Rollers are the commonly used construction equipment for compaction of soil, gravel, sand, and crushed stone layers, etc. They work on the basis of vibration, impact loading, kneading and by applying direct pressure on the respective layer. Depending on the project requirement and the type of work needed to be done, different types of rollers are used for compaction work. Here are some of the most commonly used rollers for soil compaction:
- Cylindrical Rollers
- Vibratory Roller
- Tamping Roller
- Smooth wheel Rollers
Cylinder rollers are light rollers made of iron, concrete or stone and drawn by hand or bullocks. They come in different sizes but the most commonly used cylinder rollers are about 1 meter in diameter and about 1.5 meter long. They generate ground pressure of about 7 kg/cm2 and are perfect for light compressing work that does not require heavier equipment.
Vibratory rollers consist of two smooth wheels or drums plus the vibrators. One of the two wheels is fixed at the front while the other one is on the rear side of the vibratory roller. Both wheels are identical, of same weight, length and diameter around 0.9 m to 1.5 m in diameter and 1.2 m to 1.8 m in width. A vibratory roller is used for compacting granular base courses as well as asphaltic concrete work without causing any air voids. It works by vibrating the particles, distributing them evenly and then compressing them into shape. To make a vibratory roller more efficient its vibrators are fixed with smooth wheel rollers.
A Tamping roller consists of a drum having many round or rectangular shaped protrusions on it. These rollers come in different diameters and widths of drums and different lengths and shapes of protrusions. The most commonly used tamping roller has two drums 1.22 meters wide and 1.06 either as taper-foot or club-foot rollers as per the shape of the feet. Tamping rollers are most commonly used for compaction of cohesive soils such as heavy clays and silty clays but are not usually effective on sandy soils. Heavier compressing work can be done by increasing the weight of the drum either by filing it with water or damp sand.
Smooth Wheeled Roller
A Smooth Wheeled Roller consists of a large steel drum in front and one or two wheels or drums on the back. It can either be called a Tandem Roller if it has one wheel in the front and one at the back or a Three Wheeled Roller if it has two wheels at the back and one in front. Weights of Tandem and Three Wheeled rollers vary from 2 to 8 tonnes and 8 to 10 tonnes respectively. These are perfect for doing heavier compressing works such as for consolidating stone soling, gravel, sand, hard core, ballast and surface dressings and can exert a pressure of about 10 to 17 kg/cm2 or higher. Their weight can be increased either by filling it with water or wet sand.