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GGU-AXPILE: Driven piles according to FRANKE

The approach after FRANKE is applied to driven piles (e.g. in the Geotechnical Engineering Handbook 2003, Part 3), allowing calculation of a resistance-settlement curve also for driven piles. The relationship given by Franke is:

Base resistance σ = β · (s/b*)1/c

Skin friction τ = α · qs

With:

s = pile settlement [mm]
qs = cone resistance of the CPT to DIN 4094 [MN/m²]
α, β, b*, c = coefficients according to the following table

Pile type

β
[-]

b*
[mm2c/MN]

c
[-]

α
[-]

Reinforced concrete driven piles

1.0

0.25

1.63

0.003

In-situ concrete driven piles

1.0

0.55

1.55

0.004

"Franki" piles

2.0

0.55

1.55

0.004

Plain steel piles

1.0

0.65

1.90

0.002

The above values can be adopted directly from within the program. However, you can also use your own values.

The values for the base resistance increase uninterrupted. A failure settlement cannot be read from the curve after Franke. You must therefore additionally define a failure settlement sg. This can be achieved either by means of an absolute value (e.g. sg = 0.5 cm) or a relative value as a function of the pile diameter (e.g. sg = 0.025 · pile diameter).

The GGU-AXPILE program does not check a minimum embedment in the load-bearing subsoil in accordance with the standard when this pile type is selected. The parameters β, b*, c listed in the table above describe the base resistance of a driven pile. The base resistance of a driven pile that can be activated is therefore completely independent of the soil parameters entered in the "Edit/Soils" menu item. You must therefore check yourself whether the soil in the pile toe area fulfils the parameters β, b*, c.

In general, this is the case if there is at least a medium dense compaction or at least a stiff to semi-solid consistency. The entered soil parameter qs together with the parameter α is solely responsible for the skin friction. The entered soil parameters γ' and γ are only relevant when working with tension piles.

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