Annex C.1
(informative)
Pressuremeter Test (PMT)
(1) The following is an example of the calculation of 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
where:
R is the resistance of the foundation against normal loads;
A' is the effective base area as defined in ENV 1997-1;
σv0 is the total (initial) vertical stress at the level of the foundation base;
pLM representative value of the Ménard limit pressures at the base of the spread foundation;
p0 is [K0(σv − u) + u] with K0 conventionally equal to 0,5, and Fv is the total 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 C.1;
B is the width of the foundation;
L is the length of the foundation;
De is the equivalent depth of foundation.
| Soil 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 + 0,4B/L)×De/B] 0,8×[1 + 0,50 (0,6 + 0,4B/L)×De/B] |
| sand and gravel | A B C |
<0,5 1,0—2,0 >2,5 |
[1 + 0,35 (0,6 + 0,4B/L)×De/B] [1 + 0,50 (0,6 + 0,4B/L)×De/B] [1 + 0,80 (0,6 + 0,4B/L)×De/B] |
| chalk | 1,3×[1 + 0,27 (0,6 + 0,4B/L)×De/B] | ||
| marl and weathered rock | [1 + 0,27 (0,6 + 0,4B/L)×De/B] | ||
For additional information and examples, see Annex M
ANNEX C.2
(informative)
Pressuremeter Test (PMT)
(1) The following is an example of the calculation of 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;
B is the width of the foundation;
λd and λc are shape factors given in table C.2;
α is a rheological factor given in table C.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.
| L/B | circle | square | 2 | 3 | 5 | 20 |
| λd λc |
1 1 |
1,12 1,1 |
1,53 1,2 |
1,78 1,3 |
2,14 1,4 |
2,65 1,5 |
| Type of ground | Description | EM/pLM | α |
| peat | 1 | ||
| clay | overconsolidated normally consolidated remoulded |
< 16 9—16 7—9 |
1 0,67 0,5 |
| silt | overconsolidated 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 |
For additional information and examples, see Annex M.
ANNEX C.3
(informative)
Pressuremeter Test (PMT)
(1) The following is an example of the calculation of the ultimate bearing resistance, Q, of piles from the MPM test, using
Q = A k [pLM – p0] + P Σ [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(σv – u) + u] with K0 conventionally equal to 0,5, and σv is the total vertical overburden pressure at the test level and u is the pore pressure at the test level;
k is a bearing resistance factor given in table C.4;
P is the pile perimeter;
qsi is the unit shaft resistance for soil layer i given by figure C.1 read in conjunction with table C.5;
zi is the thickness of soil layer i.
| Soil 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 |
(i) | (i) |
| (i) Choose k for the closest soil category. | ||||
| soil category | clay and silt | sand and gravel | chalk | marl | rock | ||||||||
| pile type | A | B | C | A | B | C | A | B | C | A | B | ||
| bored piles and caissons | no support mud support temp casing perm 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 |
4/5 4/5 3/4 |
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 prefab concrete cast in situ coated shaft |
1 1 1 1 |
2 2 2 2 |
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 |
For additional information and examples see Annex M.
