Alternative method to determine the liquid limit - cone penetrometer

4 Alternative method to determine the liquid limit - cone penetrometer 

In the early part of 1970, another apparatus to determine the liquid limit - the cone penetrometer - was developed and is still being used in some countries. Determining the liquid limit using this apparatus seems to be rather easier, because it does not depend on the experience of the person executing the liquid test and the results obtained have better repeatability. 

The test consists of the measurement of the penetration depth of a standard cone, with a mass of 80 g, forced into the soil material. By carrying out measurements at different moisture contents, a diagram similar to the number of blows versus moisture content is obtained. The liquid limit is determined as the moisture content at which the penetration depth is equal to 20 mm. 

The results obtained using this apparatus might be slightly different from those determined using the Casagrande device. However, the differences are not significant. A detailed description of the test is given in BS 1377 Part 2 (1990). 

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