Permeability of stabilized clay
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School of Engineering |
Master's thesis
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Authors
Date
2006
Major/Subject
Pohjarakennus ja maamekaniikka
Mcode
Rak-50
Degree programme
Language
en
Pages
97
Series
Abstract
Clays in the Nordic Countries are mainly very soft and sensitive due to their postglacial origin. These clays have behaviours and principal parameters which differ from most clays reported in the literature. But in contrast to the negative properties, Nordic clays have very low permeability and good resistance to harmful chemicals. Contaminants that have infiltrated into the ground tend to be diffused into the surroundings along with the seepage of water. The spreading of pollutants can be prevented by reducing water exchange between a contaminated area and its environment. Because Finnish clay has very low permeability, it is potentially a good material for barriers in landfill and disposal sites. In this way, in the beginning of the year 2006, a project aiming at improvement of sensitivity of clays was started at the Soil Mechanics and Foundation Engineering Laboratory of the Helsinki University of Technology (HUT). This project tries to improve clays softness by stabilizing with cement. One of the sub-tasks of the project concerns permeability. This report concerns permeability of the soft clays in order to collaborate on the project mentioned before. So, at the beginning of the year 2006 some samples were tested for this report with the objective to study their behaviours, to test different methods and models and to compare them. The samples tested are from Vanttila, Otaniemi and Murro. All the samples were tested in the laboratory by using a conventional oedometer. In this study permeability was measured as described by Leroueil (1990) in the conventional oedometer by applying a water pressure at the bottom of the sample after each loading step and measuring the pressure heads at the beginning and at the end of the test. Also, the permeability was obtained by means of indirect methods such as Taylor and Casagrande as well as of others parameters to have a greater knowledge about the soft clays. Permeability and coefficient of consolidation have been the mainparameters analyzed in this study. This report analyzes methods and models developed by the Soil Mechanics and Foundation Engineering Laboratory about permeability and coefficients of consolidation compared with other methods and models. The aim is to compare the differences and similarities among them and declare the possible advantages of the models or methods proposed for Soil Mechanics and Foundation Engineering Laboratory. The analysis of the results and the comparisons made verifies that the permeability and the coefficient of consolidation models proposed by Soil Mechanics and Foundation Engineering Laboratory give at least results similar to other models and they are more reliable because of the fact that more precise models have been used (i.e. strain-stress relationship of Janbu). It is also a very important task in this report to describe the way in which the Soil Mechanics and Foundation Engineering Laboratory has developed the Unconfined Compression Tests and the Permeability Tests since the preparation of the stabilized sample until the obtaining of results.Description
Supervisor
Ravaska, OlliThesis advisor
Lojander, MattiKeywords
permeability, stabilized clay