The soil range of importance for the Ultimate horizontal soil reaction is from ground level to the bottom of the pipeline.
For the NEN36501992 calculation methodology two formulae are given, one for sandy soil types and one for clayey/peaty soil types.
Sandy:
Clayey/peaty:
Qhor

Ultimate horizontal soil reaction

Kq

Function of φ and H*/D 1 (for sandy soil types)

σk

Vertical grain pressure at pipeline axis (see General parameters)

α

constant: 0.6

Kc

Function of φ and H*/D 2 (for clayey/peaty soil types)

cu

Undrained cohesion (averaged over range from ground level to the bottom of the pipeline)

φ

Angle of internal friction (averaged over range from ground level to the bottom of the pipeline)

H*

Height of soil coverage from ground level to pipeline axis

D

Outer diameter of pipeline


The formula for sandy soil types is not changed in the NEN36501:2017 calculation methodology. For clay/peat soil types the NEN36501:2017 calculation methodology distinguishes slow and fast deformation. The formulae for clay are:
Clayey/peaty, slow deformation:
Clayey/peaty, fast deformation:
Qhor

Ultimate horizontal soil reaction

Kq

Function of φ and H*/D 1

σk

Vertical grain pressure at pipeline axis (see General parameters)

α

constant: 0.6 for installation method trench and 1.0 for nontrench installation method. A trench installation is either 1)Trench uncompressed fill or 2)Trench compressed fill and a nontrench installation is either 3)Boring or 4)HDD.

Kcu


Kc

Function of φ and H*/D 2

cu

Undrained cohesion (averaged over range from ground level to the bottom of the pipeline)

φ

Effective angle of internal friction (averaged over range from ground level to the bottom of the pipeline, using the Effective Young's modulus of soil for the same range with a depth as at bottom of pipe)

H*

Height of soil coverage from ground level to pipeline axis

D

Outer diameter of pipeline

1The function Kq is defined as:
Where




αq


H*

Height of soil coverage from ground level to pipeline axis

D

Outer diameter of pipeline

Nc

Function of φ 3

d∞c

Function of φ 4

2The function Kc is defined as:
Where




αc


Nc

Function of φ 3


Function of φ 4

H*

Height of soil coverage from ground level to pipeline axis

D

Outer diameter of pipeline

3The function Nc is defined as:
4The function dc∞ is defined as:

The formulae for all soil types are basically not changed in the NEN36501:2020 calculation methodology. For clay/peat soil types the same distinction between slow and fast deformation is made as in the previous version. However, a correction factor (model factor) is added for the Kfunctions in all formulae:
1) 1.00 for Kq
2) 0.85 for Kc and Kcu

Last changed: 7/2/2021