Determination of Liquid Limit and Plastic Limit

 AIM 

To determine the liquid limit and plastic limit of the given soil sample

THEORY AND APPLICATION 

Liquid limit is significant to know the stress history and general properties of the soil

met with construction. From the results of liquid limit the compression index may be

estimated. The compression index value will help us in settlement analysis. If the

natural moisture content of soil is closer to liquid limit, the soil can be considered as

soft if the moisture content is lesser than liquids limit, the soil can be considered as

soft if the moisture content is lesser than liquid limit. The soil is brittle and stiffer. The

liquid limit is the moisture content at which the groove, formed by a standard tool into

the sample of soil taken in the standard cup, closes for 10 mm on being given 25

blows in a standard manner. At this limit the soil possess low shear strength. 

The moisture content expressed in percentage at which the soil has the smallest

plasticity is called the plastic limit. Just after plastic limit the soil displays the

properties of a semi solid. For determination purposes the plastic limit it is defined as

the water content at which a soil just begins to crumble when rolled into a thread of

3mm in diameter. The values of liquid limit and plastic limit are directly used for

classifying the fine grained soils. Once the soil is classified it helps in understanding

the behaviour of soils and selecting the suitable method of design construction and

maintenance of the structures made-up or and resting on soils. 

APPARATUS REQUIRED: 

1) Measuring balance 

2) Liquid limit device (Casagrandes) 

3) Grooving tool 

4) 425 micron sieve 

5) Glass plate 

6) Spatula