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Customer case

Reconstruction of Klaipeda Northern Breakwater

November 18, 2022 6 min read

retaining wall

Case details

Product RD® pile walls
Country Lithuania
Company Depenbrock Ingenieurwasserbau GmbH & Co. KG
Industry Building structures and infrastructure

In the project ‘Reconstruction of Klaipeda Northern Breakwater’, the entrance of the harbour of Klaipeda was strengthened and renewed. In the course of this construction work, a retaining wall was built underwater at the foot of the breakwater at the narrowest point of the entrance. Through the installation of this wall, it was possible to design a rectangular cross-section between the northern and southern breakwaters, thus achieving a depth independent of the breakwater slope. Main contractor for the project was Depenbrock Ingenieurwasserbau GmbH & Co. from Germany.

Case details

Product RD® pile walls
Country Lithuania
Company Depenbrock Ingenieurwasserbau GmbH & Co. KG
Industry Building structures and infrastructure
Sketch of the Klaipeda RD pile wall

Sketch of the finalized RD® pile wall. Photo courtesy Depenbrock Ingenieurwasserbau GmbH & Co.

The retaining wall consists of a combination of steel piles with a diameter of 1220 mm, which were installed using so-called Kelly method, in conjunction with sheet piles, and an RD® pile wall, which was installed by down-the-hole (DTH) drilling by Terramek Oy from Finland. The pile size of the RD® pile wall was RD800/16 and steel grade S355J2H. Total number of piles in RD® pile wall was 90 pcs with lengths varying from 19.3 meters up to 35.5 meters, totally 2371 meters. The piles were equipped with SSAB’s RM/RF connectors.

The final heights of the installed piles adjusts to the bathymetry of the existing breakwater. In addition, some piles remain above sea level to indicate the axis of the wall for shipping traffic as navigation points. The change in the method from Kelly method to DTH drilling was due to an increase in the number of massive obstacles. These made the installation using the Kelly method more difficult.

Drilling strings into RD pile

Lifting of DTH hammer and drill strings into pile from deck of jack-up-barge. Photo courtesy Depenbrock Ingenieurwasserbau GmbH & Co.

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Video courtesy Depenbrock Ingenieurwasserbau GmbH & Co.
Drilling of an RD pile wall

Drilling of an RD® pile wall from deck of the barge. Photo courtesy Depenbrock Ingenieurwasserbau GmbH & Co.

When drilling of a pile is done with a DTH method, the piles can penetrate even through massive obstacles. The drill bits, pilot pit and reamer, used in DTH drilling are usually designed to enable drilling to hard rock. In drilling method, individual chisels together with percussion power from hammer break hard rock and obstacles into small pebbles. These pebbles are then flushed up through the pile pipe with exhaust air of the hammer. During installation, it was shown that even tetrapod and granite blocks could be penetrated. With DTH method, it was possible to install up to 36 meter long piles easily to the final depth according to the design within a few hours.

The piles of RD® pile wall were drilled all the way to a depth of 28 meters below the sea level. After installing the full-length piles from the deck of a jack-up-barge, the piles were cut from level of approximately -7 meters using a specially designed construction. The resulting sections were welded to piles as extensions for clamping in the piling machine and cut off again in the further course of the piling operation. In this way, the cut ends were put to further good use and waste was minimized.

Jack-up-barge in use of drilling RD pile wall

Jack-up-barge Simone was used in the project. Photo courtesy Depenbrock Ingenieurwasserbau GmbH & Co.