Soil testing is carried out for various purposes, depending on the intended use of the land including agricultural, mining, landscaping and construction. In the construction industry, soil tests may be conducted to assess whether the soil on a particular lot of land is suitable for a proposed building construction project. Usually, soil testing is required before building permits can be issued, but the soil engineer may conduct further tests on the soil when construction work is ongoing just to make sure that prevailing soil conditions are consistent with those observed during the initial analysis of the soil.
A number of soil tests can be done to determine the suitability of soil for a building construction project. Below is a run-through of some soil tests that are typically performed for building construction, and why they are essential.
Water content test on soil
The amount of water that soil holds is an important parameter for establishing the suitability of the soil for building construction purposes. One of the key things that the amount of water content in soil affects is the compactness of the soil. Generally speaking, soils that retain too much water (like clayey soils) or drain water too fast (like sandy soils) tend to be poorly compacted, which undermines the soils' bearing capacity. Soil engineers perform tests to analyse the water content of the soil, so as to decide if it is well-compacted and can provide a stable subsurface for a building to stand on.
Plastic limit test on soil
Here, soil is generally regarded as a type of plastic, which can be moulded into various shapes without losing its plasticity. If the water content of soil is reduced below a certain minimum, the soil tends to lose its plasticity and starts to behave like a non-plastic material, which crumbles easily. Soil engineers must carry out tests to determine the plasticity index of the soil, so as to know how much water loss should occur before the soil can crumble under the weight of the building.
Liquid limit test on the soil
If the water content is increased beyond the plastic limit, the soil's water content tends to move toward the liquid limit. Here, the inclination is towards the soil behaving like a liquid rather than a solid because of the high water content. Like the plastic limit of soil, the liquid limit of soil has an impact on the bearing capacity of the soil at the construction site.