Soil compaction is a critical factor in the construction of a strong, stable foundation for any project. Civil engineers must be aware of factors affecting soil compaction when designing and constructing a structure, as variations in soil moisture content, structure, and composition can have an impact on the successfulness of the structure being built. This article highlights the various factors that civil engineers should consider when evaluating soil compaction in a construction project.
One of the primary factors affecting soil compaction is the amount of moisture present in the soil. Moisture content can have a significant impact on the density of the soil, and too much or too little moisture can lead to problems with compaction. The amount of moisture present in the soil also affects the soil’s ability to resist compaction from construction equipment.
The type of soil is also a critical factor in soil compaction. Different types of soils have different degrees of compaction. For example, sand is more compactible than clay. The structure of the soil also affects its compaction. Soils with a granular structure (i.e. sand) are more easily compacted than those with a more fibrous structure (i.e. clay).
Soil compaction is also affected by the type of equipment used during construction. Heavy equipment, such as tractors and bulldozers, can cause significant compaction of the soil. In some cases, the use of explosives is necessary to achieve the desired level of compaction.
Finally, the amount of time and effort that is expended on compaction also affects the results. In general, the more time and effort that is put into compacting the soil.
Factors affecting soil compaction
- Effect of Soil Type on Compaction
- Type of compactor
- Layer thickness
- Number of roller passes
- Moisture content
- Contact pressure
- Speed of roller
Soil type affects the rate of compaction. Soils with large amounts of organic matter, or high levels of clay, tend to compact more slowly than soils with little organic matter and looser textures. Clay soils resist compression by swelling when they are wetted, while sand and silt particles compact more easily because they have low water-holding capacity. With the right roller for the job, you can use your equipment more efficiently. A drum roller is best for working on soil that has been loosened by tillage blades.
A tandem roller is best for compacting soil that has a high water content and can be used after tilling or disking to finish leveling the surface. Because each layer exerts its own pressure as it passes under the roller, proper layer thickness is important in achieving uniform compaction throughout the field. For example, if you are using a tandem roller on a field with a 30-cm top soil layer and an underlying 7-cm subsoil layer, you should roll at least two passes to achieve full soil contact between these layers.
On fields where there is no underlying sub soil, three passes may be needed to achieve full contact between top soil layers of differing depths. The number of passes also affects compaction. Typically one pass is adequate for rolling light soils that do not need much density; however, if your field has heavy soils or contains stones greater than 1/2 inch in diameter, you may need two or three passes per layer to achieve adequate density in all areas of the field.
