P U B L I C I D A D E

ABRIR
FECHAR

P U B L I C I D A D E

ABRIR
FECHAR
Voltar

High-energy technologies

New concepts, resources and machines turn compaction into a more accurate, productive and reliable operation, bringing road construction to a new level

With the evolution of technology, compaction is being updated in an accelerated pace, turning quickly obsolete some “instinctive” practices used through decades in the road construction industry. Due to these reasons, the knowledge of these new tools and concepts was transformed in a vital step to accelerate the needed advancement of our road modal, overcoming the existing delay still present through obsolete machines and regulations. “New technologies allow users to increase load capacity, stability, elasticity, resistance to deformation and homogeneity, eliminating water and porosity and reducing road permeability”, points Marcelo Ritter, sales and marketing coordinator of Ammann do Brasil. “This way, it is possible to maintain the quality of the work in relation to density and to physical and mechanical properties of the soil.”

By the way, the classification of soils is based on their physical properties, composition.  geologic history and particle size (rock, stone, gravel, sand, silt, etc.), defined through the screen test. As we know, the equipment has to overcome the resisting friction forces (friction between particles), the apparent cohesion (presence of viscous fluid that “holds” particles together) or the cohesion itself (physical or chemical property of the material that “bonds” the material). “It is necessary to overcome these forces with a proper selection of the machine, since each size of particle has a specific force”, explains Carlos Eduardo dos Santos, product manager of Atlas Copco. “Smaller particles such as clay and silt require higher localized impact, while large particles such as stones demand more motion to reduce friction.”

In this evolution, some concepts go ahead. In soil compaction, for example, one of the current trends is the use of high-sized rollers (above 12 t), in a way to supersede the obstacles found in clay soil, which start just at the top of the layer and weaken at the base due to difficulties in transferring energy. For this reason, the industry produces different solutions for the operation.

CONCEPTS

Whatever is the solution used, two decisive factors in the procedure are frequency (stroke repetition)—which influences centrifugal force—and amplitude (height of the stroke), which causes more effect in the depth and even in the neighborhood (when is increased), affecting the structure of urban areas, for example. Therefore, higher amplitude will cause a higher effect, making possible to compact thicker layers. But some wrong practices give results opposite to the expectations. “Amplitude takes into account only the eccentric mass, the equipment mass and the eccentric distance. Therefore, it has no use in increasing pump flow, since only the frequency and centrifugal force will rise”, says Santos, from Atlas Copco. “And this is not good, since the machine was designed to work with an ideal centrifugal force.”

On the other hand, compaction improves when frequency rises but there is a point where the “ideal frequency” for that type of soil (for example, 35 to 55 Hz) is reached. “Above these values, the life of components is reduced and the equipment is damaged”, points the expert. “And production does not increase.”

In the same way, the use of the so-called “thin shell” (attached pad kit that converts smooth rollers in pad-type rollers) may also reduce the production in 15 to 20 percent, depending on the type of soil. “This is worthwhile only when high volumes of granular soils and low volumes of cohesive soils occur. In this situation, the loss of production is not so concerning”, complements Santos.

According to the experts, attention to the details defines equipment productivity, measured in cubic meters per hour. In this sense, the variables to be considered include type of soil, thickness of the layer, level of compaction, length of the section, width of the drum, time of execution (speed) and number of passes. In other words, the production of a compactor is not a fixed value, but depends on the type of material, thickness of the layer, compaction level, etc. “Everything influences productivity”, says the expert of Atlas Copco. “The compaction effect of a roller is function of the weight of the front module, centrifugal force, pad shape, frequency, amplitude... In other words, it is necessary to establish a combination. It is empirical, it has no pre-delivery formula.”