Its helps in understanding of Shrinkage limit of soil and how to do shrinkage limit test in lab.

1. Determination of Physical Properties of Soil
Shrinkage Limit Test
IS: 2720 Part 6 – 1972 Reaffirmed 2016
CENGRS GEOTECHNICA PRIVATE LIMITED
ISO 9001:2015 accredited by JAS-ANZ ISO 17025:2017 certified geotechnical laboratory (NABL)

2. What is Shrinkage limit
• A saturated soil is slowly dried, capillary menisci* form between the
individual soil particles.
• As a result, the interparticle (effective) stresses increase, and the soil
decreases in volume.
• A point is eventually reached where this volume change stops, even
though the degree of saturation is still essentially 100%.
• The moisture content at which this occurs is defined as
the shrinkage limit (wSL)
* Menisci are a manifestation of capillary action, by which surface adhesion pulls a liquid up to form a concave meniscus or internal
cohesion pulls the liquid down to form a convex meniscus.

3. Need & Scope of
Shrinkage Limit
• As the soil loses moisture, either
in its natural environment, or by
artificial means in laboratory it
changes from liquid state to plastic
state to semi-solid state and then to
solid state.
• The volume is also reduced by
the decrease in water content. But,
at a particular limit the moisture
reduction causes no further volume
change.
• A shrinkage limit test gives a
quantitative indication of how much
moisture can change before any
significant volume change and to
also indication of change in
volume.

4. Continued….
• The shrinkage limit is useful in areas where soils undergo large volume
changes when going through wet and dry cycles (e.g. expansive soils)
• The shrinkage factor helps in the design problems of structure made up of
this soil or resting on such soil. It helps in assessing the suitability of soil as
a construction material in foundations, roads, embankments, and dams.
• This limit is needed for studying the swelling and shrinkage properties of
cohesive soil.

5. Principle for Determining
the Shrinkage Limit of Soil:
• Figure shows the schematic
diagram in which a fully
saturated soil in stage I having
volume
• V1 undergoes shrinkage and
on complete drying reaches
stage III, where the entire water
is evaporated.
• Between stages I and III lies
stage II, where the soil is at
shrinkage limit water content.
• In stage II, the soil is fully
saturated, but a further decrease
in the water content does not
cause any decrease in the
volume of the soil and air
occupies the space of the
evaporated water.

6. Continued….
• The volume of the soil at shrinkage limit is equal to the total volume of
oven-dried soil. It is to be noted that the volume of soil solids is constant
throughout the shrinkage process, and the decrease in volume occurs only
due to decrease in volume of voids. So we get –
Weight of water in stage I = – W1 – Wd
Loss of water from stage I to II = (V1 – V2)γw
Weight of water in stage II = (W1 – Wd) – (V1 – V2)γw
Shrinkage limit = Water content of soil in stage II
• Where W1 is the initial total weight of soil in stage-I, Wd is the dry weight
of soil, V1 is the initial volume of the soil in stage-I, Vd is the volume of
soil in dry state (stage III), ω1 is the initial water content of soil in stage-I,
and γw is the density of water.

7. Lab Test of Shrinkage Limit
Lab procedure is in accordance with IS:2720
(Part 6)-1972

8. Apparatus
1. Cylindrical stainless steel shrinkage dish with 45-mm internal diameter and
15-mm internal height.
2. Cylindrical glass cup with 50-mm internal diameter and 25-mm internal
height.
3. Porcelain evaporating dish.
4. Square acrylic plastic plate of size 75 mm x 75 mm with three metal prongs.
5. Square plain plastic plate of size 75 mm x 75 mm.
6. Thermostatically controlled oven.
7. Mercury
8. calibrated Sieve.
9. Spatula & Calibrated balances.

9. Procedure
1. Coat the inside of the shrinkage dish with a thin layer of silicon grease to prevent
adhesion of soil to the dish. Determine its empty weight.
2. Determine the capacity of the shrinkage dish by filling to overflowing with mercury,
removing the excess by pressing the plain glass plate firmly flush over the dish, ensuring
no air is entrapped. Weigh the mercury held in shrinkage dish and divide this by unit
weight of mercury (13.6 g/cc) to obtain the volume, which is also the volume of wet soil
pet (V).
3. For test on remoulded sample fill the dish in three layers by placing soil paste about one
third the capacity of the dish at a time and tapping the dish gently on a firm surface with
proper cushioning by a rubber sheet so that the soil flows to the edges.
4. The last layer should stand a little above the run and care should be taken not to trap air
within the soil . Strike off the excess soil in level with the top of the dish and clean the
outside. For undisturbed soil pat, trim it from undisturbed soil sample approximately 44
mm in diameter and 15 mm in height. Round off their edges to prevent the entrapment of
air during mercury displacement. Measure the dimension of the pat to calculate volume
(V).

10. Continued….
5. Weigh the dish full of wet soil. Calculate the weight of wet soil pat (W). Allow it
to dry in air until the colour of soil pat turns light and the soil starts to leave the
sides of the dish. Then, dry in an oven at 105-110o C, cool the dish with dry soil
pat in a desiccators and weigh immediately after removal from the desiccators. By
weighing the shrinkage dish and dry soil calculate the weight of dry soil pat (Wo).
6. Keep the glass cup in the large porcelain on stainless steel dish, fill it to over
flowing with mercury and remove the excess by pressing the plain glass plate
firmly over the top of the cup, taking care not to entrap any air.
7. Wipe off any mercury adhering on the side and then transfer the cup full of
mercury to another large dish taking care not to entrap any air.
8. Place the dry soil pat on the surface of mercury and submerged it under the
mercury by pressing with the “glass plate with prongs”, taking care not to entrap
air.
9. Transfer the mercury displaced by the dry pat to the mercury-weighing dish and
weigh and determine the volume of dry soil pat by dividing this weight by the
unit weight of mercury (Vo).

11. Calculations
• Calculate the shrinkage limit (remoulded soil) using the
following formula:
Where:
Ws = Shrinkage limit in percentage
w = moisture content of wet soil pat in percentage,
V = volume of wet soil pat ,
Vo = volume of dry soil pat ,
W = weight of wet soil pat
Wo = weight of oven-dry soil pat in g.

12. • Calculate the shrinkage limit (Undisturbed soil) using the
following formula:
Where :
Wsu = shrinkage limit (undisturbed soil) in percentage,
Vos = volume of oven-dry specimen in ml,
Wos = weight of oven-dry specimen in g,
G = specific gravity of soil

13. TABULATION AND RESULTS
S.No Determination No. 1 2 3
1 Wt. of container in gm,W1
2 Wt. of container + wet soil pat in gm,W2
3 Wt. of container + dry soil pat in gm,W3
4 Wt. of oven dry soil pat, W0 in gm (W3-W1)
5 Wt. of water Ww in gm (W2-W3)
6 Moisture content (%), w = (Ww/Wo)*100
7 Volume of wet soil pat (V), in ml
8
Volume of dry soil pat (V0) in ml
By mercury displacement method
a. Weight of displaced mercury (Wm)
b. Specific gravity of the mercury (Gm)
V0 = Wm/Gmγw
9 Wt. of Shrinkage dish + Oven dry specimen (g)
10 Wt. of oven dry specimen, Wos, (g)
11 Volume of oven dry specimen, Vos, ml
12 Specific gravity of soil, G
13
Remoulded Soil:
Shrinkage limit (Ws%)
14
Undisturbed Soil:
Shrinkage limit (Ws%)
15 Shrinkage Index (Is) = Ip - Ws
16 Shrinkage ratio (R)

14. Engineering Description of soil

15. Foundation Damage
• The most obvious way in which expansive soils can damage
foundations is by uplift as they swell with moisture increases.
Swelling soils lift up and crack lightly-loaded, continuous strip
footings, and frequently cause distress in floor slabs.

16. Damage to foundation from expansive soil
A rectangular slab, uniformly loaded, will tend to lift up in the corners
because there is less confinement

17. Damage to
foundation from
expansive soil
Figure : Damage to home supported on
shallow piers.
(1) At the beginning of the rainy season, the
piers are still supported by friction with
the soil. When it begins to rain, water
enters deep into the soil through the
cracks.
(2) After 5 to 10 large storms, the soil swells,
lifting the house and piers.
(3) In the dry season, the groundwater table
falls and the soil dries and contracts. As
tension cracks grow around the pier, the
skin friction is reduced and the effective
stress of the soil increases (due to drying).
When the building load exceeds the
remaining skin friction, or the effective
stress of the soil increases to an all-time
high, adhesion is broken by this straining,
and the pier sinks.

18. Mitigation Measures
• The best way to avoid damage from expansive soils is to
extend building foundations beneath the zone of water content
fluctuation.
• The reason is twofold:
1. First, to provide for sufficient skin friction adhesion below
the zone of drying
2. Second, to resist upward movement when the surface soils
become wet and begin to swell.