Upgrade of Dortmund-Ems canal: lots 2c, 3 and 4 with culvert for the river Stever
Datteln Waterways Building Department (WNA) has upgraded an 8 km section of the Dortmund-Ems canal to waterways class Vb using the embankment method (trapeze profile). This section has canal side dams up to approx. 10 m high, trenches up to 20 m deep and several crossing structures.
Most of the section lies in partly high dams. The dams were initially widened and flattened on the downstream face. Subsequently, the upstream face canal profile was widened, replacing the existing loam seal by a clay seal measuring 30 cm thick (picture 1); the embankments and the bed were protected with rip-rap armourstones.
BAW was involved in the work throughout the entire planning and construction phases. Ground surveys were produced. During the planning work, we dealt with special earthworks issues as well as protecting the embankments and bed. During the construction phase we provided technical advice e.g. on excavation and shoreside water logging and seepage leaks on opening the existing loam seal. BAW was also involved in quality assurance of the rip-rap work with control tests.
The canal seal with a surface seal laid underneath the rip-rap is particularly relevant to safety in this particular section of the dam with its integrated bridge structures. Here the seal had to be produced primarily under water, which made great demands of the seal material and the installation techniques. The control tests necessary to monitor these requirements were carried out in close coordination between the WNA (with authority divers taking specimens) and BAW (materials tested in the laboratories).
Construction of the new Stever culvert
Part of the upgrading work also included making a new culvert to the river Stever through the canal dam. This replaces the previous canal bridge with which the Dortmund-Ems canal crossed the river Stever. The new culvert consists of a 3-part frame structure about 100 m long as a solid construction. It was made using the immersion method. The middle section measuring around 70 m in length was erected initially in a dry dock positioned to the side of the canal and enclosed with earth dams and sheet piling. Once the dock was flooded, the separation dam between the dry dock and the canal cross-section was removed, with the structure then immersed and lowered in a previously dredged cross channel (picture 2). This was followed by attaching the inlet and outlet structures in specially secured excavation pits that went down to a depth of 16 m. After filling and compacting any possible cavities next to and under the structure, the rest of the canal profile (embankments and bed with surface seal) was made over the structure.
The BAW produced the ground and foundations survey for the building structure with the dry dock, and provided on-going advice during the construction period. Before the actual construction work started, extensive load trials and pile driving tests were carried out to ascertain the load rating for pressure-grouted anchors and sheet piles. These tests were devised and evaluated by BAW in cooperation with the WNA.