Strand Anchors Ensure Stability against Hydrostatic Ground Water Pressure

Within the scope of what is called the Kombilösung (combined solution), Karlsruhe’s center is being converted to a pedestrian zone without any railway tracks. For this purpose, a 2.4km long, single-tube city tunnel is being built underneath Kaiser Road with a 1km long southern branch leading towards the Congress Center. The major project also includes the construction of a new road tunnel between Karlstor and Mendelssohn Square.

In this area, the high ground water levels and several obstructions in the ground such as steel sheet piles posed a special challenge. As a fact, most of the subterranean stations are located in the Upper Rhine Rift in layers that are unstable or not watertight, impermeable excavation enclosures consisting of diaphragm or bored pile walls had to be built in several sections due to the high ground water levels. To tie back the different retaining walls, DSI had previously supplied approximately 100t of DYWIDAG Strand Anchors. Recently, DSI received a follow-up order from the subcontractor Stump Spezialtiefbau GmbH.

At the Ettlinger Gate, DYWIDAG Strand Anchors were also used to tie back the walls. In total, 457 semi-permanent, 8 strand DYWIDAG Strand Anchors with a total length of 11,422m were installed to stabilize the walls against ground water pressure. DSI also supplied 572 temporary, 5-6 strand DYWIDAG Strand Anchors that were installed at a total length of 12,511m. Furthermore, DSI supplied 150 load cells to monitor the forces acting on the anchors.

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KASIG - Karlsruher Schieneninfrastruktur-Gesellschaft mbH,Germany

Joint Venture Stadtbahntunnel, consisting of BeMo Tunnelling GmbH, Austria and FCC, S.A., Spain