What implication does a low plasticity index have for soil usage?

A low plasticity index indicates that the soil has a limited range of moisture content where it maintains plasticity. Essentially, this means that the soil is less likely to behave unpredictably under varying conditions of moisture. When a soil has a low plasticity index, it is typically more cohesive and stable, which makes it suitable for construction projects.

Stable soils can support structures better than those that undergo significant changes in volume or strength when wet or dry. This characteristic contributes to the soil's ability to provide a solid foundation, minimizing risks such as settling or shifting that can occur with more plastic soils.

Conversely, soils with a high plasticity index can exhibit significant expansion or contraction, leading to instability in construction applications. Therefore, a low plasticity index is desirable as it implies a greater likelihood of stability for construction purposes.