Direct Pipe®

Direct Pipe® is a combination of microtunnelling and HDD methods and was used by SONNTAG for the first time anywhere in the world.

A steel pipe is completely prefabricated before pipe-laying begins and is laid out in its full length behind the pipe thruster.

The steel pipe, welded onto a conventional microtunnelling machine and gripped by the Pipe Thruster's clamping unit, advances through the ground towards the target pit. The supply and waste removal lines necessary for the operation of the microtunnelling machine are pre-installed in the pre-fabricated steel pipes. The tried-and-tested gyrocompass system combined with an electronic spirit level ensures spot-on accuracy all the way to the target pit.

Advantages over the microtunnelling method:

• Tunnelling time is significantly reduced as time-consuming coupling operations for lengths of pipe are no longer required.
• The pipe-jacking machine and the entire pipe length can be completely withdrawn if impassable obstacles are encountered.

Advantages over horizontal direct drilling:

• The product pipe itself (e.g. gas pipe) can be directly driven. There is no need to drive a protective pipe first.
• Only the gap between the product pipe and the bore wall is filled with bentonite (in horizontal direct drilling, the full bore must be filled with bentonite).
• Minimal space is needed around the target pit.
  
• The planned route is followed to the centimetre thanks to precise advance surveying.
  
• The driven tunnel cross-section is permanently supported by the pipe-jacking machine or the product pipe and its bentonite jacket.
• Precise excavation of the soil means the pipe length can be driven without damage to the outer shell occurring.