What type of roller is primarily used for achieving maximum density in granular soils?

The vibratory roller is specifically designed to achieve maximum density in granular soils due to its unique mechanism of operation. This type of roller uses vibration to impart energy into the soil, which helps in realigning the soil particles and reducing the voids between them. The vibration effectively enhances the compaction process, making it more efficient than other types of rollers when dealing with granular materials.

Granular soils, such as sand and gravel, respond well to the vibrations as they allow for the particles to move and settle into a denser arrangement. As the vibratory roller moves, the combination of its weight and the vibration forces helps to compact the soil more thoroughly. This is crucial in construction projects where a solid, stable foundation is necessary to support structural loads.

The other types of rollers, while useful for specific applications, do not achieve the same level of density as vibratory rollers do with granular soils. Static rollers rely on weight alone without any additional vibration, which may not sufficiently compact granular materials. Sheepsfoot rollers are typically used for clayey soils to knead and break down larger particles, and pneumatic rollers work better for fine-grained soils and asphalt where a smooth finish is required.