Ménard Pressuremeter Calculator — PLim, EM, Bearing Capacity
The Ménard pressuremeter (PMT) is an in-situ test that directly measures the soil response to cylindrical expansion using a probe inserted into a pre-bored borehole. It provides two fundamental parameters: the pressuremeter modulus EM (stiffness) and the limit pressure PLim (strength). This calculator processes test data to calculate the allowable bearing capacity qadm of footings directly from PLim without needing φ and c, and estimates settlements using the Ménard 1975 method. It is the most widely used in-situ test in France, Spain, Morocco, and French-speaking African countries; it is also used in the region for works on ports, wind turbines, and large-span bridges.
What is it and when is it applied?
A borehole is drilled with a diameter matching the probe (typically 60-74 mm), the probe is inserted, and hydraulic pressure is applied in incremental steps while recording the injected volume. The pressure-volume curve has three zones: recompaction of the soil disturbed by drilling (zone I), pseudo-elastic linear response (zone II) where EM is calculated, and plastic zone (zone III) where PLim is reached. Applicable in all soils (sands, clays, gravels, fills, tropical soils) and in soft rocks. Highly recommended when: undisturbed sampling is difficult (loose sands, sensitive clays), the soil is heterogeneous with depth, or continuous characterisation of the geotechnical profile is required.
Applied Formulas
Pressuremeter modulus (linear elastic section):
EM = 2·(1 + ν) · V · (ΔP / ΔV)
where V = average probe volume in the elastic section, ν ≈ 0.33
Limit pressure PLim: horizontal asymptote of the P-V curve; in practice taken where ΔV/ΔP stabilises or at twice the initiation volume of the plastic section
Net limit pressure: P*Lim = PLim − P0, where P0 = effective horizontal geostatic pressure at the test level
Bearing capacity (Ménard 1975):
qadm = qu / FS, with qu = P0 + kp · P*Lim
kp (bearing factor) depends on soil type and footing shape: kp = 0.8-1.1 sands; 0.25-0.70 clays; 1.3-3.0 soft rocks
Settlement (Ménard method):
s = (α/9·EM) · q · B · λd + (α·λc·B·q) / (9·EM·B/B0)^α
simplified: s ≈ (q · B · λ) / (9 · EM / α), with α = 1 clays, α = 1/3 sands, B0 = 0.6 m (reference width)
Calculation Example
| Parameter | Value |
|---|---|
| Test depth | 4.0 m below ground level |
| Soil type | Compact sand with cementation |
| EM (pressuremeter modulus) | 28 MPa |
| PLim (limit pressure) | 2.8 MPa |
| P0 (effective horizontal geostatic pressure) | 0.04 MPa |
| P*Lim = PLim − P0 | 2.76 MPa |
| kp for square footing in dense sand | 1.1 |
| FS against ultimate pressure | 3 (BS EN 1997-1) |
| Proposed footing width B | 3.0 m |
| Proposed footing load q | 250 kPa |
Ultimate bearing capacity: qu = P0 + kp·P*Lim = 0.04 + 1.1·2.76 = 0.04 + 3.036 = 3.076 MPa = 3,076 kPa. Allowable capacity: qadm = qu/FS = 3,076/3 = 1,025 kPa. With proposed load q = 250 kPa there is a 4× margin. Estimated settlement using Ménard (α = 1/3 sands, λ square geometry ≈ 1.1): s ≈ (q·B·λ)/(9·EM/α) = (250·3.0·1.1) / (9·28,000/0.333) = 825 / 756,756 = 0.00109 m = 1.1 mm. Remarkable: a settlement of barely 1 mm demonstrates that the dense cemented sand is an excellent foundation soil for wind turbines, which require high stiffness to avoid oscillations. EM/PLim ratio: 28/2.8 = 10, consistent with compact sand (typical EM/PLim 8-16 in sands). If > 20 it would indicate overconsolidated soil or soft rock; < 6 suggests remoulded soil or soft clay.
Result: qadm = 1,025 kPa · Expected s = 1.1 mm · 4× margin over proposed load
Interpretation of Results
The EM/PLim ratio = 10 confirms a dense, cemented sand, without appreciable remoulding, suitable for direct shallow foundations without improvement. The allowable bearing capacity of 1,025 kPa is very high; the proposed load q = 250 kPa leaves a significant margin for dynamic wind loads on wind turbine towers. The predicted settlement of 1 mm is well below the allowable limit (typically 25 mm in BS EN 1997-1) and meets the stiffness requirements for turbine operation (shaft inclination tolerances of 0.003 rad).
Reference Standards
- BS EN 1997-1 — Cites the pressuremeter as an accepted in-situ test for characterisation
- NF P94-110-1 (France) — Ménard pressuremeter test, field procedure
- NF P94-261 (France) — Justification of geotechnical works, shallow foundations part with PMT
- BS EN ISO 22476-5 — Standard test method for prebored pressuremeter testing
- Ménard, L. (1975). The Ménard pressuremeter interpretation and application
- Baguelin, F., Jezequel, J.F., Shields, D.H. (1978). The pressuremeter and foundation engineering
- FHWA-IF-89-008 — The pressuremeter test for highway applications
Frequently Asked Questions
Ménard pressuremeter or self-boring?
Ménard (MPT): probe inserted into a pre-bored borehole; simpler and cheaper but partially disturbs the soil. Self-boring (SBPT): the probe is pushed in cutting the soil without remoulding; much more precise but 3-5 times more expensive. In common civil projects (buildings, bridges) Ménard is sufficient; in academic research and offshore works where sensitive samples are critical, SBPT wins.
How do I recognise a poorly executed PMT test?
Signs: EM/PLim < 5 (soil was remoulded during drilling), P-V curve without a clear elastic section, PLim never reached (insufficient injected volume), bubbles in the hydraulic system visible as a jump in the curve. Recommendation: always request the graphical P-V curve, not just the EM and PLim values.
PMT for piles?
Yes, it is one of the best tests for pile design according to the French standard Fascicule 62-V: qp (tip) = kc·P*Lim with kc depending on pile type and soil, qs (shaft friction) from specific charts versus P*Lim. More reliable method than SPT correlations in clays and silty sands.
Can PMT be used in rocks?
Yes, with a reinforced probe (steel jacket) and pressures up to 10 MPa. In soft to medium rocks (UCS < 20 MPa) it provides useful parameters for structures founded on rock (mountain bridges, dam foundations). In hard rocks (sound granites, basalts) the test is of limited value because the probe cannot generate sufficient deformation.