Articles & Case Studies

Trenchless installation of a new house waste water connection

Posted: Monday 26th July 2010

The waste water connection of a family home indicated some fractured damages, causing it to block regularly and then constantly needing to be flushed free. It was therefore decided to install a new sewer line. Only 2 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.

In view of this a new house connection was to be produced from the main sewer line shaft to the house connection shaft 18 m away using the trenchless pipe installation technology. A tailored task for the TT Group’s steerable auger bore unit Grundobore 200 S. The advantage of this machine type being the fact it can work inside a manhole with a diameter of only 1 m.

There is a rainwater pipe adjacent to the previous sewer line at the same depth. The bore was therefore set inside the 4 metre deep main manhole shaft at a depth of 3 metres. The new sewer line now runs in a gradient of 5 % to the ground level of the house connection. The bore path crosses beneath the service pipes situated inside the pavement area and the foundations for the premises wall. The new sewer line 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 steerable bore was carried out from the main manhole shaft up to the pit ahead of the main shaft. The machine applied, Grundobore 200 consists of 2 components "Press frame" and "Bore drive". This makes the installation and alignment inside the manhole very easy to carry out. For this special task at a depth of approx. 3,30 metres a platform was installed. A hydraulic power unit Type TT B20 was available to drive the Grundobore 200 S.

First of all a core bore with a diameter of 250 mm was carried out into the manhole wall by the Grundobore 200 S. This process took around 10 minutes to complete. After changing the bore tools the steering head with an integrated sonde was put into action. The gradient of 5 % 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 1 hour.

The pilot bore was then 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.

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 manhole 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.

Tel: (+44) 1234 342566
Fax: (+44) 1234 352184
Email: info@tt-uk.com
Website: www.tt-uk.com




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