Hello,
I have a soil survey report, but I don’t really understand it. Could someone possibly “translate” what it says?
The area is a slightly uneven fallow land with ground levels around +0.5 to +0.7 m (1.6 to 2.3 ft) relative height, with a slight slope towards the west.
Up to 0.8 m (2.6 ft): topsoil, soil class 1
From 0.8 m to 1.6 m (2.6 to 5.2 ft): non-cohesive sands, soil class 3
Below that, cohesive sands, soil class 4 (class 2 in case of sedimentation)
It is clear that the topsoil must be removed and disposed of, or can be used for landscaping. About the next layer (non-cohesive sand), the following is stated:
After topsoil removal, a slightly uneven excavation base of approximately -0.15 to -0.2 m (-6 to -8 inches) will remain. This height difference must be compensated for by the sub-base/fill material.
When conducting static plate load tests, deformation moduli Ev2 of at least 60 MN/m2 (8,700 psi) should be achieved at the upper edge of the final coarse gravel sub-base.
If static design of the foundation slab is carried out using the bedding modulus method, a static bedding modulus of 25 to 30 MN/m3 (3,600 to 4,350 psi) can be assumed for base pressure loads of 125 to 150 kN/m2 (1,800 to 2,200 psi).
If load-bearing strip foundations are constructed in the non-cohesive, medium dense sand, they can be designed for a base pressure of 200 kN/m2 (2,900 psi). This corresponds to a design value of the soil bearing capacity of 280 kN/m2 (4,060 psi).
For backfilling working spaces, non-cohesive, compactable fill material is recommended.
In my construction specification the following is stated:
“The soil in the building footprint will be excavated to a depth of approximately 40 cm (16 inches) and stockpiled on the side. Soil up to soil class 3 and a load-bearing soil with an allowable bearing pressure of 250 kN/m2 (3,625 psi) are assumed. The excavation will be backfilled with fill sand and compacted in layers. The foundation base will be backfilled up to approximately 40 cm (16 inches) with the excavated soil.”
Since the topsoil is 0.8 m (2.6 ft) deep, does this mean that 80 cm (32 inches) must be removed instead of 40 cm (16 inches)? Are there additional works or costs I should expect?
I have a soil survey report, but I don’t really understand it. Could someone possibly “translate” what it says?
The area is a slightly uneven fallow land with ground levels around +0.5 to +0.7 m (1.6 to 2.3 ft) relative height, with a slight slope towards the west.
Up to 0.8 m (2.6 ft): topsoil, soil class 1
From 0.8 m to 1.6 m (2.6 to 5.2 ft): non-cohesive sands, soil class 3
Below that, cohesive sands, soil class 4 (class 2 in case of sedimentation)
It is clear that the topsoil must be removed and disposed of, or can be used for landscaping. About the next layer (non-cohesive sand), the following is stated:
- Soil group SE, SU
- Compaction class V1
- Not frost-susceptible (F1)
- Wet density 18.5 kN/m3 (1,180 lb/ft3)
- Density under buoyancy 10.5 kN/m3 (670 lb/ft3)
- Cohesion 0 kN/m2 (0 psi)
- Friction angle 32.5 / 35 degrees
- Modulus of elasticity 20 to 50 MN/m2 (2,900 to 7,250 psi)
After topsoil removal, a slightly uneven excavation base of approximately -0.15 to -0.2 m (-6 to -8 inches) will remain. This height difference must be compensated for by the sub-base/fill material.
When conducting static plate load tests, deformation moduli Ev2 of at least 60 MN/m2 (8,700 psi) should be achieved at the upper edge of the final coarse gravel sub-base.
If static design of the foundation slab is carried out using the bedding modulus method, a static bedding modulus of 25 to 30 MN/m3 (3,600 to 4,350 psi) can be assumed for base pressure loads of 125 to 150 kN/m2 (1,800 to 2,200 psi).
If load-bearing strip foundations are constructed in the non-cohesive, medium dense sand, they can be designed for a base pressure of 200 kN/m2 (2,900 psi). This corresponds to a design value of the soil bearing capacity of 280 kN/m2 (4,060 psi).
For backfilling working spaces, non-cohesive, compactable fill material is recommended.
In my construction specification the following is stated:
“The soil in the building footprint will be excavated to a depth of approximately 40 cm (16 inches) and stockpiled on the side. Soil up to soil class 3 and a load-bearing soil with an allowable bearing pressure of 250 kN/m2 (3,625 psi) are assumed. The excavation will be backfilled with fill sand and compacted in layers. The foundation base will be backfilled up to approximately 40 cm (16 inches) with the excavated soil.”
Since the topsoil is 0.8 m (2.6 ft) deep, does this mean that 80 cm (32 inches) must be removed instead of 40 cm (16 inches)? Are there additional works or costs I should expect?
M
Mottenhausen30 Nov 2018 10:37Present the expert report to your construction company; they can provide you with a realistic cost estimate.
I would understand it this way: the topsoil is to be removed. Then a leveling layer is applied to even out the height difference. After that, there are two options: additional fill with a fully flat concrete slab or alternatively strip footings. I suspect strip footings will be used, since 80cm (31.5 inches) of topsoil needs to be removed anyway, which fits quite well.
It sounds relatively straightforward so far. Water should not be much of an issue on the sandy subsoil.
Excavation: depending on the size of your house, you can easily expect around 100m³ (3,530 cubic feet) of topsoil, which is a huge amount.
I would understand it this way: the topsoil is to be removed. Then a leveling layer is applied to even out the height difference. After that, there are two options: additional fill with a fully flat concrete slab or alternatively strip footings. I suspect strip footings will be used, since 80cm (31.5 inches) of topsoil needs to be removed anyway, which fits quite well.
It sounds relatively straightforward so far. Water should not be much of an issue on the sandy subsoil.
Excavation: depending on the size of your house, you can easily expect around 100m³ (3,530 cubic feet) of topsoil, which is a huge amount.
Is it possible to tell from the report whether the allowable soil bearing pressure of 250 kN/m² (5225 psf) is reached? Or will this only become clear during the earthworks?
The report also states that groundwater is expected only from a depth of 4.5 m (15 feet), and that no soil improvement measures will be necessary. This sounds positive at first. We have budgeted an additional 10,000 euros for the earthworks in our planning. That might then be appropriate.
The report also states that groundwater is expected only from a depth of 4.5 m (15 feet), and that no soil improvement measures will be necessary. This sounds positive at first. We have budgeted an additional 10,000 euros for the earthworks in our planning. That might then be appropriate.
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