From the magazine, HDD

Keyhole technology – house connections installed with minimal invasion

Trenchless Technologies for the installation and renewal of pipes are generally characterised by less excavation and reinstatement work, low emissions and better environmental outcomes than open trenching works.

For shorter, inner-city pipe installations or river crossings, horizontal directional drilling (HDD) is a proven installation method. Minimal excavation work is required, so there is no need for re-filling, sealing and re-instatement of surfaces.

In Europe, the TT Group and Gaz de France Suez have worked together to develop a new type of keyhole technology for the HDD installation of pipes.

The keyhole technology has been used for the trenchless installation of service pipes to residential homes. With this new technology, a bore with a diameter of only 600 mm is all that is required. From this bore, service pipes are installed underground with HDD, and connected to homes from the surface.

Benefits of the keyhole method

The benefits of this innovative technology include:

  • Work on service pipes can be carried out with short interruptions and minimal restrictions on residents
  • Surfaces are only slightly utilised, with asphalt work and follow-on work not required
  • Soil and surface work is reduced
  • With the Grundopit-K bore rig, only a bore setting point is required, from where the underground bore is driven forward.

Economic and ecological advantages include:

  • Damages to already existing pipelines are prevented
  • The working area is free to use again approximately 30 minutes after reinstatement and sealing of the extracted bore core
  • Reduced costs, as opposed to the conventional open trenching method
  • Reduced emissions, thanks to lighter and quieter working devices.

Using the Grundopit-K bore rig

The Grundopit-K is a fully automatic bore rig which carries out the normal bore process. After the setup of the bore rig, the operator at the surface only needs to insert the required drill rods. The automated bore mode is only interrupted to carry out any necessary direction alterations. The operator can handle the bore rig safely from the surface by means of a remote control.


The keyhole technology introduced here is an important step towards minimally invasive and fully automatic working bore technologies, and towards the installation of new house connection pipes from the surface.

The benefits seen by the public and the environment through this method of installation are many. Importantly, reduced expenditure and requirement for any follow-on work
can immensely reduce the time consumption and costs, as opposed to a pipe installation using the open trenching method.

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