On the construction site for the new Wendenquartier in Hamburg, where approx. 700 micro-apartments for students and young professionals will be built, Stump-Franki is working on a large scale with a number of civil engineering challenges. In addition to excavation and explosive ordnance detection, the contract includes the construction of various shoring for the 5,100 m2 excavation pit, the installation of a dewatering system, the installation of full displacement bored piles System Atlas, clearance drilling as well as numerous core drillings through a 40 cm thick concrete slab. The in-house planning department is responsible for the execution planning and statics for shoring and pile foundations.
Different types of shoring combined in the excavation pit
"Securing the excavation pit with large bored piles along the neighbouring development is a challenge that our specialists mastered with flying colours thanks to their extensive experience," praises Markus Wenke, Stump-Franki Regional Manager for the North Region. The bending-resistant shoring consisting of 46 metres of overlapped bored pile wall with a diameter of 620 mm and lengths of 6.5 metres to 12.5 metres was supplemented by 24 reinforced large bored piles. Towards the adjacent roads, 190 metres of sheet pile wall with a profile length of 9.1 metres were installed in the correct position and height using the vibration method, braced with a steel girder chord and tied back with 73 stranded grouted anchors. For the underground demolition and earthworks, a dewatering system was installed that will remain in operation until the structural shell is buoyancy-proof. Parallel to the on-site demolition work, approx. 5,300 m³ of earth will be excavated to a depth of approx. 3.7 metres.
Complete service without interfaces
The site in Hamburg's former working-class district of Hammerbrook was previously occupied by an office building from the 1980s and a laboratory building. "When new buildings are constructed in inner-city locations, construction sites often turn out to be real miracle bags despite careful soil exploration. The many massive foundation remains challenge us anew every day," describes project manager Bernd Westendorff. A smooth process is particularly important to the client. The team convinced him with an economical solution of all special civil engineering services from one source. "With an excellent team performance, we manage to keep all promised deadlines and costs," says Westendorff.
Atlas pile meets Franki pile
Along the sheet pile route, masonry walls up to 3.5 metres high and 0.6 metres thick were found, which had to be removed with the help of clearance drilling in order to protect the adjacent footpaths and utility lines. As there is a concrete suspicion of explosive ordnance on the site, the shoring route for bored piles and sheet piles has been sounded out in advance by a specialist company. The 40 cm thick existing basement floor remains in place over two thirds of the excavation area. So that the explosive ordnance sounding and foundation work could be carried out, this had to be penetrated with a total of 1,240 core drillings D=150mm for the explosive ordnance sounding and 189 core drillings D=880mm for the Atlas piles. For the deep foundation of the buildings, another 440 Atlas full displacement bored piles were produced in July and August. During planning, care had to be taken to ensure that the new piles did not collide with the existing Franki piles. "Atlas pile meets Franki pile," Westendorff says with a grin, "or rather, doesn't meet!"