Pressuremeter Testing (PMT) for ground deformation parameters
Pressuremeter Testing (PMT) expands a cylindrical probe against the wall of a borehole at a chosen depth and records pressure and volume change. The test gives the pressuremeter modulus and the limit pressure, which are used directly in pressuremeter-based foundation design methods and to verify treated ground at depth.
When the test is used
Typically used for…
- Measuring in-situ deformation parameters at depth for foundation design.
- Ground where CPT cannot penetrate, including dense soils and weak rock.
- Verifying ground improvement at depth.
- Settlement and bearing calculations using pressuremeter-based methods.
Limitations
- Results depend strongly on borehole quality: a disturbed borehole wall reduces the measured stiffness.
- Tests are at discrete depths, not a continuous profile.
- Requires a drilling rig and experienced operators.
The test type, number and locations are agreed with the consultant for each project.
How the test works
A borehole is drilled with minimal disturbance and the probe is lowered to test depth. The membrane is inflated in pressure increments, each held for a set time, while the injected volume is recorded.
Plotting volume against pressure shows an initial seating phase, a pseudo-elastic phase from which the pressuremeter modulus (EM) is derived, and a plastic phase approaching the limit pressure (pL).
Test planning inputs
- Purpose and design method (for example the Ménard approach).
- Test depths and spacing.
- Drilling method suited to the ground.
- Expected pressures and probe type.
- Applicable standard.
Calibration and equipment checks
- Membrane resistance and system volume loss calibrated before testing.
- Pressure gauges and volume measurement checked.
- Drilling method confirmed to give a good-quality borehole wall.
Test execution controls
- Test pocket drilled just before testing to limit wall disturbance.
- Pressure increments and hold times as per the procedure.
- Volume readings at standard times in each increment.
- Test depth recorded.
- Records reviewed for borehole quality.
Interpretation and reporting
The test plan, the raw record and the interpretation are kept separate, so it is always clear what was specified, what was measured and what it shows.
What is specified
Test depths, method and use of results agreed with the consultant.
What was measured
Corrected pressure-volume readings for each test.
What it shows
Pressuremeter modulus EM and limit pressure pL, interpreted for design or verification.
Deliverables
- Borehole and test location plan
- Calibration records
- Pressure-volume curves for each test
- EM and pL values with depth
- Interpretation report
Common questions
What does a pressuremeter test measure?
The pressuremeter modulus and the limit pressure of the ground at the test depth.
When is a pressuremeter test chosen instead of CPT?
Where CPT cannot penetrate, or where the foundation design method uses pressuremeter parameters.
Why does borehole quality matter?
A disturbed borehole wall reduces the measured stiffness, so the drilling method is chosen to keep the wall intact.
Discuss the testing your project needs.
Share the project stage, the ground conditions and the specification or acceptance criteria.