19-04-2014, 01:04 PM
DETERMINATION OF LIQUID LIMIT AND PLASTIC LIMIT OF SOIL
AIM
To determine liquid limit and plastic limit of the given soil sample and to find the flow index and
toughness index of the soil.
THEORY AND APPLICATION
Liquid limit is the water content expressed in percentage at which the soil passes from zero strength
to an infinitesimal strength, hence the true value of liquid limit cannot be determined. For
determination purpose liquid limit is that water content at which a part of soil,cut by a groove of
standard dimensions, will flow together for a distance of 12.5mm under an impact of 5 blows in a
standard liquid limit apparatus with a height of fall of 1cm.
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.
RESULT
1. Liquid limit of the soil =
2. Plastic limit of the soil =
3. Flow Index of the soil =
4. Toughness Index of the soil =