Extended multivariate approach for uncertainty reduction in the assessment of undrained shear strength in clays

2014 ◽  
Vol 51 (3) ◽  
pp. 231-245 ◽  
Author(s):  
Rasmus Müller ◽  
Stefan Larsson ◽  
Johan Spross

Important features of the multivariate approach are discussed, and an extension to this approach is proposed whereby the total uncertainty in site investigation methods due to spatial averaging is assessed prior to its adoption. Results from a site investigation of spatially averaged values of undrained shear strength ([Formula: see text]) and the corresponding coefficient of variation ([Formula: see text]) in Veda sulphide clay were used as a practical illustration of the extended multivariate approach and provide a basis for discussion. The inherent variability and scales of fluctuation for different methods are presented. The study shows the usefulness of the extended multivariate approach for the evaluation of representative values of [Formula: see text] and [Formula: see text] based on results from different methods. It is also a way of implicitly reducing the transformation errors that arise when a property is derived from measurement results. Nevertheless, considerable care must be taken as a much lower COV for one method will have a significant impact on the results.

2001 ◽  
Vol 38 (2) ◽  
pp. 378-400 ◽  
Author(s):  
Hiroyuki Tanaka ◽  
Jacques Locat ◽  
Satoru Shibuya ◽  
Tan Thiam Soon ◽  
Dinesh R Shiwakoti

A soil investigation was carried out at two sites in Singapore and Bangkok, Southeast Asia, and the results were compared with those from a site in Ariake, Japan. Soil samples at all the sites were retrieved using the Japanese sampling method to nullify the effect of sampling on sample quality. From the laboratory tests, consolidation characteristics and undrained shear strength were measured. In addition to the mechanical tests, X-ray diffraction and scanning electron microscope tests were carried out to identify clay minerals and to study their microstructure. Great differences in physical and mechanical properties of these clays were observed, which may be attributed to the difference in their clay mineral components and variation in the sedimentation environment.Key words: site investigation, marine clay, undrained shear strength, anisotropy, consolidation, clay mineral.


2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Mi Tian ◽  
Xiaotao Sheng

Applying random field theory involves two important issues: the statistical homogeneity (or stationarity) and determination of random field parameters and correlation function. However, the profiles of soil properties are typically assumed to be statistically homogeneous or stationary without rigorous statistical verification. It is also a challenging task to simultaneously determine random field parameters and the correlation function due to a limited amount of direct test data and various uncertainties (e.g., transformation uncertainties) arising during site investigation. This paper presents Bayesian approaches for probabilistic characterization of undrained shear strength using cone penetration test (CPT) data and prior information. Homogeneous soil units are first identified using CPT data and subsequently assessed for weak stationarity by the modified Bartlett test to reject the null hypothesis of stationarity. Then, Bayesian approaches are developed to determine the random field parameters and simultaneously select the most probable correlation function among a pool of candidate correlation functions within the identified statistically homogeneous layers. The proposed approaches are illustrated using CPT data at a clay site in Shanghai, China. It is shown that Bayesian approaches provide a rational tool for proper determination of random field model for probabilistic characterization of undrained shear strength with consideration of transformation uncertainty.


2016 ◽  
Vol 53 (4) ◽  
pp. 603-618 ◽  
Author(s):  
Rasmus Müller ◽  
Stefan Larsson ◽  
Johan Spross

For staging the construction of embankments on soft clay, an important aspect in deterministic or probabilistic stability analyses is the assessment of the representative average values and associated uncertainties for the undrained shear strength as the height of the embankment is sequentially increased. Assessments made prior to construction can be verified by performing observations during the construction phase. All relevant available information should be incorporated into an analysis to increase the level of confidence and the objectivity of the assessment. To this end, we apply an extended multivariate approach to assess the undrained shear strength using different indirect measurement methods during the staged construction of the Veda embankment (Sweden). This multivariate approach implies that uncertainties associated with the assessments are reduced, and objectively weighted averages are obtained. The resulting implications on the calculated deterministic safety factors and the probabilistically retrieved reliability indices of the embankment are thoroughly discussed in this work.


2017 ◽  
Vol 62 (2) ◽  
pp. 367-384
Author(s):  
Sebastian Olesiak

Abstract Soil strength parameters needed for the calculation of bearing capacity and stability are increasingly determined from field testing. This paper presents a method to determine the undrained shear strength cuWST of the soil, based on the Weight Sounding Test (WST). The innovative solution which allows for a significant reduction of equipment needed for geotechnical field investigation is presented. The proposed method is based on an additional measurement of the torque during testing. It then becomes possible to estimate the undrained shear strength, cuWST of the soil, using the correlation given in this paper. The research results presented in this paper were carried out on selected cohesive soils, Miocene clays from the Carpathian Foredeep.


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