Hobart sits on some of the most variable alluvial deposits in Tasmania — from the soft estuarine clays along the Derwent River to the dense glacial tills of the foothills. For any structure founded on these compressible layers, the oedometer consolidation test is the only reliable way to predict long-term settlement. We run a full suite of incremental loading stages under AS 1289.6.6.1, reporting pre-consolidation pressure, compression index Cc, and coefficient of consolidation cv. Our lab in Derwent Park processes samples within 72 hours of arrival, so your design team gets data before the next iteration.
A 5 kPa over-consolidation ratio misjudgment on Derwent River clay can double predicted settlement for a mid-rise building.
Methodology and scope
- Fixed-ring oedometer cells with 50 mm diameter specimens
- Digital displacement transducers reading to 0.001 mm
- Back-pressure saturation for low-permeability clays
Results feed directly into the ensayo de asentamiento diferencial analysis and help calibrate capacidad de carga for shallow foundations. For deep compressible layers we also recommend a estudio de permeabilidad en laboratorio to refine consolidation rates.
Local considerations
AS 1289.6.6.1 mandates that oedometer tests on saturated clays must account for full saturation prior to loading. In Hobart, where the water table can sit just 1.5 m below ground in areas like Moonah and Glenorchy, incomplete saturation leads to under-reported settlement. We back-pressure saturate every specimen to 200 kPa minimum, then verify B-value >0.95 before starting the loading sequence. Skipping this step on Derwent soft clay can underestimate total settlement by 40% or more — a risk no structural engineer should accept.
Applicable standards
AS 1289.6.6.1:2020 (Oedometer consolidation test), AS 1726:2017 (Geotechnical site investigations), AS 1289.6.6.1/D2435M-11 (Standard Test Methods for One-Dimensional Consolidation)
Associated technical services
Consolidation test with settlement analysis
Incremental oedometer test per AS 1289.6.6.1 plus settlement calculation under service loads. Includes Cc, Cs, cv, and mv for your design report.
Swelling index determination
Unload-reload cycle on the same specimen to measure Cs. Essential for over-consolidated clays common in Hobart's elevated suburbs.
Permeability from consolidation data
Back-calculated hydraulic conductivity (k) using cv and mv. Directly comparable to falling-head tests for cross-validation.
Typical parameters
Frequently asked questions
How long does an oedometer test take in Hobart?
A standard multi-stage test with eight load increments takes 7 to 10 days from sample receipt. Rush service (4 increments, preliminary cv) is available in 4 days.
What sample quality is required for oedometer testing?
We need 100 mm diameter thin-walled tube samples or block samples trimmed in the field. Disturbed or remoulded samples are not suitable — the test relies on intact structure to measure true pre-consolidation pressure.
How does the oedometer test differ from a triaxial test?
The oedometer measures one-dimensional compression and consolidation under zero lateral strain. It gives Cc, Cs, cv, and mv. The triaxial test measures shear strength and stress-strain behaviour under controlled confining pressure. They complement each other: oedometer for settlement, triaxial for stability.
What does an oedometer consolidation test cost in Hobart?
A full multi-stage oedometer test with eight load increments and swelling index costs between AU$280 and AU$620, depending on specimen count and reporting detail. Volume discounts apply for projects with more than six tests.