6 Reasons Why You Should Insist On Soil Testing Prior To Construction

For most people building their home is the biggest dream of all.

Therefore, it is important to do soil testing, thereby making sure the site is suitable for your dream home construction. Otherwise, this may cause further problems on an established construction site.

Soil testing is done for measuring the strength and the type of land upon which the building will be built. This is the first stage of building your home. The soil profiles and strength of soil differ from place to place. Some soil can support heavily loaded high rise structures while some cannot even hold a small hut. If the soil under your home is not stable, then the foundation of your building experience differential settlement might crack. Thus, the building might fall. 

When constructing a building, it is very important to check the bearing capacity of the ground before construction starts. This is particularly important when building on clay, sand or alluvial soils. The leaning tower of Pisa is an example of what can happen if the ground is not strong enough to support the building.

Reasons why soil testing is important before any construction

Soil test is critical for anyone wishing to construct a building. You see, the most important part of any building is in fact the part you cannot see, the bit under the ground – the foundations. The larger the building, the more important this is.

Soil testing gives necessary information to determine the type of foundation required. Indeed, it also determines what sort of material to be used for construction.  Soil testing also helps eliminate various type of building failures.

1. Identifying suitable construction materials

The output of soil testing in building construction, for example, the character of the soil with respect to water content, mineral and chemical composition, decides the type of material to be used for construction. For example, high sulphur content in soil requires usage of sulphur resistant cement for construction, high moisture content area is prone to corrosion then it is important to choose only corrosion resistant TMT Bars for the construction. Besides, while deciding construction materials like concrete, make sure to go through this concrete quality check guide.

2. Identifying type of foundation needed

Soil testing reveals the physical and engineering properties of soil like moisture content, mineral presence, density permeability and bearing capacity (the soil bearing capacity is the capacity of the soil to support the superstructure load per unit area). These soil properties determine the type of foundation to be used for construction. Basically, the foundation has to be strong enough to effectively transfer the building weight to the soil underneath.

Most importantly, foundation is the backbone of the building and a defect in it can result in failure or collapse of the building. The function of foundation in a building is to sustain and transmit the load from the building to the ground without impairing damage to the building or surrounding buildings.

The type of foundation is directly relates to the strength of the house, the number of storeys it can accommodate, and the type of roofing. The type of foundation in construction is mainly determined based on the soil testing report.

Strong ground strata like rock can support the entire weight of the building. Unfortunately, rocks are not available everywhere. In some places where the strata contains sand or clay, some reinforcement is required to make the soil as strong as rock. In order to strengthen such weak strata and distribute the load, different types of foundations are used.

The different types of foundation normally used in constructing buildings are:

• Rubble Foundation
• Isolated/ Combined Column Footing
• Raft/ Strip Foundation
• Piling

3. Helps avoid resting foundations on poor soil or inadequate depth

Foundations resting on poor soil or at insufficient depth results in the movement of the building as the soil settles eventually. This movement of the building causes uniform or differential settlement of the building. The settlement (uniform or differential settlement) in the building can lead to the failure of foundation, and hence it becomes the reason for the partial or total collapse of the building.

4. Helps avoid resting foundation on reclaimed soil

The building foundation resting on reclaimed soil (new landfills from the sea or wet soil of riverbeds or lake beds, even debris.) becomes another reason for building collapse. This type of landfill soil may contains clay and silt particles, which may cause excessive consolidation settlement over the time and the strata become unstable for the building.

This type of soil has also not undergone consolidation over a period of time. The landfills from the sea also contain harmful chemical like sulphur, chloride, etc. which also affect the foundation of the building. Hence resting foundation on this type of weak soil without investigation may be the cause for building collapse. Never rest foundation on reclaimed soil.

5. Helps identify corrosive soil

Many chemicals are present in the sub-grade of soil. There are different chemicals like sulphur, chloride which are present in the soil, react with the concrete. The reaction results in the deterioration of the concrete foundation. These will eventually effect the strength of building and may also lead to the building failure over time.

6. Identify soil liquefaction possibilities during earthquake

Soil liquefaction is a phenomenon in which a saturated soil deposit loses its strength and stiffness due to the ground shaking, mainly during earthquake, which generates excess pore water pressure. So the foundations may fail during the earthquake, and it may be the reason for the partial or total collapse of the building.

Different types of soil testing

The types of soil test depend on the soil texture and quality. Methods used for testing soil include Lab Test and Field Test:

Lab Test:

1. Moisture Content Test: Moisture content test gives all information about moisture or water content of the soil. The information about water table will provides detailed impact of humidity on the foundation.

2. Atterberg Limits Test: Atterberg test gives the critical water content of the soil at different conditions like liquid limit, plastic limit and shrinkage limit.

3. Specific Gravity of soil: Specific gravity test gives the information about void ratio and degree of saturation of soil. Specific gravity value ranges from 2.65 to 2.85 for soil is ideal for construction.

4. Dry Density of Soil: Dry density test gives the weight of soil in a given volume of sample, enabling to categorise the soil into loose, medium dense and dense classifications.

5. Compaction Test: Compaction test gives the compaction characteristics of soil by reducing air voids in the soil by densification. The results of compaction test reveals maximum dry density and optimum water content of compacted soil.

Field Test:

1. Plate Bearing Test

2. Standard Penetration Test

3. Pressure meter Test

4. Field Vane Shear Test

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