Optimum compaction during car park construction at the Allianz Arena in Munich.

Boppard, 17.10.2019: At the end of 2018, work began on a new multi-storey car park in Munich to improve the current parking situation at the Allianz Arena. With their high compaction performance, two BOMAG BW 211 D-4 and BW 226 DI-5 single drum rollers provided the groundwork for the perfect foundation on behalf of Abenstein Straßen-, Tief- & Pflasterbau GmbH.

Work on a new multi-storey car park with space for 900 cars began in 2018 in the northwest of the Allianz Arena in Munich. In addition to the approximately 10,000 existing parking spaces, the new car park is intended to relieve residents and improve the flow of traffic to and from major events like FC Bayern Munich football matches. Before construction began, there was a parking lot for 93 buses on the site. The area will continue to be used as a bus park, but will be covered by a three-storey multi-storey car park that is directly connected to the stadium area by a pedestrian bridge over the suburban railway tracks. Abenstein Straßen-, Tief- & Pflasterbau GmbH used two BOMAG single drum rollers on the site from the beginning: the customer's own BW 211 D-4 single drum roller, and the BW 226 DI-5 with polygonal drum and comfort package with a rotating seat and adjustable steering column, which was hired specifically for deployment at the Allianz Arena. Both single drum rollers excelled during their three-week deployment in December 2018, particularly in the compaction of natural gravel on the up to 200 m long and 4 m wide foundations of the car park. The compaction specifications were not only achieved, but by far exceeded due to the depth effect of the BW 226 DI-5's polygonal drum.

Number 1 on the market in all weight classes

All construction projects have one thing in common: they need a sound subsurface. This is why single drum rollers play a crucial role in the construction process. However, the requirements are very different. If you compact next to a listed building, you have to proceed differently than in road construction over open land. BOMAG offers a wide range of single drum rollers to suit all requirements, and has been regarded worldwide as an experienced and reliable partner and technology leader for many years. Two BOMAG single drum rollers for medium (BW 211 D-4) and heavy (BW 226 DI-5) compaction work were used on the site facing the Allianz Arena. These D versions are ideally suited for compacting hydraulically bound materials, sand, gravel, crushed stone and poorly cohesive soils and rock. Both single drum rollers were therefore perfect for use in the former car park. The single drum rollers were particularly able to demonstrate their capabilities when compacting thick layers and re-compacting the existing layer on the foundations for the multi-storey car park. Due to the special depth effect of the polygonal drum and the BVC directed vibration of the built-in VARIOCONTROL system, the BW 226 Di-5 was tendered explicitly by the client.

Polygonal drum and VARIOCONTROL ensure optimum compaction power

The polygonal drum consists of three axially adjacent octagonal drum elements, each of which is offset from the neighbouring element. In total, the polygonal drum has 24 plate segments and 24 connecting wedge segments. In contrast to a round drum, whose direction of force does not change during the rolling process, the special compaction effect of the polygonal drum is based on a constant change in the direction of force of the plate and wedge segments. While the plate segments generate higher pressure cones than round drums in the contact zone, the subsequent wedge segments produce very high peak pressures with effective kneading and shearing effects that are significantly higher than those of a padfoot roller. The combination of peak pressure and thrust forces produces a compaction-promoting loosening of the soil at the surface and allows air to escape. In contrast to round drums, it does not cause capping, which prevents compaction. This results in a strong depth effect, which is essential for the following plate segment contact. Since the three drum elements are arranged offset to one another, lateral deflection of the soil is largely avoided. The rings welded to the outer edges of the drum prevent it from tilting when the middle element is positioned exactly on the edge, and facilitate rapid travel during transport on firm subsoils. Every polygon roller is also equipped with the VARIOCONTROL system. This is an exciter system that generates directional vibrations and has a self-regulating system that detects and adjusts the energy required during the compaction process. The automatic adjustment of the directional vibrator continuously regulates the amplitude required for compaction. The machine starts with a very high amplitude, which is advantageous for depth compaction, and automatically reduces it to the required level as compaction increases, without the drum changing to an adverse bounce mode. In addition to the automatic control, there is also a manual mode with six vibration directions in order to operate specific compaction applications with a fixed amplitude.

Compaction values up to 300 MN/m²

The combination of polygonal drum and VARIOCONTROL offers the machine operator numerous advantages. The positive depth effect of the polygon roller is further enhanced by the target value control of the VARIOCONTROL system. As the BW 226 DI-5 single drum roller was used primarily on the foundations of the multi-storey car park, targeted but nonetheless strong compaction was necessary. To avoid damage to the foundations, the target value of 45 MN/m² was set in automatic mode with the machine's selector switch. Through the integrated display, the driver was able to read off the current compaction values and carry out any necessary recompaction. This made it possible to achieve values in excess of 300 MN/m² in manual operation without having to set a target value and without over-compaction or damage to the foundations. After the BW 226 DI-5 reached the intended compaction value with its polygonal drum, the BW 211 D-4 was deployed for cosmetic purposes on the last pass. It made for a particularly smooth surface and levelled out the waves caused by the octagonal drum elements of the polygon roller. VARIOCONTROL was particularly well received by the drivers thanks to the easy-to-operate and clearly visible compaction display on the dashboard. In addition to the compaction reading, the machine's last pass was measured with BOMAG's TERRAMETER, and the final compaction result was printed out on the machine's printer. A test was then conducted with a load plate on the single drum roller and the result printed out. This enables BOMAG to record the compaction result precisely and conveniently on site.

Outstanding climbing capability

BOMAG single drum rollers are true climbing pros. In the D version, which was used on the construction site at the Allianz Arena, they achieve a gradeability of up to 53%. Here, the manual slip control enables targeted adjustment to the ground conditions. The rear axles have a NoSPIN differential with an automatic lock up to 100%. This above-average gradeability offered several advantages on the job site. Both the BW 226 DI-5 and the BW 211 D-4 were able to drive into the excavations and manoeuvre without any problems. Their excellent climbing ability also made it possible to work directly on the foundations. These were excavated to a depth of several metres and filled with natural gravel from the surrounding area of Munich. The 1 m fill layers were then easily compacted to the target value of 45 MN/m² by the BW 226 DI-5.

Never change a winning team

Background: In order to avoid unnecessary soil replacement, Goldbeck, the general contractor, opted for depth compaction at an early stage of the project. In cooperation with BOMAG and subcontractor Abenstein, a polygon roller was tendered specifically for the project because of its exceptional depth effect. They decided on the BOMAG BW 226 DI-5 single drum roller, which was rented as an addition to the BW 211 D-4 for the duration of the project. The site manager and the machine operators were highly satisfied with the performance of the two BOMAG single drum rollers. The construction manager was particularly impressed by the outstanding compaction and depth effect of the BW 226 DI-5's polygonal drum. He also praised the target value control of the VARIOCONTROL system and its simple operation. The drivers very much appreciated the excellent overview from the operator's platform. This was especially useful at the edges of the foundations, where the good all-round visibility helped to keep an eye on everything. The rotating seat and adjustable steering column also ensured a particularly ergonomic sitting position and better visibility when working on the foundations. The additional work lights on the roof also made working at night and at dusk easier. They ensured there was sufficient illumination in the dark. With their optimum compaction performance and depth effect due to the VARIOCONTROL system and the polygonal drum of the BW 226 DI-5, as well as their high climbing capacity, the two BOMAG single drum rollers created the basis for the new multi-storey car park at the Allianz Arena in Munich.

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