compaction sivakugan (complete soil mech. undestanding pakage: abhay)

1

Compaction

N. SivakuganDuration = 10 minutes

2SIVA

Copyright©2001

What is compaction?

A simple ground improvement technique, where the soil is densified through external compactive effort.

+ water =

Compactive effort

3SIVA

Copyright©2001

Compaction Curve

Water content

Dry

den

sity

(ρ d

)

optimum water content

ρd, max

Soil grains densely packed

- good strength and stiffness

- low permeability

4SIVA

Copyright©2001

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

5SIVA

Copyright©2001

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)

6SIVA

Copyright©2001

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

)

7SIVA

Copyright©2001

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

)

8SIVA

Copyright©2001

Line of Optimum

Water content

Dry

den

sity

(ρ d

)

Compaction curves for different efforts

Line of optimum

SIVA

Copyright©2001

Filed Compaction

Pneumatic rubber tired roller

Different types of rollers (clockwise from right):

Vibratory roller

Smooth-wheel roller

Sheepsfoot roller

10SIVA

Copyright©2001

Field Compaction

Compacts effectively only to 200-300 mm; therefore, place the soil in shallow layers (lifts)

Smooth Wheeled Roller

11SIVA

Copyright©2001

Field Compaction

for compacting very small areas

Vibrating Plates

effective for granular soils

12SIVA

Copyright©2001

Field Compaction

Provides kneading action; “walks out” after compaction

Sheepsfoot Roller

Very effective on clays

13SIVA

Copyright©2001

Field Compaction

Provides deeper (2-3m) compaction. e.g., air field

Impact Roller

14SIVA

Copyright©2001

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

15SIVA

Copyright©2001

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

16SIVA

Copyright©2001

Compaction Control Test

compacted ground

ρd,field = ?wfield = ?

Compaction specifications

Compare!

w

ρd

SIVA

Copyright©2001

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)

SIVA

Copyright©2001

Dynamic Compaction

Pounder (Tamper)Mass = 5-30 tonneDrop = 10-30 m

SIVA

Copyright©2001

Dynamic Compaction

SIVA

Copyright©2001

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)

compaction sivakugan (complete soil mech. undestanding pakage: abhay)

Engineering