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Deutsche Bahn rail upgrade, Oldenburg-Wilhelmshaven

Facts and Figures
Company PORR Spiezialtiefbau GmbH
Principal PFA 1 Bau in consortium / Client: DB Netz AG
Location Oldenburg - Germany
Type Foundations
Runtime 02.2021 - 05.2022

Soil stabilisation with jet-grouted columns

The approx. 8.9-kilometre stretch of the Oldenburg-Wilhelmshaven rail line identified as project approval section 1 is located in the Rastede district of Oldenburg. As part of stage IIIb of the upgrade process – electrification and reinforcing – PORR was awarded the contract for soil stabilisation works to relieve strain from the existing retaining wall. The client is DB Netz AG. This project comprises a monolithic jet grouted body across the entire area.

Connecting the line to the JadeWeser Port

The entire rail line to Oldenburg is being upgraded while the line is connected to the JadeWeserPort container port. The rail line was last refurbished in the 1960s, and the construction of a double-track extension together with extensive renovations and the electrification of the entire stretch has been underway since 2003. Rail services have operated on this line since 1867, and the track is predominantly built on a soft subsoil layer. Complex measures had to be developed to stabilise the soil. The existing retaining wall adjacent to Oldenburg’s Ziegelhofstrasse and Pferdemarkt railway bridges is not strong enough to bear expected future loads. As a result, PORR is reinforcing the area with a jet grouted body. This will transfer load from the tracks through to the lower soil levels and reduce strain on the retaining wall.

Careful preparations for increased safety

The impact of the jet grouting works on the adjacent rail traffic was thoroughly assessed with exact specifications and precision planning, as well as the creation of test columns before the actual project began. This assessment resulted in adjustments to the execution planning with respect to the order of manufacture as well as the necessary hardening time required for individual jet grouted columns.

PORR is highly qualified for railway-adjacent projects

The manufacture of jet grouted structures alongside ongoing railway

operations calls for strict adherence to schedules as well as outstanding planning. Strictly prescribed rail shutdown periods require several crews to work both day and night shifts, seven days a week, in order to successfully execute the construction. High equipment standards and personnel capacities are essential to the project. As a consequence, wear on the equipment used during such intensive daily efforts is extreme. Owing to the extremely short execution time frame, time cannot be allowed for repairs, and so replacement equipment has to be available on the site. PORR is eminently pre-qualified for rail works: excavators and drilling equipment must not be disturbed by rail traffic on the adjacent line, a distance of 30cm to the overhead line must be maintained and the construction area is strictly defined by the required minimum distance, including aerial distance, from the adjacent line.

Where the minimum distance from the nearest operational rail line cannot be ensured due to the required location of the jet grouted columns, additional night rail closures will be implemented. In this scenario, rail traffic will be discontinued on the neighbouring line for approximately four hours. This consideration, in addition to the essential pilgrim step rolling and hardening times required during manufacture, calls for extremely precise construction process planning. Daily schedule adaptations are required in response to the latest construction progress. The small, precisely defined construction site is hemmed in by operating rail lines to either side, severely limiting the space available for the necessary staff and equipment. Overhead cabling restricts the clearance height to 6m, adding an extra level of complication to manoeuvres on the construction site. In addition, the constant variation between the manufacture of full and half columns requires correctly adjusted drilling equipment and high levels of technical know-how from the operators. With years of experience and great expertise, the PORR team is ideally suited for this challenging construction project.