In the context of highway retaining walls, what is "lagging"?

The term "lagging" specifically refers to vertical boards or other materials that are installed behind a retaining wall. Their primary function is to hold back soil while also facilitating drainage. This hydraulic function is crucial because it prevents the buildup of hydrostatic pressure behind the wall, which can lead to structural failures. Lagging is typically placed in a way that supports the earth and helps maintain the stability of the overall structure, especially in the context of earth-retention systems like soldier pile walls or other similar configurations.

Understanding the role of lagging is essential for anyone working in highway construction and maintenance, as appropriate drainage and soil retention are vital for the longevity and safety of retaining structures.