Why is soil important?
For many, soil is just soil and what you see when the dog has dug in the lawn. However, this is not the case when choosing a foundation. In fact, soil type is paramount when building with screw foundations, or any other foundation for that matter. Does the earth “work”? What is the carrying capacity? Is the water table high and you can just look at a handful from one of the garden beds to assess what soil you are dealing with? We try to make you a little smarter about that here.
Both sand-based and clay-based soils can be excellent building soil, and screw foundations work in principle on all soil types. It’s just a matter of how deep you have to go into the soil in question to achieve sufficient bearing capacity. On soils with poor bearing capacity, screw foundations can be an advantage because it is much easier to reach deeper sustainable soil with screw foundations than with concrete foundations.
Why is soil important?
For many, soil is just soil and what you see when the dog has dug in the lawn. However, this is not the case when choosing a foundation. In fact, soil type is paramount when building with screw foundations, or any other foundation for that matter. Does the earth “work”? What is the carrying capacity? Is the water table high and you can just look at a handful from one of the garden beds to assess what soil you are dealing with? We try to make you a little smarter about that here.
Both sand-based and clay-based soils can be excellent building soil, and screw foundations work in principle on all soil types. It’s just a matter of how deep you have to go into the soil in question to achieve sufficient bearing capacity. On soils with poor bearing capacity, screw foundations can be an advantage because it is much easier to reach deeper sustainable soil with screw foundations than with concrete foundations.
Jordtyper i Danmark
What soil type do you have on your construction site?
When you have to assess the soil you are going to dig in, you must first dig out the 30-50cm layer of soil. It is the soil below that is interesting in terms of foundations. If you do not have a geotechnical report available, you can make a practical assessment* for secondary constructions.
*GroundPlug® Easy Mounting SystemTM does not accept responsibility for practical assessments
To determine the bearing capacity of clay soils, the “Undrained Shear Strength” (cu, [kPa]) is used. The strength of clay soils is measured by the soil’s ability to resist displacement in the soil skeleton caused by an external influence.
Cohesive Soil
Cohesive soils are fine-grained soil types whose particles clump together – i.e. the type of soil that sticks.These soil types are typically soft and can absorb large amounts of water. When they dry, they can become almost cement-hard. These soil types tend to contract and expand due to their high water absorption. Clay soils therefore “work” much more than sandy soils and are therefore considered “reactive” soils, which expand and contract depending on the water content.
Cohesive soil is organic soil consisting of varying degrees of decomposed plant materials. Organic soil typically has a high water content and a low oxygen content.
Typical examples of cohesive soil are:
- Silt (grain size 0.002-0.05)
- Clay (grain size<0.002)
- Peat (Variable)
- Mulch (Variable)
The density of clay soil can be assessed practically based on the following tests:
Soft Clay
Can be shaped with a lot of finger pressure.
Medium Clay
Can be shaped with strong finger pressure.
Dense Clay
Cannot be shaped with the fingers, but squeezed in with the thumb.
Soft Clay
Can be shaped with a lot of finger pressure.
Medium Clay
Can be shaped with strong finger pressure.
Dense Clay
Cannot be shaped with the fingers, but squeezed in with the thumb.
Friction Soil
Unlike cohesive soils, frictional soils do not clump together in any way. In other words, the grains remain separate from each other. Another way of looking at it is as an ‘unbound’ kind of soil. Some can become almost liquid if they have a low density and a high water content – this is called liquefaction. The structural strength is affected by the moisture content – a bit like building sand castles on the beach!
Friction soil includes lime, sand and gravel of different grain sizes and consists of broken down stones/rock and mineral. Mineral soils typically have no adhesion, are water permeable, and flow apart in the dry state when disturbed.
Typical examples of friction soil are:
- Sand (grain size 0.06-2mm)
- Gravel (grain size 2-20mm
- Sandy loam (grain size<2mm)
- Pebbles (grain size 2 – 20cm)
When sand settles, it settles at an angle called the angle of friction. To calculate the (break) strength of sandy soil, the designation “Effective Friction Angle” (Ø’ k , [°]) is therefore used. Soil breaks along lines. Therefore, sharp-grained sand of varying grain size has higher (better) breaking strength than round-grained sand of the same grain size because it forms fewer lines when it settles. So there is a difference in which type of sand you build on.
The density of sandy soil can be practically assessed from the following tests:
Loose Sand
Flows between the fingers. Can be easily dug with a spade. A 50mm peg is easily driven in.
Medium Sand
Can be crushed with fingers. Can be dug with a spade. A 50mm peg is driven in with some resistance.
Dense Sand
Hard to crush between the fingers. Requires hole for excavation. 50mm peg is difficult to drive in.
Loose sand
Flows between the fingers. Can be easily dug with a spade. A 50mm peg is easily driven in.
Medium sand
Can be crushed with fingers. Can be dug with a spade. A 50mm peg is driven in with some resistance.
Dense Sand
Hard to crush between the fingers. Requires hole for excavation. 50mm peg is difficult to drive in.
Gode værktøjer til at finde din jordtype
