Calculation of Vertical grain pressure at pipeline axis

The vertical grain pressure at pipeline axis is defined as:

The upper one is used if the freatic plane is not specified or below the pipeline axis. The bottom one is used if the freatic plane is above the pipeline axis level. Both formula's have a range from ground level to the pipeline axis.

σk |
Vertical grain pressure at pipeline axis |

γ* |
(Mean) volume weight (averaged over range from ground level to pipeline axis) |

H* |
Height of soil coverage from ground level to pipeline axis |

γ*1 |
(Mean) volume weight (averaged over range from ground level to freatic plane) |

H*1 |
Height of soil coverage from ground level to freatic plane |

γ*2 |
Volume weight (saturated) (averaged over range from freatic plane to pipeline axis) |

H*2 |
Height of soil coverage from freatic plane to pipeline axis |

γw |

Illustration of properties for sigma k

Calculation of Effective Young's modulus of soil

NEN3650-1:2017

The Effective Young's modulus of soil is calculated as:

It is only used in the NEN3650-1:2017 calculation methodology and only for soil types classified as sand (gravel, sand and loam).

Eeff |
Effective Young's modulus |

E100 |
Young's modulus for an effective vertical grain pressure of 100 kPa (averaged over specified range) |

σv |
Vertical grain pressure at specific depth (given in N/mm2, factor 0.1 is not dimensionless) |

In case all soil layers are custom sand Eeff = E100, in all other combination of soil layers Eeff = E100/Cn as described above.

Calculation of Effective angle of internal friction

NEN3650-1:2017

The Effective angle of internal friction of soil for a specific Effective Young's modulus of the soil is defined as:

It is only used in the NEN3650-1:2017 calculation methodology and only for soil types classified as sand (gravel, sand and loam). For the non-sand classified soil types the Effective angle of internal friction is the Angle of internal friction as supplied as soil type property.

φeff |
Effective angle of friction |

Eeff |
Effective Young's modulus for a specific range and depth |

The formula has different constants for the different sandy soil types. There is even distinction between clean, slightly silty and highly silty sand.

Gravel:

Sand, clean:

Sand, slightly silty:

Sand, highly silty:

Loam:

Last changed: 10/30/2019