Geotechnical model - Sand Material

1. Input for calculating axial resistance

Angle of soil friction \(\delta\)
Angle of soil friction on the pile wall (degrees).

Limiting unit skin friction f 1 (F/L^2)
See table below.

Bearing factor N q
See table below.

Limiting tip resistance q 1 (F/L^2)
See table below.

Initial shear modulus of soil (F/L^2)

For sands, the initial shear modulus of the soil to be used for generation of t-z curves is to be taken as

\(G_0=\frac{m\sqrt{\sigma_a\sigma_v}}{2(1+v)}\) with m=1000tan\(\phi\)

in which \(\sigma_a\)=100kPa is a reference pressure and \(\sigma_v\) is the vertical effective stress, v is the Poisson’s ratio of the soil, and \(\phi\) is the friction angle of the soil.

Recommendation from DNV-OS-J101 for the angle of soil friction \(\delta\), Bearing factor N q and corresponding limiting unit skin friction f 1 and limiting tip resistance q 1 is as following:

Table F-1 Design parameters for axial resistance of driven piles in cohesionless silicious soil 1)

Density

Soil description

\(\delta\) (degrees)

f 1 (kPa)

N q (-)

q 1 (MPa)

Very looseLooseMedium

SandSand-silt 2)Silt

15

48

8

1.9

LooseMediumDense

SandSand-silt 2)Silt

20

67

12

2.9

MediumDense

SandSand-silt 2)

25

81

20

4.8

DenseVery dense

SandSand-silt 2)

30

96

40

9.6

DenseVery dense

GravelSand

35

115

50

12.0

1) The parameters listed in this table are intended as guidelines only. Where detailed information such as in-situ cone penetrometer tests, strength tests on high quality soil samples, model tests or pile driving performance is available, other values may be justified.

2) Sand-silt includes those soils with significant fractions of both sand and silt. Strength values generally increase with increasing sand fractions and decrease with increasing silt fractions. For a more detailed description of the parameters, please refer to Offshore Standard DNV-OS-J101, May 2014, Appendix F.