Polygonal drum roller at Inden II open-cast mine

BOMAG GmbH | www.bomag.com

The BOMAG single drum roller with polygonal drum is considered one of the most efficient compaction machines in the world. Used in conjunction with the directed vibrator system, BOMAG VARIOCONTROL, the conditions are set for the best compaction results and the highest level of efficiency, as illustrated again on the Inden II brown coal mine between Cologne and Aachen.

The use of local brown coal supplies will become increasing essential to the energy industry in Germany over the coming decades. One of the largest and most significant deposits is in the Inden II open-pit mine between Cologne and Aachen. Brown coal will be mined here by RWE Power until at least 2030; brown coal that is being converted at the Weisweiler power plant into electrical energy.

An extensive infrastructure, including roads and foundations for erecting industrial buildings, must be built and maintained here to ensure the planned mining output at the open-pit mine. As part of further expansions to the development area, a conveyor junction and a main switch station had to be built on freshly imported subsoil. Conveyor junctions are junctions in an open-pit mine where conveyor belts for all the bucket-wheel excavators run together to distribute excavated material or coal over different receptacles (spreaders, coal bunkers). The main switch station ensures the power supply for all equipment and machines on the open-pit mining site.

Before the conveyor junction could be built, the building area had to be prepared. Around 2.6 million cubic metres of earth were shifted and fill heights of between 10 and 25 m were laid. To minimise settlement, the top 3 m were compacted in two layers using BOMAG BW 226 DI-4 BVC single drum rollers and its predecessor, the BW 225 DI-3 BVC.

Power and intelligence

Weighing in at 26 tonnes, the BW 226 DI-4 BVC is the heaviest single drum roller offered by BOMAG. However, the outstanding compaction performance is not solely down to the high static linear load but more to the interplay between BOMAG polygonal drum and BOMAG VARIOCONTROL. The directed vibrator system, BOMAG VARIOCONTROL, generates directed vibrations and enables a purely linear movement of the drum. This creates an especially high amplitude possible that transmits vertically into the soil at the optimum angle. The polygonal drum ensures excellent introduction of forces into the ground. The secret? Continuous interchange of wedge and plate when rolling over the ground's surface.

The polygonal drum is shaped like an octagon. As it rolls over the ground it changes between edges and plates. The exciter forces are transferred vertically and effectively into the ground by the plates, similar to a vibratory plate. The corners engage with the surface thereby preventing overcompaction and allowing the plates to unleash their full depth effect during continued rolling.

The combination of polygonal drum and BOMAG VARIOCONTROL creates an exceptional depth effect. The placed fill layers can be doubled in contrast to conventional single drum rollers. Single drum rollers with this technology are extremely effective and profitable, especially when compacting large volumes of soil; the number of passes required can be clearly reduced, which means that the compaction target can achieved even quicker.

RWE confirms positive experience

To start with, RWE Power used BOMAG single drum rollers with polygonal drum for post-compaction of the route taken for transporting bucket-wheel excavators from the Hamback open-pit mine to Garzweiler. Due to positive experience, the management then insisted on using these high-performance machines for the foundations of the conveyor junction in Inden II. A full nine passes were sufficient for installing layer thicknesses of 1.50 m. The compacted materials all came from the clearance level and comprised coarse grain sand as well as mixed grain, sandy silt. The bearing capacity requirements were defined in terms of the RSTO (Directive for the Standardization of Surfaces of Road Traffic Areas) on the formation layer as Ev2 value = 45 MN/m². Beneath the foundations, the subsoil must be able to take normal base stresses of 200 kN/m² and 400 kN/m².

A particular issue on this construction project was the coordination of compaction work with the placing of earthworks. Soil was placed onto the site of the new conveyor junction by a 7,500 t spreader which usually spreads excavated material from the mined coal seam onto a dump site. The spreader was only available for eight hours at a time so that the recovery process was impaired as little as possible. The placed material was then compacted in the remaining 16 hours. This meant that construction work had to be organised in 3 shift operation.

Two months were put aside for carrying out compaction work. A tough goal which was achieved primarily thanks to the high compaction performance of the BOMAG single drum rollers with polygonal drum. This result once again underlined BOMAG's role as global market leader in compaction technology.

About BOMAG
BOMAG is a global market leader in compaction technology. The company, situated in Boppard, Germany, belongs to the French FAYAT Group and produces compaction machines, stabilisers/recyclers, milling machines and pavers. In 2007, around 2,000 employees achieved a turnover of 634 million Euros. Six branches within Germany, 11 subsidiaries worldwide and more than 500 dealers in over 120 countries guarantee global distribution and service.

Contact details:
BOMAG GmbH
Hellerwald
D-56154 Boppar
E: info@bomag.com
www.bomag.com

The Magazine

Issue 4

Blog

Sales and the 'Talent Magnet'

White Papers

Polygonal drum roller at Inden II open-cast mine

BOMAG GmbH | www.bomag.com