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Frankipfahl NG® piles close the gap in the BAB 14

The northern extension of the BAB (federal motorway) 14 is currently the largest motorway project in Germany: Around 155 kilometres long, the new route will connect the federal states of Saxony-Anhalt, Brandenburg and Mecklenburg-Western Pomerania. During the expansion of the BAB 14, the Fritz Spieker construction company in Oldenburg commissioned the Berlin branch office of Stump-Franki Spezialtiefbau GmbH to construct the pile foundations of a bridge (BW38Ü) that takes the L30 (Landesstrasse – state motorway) over the new BAB 14 at Lüderitz, Saxony-Anhalt. They used 66 Frankipfahl NG® piles, each with a diameter of 61 cm and up to 28 meters long.

The Franki ram and a reinforcement cage © Stump-Franki

Delicate foundation soil makes pile driving a challenge

The Frankipfahl NG® piles are inserted vertically and inclined as foundation pilings for two of the bridge abutments. The piles must be driven up to 28 meters deep, which is a challenge due to the sensitive foundation soil. The soil’s sensitivity consists of a layer of sand that forms the load-bearing foundation soil atop which is loose, silty fine sand, sometimes with boulders. This repeatedly causes the pipe to dislocate and thus prolongs the pile driving process. The formation of excess pore water pressure and water-bearing strata must also be taken into account. For that reason, consecutive piles are inserted as far apart as possible, which prevents the freshly driven piles from influencing each other (for the most part) and disturbing the soil.