Liquid Limit Test (Ll)

 

Liquid limit is defined as minimum water content at which the soil flow under the application of a very small shearing force. The LL is usually determined in the laboratory using a mechanical device. Liquid limit is moisture content at which 25 blows in standard liquid limit apparatus will just close a groove of standardized dimensions cut in the sample by the grooving tool by specified amount.

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Liquid limit tests

Testing procedure

The dry soil sample that passing 0.425 mm test sieve is mixed with distilled water to a thick paste.

Some of the soil paste is placed in the cup, leveled off horizontally and divided by cutting a groove.

The two halves of the soil gradually flow together as the cup is raised and repeatedly dropped on to the base at the rate of 2 drops per second.

The number of blows required to close the bottom of the groove is calculated.

This test is repeated after adding more water.

All test samples are collected and placed on the oven for 24 hours.

The dry samples are weighed for the moisture content of soil.

From the above reading, the percent of moisture content of the soil is determined and plot the number of blows-moisture content % graph. According to the graph, the LL is defined as the moisture content at which 25 blows.

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