Factors Affecting Soil Compaction

Compaction of soil can be challenging if the soil is either too wet or too dry. When the soil is too wet, it can become sticky and difficult to handle, while excessively dry soil can become hard and resistant to compaction.

During the compaction process, the addition of water to the soil (when the soil has low moisture content) makes it easier for the soil particles to move past each other under the applied compacting forces. As the soil compacts, the voids between the particles are reduced, which results in an increase in the dry unit weight or dry density. The dry unit weight then increases with an increase in moisture content, but this increase has limits since the soil state approaches the "zero air voids line." This line indicates the maximum dry unit weight that can be achieved for a given moisture content. As the soil state approaches this line, any further increase in moisture content will cause a decrease in the dry unit weight. At the "no air voids line," the maximum dry unit weight is achieved, and the moisture content at this maximum is known as the optimum moisture content.

Soil type is an essential factor that affects the compaction process of soil. Some types of soil are easy to compact as compared to others. For instance, clay soils are more susceptible to compaction than sandy soils due to their smaller pore spaces. The soil type has a significant impact on its compaction properties. In general, heavy clay, clay, and silt have higher resistance to compaction, while sandy soils and coarse-grained or gravelly soils can be more easily compacted. Coarse-grained soils typically yield higher densities than clay soils. Additionally, it is worth noting that well-graded soil can be compacted to a higher density.

Furthermore, the arrangement of soil particles into aggregates can also impact soil compaction. Soil with a well-defined structure is easier to compact than soil that lacks structure.