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Laboratory investigation on salt migration and its effect on the geotechnical strength parameters in quick clay mini-block samples from Dragvoll
Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, Department of Geology and Mineral Resources Engineering.
2014 (English)MasteroppgaveStudent thesis
Abstract [en]

Investigations of the effect of salt diffusion as ground improvement of quick clay is important to provide a clear understanding of the method, to be able validate the potential of commercial use. Previous extensive investigations by laboratory work has been carried out. Laboratory in- vestigations of salt migration lead to extended storage time for the clay samples, as diffusion in clays is considered a slow process. TheobjectiveoftheworkistoanalyzetheeffectofKCldiffusioninrelationtopotentialweather- ing and storage effects. The effect is analyzed in the laboratory with regards to both geotchnical properties, variations in pH and salinity. A literature study of previous findings related to salt migration and storage effects on both geotechnical properties and geochemistry, is also consid- ered. A series of mini block samples are submerged in cells containing deaired, ionized water and deaired, KCl solution. The samples are stored in the cell in a time period from 42 to 102 days. The samples are investigated in the laboratory to provide results relating to undisturbed and remoulded strength parameters, compressibility and general geotechnical properties. pH and salinity is also recorded. The findings are compared to a detailed depth profile of reference parameters,fromapreviousinvestigationdoneonminiblocksamplesfromthesameborehole. Testsarealsocarriedoutinsectionsthroughoutthewaterandsalttreatedclays,tomapchanges with regard to the time dependent diffusion and weathering. Theresultsindicatedageneralincreaseinpeakundrainedshearstrengthforthesamplesstored in KCl solution, approximately 50% of the observed general increase is also observed in the clay stored in water. A minor increase of plasticity limit is seen in both the water and salt treated samples. The comparison between sections for each sample show no clear deviations between the sections. Further, results from the salt migrated samples confirm the findings from previous investigations. The samples are to some extent effected by weathering, in particular the peak undrained shear strength resulting from triaxial tests. However, the geotechnical properties observed after salt migration are changed to such an extent that the clay show a completely different behavior. The same distinct change is not observed in the clays only exposed to potential weathering. The comparability between the samples are however, considered to be relatively low due to in- homogeneity in the soil profile and varying storage time prior to testing and cell installation. Loss of samples during sampling also lead to occasional large distance in depth, between the compared results.

Place, publisher, year, edition, pages
Institutt for geologi og bergteknikk , 2014. , 208 p.
URN: urn:nbn:no:ntnu:diva-27130Local ID: ntnudaim:11359OAI: diva2:758249
Available from: 2014-10-25 Created: 2014-10-25 Last updated: 2014-10-25Bibliographically approved

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