soli comp cation - vtu edusat com
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Basics of Soil Compaction Methods & equipment
K.RamanathGeneral Manager & Dean RASTA
Road Machinery Business Line Volvo India Private Limited
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Soil Compaction
Cost of earth work – 30% Cost of road project
Increase in heavy axle load application
Well compacted sub-grade results in economy of pavement thickness
Proper compaction has great economic implications
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Road - cross section
40 mm80 mm80 mm
300 mm
300 mm
150 mm150 mm
200 mm
200 mm 200 mm
Asphalt concrete / wearing courseDBM } Aggregate 67%,stone dust 24%DBM } Sand 9% Bitumen 5%
WMM / WBM
WMM / WBM
GSB }GSB } Aggregate up to 80 mm
Soil } }
Soil } Muram }Soil }
10% Road thickness comprises of asphalt work - 65% of total value
Flexible pavement
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Objectives Of Soil Compaction
Increase in strength
Reduction in compressibility
Reduction in tendency for subsequent
changes in moisture content
Reduction in erodability
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Factors Influencing Compaction
Type of soil
Moisture content
Compactive effort - Energy applied per unit weight of soil
- Weight of rammer, height of fall, number of blows
- Weight of roller, number of passes
Thickness of lift and type of compacting equipment (for field compaction)
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Moisture Content
Water acts as a lubricant
Too much
– takes up space
– does not allow bonding
Too little
– same compactive effort, lower compaction
OMC of fine grain soils is higher than coarse grain soils
OMC - The moisture content of the soil at which maximum density can
be achieved for a given amount of compactive effort
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Moisture content - % by dry weight
Dry Density
Max Dry Density
Optimum Moisture content
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Laboratory Compaction Tests
Dynamic Compaction
– IS light compaction / standard proctor test
– IS heavy compaction/ modified proctor test Static Compaction
Kneading Compaction
Vibratory compaction
usually static or dynamic compaction is adopted
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Comparison Of Compaction Tests
Standard Proctor Test Modified Proctor Test
Soil passing 20 mm / 37.5 mm IS sieve Soil passing 20 mm / 37.5 mm IS sieve
Soil compacted in 3 layers, 25 blows / 55 blows
Soil compacted in 5 layers, 25 blows / 55 blows
Soil compaction by 2.6 kg hammer, 31 cm is height of fall
Soil compaction by 4.89 kg hammer, 45 cm is height of fall
Adopted for rural roads specifications Adopted for MORTH specifications
Used for Internal roads in urban areas and village roads
Used for NH, SH, MDR and arterial roads in urban area
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Moisture-density Relationship For Different Types Of Soils
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Field Control Of Compaction
Measurement of dry density
– Core cutter method (IS: 2720 (Part 29) - 1975)
– Sand replacement method (IS: 2720 (Part 28) - 1974)
– Nuclear density & moisture gauge (ASTM D- 2922)
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Sand Replacement Method Sand Replacement Method
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Nuclear Test
If calibrated
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Field Control Of Compaction Contd…
Measurement of moisture content
–Oven Dry Method
–Sand bath drying method
– Infrared torsion balance method
–Speedy moisture meter (IS 2720 (Part 2 - 1973)
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Rapid Moisture
Meter MethodInfra Red Torsion Moisture
Balance Meter
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Soil Compaction
Soil Compaction is the process whereby soil particles are constrained to pack more closely through a reduction in air voids by mechanical means
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What is Compaction?
The act of artificially densifying or increasing the unit weight of soil by application of external forces
Reducing the voids or pore spaces to a minimum
Increasing the solid particle content to a maximum.
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Compactive Force
Water Air
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Details of Compactive Effort ( Compaction methods )
Static Pressure - weight of the machine - Masstransmitted onto the ground.
Impact - blows like that of a hammer
Vibration - energy resonates the materialinto a state of equilibrium
Manipulation - mends, shears and kneads
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Static Pressure
Compaction in Road Building is not just applying pressure
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Compactive Effort: Static
Weight
Three Wheel Static Roller
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Compaction Effect of 8 Ton Static roller
RH Rear Drum
LH Rear Drum
Static Load 2510 Kgs
Static Load 2510 Kgs
Static Load 2980 Kgs
Front Drum
Linear applied load - 47.24
Linear applied load - 47.24
Linear applied load - 29.33
508 mm 508 mm
1016 mm
After the first pass
• 38% Lower density on Front drum
• Higher density on Rear drum.
• Uneven mat finish.
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Total applied force on rear drum = 4950 kgs ( Linear applied load = 41.25 )
Total applied force on Front drum = 4950 kgs ( Linear applied load = 41.25 ) Equal density over full
roller width. Even mat surface after first pass
Rear Drum
Front Drum
Tandem Roller - Compaction effectDrum width - 1200 mm
1200 mm Compacted width
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Two Wheel Static roller
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Compaction Effect - Impacts
Achieve compaction -
through a series of blows
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Compaction Effort: Vibration
More effective in overcoming internal friction and cohesion Higher in-place density
Proven the most cost effective
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AMPLITUDEAMPLITUDE
1.7 mm
Vertical Distance of Drum Travel
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Frequency
ROLLER DRUM
Defined: Number of complete cycles, (speed) of the rotating device, (weight) measured in vibrations per minute (vpm).
IMPACT SPACING
( 1 Impact every 20 - 25 mm of travel )
LOW HIGH
Impact Spacing
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Vibrations
Compaction occurs from the bottom to thetop of the surface.
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Compactive Effort: Vibration & Impact
Weight
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Material Natural Frequency
Soil type Graded sand
Graded sand, wet
Coastal sand, dry
Clay
Clay, dry, mixed w/gravel
Sandy gravel
Firm silt
Loose silt
Frequency
1980 VPM (33hz)
1440 VPM (24hz)
1320 VPM (22hz)
1200 VPM (20hz)
1110 VPM (18.5 hz)
1500-1740 VPM (25-29hz)
1500-1740 VPM (25-29hz)
1260-1980 VPM (21-33hz)
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Compactive Effort: Vibration & Manipulation
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Pad foot Soil Compactor
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References
1.IRC Special Report “ State of Art : Compaction of Earthwork and Subgrades”HRB , 1999
2.HMSO publication, Soil Mechanics for Road Engineers
3.Specifications for Road and Bridge Works, IV Edition, MoRTH, IRC Publication
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Thank you for your attentionThank you for your attention
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