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Coefficient of Reduction of a Pile Base Bearing Capacity ALFA p

The coefficient of reduction of pile base bearing capacity αp identifies the type of pile. Its values are determined from one of the available calculation methods or they can be entered manually by the user.

For NEN 6743 and EN 1997-2 methods the following built-in values of the coefficient αp are available:

Piles

αp [-]

prefabricated driven piles or steel piles

1.0

Franki pile

1.0

driven wooden pile

1.0

Vibrating

1.0

cast in place screw piles

0.9

prefabricated screw pile

0.8

cast in place screw piles with additional grouting

0.9

prefabricated screw pile with additional grouting

0.8

steel tubular piles

1.0

continuous Flight Auger (CFA)

0.8

bored piles or piles sheeted by bentonite suspense

0.5

bored piles with steel casing

0.5

For LCPC and Schmertmann the coefficient is back-calculated based on the value of cone resistance qc (the values are presented in the following table):

Orientation values of the coefficient αp based on the cone resistance qc

LCPC (Bustamante) Soil type

Cone resistance

qc [MPa]

αp

for bored piles

αp

for driven piles

Clay

< 1

0.04

0.50

1 < qc < 5

0.35

0.45

5 < qc

0.45

0.55

Sand

qc < 12

0.40

0.50

13 < qc

0.30

0.40

For NBN EN 1997-1 ANB standard, the following built-in values of the coefficient αp are available:

Piles

αp, tert. clay [-]

αp [-]

prefabricated driven piles or steel piles

1,0

1,0

Franki pile

1,0

1,0

driven wooden pile

1,0

1,0

Vibrating

1,0

1,0

cast in place screw piles

0,8

0,5

prefabricated screw pile

0,8

0,5

cast in place screw piles with additional grouting

0,8

0,5

prefabricated screw pile with additional grouting

0,8

0,5

steel tubular piles

1,0

1,0

continuous Flight Auger (CFA)

0,8

0,5

bored piles or piles sheeted by bentonite suspense

0,8

0,5

bored piles with steel casing

0,8

0,5

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