For the 9m deep excavation pit, Bauer is constructing a 6,000m² single-anchored, mixed-in-place cut-off wall (MIP) with a thickness of 550mm and embedded double U king piles up to a depth of 17m.

Moreover, 750m² of sheet pile wall are being installed with a maximum depth of 16m for dewatering. After sufficient uplift prevention has been achieved for the structure, the sheet pile wall will then be pulled out again. In addition, 3,000 running meters of anchors are being installed.

Due to impermeable tertiary layers in the area of the excavation base, depth drainage was used. This requires high logistics efforts and precise coordination with earthworks. Due to large soakaways in the public ground, it is also necessary to pivot the anchor in the MIP wall and increase the anchor distances, which means that staggered anchors with a load of up to 1,800KN are being used.

Because the level of the impermeable tertiary layer fluctuates widely throughout the site, the retaining wall is also being constructed with a final depth that varies by up to 5m.

"With our MIP method, we are able to vary the drilling depth as needed or adapt to the soil conditions. This offers us a major advantage compared to sheet pile walls, which were originally planned, since the lengths of the sheet pile wall have to be defined and ordered in advance," explained Bauer project manager Michael Doll.

An RG 27 and an RG 19 pile driver from RTG Rammtechnik GmbH are being used, respectively, for the construction of the MIP wall and the sheet pile walls, and a Klemm KR 806 rig is executing the anchor work.

Bauer started works in May this year and the dewatering system and dismantling of the anchors and sheet pile walls is expected to be completed by early 2022. The completion of the office building is planned for 2024. 

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