Calculation

Calculations of the Soil Model Wizard

The NEN3650 specified formula's for soil mechanical values form the basis of the Soil Model Wizard calculations. The following topics provide detailed information on the results of the Soil Model Wizard. Results for a vertical oriented pipeline (part) are determined in a different way and are described in the calculation of Vertical parts.

The formula's presented in NEN3650 are based on the soil type properties of a single soil type. The Soil Model Wizard is able to take the different soil type layers into account. This is done by using the weighted averages of soil type properties for the soil range of importance for a particular soil mechanical value.

Some soil mechanical values described by the NEN3650 have distinct formula's for sand and clay/peat soil types. In such cases the weighted average of the mechanical values is defined by only the soil types belonging to the specified soil type main category (sand or clay/peat). The final result is then again received by taking the average of the outcomes of the two distinct soil type main categories formula's (weighted over the summed soil layer heights of the soil type main categories).

The weighted average of a soil property p is defined as:

Formula_WeighedAverage

pw

Weighted average of soil property

n

Number of soil layers present in the soil range of importance

pi

Soil property value of soil layer i

hi

Height of soil layer i within the soil range of importance

Example:

Say the soil range of importance is the soil from ground level to the top of the pipeline. The averaged soil property pw is, for the situation as depicted below, calculated as:

Formula_SampleWeighedAverage

Illustration_WeighedAverageSimple

p1

Soil property value of soil layer sand1

p2

Soil property value of soil layer clay1

h1

Height of soil layer sand1 within the soil range of importance

h2

Height of soil layer clay1 within the soil range of importance

 

The weighted average soil mechanical value s is defined as:

Formula_WeighedAverageSoilMechanicalValue

sw

Weighted average of soil mechanical value

sw, sand

Weighted average of soil mechanical value s for sandy soil layers being present in the soil range of importance

hsand

Summed height of sandy soil layers within the soil range of importance

sw, clay

Weighted average of soil mechanical value s for clayey soil layers being present in the soil range of importance

hclay

Summed height of clayey soil layers within the soil range of importance

The weighted average of soil property p for sandy soil types is defined by taking only the sandy soil layers within the soil range of importance into account. The weighted average of soil property p for clayey soil types is done in a similar way.

Example:

Say the soil range of importance is the soil from ground level to the bottom of the pipeline. The averaged soil property pw, sand and pw, clay are, for the situation as depicted below, calculated as:

Formula_SamplePwsandFormula_SamplePwclay

The heights hsand and hclay are calculated as:

Formula_SampleHsandFormula_SampleHclay

Illustration_WeighedAverageComplex

 

Formula's presented are taken from NEN3650-1992 and/or NEN3650-1:2012 and specified otherwise.


Last changed: 14/09/2016