Built by 1914, the Klingenberg impounding reservoir in the Ore Mountains near the German-Czech border had been providing drinking water for almost 90 years when it was severely damaged by the big flooding in 2002. Its owner, the state of Saxony, decided to have the entire reservoir including hydro-engineering equipment overhauled, rebuilt and upgraded to state-of-the-art standards. Renovation started in 2005 and in 2010 it was the dam’s turn. Its historical semi-circular quarrystone wall – 46 m high, 34.7 m thick at the base and 312 m wide at the crest – had to be left as it was because it is under monumental protection. This constraint, special hydro-engineering requirements and the project’s size and nature required a project-tailored formwork solution. MEVA engineers combined standard formwork with special solutions that efficiently handled the complex job, its technical challenges and tight schedule.
Four new layers added to what looked like a “hedgehog wall”
The dam’s upstream face was to be equipped with new sealing and drainage systems. Hence four new layers needed to be added to the existing quarrystone wall that looked like a hedgehog because it had over 2,000 permanent wall anchors implemented on the upstream face to hold the new layers:
The wall anchors, each with a diameter of 40 mm, are implemented 2.50 m deep in the quarrystone wall and protrude some 80 cm. The entire wall is divided into blocks, each 8 m wide and 4 m high. Each block has three wall anchors that are 2.50 m apart from each other. The contractor’s order was to use the wall anchors to suspend the climbing formwork. MEVA engineers developed an ingenious solution that turned the wall anchors, a big obstacle to climbing at first sight, into an efficient climbing assistance.
Up the wall block by block and with back-step method
performing several jobs simultaneously
The four layers were constructed one after the other in two steps and using the back-step method to first pour the equalising layer and then protect it with a foil against the low temperature. In a second step, the insulating bitumen foils were attached, the bricks for the drainage layer laid, the sealing layer poured and thermally cured. The jobs of the second step were performed consecutively or simultaneously from climbing units that had up to four working platforms for multi-tasking. A total of 10 units climbed the wall block by block and independently of each other.
Support Frame STB 450 for starter cycles
The first cycle of each block at the wall base was poured using support frames STB 450 for single-sided pouring. Three formwork units, each with seven STB 450, were used and one end of each support frame placed on a job-built base to cater for the wall’s 10% inclination. 250 cm and 350 cm high Mammut 350 panels were horizontally combined to create the 6 m high and 8.50 m wide forming area required for each block. On top of the support frames, the formwork was attached at the block’s three wall anchors. Since they did not allow the support frames to be height-extended using standard extensions, vertical rails were attached to the support frames and the top facing attached to the rails to achieve a height of 6 m.
Climbing Systems: Climbing upwards using the wall anchors
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