Oedometer Test: One Dimensional Compression
The oedometer test in accordance with DIN EN ISO 17892-5 is a uniaxial compression test that determines the axial compressibility of a cylindrical specimen with lateral deformation restraint. The specimen is incrementally loaded or unloaded while it is allowed to drain or absorb water. The test provides parameters to describe the compression, consolidation and swelling behavior. A so-called compression curve is generated from the test data, presented in diagram with the vertical pressure on the x-axis and the void ratio or the settlement on the y-axis. In order to evaluate the creep or swelling behavior, an additional evaluation of the time component can be performed.
Application and Potentioal
The oedometer modulus Eoed (secant modulus) and the compression index Cc can be determined as the most important values for characterizing the compressibility of soil. Among other things, they serve as crucial parameters in the design of flat foundations. The swelling index Cs and the swelling modulus Ee describe the behavior of soils under decreasing and re-increasing pressure. The creep coefficient Cα and the coefficient of consolidation cV can be used to derive information on long-term settlement behavior. Performing swelling tests can help to assess the risk of soil- or binder-induced swell phenomena. Furthermore, in the case of soils that have had a stress history, the overconsolidation rate (OCR) can be determined.
The tests can be performed on undisturbed or disturbed and recompacted specimens. The in-situ stress conditions need to be taken into account for an accurate interpretation of the results.
Usual dimensions of the specimen are d = 71.3 or 100 mm with a height of h = 20 or 30 mm. The maximum grain size is limited to 1/5 of the height (for very homogenous soils 1/10 is recommended). Non-cohesive soils can be compacted directly in the oedometer ring.
For preparing disturbed specimens the following must be known:
- in-situ/desired density
- desired moisture content and type of fluid to be added
- OCR if required
We offer tests in all common standard sizes using the fixed or floating ring setup. The stress can be applied by controlling the distance, velocity or load up to 50 kN. High-precision measuring devices that automatically collect data are available for the evaluation of swelling or creep processes.
- DIN EN ISO 17892-5 (2017): Ödometerversuch mit stufenweiser Belastung
- Kolymbas, Dimitrios (2019): Geotechnik. Bodenmechanik, Grundbau und Tunnelbau. 5th ed. Chapter 6.7
- Boley, Conrad (2012): Handbuch Geotechnik. Grundlagen – Anwendungen – Praxiserfahrungen. Chapters 2.3.3 und 220.127.116.11
- Eurocode 7 (DIN EN 1997-2): Chapter 5.9: Versuche zur Bestimmung der Zusammendrückbarkeit und der Verformungen von Böden