Which device is used in testing for the liquid limit test?

The liquid limit test is a standardized procedure used to determine the water content at which soil changes from a plastic state to a liquid state. The device specifically designed for this test is the liquid limit device, which features a groove tool. This instrument allows the operator to create a groove in a soil sample that has been placed in a cup. By dropping the cup from a specified height onto a hard surface, the operator can assess how much water is needed to cause the soil to flow together, overcoming internal friction. This test is crucial for understanding the behavior of fine-grained soils and their suitability for construction and engineering projects.

Other options do not serve this specific purpose. For example, a cone penetrometer is primarily used for determining soil consistency and bearing capacity, not for measuring the liquid limit. A Proctor compactor is utilized to assess soil density and moisture content for compaction tests, making it unrelated to the liquid limit assessment. Finally, a hydrometer is used for determining the particle size distribution of soil in suspension, which is a different aspect of soil analysis entirely. Thus, the liquid limit device with a grooving tool is uniquely suited for the purpose of determining a soil's liquid limit.