Method of soil compaction

   Impact equipment:-

     (a). Rapid impact compactor :-

Rapid impact compaction is a high- frequency controlled energy soil compaction  technique used to densify surface layers of soils (to a depth of 5 to 7 meters in most cases) with minimum impact on the immediate worksite environment.

 Rapid Impact Compaction is a shallow ground improvement and densification technique. This method densifies shallow, granular soils, which repeatedly strike an impact plate on the ground surface using a hydraulic hammer. The energy is transferred to the underlying loose soils and regroups the particles into a denser formation. The impact locations are located on a grid pattern and the spacing of those locations is calculated by the subsurface conditions and foundation loading and geometry. 

     (b). Vibrating Plates :-

In this system, there are numbers of smaller plates, each plate are vibrated by a separate vibrating unit. Hand operated vibrating plates are also available. these compactors are suitable for compacting soils having smaller thickness.

The main use of vibrating plates is to compact granular base courses for highways and runways where the thickness of layers is small. Vibrating plates are suitable to coarse-grained soils containing up to 12 % fines.

     (c). Ramming :-

Impact rammer consist of a block of iron about 3 to 5 kg wooden rod. The rammer is lifted by about 30 cm and dropped on the soil to be compacted. A mechanical rammer is operated by compressed air gasoline power. It is much heavier and weight’s 30 to 150 kg.

Mechanical rammers have been used up to a weight of 1000  kg.  Power controlled or manually operated impact rammers are used where the area to be compacted are small, the area is inaccessible and use of large equipment is not justified. They are also used for compacting backfill behind retaining walls or small trenches.  They can be used for all types of soils.

  Roller equipment's :-

The equipment which consist roller, drum are termed as roller equipment. These equipment's generally weight's around 2 to 15 Tons. The types of roller equipment's are listed below :-

 (a). Cylindrical roller :-

One type of walk behind roller is a cylindrical roller. These ones are traditional equipment's that are relatively lightweight and are pushed by a person. All the types of rollers on this list have walk behind and ride on counter parts and are sometimes still powered by an engine.

Cylindrical rollers are used mainly for small and private project, like yard work. cylindrical rollers are typically 1 meter in diameter and are generally made of iron, stone or concrete.

  

     (b). Smooth roller :-  

A smooth-wheel roller generally consists of three wheels. There are two large wheels in the rare part and one small in the front. The weight of smooth wheel roller varies from 2 to 15 tons. The roller is operated by internal combustion engine. There is another version of smooth wheel roller known as tendem smooth wheel roller. It consists of only two drums: one at front part and another at rear part. Smooth wheeled rollers mostly suited to seal the surface of the fill at the end of day’s work to provide a smooth surface to quickly drain the rain water.

They are not suitable for deep layers of soil such as uniform sands and silty sands because the resulting compaction pressures induced are low. In addition these rollers cause stratification in deep layers due to none-uniform compaction. They are used to compact well-graded  coarse grained soils for use in  highway base courses and non – plastic fine-grained soils. 

     (c). Sheep foot roller :-

Sheep foot rollers are named from sheep because, in ancient times, a flock of sheep were used to compact a newly formed fill. The roller is similar to the smooth wheel roller except that it contains numerous projecting feet about 200 mm to 250 mm long with an end area of 40 to  65 cm2.  The wheels of the roller consist of hollow drums and can be filled with water and ballasts to increase their weight.  The drums are mounted on a steel frame. 

Sheep foot rollers are available in both type either as a self-propelled unit or a towed unit.  The projections of the roller penetrate the soil layers during rolling and cause compaction.  During rolling the weight of roller is transmitted to fill through projecting feet. The pressure imposed range from 7 to 42 kg/cm2. These rollers are suitable for both plastic and non-plastic fine-grained soils and for coarse-grained soils with more than 20% fines.  

     (d). Pneumatic roller :- 

Pneumatic rollers, sometimes called pneumatic tired rollers, are a type of large, ride-on roller with several rows of rubber tires on the front or rear end. The rubber tires provide an 80% coverage area and uniform pressure throughout the width of the tires.

They are typically used for pavements and can help smooth out and polish a project, but are also great for cold-laid bituminous or cold mixed pavements and layers of loose soil.

     (e). Vibratory roller :-                                                                                              

Vibratory rollers are almost identical to smooth wheel rollers (including the single and double drum) except for one major difference: they come with a specialized vibrating component. As the roller compacts and flattens the surface, it will vibrate.

Since soil, asphalt, and concrete have natural empty spaces, they can cause a building to warp and sink, causing damage to the structure. Using a vibratory roller on your construction project can help keep the building’s structural integrity. Other types of soil that vibratory rollers are great at compacting are crushed rock or gravel.

     (f). Grid Roller :-

Grid rollers are a type of roller that has a network of steel bars, which create a grid-like pattern on the steel drum. The grid may also be ballasted with concrete blocks or steel attachments for more contact pressure. These types of rollers are generally towed or pulled behind a tractor or another heavy machine.

The grid design on the cylinder drum produces a high contact pressure with little kneading action on compaction work. Because of this, they’re most suitable on well-graded, coarse soils, weathered rocks and for subgrade and sub-base road constructions.