Index Properties of Soil Part I

CE6405 SOIL MECHANICS
V.Nageshwaran, M.E.,
Assistant Professor,
Department of Civil Engineering,
UCET

DETERMINATION OF INDEX PROPERTIES

INDEX PROPERTIES
 Water Content
 Specific Gravity
 Particle/Grain Size Distribution
 Consistency Index
 In-situ Density
 Density Index

WATER CONTENT
 Oven Drying Method
 Sand Bath Method
 Alcohol Method
 Calcium Carbide Method
 Pycnometer Method
 Radiation Method
 Torsion Balance Method

OVEN DRYING METHOD
 Most Accurate Method.
 Laboratory Method.
 Specimen – Soil Sample – Clean Container –
Thermostatically Controlled Oven with Interior of Non-
corroding material – 105˚C to 110˚C.
 Sandy Soil (24 h) – > 110˚C breaks the Crystalline
Structure of Clay particles – Loss of Chemically bound
Structural Water.
 High Organic Soil – Peat – 60˚C – To prevent the Oxidation
of the Organic Matter.
 Soil Containing Gypsum – Heating losses its Water of
Crystallization – ≤ 80˚C for a longer time.
 IS:2720 Part II-1969.
 Clean Non-corrodible Container with Lid.
 Weighing Balance – 0.01 g accuracy.

PROCEDURE
 Empty Weigh Container with Lid, M1.
 Take Soil Specimen.
 Soil Specimen (Wet) placed in Container with Lid, M2.
 Weigh the Specimen (Wet) + Container with Lid.
 Placed in the Oven for Drying at 105˚C to 110˚C.
 Allow to Cool the Container in a Desiccator.
 Weigh the Specimen (Dry) + Container with Lid, M3.

FORMULA & CALCULATION
where, M1 = Mass of Container with Lid.
M2 = Mass of Container with Lid and Wet Soil.
M3 = Mass of Container with Lid and Dry Soil.
100
MM
MM
w
13
32





SAND BATH METHOD
 Field Method.
 Rough Method.
 Applicable where Oven Facility is not available.
 Container with Soil placed on a Sand Bath.
 Sand Bath is heated over a Kerosene Stove.
 Soil dried within 0.5 to 1 h.
 Not suitable for Organic Soils/Soils having Higher % of
Gypsum.
 B.S. 1377:1961

ALCOHOL METHOD
 Crude Field Method.
 Evaporating Dish with Wet Soil Sample + Sufficient Quantity
of Methylated Spirit.
 Dish is properly covered and ignited.
 Stirred during Ignition with a Wire.
 Not applicable for Soils containing large % of Organic
Matter or Gypsum – No temp. control.

FORMULA & CALCULATION
where, M1 = Mass of Dish with Lid.
M2 = Mass of Dish with Lid and Wet Soil.
M3 = Mass of Dish with Lid and Dry Soil.
100
MM
MM
w
13
32





CALCIUM CARBIDE METHOD
 Quick Field Method – 5 to 10 mins.
 6 g of Soil Sample is taken + Sufficient Quantity of Fresh
Calcium Carbide Powder.
 Air-tight Container – Moisture Tester.
 Shaken Vigorously.
 Acetylene Gas – Produced from reaction of Moisture and
Calcium Carbide – Exerts Pressure on a Sensitive
Diaphragm placed at the end of the Container.
 Dial Gauge in the Diaphragm reads the Water Content
directly.
 Water Content, w’ read is based on Wet Weight of the Soil
Sample.
'
'
w1
w
w



CONT…
 Field Kit – Moisture Tester, Small Single-pan Weighing
Balance, Bottle containing Calcium Carbide and a Brush.
 Two 30 mm diameter balls – placed for proper pulverization
of clay soils.
 Suitable for Proper Field Control – Compaction of an
Embankment.

PYCNOMETER METHOD
 Quick Method.
 Applicable only for Soils whose Gs is accurately known.
 Pycnometer – Large Size Density Bottle of about 900 ml capacity.
 Conical Brass Cap – 6 mm diameter hole at top is screwed to the
open end of the Pycnometer.
 Rubber Washer is placed between Conical Cap and Rim of the
bottle so that there is no Leakage of Water.

PROCEDURE
 Take a Clean, Dry Pycnometer, and find its Mass with its
Cap and Washer, M1.
 Put about 200g to 400g of Wet Soil Sample in the
Pycnometer and find its Mass with its Cap and Washer, M2.
 Fill the Pycnometer to Half its Height and Mix it thoroughly
with the Glass Rod.
 Add more Water, and Stir it.
 Replace the Screw Top and Fill the Pycnometer flush with
the hole in the Conical Cap.
 Dry the Pycnometer from outside, and find its Mass, M3.
 Empty the Pycnometer, Clean it thoroughly, and Fill it with
Clean Water to Hole of the Conical Cap, and find its Mass,
M4.
1001
G
1G
.
MM
MM
w
s
s
43
12











 










CONT…
 Suitable for Coarse Grained Soils only.
s
d
d34
G
M
MMM  or 43
s
s
d MM
G
1G
M 




 
 
1G
G
MMM
s
s
43d


  d12w MMMM 
100
M
M
w
d
w

100
M
MMM
w
d
d12



1001
G
1G
MM
MM
1001
M
MM
w
s
s
43
12
d
12











 


















RADIATION METHOD
 In-Situ Method.
 Two Steel Casings – A & B are placed in 2 Bore holes at some
distance apart, in the Soil Deposit.
 Device – Radio-active Isotopes – Cobalt 60 – placed in a capsule
which in turn is lowered into Casing A.
 Detector Unit – lowered in Steel Casing B.
 Small Openings – made in both Casings A & B – facing each
other.
 Radio-active device is activated, it emits Neutrons.
 Neutron Strikes Hydrogen atoms of Water in the Sub-Soil, they
loose energy.

CONT…
 Loss of Energy = Amount of Water Content in the Soil.
 Detector Device is Calibrated to give directly the Water
content of the Sub-Soil, at that Level of Emission.
 Shielding Precaution required – Radiation Problems.

INFRA-RED/TORSION BALANCE METHOD
 2 Main Parts – Infra-Red Lamp & Torsion Balance.
 IS:2720, Part II-1973.
 IR – 250 watt Lamp built in the Balance – 220 to 230 V (AC ), 50
Cycle, Single Phase Mains Supply.
 Weighing Mechanism – Torsion Balance built in Magnetic
Damper to Reduce Pan Vibration during Quick Drying.
 Balance Scale is divided in terms of Water % from 1 to 100 in 0.2
% division.
 Moisture Meter – Calibrated to use 25 g of Soil.
 Maximum Size of Particle present in the Specimen < 2 mm.
 Suitable Container – Water Content – Not affected by Ambient
Conditions.
 Torque – applied to one end of the Torsion wire – Means of a
Calibration Drum to Balance the Loss of Weight of the Sample as
it dries out under Infra-Red Lamp.

CONT…
 To Determine the % Reduction of Mass at any instant,
rotate the Drum Scale by turning the Drum drive Knob until
the point returns to the Index.
 Water Content is read directly and it is based on the Wet
Mass.
 Input Voltage to IR Lamp – Adjustable – Control the Heat
for Drying the Specimen.
 Suitable Thermometer graduated from 40˚C to 150˚C.
 Temperature – 110 ˚C ± 5˚C.
 Time Required – Depends on Soil type and Quantity of
Water present (Simultaneously).
 Suitable – Soils which re-absorb moisture quickly on drying.
 Final Reading – Pointer should remain Steady on Index
Mark – Sample – Dried to Constant Mass.
'
'
w1
w
w



Index Properties of Soil Part I

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Index Properties of Soil Part I