What characterizes overconsolidated clay?

Overconsolidated clay is characterized by having experienced higher stress levels in the past than what it currently endures. This occurs during geological processes where layers of soil are subjected to significant overburden pressure and then may have that overburden removed due to erosion or other processes. As a result, the clay retains the memory of that former, greater stress, which leads to its overconsolidated state.

This state affects the mechanical properties of the clay, making it more stable and less compressible compared to normally consolidated clay, which has only been subjected to its current stress level. Understanding this characteristic is crucial for geotechnical engineering applications, especially when predicting settlement behavior and stability in construction scenarios.

The other options do not accurately depict the conditions of overconsolidated clay. For instance, clay that has never experienced stress would be in a virgin state rather than overconsolidated. A low plasticity index is unrelated to the overconsolidation process itself and pertains to soil classification based on its plasticity, while soil that remains saturated under stress refers more to pore water pressure conditions rather than the history of stress that defines whether the clay is overconsolidated or not.