Page 150 - Pipelines and Risers

Vortex-induced Vibrations (VIV) and Fatigue 123

Table 9.2 Recommended values of key parameters and coefficients for typical offshore soils.

USCS symbol IWddescription I Submergeddensity I PlaneAngleof I C.

- very dense 10.6 40
SM Silty sands, poorly 8.0-11-5 3 1-37
graded I
- very loose 8.9 27
- medium loose 10.1 32
- very dense 11.4 38
sc Clayey sands, poorly 8.0-1 1 .o 29-35
graded
m Silts and clayed silts 8.0- 1 1 .o 26-33
CL Clays of low to 8.0- 1 1 .o NIA
medium plasticity
Clays of high I 3.09.0 I I io-iGQ I
I CH I Dlasticitv N/A
I - very loose I I 10 1
- medium loose 50
- very dense 100

The recommended value of modulus of subgrade reaction (K,) are listed in Table 9.3
Table 9.3 Estimates of modulus of subgrade reaction for different types of soil.
I Soil tvDe I Suberade reaction K. WPa) I
I Very soft clay I 1-10 B
Soft clav I 3-33 I
Medium clay 9-33
Hard clay I 30-67
Sandv clay/ moraine clav I 13- 140
Loose sand I 5-13 I
Dense sand 25-48

Rock 550-52000
Rock with marine growth 550-52000