Identifying the Soil Liquid Limit Apparatus

The liquid limit test determines the moisture content at which a soil transitions from a plastic to a liquid state. This is a key parameter in soil classification.

Casagrande Apparatus Functionality

The standard apparatus used to determine the liquid limit of soil is the Casagrande apparatus. This device consists of a brass cup hinged on a base and operated by a cam mechanism. The cup is raised and dropped onto the base from a height of 10 mm at a rate of 2 drops per second. The soil sample is placed in the cup, and a groove is made down the center. The number of blows required for the groove to close over a distance of 12.5 mm is recorded, along with the corresponding moisture content. Typically, three tests are performed, and the liquid limit is determined by plotting the moisture content against the number of blows and interpolating at 25 blows.

Analysis of Other Apparatus

Other listed apparatus are used for different soil properties:

• Pycnometer: Primarily used to determine the specific gravity and void ratio of soil samples.
• Ring and ball apparatus: Used in materials science, particularly for determining the softening point of bitumen and asphalt, not soil properties.

Therefore, the Casagrande apparatus is the correct choice for measuring the liquid limit of soil.