uitgraving – BuildSoft Support https://support.buildsoft.eu BuildSoft Support Thu, 13 Aug 2026 15:00:11 +0000 en-US hourly 1 https://wordpress.org/?v=6.2.13 Webinar Settlement Calculations https://support.buildsoft.eu/knowledge-base/webinar-settlement-calculations/ Wed, 21 Aug 2024 11:31:49 +0000 https://support.buildsoft.eu/?post_type=ht_kb&p=13379 The webinar Settlement Calculations can be watched on-demand

]]> How to add soil layers, how to add a soil layer profile https://support.buildsoft.eu/knowledge-base/how-to-add-soil-layers-how-to-add-a-soil-layer-profile/ Mon, 26 Apr 2021 13:58:06 +0000 https://buildsoftsupport.com/?post_type=ht_kb&p=6508 Before we get started

How to assign a soil layer profile?

  1. Select the beams/ plates under which you want to apply soil layers and click on .
  2. With the Y-displacement, choose for Soil layers and click on .
  3. Then, click on and enter the general settings:
    • Choose between a CTP (often used in Belgium/ the Netherlands) or Ménard test (used in France).
    • Enter the position of the water level below the original ground level. This position is used to determine if Diamonds should calculate the soil stresses using the wet or dry density of soil. You should define any water and/or soil pressures manually as a load!
    • Select if the bottom layer should be extended to infinity. This option is checked by default because it results in a conservative value for the settlement.
  4. Click on  to add a new soil layer.
    Enter the properties of one soil layer (see below).
    If you have foundation slabs on different levels (Y-coordinate), you enter the soil layers starting from the ground level.
  5. Add as many soil layers as necessary.
  6. Hit OK to close all the dialogs.
  7. Click on  to run the elastic analysis.
    In the tab page Soil, set the reference load group/ combination to an SLS combination.

    A table with soil layers is not suitable for FEM-calculations. So the soil layers are translated into functions. Each mesh node in the foundation, will have its function depending on the loads present in that mesh node… That’s why you have to choose a reference combination
    The loads in the reference combination will determine the behaviour of the soil function.
    Soil functions in Diamonds, can only be trained to do one thing: either understand how compressed soil works or either understand how soil under tension works.
    By consequence: if you need the settlement in combinations that contains mainely vertical downward loads, you should take a reference combination that contains mainely vertical loads.If your model also contains combinations that mainely consist of vertical upward loads (water pressure) then you should redo the calculation a second time, using a reference combination that also contains mainely vertical upward loads.
    If you try to calculate a combination that consists mainely of vertical upwards loads, with a reference combinations that contains mainely vertical downward loads, that can lead to iteration problems.

Soil parameters for a CPT test

For a Cone Penetration Test (CPT for short) you need to enter the following data:

  • The layer thickness
  • The compressibility constant C is usually given in the report of the CPT-test.
    Otherwise it can be calculated from:

        \[C = \frac{\alpha \cdot q_c}{\sigma'_{v.0}}\]

    With

    • q_c the conical resistance
    • \sigma'_{v.0} the granulometric tension at the depth h
    • \alpha correlationfactor (see EN 1997-1-2 Table D.2)
  • The recompressibility constant A can be calculated using C depending on the soil type
    (source: Afleiden van de samendrukbaarheid uit in-situ proeven’ – KVIV-TI)

    • Sand: A = 8 to 10 x C
    • Loam: A = 4 to 5 x C
    • Clay: A = 3 x C
    • Peat: A = C
  • The drainage ratio CC [%]
    This value is a measure for how much of the consolidation (relaxation) has occurred between the moment of excavation and (re)loading.

    • CC = 0%
      Excavation and loading by the foundation happen quickly one after the other. There is no soil relaxation possible. At foundation level, the soil stress is equal to the original geostatic stress.
    • CC = 100% (default value)
      There is a long time between the excavation and loading by the foundation, causing all preconsolidation to fade out. At foundation level, the soil stress is equal to 0 kN/m, and it will act like the natural ground surface.
      This results in larger settlements (more conservatice) than CC=0%. More info here.

    CC does not only depend on the time between excavation and loading, but also on the soil type, in the particular the drain capacity. The more easy it is for a soil to drain the pore water, the faster the soil will relax and the preconsolidation will be gone.

    • For a foundation pit that is being drained, CC will be 100%.
    • Sand drains well, so CC will be approximately 100%.
    • Thin top layers of clay will drain quite quickly, so CC will between 50 and 75%.
    • Thick lower layers of clay will drain rather slow, so CC will be between 25 and 50%.
    • Thick deep layers of clay will drain slow, so CC will be between 0 and 25%.

    In practice 0% and 100% are used the most often.

  • The overconsolidation ratio OCR takes préloading, different from an excavation, into account. For example: an old building will be demolished before building a new one. Or a large pile of soil (above the ground level) will be removed before construction starts.
    The old building and the pile of soil are a preloading of the soil which cannot be considered as an excavation. You’ll need to increase the OCR-value for that.

Soil parameters for a Ménard test

A pressuremeter test also provides soil parameters necessary for the settlement calculation with the use of iterative method.
This test is conducted with the help of an expanding cylinder. It is either directly situated in a pre-drilled hole, or brought to a proper depth by autoforage, sinking, vibration or any other suitable procedure. The measurements of the ground deformations based on the pressures put on the probing head allow you to make a chart of deformations in terms of exerted forces and to deduce the mechanical characteristics of the soil.
The pressuremetric compression modulus EMK determined this way at different depths is perfectly analogous to the compression constant C. The settlements are determined by Terzaghi’s law but with the use of the following equation:

    \[s(i)=\sum \frac{\alpha _{k}\cdot \Delta h}{E_{MK}}\cdot \Delta \sigma _{z}(i)\]

In this formula, Δσz(i) corresponds to the vertical tension resulting from upper loads and observed at point i situated at depth z. Δh corresponds to the thickness of a layer of the soil in question.
The coefficient αk depends on the nature of the soil and can be taken from the table below:

Nature of the soil Peat Clay Lime Sand Gravel
Very compacted – 1 2/3 1/2 1/3
Normally compacted 1 2/3 1/2 1/3 1/4
Non-compacted – 1/2 1/2 1/3 1/4


]]> Where is the ground level used for? https://support.buildsoft.eu/knowledge-base/where-is-the-ground-level-used-for/ Fri, 07 Aug 2020 08:06:49 +0000 https://buildsoftsupport.com/?post_type=ht_kb&p=5590 The ground level in Diamonds is used to

If you do not use any of the above, the value for the ground level is not important.

Note: the snow loads are not affected by the position of the ground level. The size of the snow loads depends on the high of the building in relation to the sea level.

]]> How to take an excavation into account https://support.buildsoft.eu/knowledge-base/how-to-take-an-excavation-into-account/ Tue, 08 May 2018 15:07:07 +0000 http://buildsoftsupport.com/?post_type=ht_kb&p=2696 An excavation means that the soil was consolidated, resulting in less settlement. By default, Diamonds will not take the excavation is not taken into account (= safest approach). It’s up to you to configure the necessary settings to ensure that any existing excavation is charged correctly. This article outlines what you need to do.

You can find a comprehensive course on soil calculations in Diamonds on our e-learning platform (available in Dutch).

Necessary adjustments

  1. Enter the soil layers starting from the original soil level.
    Diamonds calculates for you how many metres of soil you will excavate, based on the Y-coordinate of your foundations and the position of ground level.
  2. Define the ground water level.
    The groundwater level is only used to determine if Diamonds has to calculate with the dry or wet selfweight of the soil.
    It’s always up to you to define water and soil pressures.
  1. The recompression index A should be larger than the compression index C for sand, loam and slay soils.
  1. Set the drainage coefficient CC to 0% for all soil layers.
    This coefficient is a measure of how well the soil can remember the preload due to the excavation. 100% means that the soil has completely forgotten about the excavation. For example: you dig a well in prehistoric times and start building in it today. That ground has long forgotten that you ever dug a well there. 0% means that the soil can fully remember the excavation. For example: you dig a well today and start building in it tomorrow.
  1. At some point settlement calculations must stop. Eurocode allows 2 standards:
    • Or you use the stress tolerance (see step 9).
      We do not recommend this option as much because it sometimes causes iteration problems.
    • Or you adjust the layer thickness of the bottom soil layer in such a way that the total package of soil layers is as deep as once to twice the width of the foundation (EN 1997-1-1 §6.6.2 (7)).
      For example: a soil layer profile of 7m deep is entered using soil layers that are 0.2m thick. The width of the foundation plate is 10m.
      Assume we conservatively want to calculate with twice the width of the foundation, then the soil layer profile must be 20 m deep in total. So the bottom layer must be 14m thick.
      Don’t forget to uncheck the option ‘Bottom layer extends infinitely deep’ (see step 8).
      Leave the stress tolerance on 0% (see step 9).
  1. Define the reference load group / combination.
    A table with soil layers is not suitable for FEM-calculations. So the soil layers are translated into functions. Each mesh node in the foundation will have it’s own function, depending on the loads present in that mesh node… That’s why you have to choose a reference combination. The loads in that reference combination will determine the behaviour of the soil function in that mesh node.
    Soil functions in Diamonds, can only be trained to do one thing: either understand how compressed soil works, or either understand how soil under tension works.

    By consequence, if you need the settlement in combinations that contains mainely vertical downward loads, you should take a reference combination that contains mainely vertical loads.
    If your model also contains combinations that mainely consist of vertical upward loads (water pressue) then you should redo the calculation a second time, using a reference combination that also contains mainely vertical upward loads.

    We generally opt for a quasi-permanent load combination SLS QP1 to start with and see how far it gets us.

Optional adjustments

  1. Has the soil ever been préloaded with a load different from the escavation? For example: an old building that was demolished or a pile of sand that was removed.
    Then define the overconsolidation ratio OCR > 1
  1. Uncheck the option Bottom layer continuous into infinity.
    By default Diamonds will assume that the bottom layers continuous to a depth of 200m. In some cases this gives conservative results. When you uncheck this option, Diamonds will stop the calculations after the last layer. This actually means implying there is a very stiff material (like rock) below the last soil layer.
  1. In step 5, we saw two ways to stop the calculations. If you choose the method with the stress tolerance, you can apply it here.
  1. Check the option Apply removed ground at interface.
    This option handles how the excavation should be taken into account.
    The option is ticked off, then Diamonds assumes that the ground will be removed in different steps, leading to a reduction of stress, under as well as next to the excavation.
    The option is ticked on, then Diamonds assumes that all removed ground is taken away at once, leading to a larger prestress at the excavation level.
]]> What is soil and how does it behave? https://support.buildsoft.eu/knowledge-base/what-is-soil-and-how-does-it-behave/ Wed, 02 May 2018 14:36:22 +0000 http://buildsoftsupport.com/?post_type=ht_kb&p=2669 Soil is a mixture of soil grains, water and air. The air is the space between the soil grains. When soil is loaded, the space between the soil grains will decrease, the compressibility of the soil will descrease. The soil will become stiffer. The relation between loading and deformation is non-linear. When soil is unloaded, the soil will not return to it’s original position. Soil behaves plastic.

The relation between load and deformation in soil is given by Terzaghi’s law.

When soil is loaded, the settlement s is determined as (curve a):

    \[ s=\frac{h}{C} \ln {\frac{\sigma'_0 +\Delta \sigma'}{\sigma'_0}} \]

  • h is the layer thickness [m]
  • C is the compression index [-]

        \[C=\alpha \frac{q_c}{\sigma'_0}\]

    q_c is the cone resistance [kN/m²]
    \alpha= 1,5 (default value soil report, also see EN 1997-1-1 Annex D)

  • \sigma'_0 is the vertical grain stress [kN/m²]
  • \Delta \sigma' is the change in the the vertical grain stress [kN/m²]
  
When soil is unloaded, the settlement s is determined as (curve b):

    \[s=\frac{h}{A} \ln {\frac{\sigma'_0 +\Delta \sigma'}{\sigma'_0}}\]

  
When the soil is loaded again, it will react stiff when the stress \sigma' is less than the prehistorical stress \sigma'_h (curve c).

From the moment the stress \sigma' is higher than the prehistoraical stress \sigma'_h, the soil will react less stiff (curve d).

This is called overconsolidated soil.

The settlement s is the combination of both laws above:

    \[ s=\frac{h}{A} \ln {\frac{\sigma'_0}{\sigma'_0}}+\frac{h}{C} \ln {\frac{\sigma'_0 +\Delta \sigma'}{\sigma'_0}} \]

The ratio \frac{\sigma'_0}{\sigma'_0} is called the overconsolidation ratio OCR.

    \[ s=\frac{h}{A} \ln {OCR}+\frac{h}{C} \ln {\frac{\sigma'_0 +\Delta \sigma'}{\sigma'_0}} \]

  
]]> Template soil layer import https://support.buildsoft.eu/knowledge-base/template-soil-layer-import/ https://support.buildsoft.eu/knowledge-base/template-soil-layer-import/#respond Tue, 28 Mar 2017 14:21:01 +0000 http://buildsoftsupport.com/?post_type=ht_kb&p=379 Template file with 1 soil layer present for importing soil layers from a Cone Penetration Test (CPT).

This is a simple notepad file (*.TXT) with a header containing the variables and corrects units. Each line represents a new soil layer. The soil layers start from the initial ground level.

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