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New storm water overflow basin at Chemnitz traffic junction

New storm water overflow basin at Chemnitz traffic junction

As part of the construction of a new traffic circle at Chemnitz Südbahnhof station, all services such as sewer, electricity, gas, drinking water, lighting and communications were renewed or renovated, and a rainwater overflow structure was also built in the area of the busy traffic junction. In order to secure the excavation pit for the construction of the rainwater overflow structure, the customer relied on a special proposal that included the use of an e+s linear shoring system. And with success: With the in-situ concrete-suitable linear shoring system, which can be used flexibly for many construction measures, the ground outside the trench remains largely untouched and the development and flow of traffic is not impaired. Technological features such as these made a major contribution to ensuring that the 16-meter long, 5.50-meter wide and 5.20-meter high in-situ concrete structure with overflow sill could be constructed smoothly and on time despite the cramped conditions on the inner-city construction site, with the walls of the structure being concreted directly against the shoring.

Due to the spatial conditions on site and in particular with regard to the narrow development in the construction area, the excavation pit was secured with the e+s linear shoring system instead of sheet piling, contrary to the original variant. This resulted in many technical and economic advantages during installation and removal of the modules as well as during the work in the excavation pit. Five modules of the shoring system - consisting of inner and outer base panels and an inner top panel as well as 6.13 meter long linear shoring soldiers and the roller units - were kept on site. The advantages of the linear shoring system became clear as soon as the first shoring unit was installed. After pre-assembly of the pairs of shoring soldiers with the roller units and the required widening, the trench was excavated to a depth of around 1.50 metres for a panel length of around 1.5 metres. The next step was to set the first pair of beams. The excavator then swivelled the outer base plates into the beams not from above, as is usual with other systems, but laterally, just above ground level. This procedure is made possible by the large open guide profiles of the linear shoring soldiers. As soon as the panels are aligned at right angles to the roller unit and parallel to each other, the second pair of beams can be easily inserted into the panel ends from above.

After installation, the beams and shoring panels were provided with a separating layer of polystyrene. This procedure was necessary to prevent direct contact between concrete and steel shoring elements and to reduce the frictional forces when pulling the panels and girders. In the next step, the bottom of the rainwater overflow basin was concreted. Once the minimum strength of the cured concrete had been reached, the excavator was used to change the position of the carriages in accordance with the manufacturer's static specifications. In this way, the necessary working space was created to produce the internal formwork for concreting the walls of the rainwater overflow basin. After the slab had been constructed, the excavator could start with the dismantling. Since the deconstruction forces are much lower than with most other shoring systems, the overall economy of the system is increased. Rigid carriages, which can be adjusted in height in accordance with the advancing depth of the trench, keep beams and shoring panels at the same distance from each other at all times; the trench width remains the same in every phase of construction. This ensures more effective, faster, better quality and noticeably more economical work.