Excavation pits & pile foundations

Headquarters Marquard & Bahls AG,
Hamburg HafenCity (construction field 65)

Petroleum company Marquard & Bahls AG is relocating its headquarters
to the HafenCity district of Hamburg. For the new head office building, a
consortium comprising FRANKI Grundbau and HTG Hoch- und Tiefbau
Gadebusch was contracted to excavate the canalside pit, install a pile
foundation and perform the concreting works for the two basement

Five highlights

1. Waterfront location

The site adjoins a canal in Hamburg‘s HafenCity quarter. Working from
a pontoon, FRANKI vibrated into place over 1,510 m² of sheet piles (up
to 22.50 m long) in the canal in front of the existing quay wall. This
allowed some 400 m² of land to be reclaimed while aligning the deve-
lopment with the neighbouring plots. At this location, the River Elbe is
directly subject to tidal currents. Ebb and flow bring about water level
fluctuations of up to 5 m, with hydraulic pressure acting directly on the
sheet piling. During a storm surge on 22 October 2014, the water of
the Elbe rose to just 5 cm below the top edge of the sheet-pile wall. Luckily, the sheet piling held and the pit remained dry.

2. Obstructions

The plot used to be occupied by a building that served as the main customs office. Originally built in 1886, the existing quay wall had been successively strengthened over the years. The numerous obstructions in the ground prevented certification of the site as being free from explosive ordnance. This necessitated permanent supervision of the demolition and excavation works by the explosive ordnance disposal (EOD) service. Overall, FRANKI demolished some 1,200 m³ of quay wall and existing foundations, and extracted some 50 timber piles. Together with the excavated spoil, the contract entailed the proper disposal of approx. 16,000 m³ of material.

3. Internal bracing

The site is bounded to the east and west by bridge abutments. The Brooktorhafen canal marks the northern boundary while the road to the south carries a high-pressure DN 400 gas main and a DN 3000 rainwater sewer. All surrounding roads have been raised above flood levels by means of lightweight fill or deep foundations. This meant that the basement retaining wall could not be tied back. Nor was full cross-bracing an option due to the canal on the northern perimeter. The solution adopted by FRANKI was thus to brace the retaining wall against the building shell. This involved the incorporation of some 100 tonnes of steel for the struts and walings.

4. Pile foundation and contiguous bored pile wall

The weak foundation soil at the HafenCity location necessitated the use of a pile foundation. FRANKI installed 318 displacement auger piles up to a depth of 28 m using the special KC – S 6100 heavy-duty rig. A smaller Soilmec drilling rig was used near the canal-side sheet piling to rule out any risk of deformation there. A secant pile retaining wall was built on the sides facing the roads. Some 1,810 m² of bored pile walling was installed, comprising up to 18 m long, 63 cm and 75 cm diameter piles.

5. High requirements in terms of site logistics

In co-ordinating the site logistics, FRANKI‘s site management team had to overcome several major challenges. Hardly any on-site storage space was available and, at times, there were three drilling rigs simultaneously in operation. The site was also trafficked by excavators, heavy trucks to cart away the spoil and concrete transit mixers. The wholehearted commitment of FRANKI‘s site managers and close co-ordination with the entire project team allowed all trades to work simultaneously to meet the tight completion deadlines set by the client.

Would you like to know more?
Project manager:
Dipl.-Ing. Christoph Schwanz
Tel.: +49 4105 869-160

Heijmans NV

Completed work:
1.810 m² bored pile wall,
d = 75 und 63 cm, L ≤ 18,0 m
1.510 m² vibrated sheet
pile wall, length ≤ 22,5 m
318 displacement
foundation piles, d = 61 cm,
Nk ≤ 2400 kN, L ≤ 28,0 m
17 permanent anchors,
GEWI 63,5 mm, Zk ≤ 850 kN,
L ≤ 30 m
50 t reinforcement for the
bored pile wall
15.500 m³ demolition of old foundations and digging of the excavation pit incl. professional disposal

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