What is the main advantage of using test pits in soil investigation?

The main advantage of using test pits in soil investigation is that they allow for visual inspection and direct sampling. This method provides a clear view of the soil layer profile, allowing the engineer or geologist to observe soil conditions directly. By excavating a test pit, one can examine the physical characteristics of the soil, such as texture, color, moisture content, and the presence of any contaminants or clays. Additionally, this direct interaction with the soil enables more accurate interpretation of the subsurface conditions, leading to better-informed design and construction decisions for the project.

Visual inspection also helps in identifying variations in soil types across different layers, which can inform engineering practices and assessments more effectively than many other forms of subsurface exploration. While other methods may provide samples, they may not allow for the same level of visual assessment, which is crucial in understanding the overall site conditions.