What does the shrinkage limit indicate about a soil's moisture content?

The shrinkage limit is a critical concept in soil mechanics, particularly concerning the behavior of cohesive soils as they undergo changes in moisture content. This limit specifically indicates the moisture content at which a soil, upon drying, will begin to exhibit noticeable cracking and irreversible volume change.

When soil moisture content drops to this level, the soil transitions from a plastic state, where it can be molded or deformed without cracking, into a drier state where the soil particles can no longer easily rearrange themselves. At or below the shrinkage limit, the soil is no longer able to maintain its structure effectively, leading to the development of cracks as the moisture continues to reduce. This phenomenon is crucial in understanding soil behavior in construction and agriculture, as it directly impacts soil stability and health.

The other options do not accurately characterize the shrinkage limit. For instance, the statement regarding soil liquefaction pertains more to saturated soils and is not relevant at the shrinkage limit. The moisture content where soil remains unchanged corresponds more closely to the plastic limit, while the notion of reflecting the highest plastic limit misrepresents the purpose of the shrinkage limit, which is distinct from the plastic limit in that it assesses soil behavior at lower moisture levels.