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
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
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.
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.
Instrument of Filed Compaction Different types of rollers (clockwise from right): Vibratory rollerPneumatic rubber tired roller Smooth-wheel 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 definethe optimum water content and maximumdry density for a specific compactive effort. hammer Modified ProctorStandard Proctor •5 layers•3 layers • 25 blows per• 25 blows per layer layer •4.9 kg hammer•2.7 kg hammer • 450 mm drop• 300 mm drop 1000 ml compaction mould