Classification of soil is crucial when building your home. Depending on the ground where your home stands, it is deemed necessary to know them very well as contractors will still survey on what foundation they can put so your homes will be built on the durable ground. In cases where the foundation is not suitable with the ground, there is a great chance that your house will be put at a major stake.
With this, a site investigation is always necessary before constructing any buildings. Whether it is a house or a commercial building, contractors are obliged to follow standardized procedures when erecting infrastructure so it will not dismantle easily. Thus, there are Geotechnical Investigations in order to avoid such instances.
AS2870-1996: “Residential Slabs and Footings – Construction”
The sole purpose of this standard is to establish performance requirements for footing systems commonly found in Australia and to provide guidance in such footing systems or foundations. It considers swelling and shrinkage due to reactive soil caused by moisture and dryness, subsidence of soils, distribution of the foundation to varying loads, and durability and tolerance of foundations from a disturbance in soil. Moreover, it connotes the most preferable foundations for differences in the soil so it would still be intact no matter what weather changes there might be.
Classification of Soil
Differences in the soil can also have individual needs for foundations. Some can shrink due to moisture, and some can be durable even in the wettest seasons. Consequently, these classes are referred to as Site Classes. Here are their definitions:
Site Class A
These are soils that have less to zero ground movement even when moisture arises. They are mostly sand and rock which can still hold into place regardless of any weather changes.
Site Class S
These are sites that are slightly reactive to moisture and can go from a surface movement of 0-20mm due to moisture changes. Typically, clay sites are under this site class.
Site Class M
These are sites that are moderately reactive when too much moisture occurs and can have a ground movement of 20-40mm. This is usually experienced in clay and silt grounds.
Site Class H1
These are sites that are highly reactive to moisture changes, which can have a surface movement of 40-60mm; clay sites have the most persistence of experiencing this.
Site Class H2
These are sites that are also very reactive to moisture changes, which can have a surface movement of 60-75mm.
Site Class E
These are sites that are extremely reactive to moisture which can also have an extreme surface movement of >75mm.
Site Class P
These are sites that can be classified with abnormal behaviour when moisture arises and can be referred to as unclassified sites. They usually consist of soft soils and sands, collapsing soils, mine subsidence, or anything beyond the limitations of Geotechnological Investigations.
Most reactive sites are found in clay and silt soils. Their properties are dependent on moisture, so it is best to first have a survey on them on how they are affected by moisture changes. Additionally, climate, vegetation, and watering are also considered for these types of soils. This enables contractors to know how much moisture the soil can accumulate causing surface movements below buildings.
In line with this, contractors also depend on soil classes before deciding what foundation to put on the base of infrastructures. Significantly, soil classes also have differences in costs as differences in foundations are correlated with them. This will also affect the overall cost of the construction in regards to the most efficient foundation for varying soil types. Still, it is important to know these classes, so the right foundation would be chosen before constructing a building.