Smooth Rollers
For large-quantity production of compacted granular soils, smooth rollers are the machines of choice. Whether in single-drum or dual-drum configurations, smooth-drum rollers are suitable for compaction of granular soil base layers. This includes building foundations and roadway sub-bases, as well as the compaction of surface courses of asphalt paving. Like sheepsfoot drums, smooth-drum rollers are available in either tow-behind or self-propelled ride-on models. Their operating weights range from 2 to 20 tons, and (again, like other rollers) they are hollow with weight provided by sand or water fill. While useful for compacting granular soils such as well-graded sands and gravels, they are not used for the compaction of cohesive silts and clays with low plasticity and/or high moisture content and are not as effective on uniform sands or silty sands.
Similar to the smooth-drum roller is the not-so-smooth grid roller. Ranging in weight from 5 to 12 tons, grid rollers have surfaces of spaced heavy bar stock constructed in a cylinder or raised surface Z-patterns that resemble basket weaving. This raised drum surface impresses grooves into the soil while leaving raised knobs of earth in between. When used on wet clays, the soil tends to adhere to the lower portion of the surface pattern, filling it in and effectively transforming the grid drum into a smooth roller. More suitable soils include well-graded sands, soft rocks, and stones. In fact, one of the primary uses of grid is the breaking up or “rubble-ization” of existing concrete pavement surface and the pulverization of stone and rubble into finer particles.
In addition to its heavy weight padded foot static compactors, Bomag manufactures a line of tandem vibratory smooth rollers, the BW series running from the lightweight BW120AD-4 (5,732-pound operating weight) to the hefty BW284 (28,425 pounds). What makes these machines unique are the little things that make for a more efficient compaction effort: slanted drum supporting improving operator visibility of the drum edges, central lifting point for ease of loading and off-loading, easy access to daily maintenance check points, bolt-on heavy-duty articulation joints, and so on. All are designed for high-production soil compaction tasks.
The Case Corp. (aka CNH Global) manufactures a line of SV series machines that can be equipped with either a smooth or padfoot drum. Equipped with high-traction, hydrostatic drive that synchronizes the rear wheels with the compaction drum and a low center of gravity, Case’s SV compactors are suitable for work on steep grades. The drum’s vibration oscillation can be set to either low amplitude and high frequency for granular materials or high amplitude and low frequency for cohesive soils.
Sakai America offers a wide range of high-force vibratory soil compactors designed for rapid compaction of all types of soil, rockfill, recycled base materials, and soil cement at the lowest possible cost. Featuring high-centrifugal-force outputs; dual amplitude/dual frequency; choice of drum configurations; drum and axle drives for traction; heavy-duty, center hitch design; and three braking choices, Sakai has four compactors in its SV510 line ranging in weight from 24,140 to 29,875 pounds. Sakai also offers a full complement of high-frequency vibratory asphalt rollers for superior density and smoothness.
Reflecting its overall diversified product lines, Ingersoll-Rand produces a line of SD series large soil compactors with diverse applications. This product line includes the 16,350-pound SD-77 (smooth or two different padded foot drums); the SD-116, which operates well on steep grades due to its Ultra-Grade traction system and axles and drive motors designed for climbing; the high-powered SD-160 with its six-cylinder turbocharged engine, which can handle thicker lifts with fewer passes; and the 205-hp SD-200 for heavy-duty applications. Ingersoll-Rand also provides an auxiliary line of small soil compactors ranging from the 2.6-ton SD-2D TF to the SD-70 D/F. All the company’s models come with two-piece, clamp-on padfoot shell kits for conversion to cohesive soil compaction.
Pneumatic Tires
Pneumatic-tired rollers utilize heavy wheels aligned to produce a rolled track the width of the compaction vehicle. When not a tow-behind single-axle model, a pneumatic tire compactor usually is configured on a two-axle self-propelled ride-on vehicle. Dead loads for pneumatic tire compactors range from 12 to 40 tons. The tires provide soil compaction through a kneading action and are best suited for both coarse and fine grained soils, with the exception of very soft clays and variable soils. Pneumatic tire compactors are extensively used in roadway construction to compact base, sub-base, and wearing course materials.
In addition to sheepsfoot, padded foot, and smooth drum rollers, Caterpillar also manufactures a line of pneumatic tire compactors. From the 23,100-pound PF-300B to the high-productivity PS-360C (which can operate as heavy as 40,785 pounds when its drums are filled with wet sand), these pneumatic compactors are suitable for use on base, sub-base, or wear course materials by providing a kneading action and a high weight-per-wheel ratio.
