What is the purpose of soil compaction in highway construction?

The purpose of soil compaction in highway construction is primarily to increase the density of the soil to support structural loads and prevent settling. When soil is compacted, the particles are pressed closer together, reducing air voids and increasing overall density. This enhanced density is critical because it can significantly affect the stability and load-bearing capacity of the soil, ensuring that the infrastructure—such as roads and bridges—remains stable over time.

A well-compacted soil layer creates a stronger foundation, minimizing the risk of settlement or shifting under the weight of vehicles and other loads. Additionally, it plays a critical role in the durability and longevity of the pavement structure, which must withstand traffic loads and environmental factors without deforming or cracking.

While improved appearance might be a superficial benefit and quicker drainage or ease of excavation can be incidental outcomes, the primary aim of soil compaction is indeed to ensure that the subgrade and subbase are solid enough to carry the required loads over an extended period while minimizing the risk of structural failure.