Updated 14 December 2010
Concept
The
standard
oedometer test, also referred to as consolidation test or
one-dimensional compression test, is a classical laboratory test that
allows characterizing the soil
stress-strain behavior during one-dimensional compression or swelling. Carried
out on saturated soil specimens, this test can be used to determine
consolidation and swelling parameters. The standard oedometer test is
one of the most commonly used tests in geotechnical laboratory testing
program.
Description and test procedure
The standard oedometer test is
carried out on a cylindrical specimen of saturated soil with the
dimension of usually 75 mm diamater and 14-20 mm thick. The soil sample
is enclosed in a metal ring and is placed on a porous stone. The
loading cap has also a porous stone, so the sample is sandwiched
between two porous stones. When preparing the sample, filter papers are
added between the soil and the porous stones. The sample is then
mounted in the consolidation cell and the loading unit. Water is added
into the cell around the sample, so the sample remains saturated during
the test. The two porous stones at the top and bottom of the sample
allow a two-way drainage of the sample.
The test involves
applying increments of vertical static load to the sample and recording
the corresponding settement. Increments of vertical static load are
usually applied using dead loads and a static loading system. The
change in the thickness of the sample against time is recorded during
each loading increment. The duration of the application of each load depends on the soil ans its consolidation characteristics. Once equilibrium reached for a loading step, the next incremendt is applied. The load is doubled at each increment until reaching the maximum required load, e.g. 25, 50, 100, 200, 400, 800 kPa. The
range of applied stress depends on the range of effective stress which
is needed in the consolidation analysis of the case under consideration.
When
the full consolidation at the maximum applied load is rechaed, the
sample is unloaded in one or several stages and the swelling of the
sample is recorded. At the end of the test, the sample is carefull
yremoved and its thickness and water content is measured.
The
consolidation test results include the presentationo of stress-void
ratio in a semi-logarithmic scale. From the changes in thickness at the
end of each loading step, one can determine the Swelling Index (C s), Compression
Index (C c) and, Coefficient of Volume Compressibility (m v). The coefficient
of consolidation (c v)
and the rate of consolidation can be also measured using the results of
the thickness changes of the sample against time during a load step.
Test Standards
- BS 1377-5:1990
- ASTM D2435 - 04 Standard Test Methods for One-Dimensional Consolidation Properties of Soils Using Incremental Loading Link
Related experimental results on Database
- GD001: Standard oedometer test on dry reconstituted silty clay, Azad Koliji, Laurent Vulliet, Lyesse Laloui Access
- GDL001: Determining the Intrinsic Compressibility of Fine-Grained Soils,
A.B. Cerato, A.J. Lutenegger. 2004. Access
- GDL012: Laboratory hydro-mechanical characterisation of Boom clay at Essen and Mol, Y. F. Deng, A. M. Tang, Y. J. Cui, X. P. Nguyen, X. L. Li, L. Wouters, Access
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External Links
- Detailed description of Consolidation test, Chap 6.2 of Experimental Soil Mechanic Bardet, J. P., Experimental Soil Mechanics, 1997, Prentice-Hall, Upper Saddle River, New Jersey.
- Detailed description of Consolidation test with photos and an example data Engineering Properties of Soils Based on Laboratory Testing, Experiment 11: Consolidation, Prof. Krishna Reddy, UIC
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