What is the definition of the Liquid Limit in soil mechanics?

The Liquid Limit in soil mechanics is defined as the water content at which a soil changes from a plastic state to a liquid state. More specifically, it represents the moisture content at which a soil material flows at just the point of being fluid, typically evaluated by performing a standardized test where a soil sample is subjected to a specific number of blows—25 in this case—within a casagrande apparatus. This point is crucial as it helps classify the soil's behavior under varying moisture conditions and provides insight into its engineering properties, such as plasticity and compressibility.

The rationale for the specific choice is that 25 blows indicate the point where the soil starts to behave like a liquid, which is a critical threshold in soil mechanics. Other definitions fail to capture the essence of this transition. For instance, referring to the soil crumbling or becoming solid does not accurately describe the transition at the liquid limit, as these scenarios relate to different moisture contents and physical states of the soil. The Liquid Limit is specifically about the balance point where the soil's behavior shifts toward liquidity.