1997-1:2004 and possible implications of not harmonising the current safety format with reliability-based design. One of several challenges highlighted is how EN 1997-1:2004 defines the characteristic value and design value. The characteristic value is therein defined based on a classical frequentist approach through a confidence interval. From a Bayesian point of view, the current definition does not treat the characteristic value as an uncertain variable. Consequently, the definitions of the characteristic value and design value in EN 1997-1:2004 feature weak connections between uncertainties in the geotechnical properties and the consequences of failure, as regulated by the target reliability index.

Preloading  is  commonly  used  to  accelerate  primary  consolidation  and  increase  strength  under  embankments founded on highly compressible clay. By installing prefabricated vertical drains, this process can be even further accelerated. Because of significant geotechnical uncertainties, primarily regarding the vertical and horizontal coefficients of consolidation, prediction of settlement development with time is difficult. This paper shows how Bayesian statistics can be used to update a prior prediction of  the  final  settlement  from  the design  stage, with observations of  settlement made during  the preloading. With  this  approach,  the  observations  during  construction  are  used  to  significantly  reduce  the  considerable  epistemic uncertainty present at the design stage. This allows the surcharge design to be adjusted to suit the actual ground conditions, which is done by increasing the surcharge height if the settlement develops too slowly.

The Swedish national guidelines for design of the main structural support system in road and railway rock tunnels have been adjusted to cohere with Eurocode 7. In the design guidelines, the limit states that the designer should consider are specified. The main method to account for uncertainties in the Swedish guidelines is similar to the method preferred in Eurocode 7: the partial factor method. For each limit state, fixed partial factors retrieved from different sections of the Eurocodes are specified. However, fixed partial factors may not correspond to the same structural reliability for all design situations. In this paper, we show for a common design situation in rock engineering design how partial factors in theory should vary with design geometries and uncertainties. The derived partial factors are compared to the Eurocodes’ fixed values. We find that using fixed partial factors to ensure structural safety in these limit states might not be suitable. The implications are discussed along with suggestions of other more suitable methods to account for uncertainties in rock engineering design.

One of the essential inputs in settlement prediction models is the soil modulus, which may be obtained from laboratory tests or estimated from in situ measurements. The total uncertainty in predicting the confined modulus of a sandy soil is quantified with data from side-by-side in situ testing using the standard penetration test, the static cone penetration test, the light dynamic probing and the laboratory oedometer test. To estimate transformation errors, correlations are proposed between in situ and laboratory data. The results indicate that similar magnitudes of total uncertainties are associated with the in situ methods, which are approximately twice as high as those from the direct oedometer method. The quantified uncertainties are an important input for reliability-based designs of foundations under similar soil conditions.

Several corrections should be made to the original paper. The errors include corrections to Eqs. (8) and (9). Furthermore, a mistake in the calculation of the uncertainty related to random measurement error, COVe;Di , requires corrections to Table 4 and to Figs. 7, 9, and 10. The corrections of the calculation results are inconsequential and do not alter the conclusions of the published paper. The corrections are given subsequently.Corrections to Section “Project Description and Site Characterization” [Eqs. (8a), (8b), and (9)] In Eqs. (8) and (9), the braces defining the measured or evaluated property, δi, and transformation factor, Ci, are incorrectly stated. The correct equations are provided as follows: (Formula Presented) (Table Presented) Thus, when α varies between 1.0 and 0.6, γM=η ranges from 1.16 to 1.29. 

Limitations with the current design using partial factors in Eurocode 7 have been identified. Uncertainties in the material properties are incorporated in both the cautious estimate of the characteristic value and the partial factor. Furthermore, the partial factor is fixed, which limits the opportunities to update the design when additional information is available. A more rational procedure of managing uncertainties in design with partial factors is proposed based on the Bayesian methodology referred to as the extended multivariate approach. The benefits of the approach are illustrated with a case study in which uncertainties of undrained shear strength are characterized for a Swedish clay. The characteristic value and design value is calculated in accordance with the Swedish national annex to Eurocode 7 by adjusting the otherwise fixed partial factor with a conversion factor allowable through EN 1990. The study highlights major benefits in managing uncertainties in a quantifiable and rational way.

One major question to deal with in the process of updating the current version of Eurocode 7 is how to convert thequality of a performed site-investigation into a measurable context. This should, in turn, affect the safety factor applied to the soil-strength properties in a limit state. This paper presents a study in which the total uncertainty from the evaluation of undrained shearstrength in clay is assessed from single and multiple site-investigation methods with regard to both random and systematicuncertainties. A Bayesian procedure is used to convert potential reduction of random and systematic uncertainties into a measurablecontext in relation to: (1) the type of site-investigation method, (2) the combination of methods, and (3) the number of measurementsperformed.

L’une des questions majeures qui se posent lors du processus de mise à jour de la version actuelle de l’Eurocode 7est la suivante : comment convertir la qualité d’une investigation de site en une quantité mesurable ? Cela devrait alors affecterle niveau de sécurité appliqué aux propriétés de résistance du sol dans un état limite. Cet article présente une étude au cours de laquelle l’incertitude totale découlant de l’évaluation de la résistance au cisaillement de l’argile non évacuée est évaluée à partir de méthodes d’investigation de site uniques et multiples en relation avec des incertitudes aléatoires et systématiques. Une procédure bayésienne est utilisée pour convertir la réduction potentielle des incertitudes aléatoires et systématiques en une incertitude mesurable en rapport avec : (1) le type de méthode d’investigation de site, (2) la combinaison des méthodes, (3) le nombre de mesures effectuées.