Transcript Compaction - Geoengineer.org

Compaction
N. Sivakugan
Duration = 10 minutes
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What is compaction?
A simple ground improvement technique, where the soil
is densified through external compactive effort.
Compactive
effort
+ water =
2
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Compaction Curve
Dry density (d)
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Soil grains densely packed
- good strength and stiffness
- low permeability
d, max
optimum
water content
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Water content
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Compaction Curve
Dry density (d)
What happens to the relative quantities of the three phases
with addition of water?
air
water
soil
difficult to expel all air
lowest void ratio and
highest dry density at
optimum w
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Water content
Zero Air Void Curve
Dry density (d)
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- corresponds to 100% saturation
Zero air void curve (S=100%)
S<100%
Gs  w
Eq :  d 
1  wGs
S>100% (impossible)
All compaction points should lie
to the left of ZAV curve
Water content
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Dry density (d)
Effect of Compactive Effort
Increasing compactive
effort results in:
E2 (>E1)
 Lower optimum water
content
 Higher maximum dry
density
E1
Water content
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more dispersed fabric
Dry density (d)
Compaction and Clay Fabric
Higher water content or higher
compactive effort gives more
dispersed fabric.
more dispersed fabric
Water content
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Line of Optimum
Dry density (d)
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Compaction curves
for different efforts
Line of optimum
Water content
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Filed Compaction
Different types of rollers (clockwise
from right):
 Smooth-wheel roller
 Vibratory roller
Pneumatic rubber tired roller
 Sheepsfoot roller
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Field Compaction
Smooth Wheeled Roller
Compacts effectively only to 200-300 mm; therefore,
place the soil in shallow layers (lifts)
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Field Compaction
Vibrating Plates

for compacting very small areas

effective for granular soils
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Field Compaction
Sheepsfoot Roller
 Provides kneading action; “walks out” after compaction
 Very effective on clays
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Field Compaction
Impact Roller
 Provides deeper (2-3m) compaction. e.g., air field
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Compaction Control
-a systematic exercise where you check
at regular intervals whether the
compaction was done to specifications.
e.g., 1 test per
1000 m3 of
compacted soil
• Minimum dry density
• Range of water content
Field measurements (of d) obtained using
• sand cone
• nuclear density meter
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Laboratory Compaction Test
- to obtain the compaction curve and define the
optimum water content and maximum dry density for a
specific compactive effort.
Standard Proctor:
hammer
Modified Proctor:
• 3 layers
• 5 layers
• 25 blows per layer
• 25 blows per layer
• 2.7 kg hammer
• 4.9 kg hammer
• 300 mm drop
• 450 mm drop
1000 ml compaction mould
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Compaction Control Test
Compaction
specifications
d
Compare!
w
d,field = ?
wfield = ?
compacted ground
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Dynamic Compaction
- pounding the ground by a heavy weight
Suitable for granular soils, land fills
and karst terrain with sink holes.
Pounder (Tamper)
solution cavities in
limestone
Crater created by the impact
(to be backfilled)
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Dynamic Compaction
Pounder (Tamper)
Mass = 5-30 tonne
Drop = 10-30 m
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Dynamic Compaction
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Vibroflotation
Suitable for granular soils
Practiced in several forms:

vibro–compaction

stone columns

vibro-replacement
Vibroflot (vibrating unit)
Length = 2 – 3 m
Diameter = 0.3 – 0.5 m
Mass = 2 tonnes
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(lowered into the ground
and vibrated)
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Vibroflotation
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Vibroflotation
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Vibroflotation
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Vibroflotation
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Vibroflotation
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Vibroflotation
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vibrator makes a
hole in the weak
ground
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Stone Columns
hole backfilled ..and compacted Densely compacted
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Blasting
For densifying granular soils
Fireworks?
Aftermath of blasting
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Earthmoving Equipment
David and Goliath?
Large Excavator (see minivan on left for scale)
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Earthmoving Equipment
Grader for spreading soil
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Earthmoving Equipment
Bulldozer for spreading soil evenly
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Earthmoving Equipment
Loader
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Earthmoving Equipment
Backhoe
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Earthmoving Equipment
Crawler mounted Hydraulic Excavator
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Earthmoving Equipment
Rock Breaker
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