What is compaction?

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

COMPACTIONCompactive effort

+ water =

There are three method in field compaction

Rolling Ramming Vibration

Methods of field compaction

Rolling - a heavy cylinder is rolled over the surface of the soil. Commonly used on sports pitches. Roller-compactors are often fitted with vibratory devices to enhance their ability.

Different types of rollers are used for Compaction. which are depend on following factors

Contact pressure Number of passes(normally 5 to 15) Layer thickness (less than 15 cm) Speed of roller

rolling

A hand operated rammer consist of a block of iron,about 3 to 5 kg in mass,attached to a wooden rod.the rammer is lifted for about 0.30 m and dropped on the soil to be compacted

A mechanical rammer is operated by compressed air or gasoline power.it is much heavier about 30 to 150 kg. mechanical rammers have been used up to a mass of 1000 kg in some special cases.

Tampers are used to compact soil adjecent to existing structures or confined area as trenches,within plinth of building.

ramming

Vibration are induced in the soil during compaction.the compactors are available in a variety of forms.when the vibrator is mounted on adrum,it is called a vibratory roller. these rollers are available both as pneumatic type and the smooth wheel type.in a smooth wheel type, a separate motor drives an arrangement of eccentric weights to create high frequency,low-amplitude,up and down osicillations of the drum.

These rollers are suitable for compacting granular soils. Another form of vibratory compactor is a vibrating plate

compactor. hand operated vibrating plates are also available.

vibration

Instrument of Filed Compaction

Different types of rollers (clockwise from right):

Smooth-wheel roller

Vibratory roller

Pneumatic rubber tired roller

Sheepsfoot roller

Smooth Wheeled Roller

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

Vibrating Plates

for compacting very small areas

effective for granular soils

Sheepsfoot Roller

Provides kneading action; “walks out” after compaction

Very effective on clays

Impact Roller

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

Laboratory Compaction Test

- to obtain the compaction curve and define the optimum water content and maximum dry density for a specific compactive effort.

Standard ProctorModified Proctor

•3 layers

• 25 blows per layer

•2.7 kg hammer

• 300 mm drop

•5 layers

• 25 blows per layer

•4.9 kg hammer

• 450 mm drop

hammer

1000 ml compaction mould