Each new road begins with site preparation

Nature does not always provide the ideal ground conditions – whether for civil engineering or structural engineering projects. Often, the existing soil requires preliminary treatment to improve its bearing capacity. In other places, massive rock formations need to be leveled. What methods are used for laying the foundations?

Soil compaction

Since the soil is frequently loose and insufficiently cohesive, site preparation is required before the base course, binder course and surface course can be laid. Compaction is the most important process in site preparation. The purpose of compaction is to reduce the volume of soil filled with air and water. This gives the soil the desired properties: it becomes more resistant to the stresses imposed by traffic and climate. Dynamic compaction with vibrating or oscillating rollers has proved particularly effective in this process, as it compacts the soil through the combination of vibrations from the roller drum and the weight of the roller.

Cohesive soils are best compacted using compactors with padfoot drums and high amplitudes, while non-cohesive soils are more effectively compacted with smooth drums and lower amplitudes. The ground is then ready to be paved - provided that it does not still contain too much moisture. In that case, it must be stabilized.

Soil stabilization

Extremely cohesive and wet soils are not suitable for compaction by rollers. In such cases, the existing soil needs to be stabilized first to improve its bearing capacity and prepare it as a suitable base for the pavement structure.

Stabilization ensures that the water is durably bound in the soil. This is achieved by mixing a lime or cement binder into the soil. Particularly when stabilizing the soil with cement, the base becomes more resistant to traffic loads, ingress of water and frost in the long term. Soils requiring stabilization are frequently boggy and can only be driven over by powerful vehicles with all-wheel drive. For this reason, soil stabilizers have large studded tires, high traction and a powerful drive system. Their mixing rotors mix the previously spread binder into the soil to depths of up to 56 cm in a single pass. This reduces the water content and makes the soil suitable for subsequent compaction by vibratory compactors.

Routing operations

When roads are needed through rocky terrain, cold milling machines or surface miners are used to prepare the ground for road construction - or to cut the route, as the professionals would say.

Blasting is common when building roads on bases of limestone, slate, granite or other rock. This causes vibrations, noise and dust. If blasting is prevented due to nearby buildings, industrial plants or railway sidings, the routes are produced by cutting through the rock. This eco-friendly method extracts the rock without vibration.

Even as the carbide cutters on the cutting drum continue to cut, the crushed stone is loaded onto trucks by a pivotable discharge belt . Due to the uniform grain size, it can be reused as filler without further processing. The road can now be paved without difficulty on the accurately profiled surface.

WIRTGEN AMERICA, Inc. is a member of the WIRTGEN GROUP, an internationally operating group of companies in the construction machinery sector incorporating the traditional product brands: WIRTGEN, VÖGELE, HAMM, KLEEMANN and BENNINGHOVEN. As technological leader, we can offer our customers mobile machine solutions for road construction and road rehabilitation, plants for mining and processing minerals or recycling material and for the production of asphalt.
Our ratios: In 2016 the WIRTGEN GROUP generated consolidated sales of 2.59 billion euros. Presently the WIRTGEN GROUP employs 8,000 people.

© 2017 WIRTGEN AMERICA, Inc.