Methodology
Our triaxial testing follows BS 1377-7:1990 and ASTM D4767, employing consolidated undrained (CU) and consolidated drained (CD) methods. Specimens are saturated to a B-value ≥ 0.95 before shearing at strain rates of 0.1–1.0% per minute. Consolidation tests adhere to BS 1377-5:1990, using oedometers with incremental loading up to 1600 kPa. Each test records void ratio versus log pressure, and our team calculates the pre-consolidation pressure using Casagrande’s method. All equipment is calibrated annually to UKAS standards, and data acquisition is automated for precision. For a deeper understanding of our overall approach, visit our Soil Mechanics Laboratory page.
Reference Technical Parameters
| Parameter | Reference Value |
|---|---|
| Consolidation Coefficient (cv) | 1.0 × 10⁻⁸ to 1.0 × 10⁻³ m²/s |
| Undrained Shear Strength (su) | 10–500 kPa (CU triaxial) |
| Effective Friction Angle (φ') | 20°–45° (CD triaxial) |
| Pre-consolidation Pressure (σ'p) | 50–800 kPa (oedometer) |
| Strain Rate (Triaxial) | 0.1–1.0 %/min (per BS 1377) |
Local Considerations — United Kingdom
The United Kingdom’s varied geology—from London Clay to glacial tills in Aberdeen—requires tailored triaxial and consolidation programs. In cities like London, deep foundations often encounter high-plasticity clays requiring long-term consolidation analysis. For coastal developments in Aylesbury, our team evaluates settlement under cyclic loading. In Bangor, where peat deposits are common, we adjust testing to capture high compressibility. Our firm coordinates with local geotechnical engineers to select appropriate stress paths and drainage conditions, ensuring results reflect in-situ behavior. This regional expertise, combined with our national coverage, allows us to deliver cost-effective solutions without compromising technical rigor. For more on our work in specific cities, see our Aberdeen page.
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Applicable Standards
- BS 1377-5:1990 – Methods of test for soils: Consolidation and permeability tests
- BS 1377-7:1990 – Methods of test for soils: Shear strength tests (triaxial)
- ASTM D4767-11 – Standard Test Method for Consolidated Undrained Triaxial Compression Test
- Eurocode 7 – Geotechnical design (EN 1997-1:2004)
Frequently Asked Questions
What is the difference between consolidated undrained (CU) and consolidated drained (CD) triaxial tests?
In CU tests, drainage is allowed during consolidation but prevented during shearing, measuring undrained shear strength. In CD tests, drainage is permitted throughout, yielding effective stress parameters. Our laboratory selects the method based on project drainage conditions and loading rate.
How long does a typical consolidation test take?
A standard oedometer test with 5–7 load increments, each maintained for 24 hours, takes approximately 7–10 days. Step loading accounts for primary consolidation completion. For projects requiring faster results, we offer constant rate of strain (CRS) tests.
What sample quality is required for triaxial testing?
Samples must be undisturbed, with a diameter of at least 38 mm and a height-to-diameter ratio of 2:1. They should be sealed immediately after extraction to preserve moisture content. Our team inspects each specimen for fissures or disturbance before testing.
How much does triaxial and consolidation testing cost in the United Kingdom?
Costs vary based on sample depth, number of stress stages, and site accessibility. A typical triaxial test (CU with three specimens) ranges from £250 to £500, while a full consolidation curve (5 increments) is approximately £200–£400. Contact our team for a project-specific quotation.