The Influence of Soil and Space in Construction Soil Compaction Method Selection

tractor compacting the soil

Compacting the soil is vital for increasing the load-bearing stability of the ground a building or pavement is placed in. The means of compaction is heavily dependent on the type of soil and construction area.

At its core, soil compaction to create a much denser base to provide a solid, stable foundation for structures by tamping the earth enough to remove enough air voids and loose water, creating a more contiguous structure with fewer loose particles. Soil naturally settles over time, becoming more compact and firm. Mechanical compaction accelerates this process by applying force to the soil.

Soil that has undergone compaction has a density approaching that of brick. Soil compaction is thus a key part of construction regardless of the soil type. The surface created by compaction provides invaluable load-bearing stability for the structures atop it. In addition, compacted soil is more likely to restrict the movement of water, protecting the foundations from water damage and liquefaction.

In some cases, soil compaction could even make building in otherwise marginal soils possible.

A Question of Soils

However, not all soils are alike. Key among the various factors affecting the type of machine needed for compacting on site is the soil itself. Compacting different types of soil would require specialized techniques, which makes some compaction machines work better than others in specific types of soil.

Soils can be divided into two basic types: cohesive and granular. Granular soils tend to be sandy and have particles that can be visually distinguished with the naked eye. Soil rich in sand and gravel are the most familiar types of granular soils. Due to their particulate nature, granular soils are compacted through vibrations, which allow the particles to fall into each other’s spaces to create a denser structure.

Cohesive soils, meanwhile, have tiny particles that are so fine, they cannot readily be identified. They have a powdery feel when dry and are dense and are sticky and mouldable when wet. Silt and clay soils are the most commonly encountered cohesive soils. Because its particles are smaller and more tightly bound, cohesive soils are compacted through pressure.

A Selection of Machinery

Rollers, vibratory plates, and trench rammers are just some of the compacting machinery available for sale in the market today. Each one is suited for a specific soil type and is useful for a specific application and vary immensely in size. Rammers are among the most versatile of compactors and can be used in cohesive and some types of granular soils.

Coarser, granular soils typically require specialist rollers like pneumatic-tyre rollers or grid rollers, whereas finer, cohesive soils would require sheep’s foot rollers. The standard, smoothed wheeled rollers are usually reserved for soils that do not need excess pressure for compaction.

Surface, Trench, Or Excavation

man using a compactor to pressed the soil together

Once the type of soil has been identified, contractors would now have an idea on the best types of tools to use in the project. The second factor determining the type of roller would be the scale of the construction project, which will determine how big the compactor would need to be to finish the project in a timely manner.

The area where the soil would be compacted also plays a significant role in selecting the appropriate tool for soil compaction. Smaller construction projects would typically require compaction in the tighter corners of excavated trenches, which are ideal for rammers and vibratory plates.  These are often the only compacting tools needed for smaller construction projects. Larger machines such as rollers, meanwhile, are typically used in wider areas, with smaller compactors used in corner spaces.