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Hydraulic Conductivity and Coefficient of Consolidation of Two Sulphide Clays in Sweden
Tyréns AB.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.ORCID iD: 0000-0001-9615-4861
2012 (English)In: Geotechnical and Geological Engineering, ISSN 0960-3182, E-ISSN 1573-1529, Vol. 30, no 1, 173-186 p.Article in journal (Refereed) Published
Abstract [en]

The variation and anisotropy in hydraulic conductivity and the coefficient of consolidation was investigated for two Swedish sulphide clays. A series of constant rate of strain oedometer tests was performed on samples trimmed in the vertical and horizontal direction. A methodology to evaluate the horizontal coefficients of consolidation c h via the horizontal hydraulic conductivity k h and the vertical compression modulus M v is proposed. Laboratory evaluations of c h are also compared with determinations of c h from in situ piezometer measurements in vertically drained sulphide clay. Furthermore, the validity of the empirical correlation between hydraulic conductivity change index C k and initial void ratio e 0, C k = 0.5e 0 (Tavenas et al. in Can Geotech J 20(4):645-660, 1983b), was investigated for the sulphide clays. The results from the investigation show large ranges in measured hydraulic conductivities and coefficients of consolidation. However, the results indicate that the correlation C k = 0.5e 0 is valid. The anisotropy in hydraulic conductivity and the coefficient of consolidation of the sulphide clays tested seems to be small. For design purposes, multiple tests for assessment of hydraulic conductivity and the coefficient of consolidation should be made, and a partial factor of safety, depending on the requisite level of safety and the spatial variability of the parameters, should be introduced. For design purposes in this type of clay, k h = k v and c h = c v are suggested.

Place, publisher, year, edition, pages
Springer, 2012. Vol. 30, no 1, 173-186 p.
Keyword [en]
Anisotropy, Coefficient of consolidation, CRS test, Hydraulic conductivity, Prefabricated vertical drain, Sulphide clay
National Category
Geotechnical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-25823DOI: 10.1007/s10706-011-9459-0Scopus ID: 2-s2.0-84155180932OAI: oai:DiVA.org:kth-25823DiVA: diva2:359966
Note
QC 20120618Available from: 2010-11-01 Created: 2010-11-01 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Embankments founded on sulphide clay: - some aspects related to ground improvement by vertical drains
Open this publication in new window or tab >>Embankments founded on sulphide clay: - some aspects related to ground improvement by vertical drains
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, some aspects concerning building embankments founded on sulphide clay are studied, with special reference to ground improvement by preloading in combination with prefabricated vertical drains (PVD’s). The main purpose of the research was to increase empirical knowledge of the mechanical behaviour of sulphide clays subjected to embankment loadings and of the interaction between vertical drains and sulphide clays. Important aspects related to ground improvement with PVD’s in more general terms are also treated, in particular how various uncertainties regarding the properties of the clay and the clay-drain interaction imposed in the design phase can be addressed. The benefits of using theobservational method for handling these uncertainties are discussed, and a description of how the method was used in an embankment project is presented. The results from the research are presented in one conference paper and two papers submitted to peer-reviewed international journals, which are appended.

The design of PVD’s involves describing the consolidation characteristics of the clay and the interaction between the drains and the clay. Primarily, the rate of consolidation is determined by the hydraulic conductivity (permeability) of the clay in the horizontal direction. Hence, accurate determination of this material property is of paramount importance in making reliable design predictions. As conventional laboratory tests for assessing the consolidation characteristics of a clay only provide information about its properties in the vertical direction, one is often left to make assumptions about the horizontal properties based on empirical correlations. Reliable empirical knowledge of these correlations for a certain clay is there forevital. A large number of CRS tests were performed on horizontal and vertical samples ofsulphide clay in order to investigate the correlation between the horizontal and verticalhydraulic conductivity and coefficient of consolidation. The results show that there is very small anisotropy in these parameters and that the scatters in the results are large. For designpurposes, sulphide clays should therefore be assumed to be isotropic in this respect. In orde rto handle the variation in properties, several parallel tests should be made and partial factors of safety should be introduced in the design. Introducing partial factors of safety in the design of PVD’s is one of the main topics suggested for further research. Regarding the clay-drain interaction, a study of the disturbance effects (smear effects) during the installation of drains in sulphide clays was performed. Back-calculations of measurements of pore pressure dissipation were made via a parameter study. It was shown that smear affects the consolidation rate to some extent but that the natural (undisturbed) hydraulic conductivity is more significant.

The undrained shear strength su of a clay is dependent on the preconsolidation pressure σ 'p . As the clay consolidates under a loading, the effective stress increases, possibly to magnitudes surpassing the initial preconsolidation pressure and thereby leading to increased undrainedshear strength of the clay. The relation between su and σ 'p, i.e. the ratio su /σ 'p for asulphide clay, was investigated based on results from a large number of in situ tests andlaboratory tests. There were large scatters in the measurements, but su /σ 'p =0.25 is suggested as being relevant in the direct shear zone for design purposes in sulphide clays.

Place, publisher, year, edition, pages
Stockhollm: KTH, 2010. xiv, 48 p.
Series
TRITA-JOB. LIC, ISSN 1650-951X ; 2015
Keyword
geotechnical engineering; embankments; vertical drains; sulphide clay
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-25802 (URN)
Presentation
2010-10-11, E2, Lindstedtsvägen 3, KTH, Stockholm, 15:06
Opponent
Supervisors
Note

QC 20101101

Available from: 2010-11-01 Created: 2010-11-01 Last updated: 2014-06-16Bibliographically approved
2. Probabilistic stability analysis of embankments founded on clay
Open this publication in new window or tab >>Probabilistic stability analysis of embankments founded on clay
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xviii, 74 p.
Series
Trita-JOB PHD, ISSN 1650-9501 ; 1018
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-122886 (URN)
Public defence
2013-06-04, Sal B1, Brinellvägen 23, Brinellvägen 23, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20130529

Available from: 2013-05-29 Created: 2013-05-29 Last updated: 2013-05-29Bibliographically approved

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