What does the liquid limit of soil refer to?

The liquid limit of soil is defined as the moisture content at which a soil transitions from a plastic state to a liquid state. At this point, the soil can flow and is capable of being deformed under its own weight. This characteristic is crucial in geotechnical engineering as it helps determine how the soil will behave under different moisture conditions.

When conducting a liquid limit test, the soil is mixed with water and subjected to a specific shaking or agitation. The determination is based on the point at which the soil begins to flow or deform easily when force is applied. This specific moisture content is a key parameter for classifying soils and assessing their engineering properties.

Understanding the liquid limit can inform decisions about soil stability, construction, and design, making it a vital aspect of geotechnical investigation. The other options relate to different properties of soil, but do not capture the specific definition of liquid limit as it pertains to the soil's behavior under varying moisture levels.