The 5th lock of Brunsbüttel is located at the entry from the North Sea to the Kiel Canal. The lock system of Brunsbüttel comprises 4 locks at present, the larger of which date back to 1914. Due to their intense use and the significant demand for maintenance, it is not possible to repair the existing locks during normal operation. For this reason, another lock must be provided for the period of general refurbishment to maintain the existing capacities. This necessitates the construction of a 5th lock. This means that additional capacity will be available after the refurbishment of all existing locks.
The North Sea is characterised by intense tides, the Kiel Canal has a constant water level of approx. ±0.00 m asl. The regular tidal range of the North Sea is approx ±3.00 m. Apart from managing the tidal range, the lock is an integral part of the flood protection line on the North Sea Coast. According to a forecast, storm tides may reach a level of around 9.00 m including waves.
Consequently, the structure must meet very high requirements, regarding both protection against floods and the drainage of the Canal. The structure is largely characterised by these to contrary but also complementary requirements.
The selected gate types are rolling gates, designed so that they may also be used in the existing chambers of the large locks after their refurbishment. Therefore, the wheel-barrow system as used in the existing locks was selected. An upper carriage to which the rolling gate connects has been designed. This means that only an upper carriage with the same connection technology and a rail system as implemented for the new lock must be available in order that the gates may easily be used in the old locks. This may allow to waive spare gates, and maintenance can be standardised. The investment costs for additional gate chambers and drive technology can hence be saved.
In consideration of the required response times and the comparatively high number of locks with the same dimensions, it was possible to make the provision of a permanently operational second gate on each lock head redundant by selecting the proper response time. This reduces investment costs. Apart from a dry dock, only the space for the selected number of spare gates has to be provided. Therefore, the drive technology and the upper carriage have to meet redundancy requirements comparable to the requirements of the gates, making a failure of the lock chamber unlikely.
The manufacturing methods, safety requirements and other statutory requirements, e.g. occupational safety, have considerably changed since the manufacture of the large locks in 1914. As a result of all factors, up-to-date gates are heavier than in the past. Contrary to the old gates, the new gates have been fitted with filling and emptying gates. This allows for performing maintenance work (e.g. in a dry dock) on the filling and emptying devices irrespective of the lock operation.
A significant factor for safe filling is the structural and flow-related design of the filling channels. Damage caused by vibration and abrasion is rather likely. The structural and flow-related design of the filling gates is essential for the function of the overall lock.
Apart from the filling gates, flushing devices are accommodated in the lock gate to keep both the rails and, in particular, the gate tank ceiling free from silt sediments. In addition, a pump system is provided to fill and/or empty the ballasting tanks. This requires complex piping for this pump system on and in the gate. The control devices for these components are partially located on the gate. For this reason, it is required to fit an engine room in the gate, where all these units are accommodated.
The gate is designed as a self-floating structure, since this is the easiest and least expensive approach to transport such a structure. The floating depth must be limited so that the structures may overcome all obstacles. These are especially the lock sills. The gate must meet specific floating stability criteria so that occupational safety requirements may also be met by the gate when it is affected by waves and wind. The gate position is a parameter in this regard, since the gates are balanced in a manner so that their comparatively high dead weight has a considerable effect on floating stability. The filling gate dead weight was selected that high to ensure that they are independently closed by it. These parameters have an influence on the determination of the gate system reliability.
Safety against buoyancy is stipulated by a standard in Germany, since a floating to the surface of the gates would imply a considerable storm flood risk for the cities behind the flood protection line. The main element of the acting forces is the buoyancy of all ballasting cells and the engine room. The size and location of the ballasting cells must be selected in a manner so that the overall gate floats safely on the one hand; on the other hand, the buoyancy of the ballasting cells must be countered by the dead weight of the gate as well as of all permanently installed equipment and, in addition, by ballasting water including a buffer to ensure safety against buoyancy of the installed gates. This results in comparatively high bearing loads, which in turn necessitate a specific ratio between floating and submerging forces. This approach to safety is applied in Germany irrespective of the size and significance of a structure.
The dimensions of the rails and their anchors are of particular importance, since they are very sensitive components that are difficult to replace, especially if submerged. In this regard, all impacts have to be fully identified and their transfer has to be tracked consistently. The rail structure must especially be contemplated as regards possible structural designs.