A high plasticity index indicates a soil with what characteristic?

A high plasticity index indicates that the soil has a high degree of compressibility. The plasticity index is a measure of the range of moisture content over which a soil exhibits plastic behavior, which primarily pertains to clays. Soils with a high plasticity index are typically more sensitive to changes in moisture content, leading to significant volume changes when subjected to moisture variations.

This characteristic of high compressibility is critical in engineering and construction because it influences the soil's behavior under load and its ability to support structures. High plasticity soils can deform significantly when moisture levels change, which can lead to potential issues in foundation stability and infrastructure integrity.

In contrast, soils with low plasticity tend to have relatively stable characteristics across moisture changes and are less compressible, making them typically more favorable for construction purposes. The other options, while related to soil properties, do not directly correlate with the significance of a high plasticity index as a measure of compressibility.