Compaction sivakugan (Complete Soil Mech. Undestanding Pakage: ABHAY)
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Transcript of Compaction sivakugan (Complete Soil Mech. Undestanding Pakage: ABHAY)
1
Compaction
N. SivakuganDuration = 10 minutes
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What is compaction?
A simple ground improvement technique, where the soil is densified through external compactive effort.
+ water =
Compactive effort
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Compaction Curve
Water content
Dry
den
sity
(ρ d
)
optimum water content
ρd, max
Soil grains densely packed
- good strength and stiffness
- low permeability
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Compaction CurveWhat happens to the relative quantities of the three phases with addition of water?
Water content
Dry
den
sity
(ρ d
)
soilwater
air
difficult to expel all air
lowest void ratio and highest dry density at optimum w
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Zero Air Void Curve
All compaction points should lie to the left of ZAV curve
- corresponds to 100% saturation
Water content
Dry
den
sity
(ρ d
)
Zero air void curve (S=100%)
s
wsd wG
G
+=
1 :Eq
ρρS<100%
S>100% (impossible)
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Effect of Compactive EffortIncreasing compactive effort results in:
E1
E2 (>E1)
Lower optimum water content
Higher maximum dry density
Water content
Dry
den
sity
(ρ d
)
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Compaction and Clay Fabric
Higher water content or higher compactive effort gives more dispersed fabric.
more dispersed fabric
mor
e di
sper
sed
fabr
ic
Water content
Dry
den
sity
(ρ d
)
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Line of Optimum
Water content
Dry
den
sity
(ρ d
)
Compaction curves for different efforts
Line of optimum
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Filed Compaction
Pneumatic rubber tired roller
Different types of rollers (clockwise from right):
Vibratory roller
Smooth-wheel roller
Sheepsfoot roller
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Field Compaction
Compacts effectively only to 200-300 mm; therefore, place the soil in shallow layers (lifts)
Smooth Wheeled Roller
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Field Compaction
for compacting very small areas
Vibrating Plates
effective for granular soils
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Field Compaction
Provides kneading action; “walks out” after compaction
Sheepsfoot Roller
Very effective on clays
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Field Compaction
Provides deeper (2-3m) compaction. e.g., air field
Impact Roller
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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
e.g., 1 test per 1000 m3 of
compacted soil
• Minimum dry density• Range of water content• Minimum dry density• Range of water content
Field measurements (of ρd) 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.
hammerStandard Proctor: Modified Proctor:
• 3 layers
• 25 blows per layer
• 5 layers
• 25 blows per layer
• 2.7 kg hammer
• 300 mm drop
• 4.9 kg hammer
• 450 mm drop
1000 ml compaction mould
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Compaction Control Test
compacted ground
ρd,field = ?wfield = ?
Compaction specifications
Compare!
w
ρd
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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.
Crater created by the impact
Pounder (Tamper)solution cavities in limestone
(to be backfilled)
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Dynamic Compaction
Pounder (Tamper)Mass = 5-30 tonneDrop = 10-30 m
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Dynamic Compaction
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Vibroflotation
Vibroflot (vibrating unit)Length = 2 – 3 mDiameter = 0.3 – 0.5 mMass = 2 tonnes
Practiced in several forms:
vibro–compaction
stone columns
vibro-replacement
Suitable for granular soils
(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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Stone Columns
vibrator makes a hole in the weak ground
hole backfilled ..and compacted Densely compacted stone column
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Blasting
Aftermath of blastingFireworks?
For densifying granular soils
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Earthmoving Equipment
Large Excavator (see minivan on left for scale)
David and Goliath?
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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