Trenchless Installation of a New House Connection Canal

The wastewater connection of a family in Wildeshausen, Germany, indicated some fractional damages, causing it to block regularly and then constantly needing to be rinsed free. For this reason a decision was made to install a new canal. Only two years ago the road had been renewed and a repair or new installation for the house connection using the open-trenching method would have split the supporting layer of tarmac and caused subsequent road subsidences.

Therefore a new house connection was to be produced from the main canal shaft to the house connection shaft 18 m away using the trenchless pipe installation technology. A tailored task for the steerable auger bore unit Grundobore 200 S, manufactured by TRACTO-TECHNIK, Lennestadt, Germany. The advantage of this machine type was that it can work inside a shaft with a diameter of only 1 m.

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There is a rainwater canal adjacent to the previous wastewater canal at the same depth. The bore was therefore set inside the 4-m deep main canal shaft at a height of 3 m. The new canal pipe now runs in a gradient of 5 percent to the ground level of the house connection canal. The bore path crosses beneath the service pipes situated inside the pavement area and the foundations for the premises wall. The new canal pipe ends at a specially excavated pit (L x W x H: 1.20 x 1.20 x 2.50 m), which also helped to facilitate and make the expanding and installation work much easier, as well as the connection to the house connection canal. It would have also been possible to connect directly to the house connection shaft.

The company Huneke, from Leer, was assigned with the completion of this task. The steerable bore was carried out from the main canal shaft up to the pit ahead of the main connection shaft. The machine used, a Grundobore 200, consists of two components: a Press frame and Bore drive. This makes the installation and alignment inside the shaft easy to carry out. For this special task at a depth of approximately 3.30 m per platform was installed. A hydraulic power unit Type TT B20 was available to drive the Grundobore 200 S.

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First, a core bore with a diameter of 250 mm was carried out into the shaft wall by the Grundobore 200 S. This process took about 10 minutes to complete. After changing the bore tools, the steering head with an integrated sonde was put into action. The degrading of 5 percent had to be maintained at the same time. Inclination, depth, position, direction and roll angle of the bore head were constantly checked and, whenever necessary, the direction or inclination deviations were evened out accordingly. The pilot bore with an 82.5-mm diameter was completed in exactly one hour.

In the following process, the pilot bore was expanded in the opposite direction with a winged bore head. The spoils produced during the bore were conveyed out of the bore hole, protected by the retrievable pipes (Ø 170 mm) with a spiral conveyer back to the excavated pit.

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After this step had been completed, the Schöngen protection pipes PP-HM 170 x 12 mm, effective length 450 mm were pushed in from the canal shaft and connected with sockets in both shafts and sealed off accordingly.

Once again the trenchless method has shown how a house connection can be completed without any comprehensive civil engineering work and with very minimal interferences.

This article was submitted by TRACTO-TECHNIK GmbH & Co. KG, Lennestadt, Germany.

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