What does a Group Index (GI) number indicate?

The Group Index (GI) is specifically designed to assess the quality of soil within a particular soil group, particularly in the context of highway and pavement design. It serves as an indicator of how well a specific type of soil can be expected to perform under loading and whether it will exhibit desirable engineering properties.

The GI is computed using the Plasticity Index and other properties of the soil, giving insights into its potential for expansion, shrinkage, or other behaviors that could affect stability and performance in construction and civil engineering projects. This metric is especially important in transportation engineering, where the consistency and durability of the soil can significantly influence the longevity and integrity of roadways.

The other options, while related to soil and engineering principles, do not accurately capture the function of the Group Index. For instance, comparing different soil groups does not provide insights into the quality of a specific soil group, and the average moisture content or density of construction materials is unrelated to the GI's role in establishing soil characteristics.