LIQUID LIMIT TEST

 

STANDARD FOLLOWED :- As Per IS: 2720 (Part- 5) – 1985 (Reaffirmed 2015)

OBJECT :     To Determine the liquid limit of the soil.

THEORY :    This method of test, for determination of Liquid Limits, was first

                      published in 1965 and revised in 1970.

APPARATUS :

1. Casagrande's Liquid Limit Apparatus
2. Grooving Tools, Spatula
3. Porcelain Evaporating Dish & Containers
4. Flat glass plate
5. 0.425mm {425 Microns} IS Sieve
6.  Palette Knives
7.  Hot Air oven
8.  Balance { Sensitive to 0.01gms}
9. Wash Bottle or Beaker {full of distilled water}

fig-01

fig.02 

fig-03

PROCEDURE:

1.      Take 120 g of specimen passed through 425 microns IS sieve.

         Mix it thoroughly with distilled water in an evaporating dish.

2.      The paste shall have a consistency that will require 30 to 35 drops of the

         cup to cause the required closure of the standard groove.

3.      In case of the clayey soils, the paste shall be left to stand for a sufficient

         time (24 hours) so as to ensure uniform distribution of moisture throughout the soil mass.

4.      Place an amount of paste in Casagrande apparatus & level it so as to  achieve maximum depth of         1cm.

5.     Draw the grooving tool through the sample along the symmetrical axis of  the cup, holding the tool         perpendicular to the cup.

6.     Rotate the handle of apparatus at a rate of 2 revolutions per second and  the number of blows to be         counted till the two parts of soil sample comes into contact at the bottom of the groove along a                distance of about 12 mm.

7.     The length shall be measured with the end to the grooving tool or a ruler.

8.    The number of drop required to cause the groove close for the length of  12 mm shall be recorded.

9.    Take about 15 gm of soil near the closed groove and determine the  water content of the soil by                oven drying method.

10.   By altering the water content of soil and repeating the forgoing  operations, obtain at least 5                    Readings in the range of 15-35 blows.

11.  The moisture content corresponding to 25 drops shall be reported as the  liquid limit of the soil.

12. The test should proceed from the drier to the wetter condition of the soil. 

The test may also be conducted from the wetter to the drier condition  provided drying is achieved by kneading the wet soil and not by adding dry soil.

01

Liquid Limit (WL) =

Plastic Limit (WP) =

Plastic Index (IP)= Liquid Limit (WL) - Plastic Limit (WP) =

02

RESULT:

The moisture content corresponding to 25 drops shall be reported as the

liquid limit of the soil.

PRECAUTIONS & MAINTENANCE :

 Also keep the bolts tight and clean & lubricated