Backfilling of shafts XII and 2 at Zollverein completed
Backfilling of shafts XII and 2 on the grounds of the Zollverein World Heritage Site in Essen/Germany began in spring 2023. The shaft work is now being completed (Figure 1). In consultation with authorities, politicians and scientists, RAG Aktiengesellschaft, Essen, has developed a concept for the long-term optimisation of mine water management in the Ruhr area. To this end, water management in the Ruhr area will be concentrated at six locations. However, the Zollverein site will remain part of the overall concept. The shafts serve as reserve locations in case the mine water does not overflow into the Prosper Haniel mine building on its way to the Rhine in the next stage, as expected. Zollverein thus combines monument and tradition with the classic tasks of post-mining. And it does so in the middle of a world cultural heritage site that is visited by tens of thousands of people from all over the world every year.
A few figures: Shaft 2 has a diameter of 5.5 m, Shaft XII 7.50 m. They extend from the surface to a depth of approximately 1,050 m. For backfilling, formwork platforms were installed at both shafts above the 14th level at a depth of approximately 1,000 m. These formed the basis for the subsequent backfilling. Before that, the lowest part of the shaft, the so-called shaft sump, was filled with concrete. It serves as the foundation for the steel structure of the formwork platforms. The height of the level itself, approximately 5 m, remains free so that any mine water can be collected there in the future.
To ensure that the shafts remain stable in the long term, casing pipes were installed in sections, aligned and concreted in place so that submersible pumps can be lowered vertically through the pipes into the depths if necessary. For this purpose, three casing pipe strings were installed in shaft XII and two casing pipe strings in shaft 2. More than 20,000 m³ of concrete was required for shaft 2 and almost 39,000 m³ for shaft XII. The concrete column also ensures the long-term stability of the shaft.
Before the backfilling work could begin, numerous shaft installations – including those above ground – had to be dismantled. They were removed, professionally stored and will now be reinstalled in accordance with conservation guidelines after backfilling. This was done in close coordination with the Düsseldorf district government and the Zollverein Foundation.
The backfilling of the two shafts at the World Heritage Site presented RAG with major challenges. The work took place on a site with numerous residents and thousands of visitors in the vicinity of the shafts. Disruption to residents and visitors was kept to a minimum. The transport and pouring of the concrete, e. g., took place in soundproof lightweight halls. The work after backfilling will be just as challenging. Ultimately, the entire shaft complex must look exactly as it did before – with every screw in its original place.
Incidentally, the entire underground shaft filling work was completed without any accidents.This is further proof of the exemplary approach to occupational safety within the company and its partner companies.
“The Zollverein site with shafts 2 and XII is a very special location for us. Nowhere else is mining culture as alive as it is here. But Zollverein is also an active post-mining site. The site is home to the RAG-Stiftung, RAG and RAG Montan Immobilien. And Zollverein is also an important location for the implementation of RAG’s mine water concept. This combination of mining culture and active post-mining tasks is unique in the world and makes the site so exciting,” says Peter Schrimpf, CEO of RAG.
“Thanks to the meticulous preparation of the planned construction processes, the pre-assembly of all components above ground and close daily coordination, the technical closure of the Zollverein mine and the construction of the well structure were completed smoothly,” says Stefan Roßbach, Head of Department at RAG Mine Water Management. (RAG/Si.)
