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 [K0vu) + 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.

Table C.1: Derived values for the bearing resistance factor, k, for spread foundations
 Soil Category pLM[MPa] k clay and silt ABC <0,71,2—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 ABC <0,51,0—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.

Table C.2: The shape coefficients, λc, λd, for settlement of spread foundations
 L/B circle square 2 3 5 20 λdλc 11 1,121,1 1,531,2 1,781,3 2,141,4 2,651,5

Table C.3: Derived values for the coefficient α for spread foundations
 Type of ground Description EM/pLM α peat 1 clay overconsolidatednormally consolidatedremoulded < 16 9—167—9 1 0,670,5 silt overconsolidated normally consolidated > 14 5—14 0,67 0,5 sand > 125—12 0,50,33 sand and gravel > 106—10 0,330,25 rock extensively fracturedunalteredweathered 0,330,50,67

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 [pLMp0] + 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 [K0vu) + 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.

Table C.4: Derived values of the bearing resistance factor, k, for axially loaded piles
 Soil category pLM[MPa] Bored piles and small displacement piles Full displacement piles clay and silt ABC < 0,7 1,2—2,0> 2,5 1,1 1,21,3 1,4 1,51,6 sand and gravel ABC < 0,5 1,0—2,0> 2,5 1,0 1,11,2 4,2 3,73,2 chalk ABC < 0,7 1,0—2,5> 3,0 1,1 1,41,8 1,6 2,22,6 marl AB 1,5—4,0> 4,5 1,8 1,8 2,6 2,6 weathered rock AB 2,5—4,0> 4,5 (i) (i) (i) Choose k for the closest soil category.

Table C.5: The selection of design curves for unit shaft resistance
 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 supportmud supporttemp casingperm casing 1111 1/21/21/21 2/31/21/21 –111 –1/21/21 –2/32/32 111 4/54/53/4 4/54/53/4 3332 4/54/543 66–– hand dug caisson 1 2 3 – – – 1 2 3 4 5 6 displacement piles closed endprefabconcretecast in situcoated shaft 1111 2222 2222 2323 2323 3334 1 2 3 3333 4444 44–– grouted piles low pressurehigh pressure 11 24 25 35 35 36 2– 35 46 56 56 –7
Figure C.1: Unit shaft resistance for axially loaded piles

For additional information and examples see Annex M.

Eurocode 7 Geotechnical design — Part 3: Design assisted by fieldtesting