Annex E
(Informative)
Pressuremeter Test (PMT)
E.1 Example of a method to calculate the bearing resistance of spread foundations
(1) The following is an example of a method to calculate the bearing resistance of spread foundations using a semi-empirical method and the results of an MPM test.
(2) The bearing resistance is calculated from:
R/A' = σv0 + k(pLM – p0)
where
R
is the resistance of the foundation against normal loads;
A'
is the effective base area as defined in EN 1997-1;
σv0
is the total (initial) vertical stress at the level of the foundation base;
pLM
is the representative value of the Ménard limit pressures at the base of the spread foundation;
p0
is [K0(σv0 – u) + u] with K0 conventionally equal to 0,5, σv0 is the total (initial) vertical stress at the test level and u is the pore pressure at the test level;
k
is a bearing resistance factor given in Table E.1;
B
is the width of the foundation;
L
is the length of the foundation;
De
is the equivalent depth of foundation.
Table E.1 — Correlations for deriving the bearing resistance factor, k, for spread foundations
| Soil category | category | pLM MPa |
k |
| Clay and silt | A B C |
< 0,7 1,2–2,0 >2,5 |
0,8 [1 + 0,25 (0,6 + 0,4 B/L) × De/B] 0,8 |1 + 0,35 (0,6 + 0,4 B/L) × De/B] 0,8 [1 + 0,50 (0,6 + 0,4 B/L) × De/B] |
| Sand and gravel | A B C |
<0,5 1,0–2,0 >2,5 |
[1 + 0,35 (0,6 + 0,4 B/L) × De/B] [1 + 0,50 (0,6 + 0,4 B/L) × De/B] [1 + 0,80 (0,6 + 0,4 B/L) × De/B] |
| Chalk | 1,31 [1 + 0,27 (0,6 + 0,4 B/L) × De/B] | ||
| Marl and weathered rock | [1 + 0,27 (0,6 + 0,4 B/L) × De/B] |
NOTE This example was published by the French Ministère de l'Equipement du Logement et des Transport (1993). For additional information and examples, see X.3.2.
E.2 Example of a method to calculate the settlements for spread foundations
(1) The following is an example of a method to calculate the settlement, (s), of spread foundations using a semi-empirical method developed for MPM tests.
where
B0
is a reference width of 0,6 m;
λd, λc
are shape factors given in Table E.2;
α
is a theological factor given in Table E.3;
Ec
is the weighted value of EM immediately below the foundation;
Ed
is the harmonic mean of EM in all layers up to 8 × B below the foundation;
σv0
is the total (initial) vertical stress at the level of the foundation base;
q
is the design normal pressure applied on the foundation.
Table E.2 — The shape coefficients, λc, λd for settlement of spread foundations
| L/B | Circle | Square | 2 | 3 | 5 | 20 |
| λc λd |
1 1 |
1,12 1,1 |
1,53 1,2 |
1,78 1,3 |
2,14 1,4 |
2,65 1,5 |
Table E.3 — Correlations for deriving the coefficient α for spread foundations
| Type of ground | Description | EM/pLM | α |
| Peat | 1 | ||
| Clay | Over-consolidated Normally consolidated Remoulded |
> 16 9—16 7—9 |
1 0,67 0,5 |
| Silt | Over-consolidated Normally consolidated |
>14 5—14 |
0,67 0,5 |
| Sand | >12 5–12 |
0,5 0,33 |
|
| Sand and gravel | >10 6–10 |
0,33 0,25 |
|
| Rock | Extensively fractured Unaltered Weathered |
0,33 0,5 0,67 |
NOTE This example was published by the French Ministère de l'Equipement du Logement et des Transport (1993). For additional information and examples, see X.3.2.
E.3 Example of a method to calculate the compressive resistance of a single pile
(1) The following is an example of a method to calculate the ultimate compressive resistance, Q, of piles from the MPM test, using:
Q = A × k × [pLM – p0] + PΣ[qsi × zi]
where
A
is the base area of the pile which is equal to the actual area for close ended piles and part of that area for open-ended piles;
pLM
is the representative value of the limit pressure at the base of the pile corrected for any weak layers below;
p0
is [K0(σv0 – u)+ u] with K0 conventionally equal to 0,5, and σv0 is the total (initial) vertical stress at the test level and u is the pore pressure at the test level;
k
is a compression resistance factor given in Table E.4;
P
is the pile perimeter;
qsi
is the unit shaft resistance for soil layer i given by Figure E.1 read in conjunction with Table E.5;
zi
is the thickness of soil layer i.
NOTE This example was published by the French Ministerè de l'Equipement du Logement et des Transport (1993). For additional information and examples, see X.3.2.
Table E.4 — Values of the compression resistance factor, k, for axially loaded piles
| Soil category | Category | pLM MPa |
Bored piles and small displacement piles | Full displacement piles |
| Clay and silt | A B C |
< 0,7 1,2—2,0 > 2,5 |
1,1 1,2 1,3 |
1,4 1,5 1,6 |
| Sand and gravel | A B C |
< 0,5 1,0—2,0 > 2,5 |
1,0 1,1 1,2 |
4,2 3,7 3,2 |
| Chalk | A B C |
< 0,7 1,0—2,5 > 3,0 |
1,1 1,4 1,8 |
1,6 2,2 2,6 |
| Marl | A B |
1,5—4,0 > 4,5 |
1,8 1,8 |
2,6 2,6 |
| Weathered rock | A B |
2,5—4,0 > 4,5 |
a | a |
| a) Choose k for the closest soil category. | ||||
Table E.5 — The selection of design curves for unit shaft resistance
| Soil category | Clay and silt | Sand and gravel | Chalk | Marl | Weathered rock | ||||||||
| pLM category | A | B | C | A | B | C | A | B | C | A | B | ||
| Pile type | |||||||||||||
| Bored piles and caissons | No support Mud support Temporary casing Permanent casing |
1 1 1 1 |
1/2 1/2 1/2 1 |
2/3 1/2 1/2 1 |
— 1 1 1 |
— 1/2 1/2 1 |
— 2/3 2/3 2 |
1 1 1 — |
3 3 2 — |
4/5 4/5 3/4 — |
3 3 3 2 |
4/5 4/5 4 3 |
6 6 — — |
| Hand-dug caisson | 1 | 2 | 3 | — | — | — | 1 | 2 | 3 | 4 | 5 | 6 | |
| Displacement piles | Closed end steel tube Prefab. Concrete Driven cast in-situ Coated shaft (concrete driven steel a) |
1 1 1 1 |
2 2 2 1 |
2 2 2 2 |
2 3 2 3 |
2 3 2 3 |
3 3 3 4 |
1 | 2 | 3 | 3 3 3 3 |
4 4 4 4 |
4 4 — — |
| Grouted piles | Low pressure High pressure | 1 1 |
2 4 |
2 5 |
3 5 |
3 5 |
3 6 |
2 — |
3 5 |
4 6 |
5 6 |
5 6 |
— 7 |
| a A preformed steel pile of tubular or H-section, with enlarged shoe, is driven with simultaneous pumping of concrete (or mortar) into the annular space. | |||||||||||||
Key
- (X) Limit pressure (pLM), (Y) Unit shall resistance (qsi)
- 1 to 7 design curves for unit shaft resistance
Figure E.1 — Unit shaft resistance for axially loaded piles
