Geo-technical Engineering

1. Experiment No.: 05 (A) Date:
DETERMINATION OF CONSISTENCY LIMITS AND THEIR USE IN SOIL
CLASSIFICATION AS PER IS CODES.
A. DETERMINATION OF LIQUID LIMIT OF SOIL
Object and scope:
To determine the liquid limit of the soil sample using Casagrande type mechanical liquid limit apparatus
and plot graph using one point method.
Reference:
IS: 2720 (Part V) -1985
Theory:
Consistency means the relative ease with which soil can be deformed. This term is mostly used for fine
grained soils for which the consistency is related to a large extent to water content. Consistency denotes
degree of firmness of the soil which may be termed as soft, firm, stiff or hard. Most of the fine grained
soil passes from one state to another state depending on the water content which is called states of
consistency. In 1911, the Swedish agriculturist Atterberg divided the entire range from liquid to solid
state into four stages
1) Liquid state
2) The plastic state
3) Semi-solid state and
4) Solid state
They are called arbitrary limits/ consistency limits or Atterberg limits in terms of water contents. Thus
the consistency limits are the water contents at which soil mass passes from one state to the next. The
Atterberg limits which are most useful for engineering purposes are
1) Liquid limit
2) Plastic limit
3) Shrinkage limit
Liquid Limit (WL):
It is the water content corresponding to arbitrary limit between liquid and plastic state of consistency of
a soil. It is defined as the water content upto which the soil will remain in a liquid state.
With reference to standard liquid limit device, it is defined as the water content at which pat of soil cut
by a grooving tool of standard dimensions, will flow together for a distance of 13 mm under an impact
of 25 blows in the device.
Plastic Limit (Wp):
Plastic limit is the water content corresponding to an arbitrary limit between the plastic and the semi-
solid states of consistency of a soil. It is defined as the water content at which a soil will just begin to
crumble when rolled into a thread approximately 3mm in diameter

2. Shrinkage Limit (Ws):
Shrinkage limit is defined as the water content at which a reduction in water content will not cause a
decrease in the volume of a soil mass. It is lowest water content at which a soil can still be completely
saturated.
Plasticity:
Plasticity is defined as the property of a soil which allows it to be deformed rapidly, without rupture,
without elastic rebound, and without volume change.
Plasticity index (Ip):
It is range of water content within which a soil is in plastic state which can be moulded into any shape. It
is given by
Ip = WL - WP
Liquid Limit, Plastic Limit and Shrinkage limit are very useful parameters which can be used to identify
and classify a given fine grained soil. Plasticity chart as per I.S. is used to classify the soil.
Fig.1. Plasticity Chart
Equipment:
1) Mechanical liquid limit device (Casagrande type)
2) Grooving tool ‘a’ (Casagrande or I.S. tool) and grooving tool ‘b’ (ASTM tool)
3) Porcelain evaporating dish 12 cm in diameter
4) Flexible spatula with blade about 8cm along and 2cm wide
5) Balance accurate to weight of 0.01gm
6) Air tight container for water content determination
7) Thermostatically controlled oven to maintain temperature between 105 - 110 °C.
8) Wash bottle containing distilled water
9) 425 micron I.S. sieve.
10) Desiccators

3. Procedure:
A) Adjustment of liquid limit device:
By means of the gauge on the handle of the grooving tool and the adjustment plate, adjust the height
through which the cup is lifted and dropped so that the point on the cup which comes in the contact
with the base falls through exactly 1cm when the handle is rotated by one revolution. When the
adjustment is complete, secure the adjustment plate by tightening its screw.
B) Liquid limit test:
1) Take about 120 gm of soil specimen, passing through 425 micron sieve, and mix it thoroughly with
distilled water in the evaporating dish so that uniform paste is formed. Leave the soil for sufficient
time so that water may permeate through the soil mass.
2) Take a portion of the paste with the spatula and place it in the centre of the cup so that it is almost
half filled. Level the top of the wet soil symmetrically with the spatula, so that it is parallel to the
rubber base and maximum depth of the soil is 1cm.
3) With the help of the grooving tool ‘a’, the paste in the cup is divided along the cup diameter by
holding the tool normal to the surface of the cup and drawing it firmly across. Thus a V shape gap, 2
mm wide at the bottom and 11 mm at the top and 8 mm deep will be formed. However, in the case of
sandy soil tool ‘a’ do not forms a neat groove and hence tool ‘b’ is used.
4) Turn the handle of the apparatus at the rate of 2 rev/sec, until the two parts of the soil comes in
contact with the bottom of the groove along a distance of 10mm. Record the number of blows
required to cause the groove close for approximately through a length of 13 mm.
5) Collect a representative slice of soil by moving the spatula width wise from one edge to the other
edge of the soil cake at right angle to the groove, including the portion of the groove in which the
soil flowed together, and put it in an air tight container. Its water content is later determined by oven
drying method.
6) Remove the remaining soil from the cup and mix it with the soil left earlier in the evaporating dish.
Change the consistency of the mix by either adding more water or leaving the soil paste to dry and
repeat Step No. 3, 4, 5 and 6. Note the number of revolutions to close the groove and keep the soil
for water content determination. These operations are repeated for 3 or 4 more additional trials. The
soil paste in this process should be of such consistency that number of revolutions or drops to close
the groove is between 10 and 50.
Observation Table:
Determination No. 1 2 3 4 5
No. of blows
Container No.
Mass of container M1 (gm)
Mass of container + wet soil M2 (gm)
Mass of container + dry soil M3 (gm)
Mass of water M2 - M3 (gm)
Mass of oven dry soil M3 - M1 (gm)
Water content = (M2 - M3)/ (M3 – M1) ×100 (%)
Liquid limit (from graph) = ωL=

4. Calculations:
Plot the flow curve with water content as the ordinate and log of number of blows as abscissa. The water
content corresponding to 25 blows is taken as the liquid limit of the soil.
Result:
Liquid Limit of given soil =

5. Fig.2. Liquid Limit Apparatus

6. Experiment No.: 05 (B) Date:
B. DETERMINATION OF PLASTIC LIMIT OF SOIL
Object and scope:
To determine the plastic limit of the soil sample and calculate the plasticity index.
Reference:
IS: 2720 (Part V) - 1965
Equipment:
1) Glass plate of 30 cm2 size.
2) Balance accurate to weight of 0.01gm
3) Air tight container for water content determination
4) Thermostatically controlled oven to maintain temperature between 105 - 110 °C
5) Wash bottle containing distilled water
6) 425 micron I.S. sieve.
Procedure:
1) Take about 20 gm of air dried soil passing through 425micron IS sieve.
2) Mix it with sufficient distilled water on the glass plate to make it plastic enough to be easily moulded
with fingers. Leave the plastic soil mass for some time to mature.
3) Prepare the ball of uniform diameter of the above sample and roll it on the glass plate with just
sufficient finger pressure to roll the mass into a thread of uniform diameter of 3 mm. Continue the
process until thread just crumbles thus making soil unable for further rolling.
4) Collect the crumbled soil thread in the airtight container and keep it for water content determination.
5) Repeat the above process for 3 observations. Record the average value as plastic limit of the given soil
sample.
Observation Table:
Sr.
No.
Determination Number 1 2 3
1 Mass of container M1 (gm)
2 Mass of container + wet soil M2 (gm)
3 Mass of container + dry soil M3 (gm)
4 Mass of water M2 - M3 (gm)
5 Mass of oven dry soil M3 - M1 (gm)
6 Plastic limit of soil = Water content
= (M2 - M3)/ (M3 – M1) ×100 (%)
Average value of Plastic limit =

7. Calculations:
Plastic Limit = WP =
Plasticity Index = IP = WL - WP
Result:
Plastic limit of the soil =
Plasticity Index =
From Casagrande’s Plasticity Chart soil can be classified as __________________

8. Fig.1. Determination of Plastic Limit

9. Experiment No.: 05 (C) Date:
DETERMINATION OF SHRINKAGE LIMIT OF SOIL
Object and scope:
To determine shrinkage limit of a given soil sample
Reference:
IS: 2720 (Part VI) - 1972
Equipment:
1) Two Porcelain evaporating dish of 12 mm diameter with flat bottom.
2) Stainless steel Shrinkage dish 45 mm in diameter and 15 mm in height having flat bottom.
3) Glass cup 50 mm in diameter and 25 mm in height.
4) Two Glass plates each of 75×75 mm. One plate should be of plain glass and the other should have
three metal prongs
5) Spatula
6) Straight edge
7) 425 micron IS sieve
8) Balances, sensitive to 0.1 gm and 0.01gm
9) Thermostatically controlled oven to maintain temperature between 105 - 110 °C.
10) Mercury
11) Desiccators
12) Wash bottle containing distilled water.
Procedure:
1) Preparation of soil paste: Take about 100 gm of soil sample passing 425 micron IS sieve and mix it
thoroughly with distilled water. Water added should be sufficient to fill the voids in soil completely
and make the soil pasty enough to be readily worked into the shrinkage dish without entrapping air
bubbles.
2) Determination of mass and volume of the shrinkage dish: Clean the shrinkage dish and determine
its mass accurate to 0.1gm. To determine its volume place the shrinkage dish in the evaporating dish
and fill it to overflow with the mercury. Remove the excess mercury by pressing the plain glass plate
firmly on its top, taking care that no air is entrapped. Wipe off carefully any mercury which may be
adhering to the outside of shrinkage dish. Carefully transfer the mercury of the shrinkage dish to the
other evaporating dish and then determine the mass of mercury accurate to 0.1gm.The mass of
mercury divided by its density would give the volume of the shrinkage dish which is also the volume
of the wet soil pat.
3) Filling the shrinkage dish with soil pat: Coat the inside of the shrinkage dish with a thin layer of
grease. In the centre of the dish, place the soil paste, with the help of spatula. Tap the dish gently on
a firm surface, and allow the paste to flow towards the edges. Place another equal amount of paste in
the dish and make it flow toward the edges by tapping. Tapping should be continued till the paste is
compacted and all the entrapped air is brought to the surface. Repeat the process till the dish is
completely filled and the excess soil overflows. Strike off the excess soil paste with a straight edge.
Wipe of the soil adhering to the outside of the shrinkage dish.

10. 4) Determination of wet and dry mass of soil pat: The shrinkage dish is weighed along with the wet
soil pat. Keep the shrinkage dish in oven at 105 to 110 degree Celsius for 18-24 hours depending
upon the type of soil. Then take it out and allow it to cool and weigh it.
5) Determination of volume of dry soil pat: To determine the volume of dry soil pat, a glass cup kept
in a tray is filled with mercury. The dry soil pat is kept on the surface of the mercury and it is slowly
pushed into the mercury using glass plate with three prongs. The mass of mercury displaced by the
dry soil pat is obtained. Mass of displaced mercury divided by density of the mercury gives the
volume of dry soil pat.
Observation Table:
Sr.
No.
Description Sample-1 Sample-2 Sample-3
(A) Water content of wet soil
1 Shrinkage dish no.
2 Mass of shrinkage dish M1 (gm)
3 Mass of shrinkage dish + wet soil pat M2 (gm)
4 Mass of shrinkage dish + dry soil pat M3 (gm)
5 Mass of dry soil pat Ms = M3 - M1 (gm)
6 Mass of water = M2 - M3 (gm)
7 Water content of soil pat ω (%)
(B) Volume of wet soil pat.
8 Evaporating dish No.
9 Mass of evaporating dish m1 (gm)
10 Mass of mercury filling shrinkage dish +
mass of evaporating dish m2 (gm)
11 Mass of mercury filling shrinkage dish
Mg = m2 – m1 (gm)
12 Volume of mercury = Volume of wet soil pat
V1 = (Mg / density of mercury) (cm3)
(C) Volume of dry soil pat.
13 Evaporating dish No.
14 Mass of evaporating dish m1 (gm)
15 Mass of mercury displaced by dry soil pat +
mass of evaporating dish m3 (gm)

11. 16 Mass of mercury displaced by dry soil pat
Md = m3 – m1 (gm)
17 Volume of mercury displaced by dry soil pat
= Volume of dry soil pat
Vd = (Md / density of mercury) (cm3)
18
Shrinkage limit ωS (%)
Calculations:
Water Content ω =
(M2−M3)
(M3−M1)
×100
Shrinkage limit of soil ωS = ω -
(V1−Vd)
Md
×100
Shrinkage ratio SR =
Md
Vd×ρω
Volumetric Shrinkage VS = SR (ωL − ωS) × 100
Result:
Shrinkage limit of the soil =
Shrinkage ratio =
Volumetric Shrinkage =

12. Fig.1. Shrinkage limit apparatus
Fig.2. Determination of Shrinkage limit