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NF P94-261 (PMT)

Settlement of spread footing using PMTs according to NF P94-261 method is based on the formula:

where:

s

-

overall settlement

Ec, Ed

-

equivalent pressiometric modulus

α

-

rheological coefficient

q

-

stress in the footing bottom

λc, λd

-

shape coefficients

B

-

footing width

B0

-

reference width (0,6 m)

Approximate values of rheological coefficient α for soils:

Clay

Silt

Sand

Gravel

Overconsolidated

1

2/3

1/2

1/3

Normally consolidated

2/3

1/2

1/3

1/4

Non-consolidated

1/2

1/2

1/3

1/4

Approximate values of rheological coefficient α for rocks:

Rocks

Type

α

Almost intact

2/3

Normally fractured

1/2

Very fractured

1/3

Very altered

2/3

Shape coefficients λc, λd are interpolated according to the following table:

L/B

circle

square

2

3

5

20

λd

1

1,12

1,53

1,78

2,14

2,65

λc

1

1,1

1,2

1,3

1,4

1,5

Equivalent pressiometric modulus Ec and Ed are determined according to the pressiometric modulus measured in layers of B/2 thickness below the foundation bottom.

Modul Ec is determined as an average pressiometric modulus in the first layer of B/2 thickness below the foundation bottom.

The determination of modulus Ed depends on the overall depth of PMT (dPMT).

Literature:

CSN EN 1997-2 Annex E

NF P94-261

Menard, L. (1975): "The Menard Pressuremeter: Interpretation and Application of the Pressuremeter Test Results to Foundations Design", Sols-Soils, No. 26, Paris, France.

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