Principle and application
The triaxial test measures the strength and deformability of soil under controlled stress, reproducing the field stress state in the laboratory. By shearing the specimen under drained or undrained conditions, the strength envelope is obtained (cohesion and friction angle); the Damasco Penna laboratory tests up to 5,000 kPa.
The test in stages
Specimen trimming
The undisturbed sample is trimmed and mounted in the triaxial cell.
Saturation and consolidation
Back pressure is applied and the specimen is consolidated under the design stress.
Shearing
The specimen is sheared in a controlled manner, measuring stress and strain.
Interpretation
The strength envelope is derived (cohesion and friction angle).
To ASTM D4767 / D7181
| Strength | Cohesion (c) and friction angle (φ) |
|---|---|
| Stress path | Drained/undrained behaviour |
| Pore pressure | Measured during shearing (CIU) |
| High stress | Testing up to 5,000 kPa |
Quality and field operation
Data quality
- Calibrated and traceable load frames and transducers.
- Control of saturation (B parameter) and consolidation.
- Digital recording of stress, strain and pore pressure.
- Interpretation and report by an engineer.
Safety and operation
- Qualified for high-compliance areas: mining, industry and ports.
- Organised, signed work front with an HSE procedure in place.
- Own crews and fleet, including night shifts.
The deliverable
| Test report | Stress-strain curves and strength envelope |
|---|---|
| Parameters | c, φ and pore pressure behaviour |
| Conditions | Test type, stresses and saturation |
| Typical lead time | According to the number of specimens |
Sectors and project types
Frequently asked questions about the triaxial test
What is the triaxial test for?
The triaxial test measures the strength and deformability of soil under controlled stress, reproducing the field stress state in the laboratory. By shearing the specimen under drained or undrained conditions, the strength envelope is obtained (cohesion and friction angle); the Damasco Penna laboratory tests up to 5,000 kPa.
What is the difference between CIU, CID and UU?
They are drainage conditions: UU (unconsolidated, undrained), CIU (isotropically consolidated, undrained, with pore pressure measurement) and CID (consolidated, drained). The choice depends on the design situation to be represented.
Why test up to 5,000 kPa?
Tall dams and deep foundations impose high stresses. The Damasco laboratory tests at this range to represent those real conditions.
High-stress triaxial testing
Technical bulletin on triaxial tests up to 5,000 kPa in dam projects.
Triaxial testing for your project
Tell us about your project and we will prepare the investigation plan and the quote.