Fall cone test

The Fall cone test apparatus is an alternative method to the Casagrande Device in measuring the Liquid Limit of a soil sample (See:Atterberg Limits). It is usually considered to be a more scientific approach because it is based less upon human judgment^{[citation needed]}. In this method, a sample is placed in a 55 mm diameter, 40 mm deep metal cup. A stainless steel cone weighing 80 g (including the shaft) and having a 30° angle is positioned so that its tip just touches the sample. The cone is released for 5 seconds so that it may penetrate the soil. The liquid limit is defined as the water content of the soil which allows the cone to penetrate exactly 20 mm during that period of time. Because it is difficult to obtain a test with exactly 20 mm penetration, the procedure is performed multiple times with a range of water contents and the results are interpolated.