Pile foundation for motorway cover (First BA)

2,620 piles for motorway cover in Hamburg-Stellingen

Three noise protection tunnels are planned in the course of the A7 motorway within Hamburg’s urban area. In this way, the Schnelsen, Setllingen, Othmarschen and Bahrenfeld districts should “grow together” again and the local residents will be protected from traffic noise. The motorway will thereby expand to eight lanes so that traffic will flow better. The DEGES public tender for the 1,970 m long Stellingen section could be won by the FRANKI/Hochtief Infrastructure GmbH bidding consortium. Contrary to the original plan with pressure grouted large bored piles (d = 120 cm), FRANKI’s separate proposal with partial displacement bored piles will be carried out. In the 900 m tunnel section area, sand and boulder clay stand in variable layers of thickness and altitudes. The piles are set down on the sand. Multiple static test loads were carried out in advance in order to optimise the bond length in the sands. From this, a minimum bonding depth of one meter resulted in the stable sand.

The so called cover in Stellingen is set on deep foundations with a total of 2,583 piles. The piles are built at an angle so as to already be able to bear horizontal loads during construction. A particular challenge in construction site logistics and workplace safety was present during construction. Other trade or subcontractor activities on the closed road next to the construction traffic also had to be taken into account. The motorway traffic with a distance of just two meters from the unit was also not an everyday business. In July 2017 we were able to complete the works on the roads in the north direction accident-free and on time. Next year we are coming back, when the traffic will be led through the first tunnel section and the pile foundation for the opposite traffic lane is to be built.

Some large bored piles were manufactured under more limited working heights because of a culvert and an existing bridge.

Services of construction phase 1:1,300 partial displacement bored piles, d = 78 cm,
Nd ≤ 2,811 kN, L ≤ 14,0 m
7 static test loads
150 m² pressed sheet pile wall
37 large bored pile, d = 120 cm, L ≤ 8,0 m