Prague: Quality check after an underpass of the Vltava river
To establish a connection to the central sewage plant on the island of Císařský in Prague in the Vltava river, a pipeline was laid underneath the river using the HDD method. Narrow bending radii made pipe insertion more difficult. Moreover, the geological conditions were unstable due to the presence of shale, which implied the necessity to examine the integrity of the new pipeline following installation. In view of this situation, the egeplast SLM® DCT (Detection and Checking Technology) pipe system was used.
The connection of the Podbabsk sewage plant in Prague to the central sewage plant located on the island of Císařský in the Vltava river posed major challenges to the general contractor, ZEPRIS. To increase the transportation capacity, a double pipeline measuring 400 x 23.7 mm as well as five shaft structures were installed on the island. The total length of the pipe string is approx. 1050 m. The trenchless segments ran underneath the Vltava river as well underneath an old stock of trees at the along the river.
Trenchless installation underneath the Vltava riverbed using the HDD method was performed by TALPA-RPF. The starting and end points of the river crossing were predetermined by the connection points of the original pipeline. These constraints as well as a relatively short distance and the resulting bending radius made drilling quite challenging. The pilot bore, too, presented major challenges, particularly on the riverbank. Shale in the area of the drilling channel rendered the geological conditions unstable, which might have resulted in difficulties around the drillhole when inserting the pipes. Therefore, keeping the longitudinal profile of the culvert and the very challenging geology of the substrate in mind, a SLM® DCT pipe which allows for a verification of pipe integrity immediately after installation was selected.
After 18 days, the horizontal drilling procedure related to the two 160-m long pipe strands underneath the Vltava river was completed. In the course of the technical monitoring of the construction, the operator was able to check the quality of the system and the integrity of the installed pipelines multiple times, enabling the planning office to successfully complete its project documentation.
“This was the first time we applied the system which enables us to inspect the PE pipes following installation. Our positive experiences, however, will definitely result in us using it for other applications in the context of our trenchless construction measures”, Ivan Demjan, TALPA-RPF s.r.o. Managing Director explained.
|Project description:||Linkage of a sewage plant to the central sewage plant located on an island|
|Challenge:||Narrow bending radii and geologically unstable conditions owing to presence of shale|
|Solution:||Verification of the integrity of the new pipeline following trenchless pipe insertion under difficult conditions|
|Pipe system:||1.050 m SLM® DCT for sewage pressure; Dimensions: 400×23,7 mm|
|Parties involved in the project:||General contractor: ZEPRIS s.r.o., Prag; Spülbohrung / Flush drilling: TALPA-RPF s.r.o., Ostrava; Projektdokumentation / Project documentation: D-PLUS|
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