The asphalt work in the Visp South tunnel is finished. The Ulrich Imboden AG team and the Ammann machinery played an important part in keeping the project on schedule while also meeting the required quality goals. If all goes according to plan, the tunnels will come back into use in 2022.
Recently, work was completed on the A9 motorway in the canton of Valais between Siders and Brig (about 32 km long), with Ammann machines working throughout the construction site. With a revised alignment, the route has been designed to group the traffic lanes as efficiently as possible given the narrowness of the Rhone Valley. Around 50% of the new route of the A9 motorway through the Upper Valais runs underground, which made construction work particularly difficult.
The Valais, a mountainous canton, has topographically little space and few location choices for upgrading major transportation routes, given the constrictions of the Rhône valley. Successfully extending this motorway, without isolating the canton from the rest of Switzerland, was a difficult task and has been under discussion for decades. Construction of the new A9 circumvents the problem by including numerous tunnels and improves connections between the whole Valais region and Switzerland’s national road network.. A consortium of businesses named ARGE ATV was assigned the multi-phased project. Ulrich Imboden AG handled the paving portion of the roadbuilding. Ammann machinery, in the form of an asphalt-mixing plant, a road paver and vibratory and pneumatic tyred rollers, supported the demanding paving work in the tunnel.
Asphalt Paving at the Highest Level
The work has brought many difficulties, technical and bureaucratic. Firstly, the Swiss authorities set maximum standards for the quality of the pavement in road tunnels in order to extend the intervals between maintenance work. Secondly, a high volume of traffic on this section with a strong impact on the asphalt had already been expected.
High quality work like this required the use of a special mixing formula with PMB (polymer modified bitumen) because of its robust nature. However, this required particularly high compaction standards and expert machinery that could work together during all stages of the process, from paving to asphalt mixing, paver and rollers.
The staff of Ulrich Imboden AG had to face even more complications during paving. The laying of asphalt paving creates vapours that are not easily dispersed inside a tunnel. Ventilation of the new road tunnel was therefore a key factor in the design phase, as well as in the asphalt paving phase.
The wind in the Valais is constantly changing direction, and the ventilation system had to be repeatedly adjusted to extract the vapours from the tunnel.
At the Heart of the Process Chain
Since 2004, Ulrich Imboden AG has been operating a stationary Ammann asphalt-mixing plant in the immediate vicinity of the tunnels. The plant is an Ammann Global 160, which in 2018 was fitted with an RAH feed to process recycled asphalt (RAP). This plant, designed to be at the cutting edge of technology, produces the asphalt for various projects in the Valais. It had sufficient capacity to reliably supply mix for a major project such as the extension to the A9.
The proximity of the site to the work site has saved a lot of time in transporting the mix from the plant to the paver.The AFT 700-3 from Ammann was the “heart” of the paver and therefore determined the pace of the entire paving process.
The AFT 700-3 tracked paver is a technologically advanced model with various options for the paver. The machine offers outstanding grip and power, enabling the use of high-compaction, rigid-frame pavers. The intelligent paving control system ensures complete monitoring of the paver. The user interface uses an intuitive tool panel, which makes the technology easy for operators to understand. A sliding operator platform with a control panel that can be adjusted to any position allows the operator to keep the working process under control at all times.
High-Level Compaction and Fast Paving
At least, an ARP 95 Pivot-Steer Tandem Roller with ACE technology and an AP240 Pneumatic Tyred Roller, both from Ammann, worked behind the paver. The latter has a higher static weight than the tandem roller, with its pneumatic action creating a “kneading” effect that increases the compaction performance.
A ballasting range of 9 tonnes to 24 tonnes helps make the Ammann AP 240 Tier 2 Pneumatic Tyred Roller a good fit on diverse jobsites. Also helping with flexibility is the Air-on-run system, which the operator uses to adjust tyre pressure without ever leaving the cab. The optional Ammann Traction Control (ATC) boosts productivity on tough terrain. The proven hydrodynamic propulsion system ensures efficiency.
Thanks to Ammann Compaction Expert (ACE), the company’s proprietary intelligent compaction system, the operator was always able to check the current compaction status during work; this saved valuable time and fuel, but also proved to be a cost advantage. Only the tandem roller was required to compact the PMB surface layer.