Horizontal Directional Drilling (HDD)
Horizontal Directional Drilling (HDD) is a unique technology proposed in the eighties of the last century by the US engineers. The main purpose of the new technology was to minimize the inconveniences caused by a violation of the infrastructure and the normal rhythm of life in areas where work for laying pipes and cables is in progress. Nowadays, the horizontal directional drilling, along with other methods of trenchless laying, has almost completely replaced the traditional open (trench) method in Europe. The open method is simply banned in many major European cities. For laying pipes under the ground, in addition to horizontal directional drilling, there is used a variety of trenchless techniques.
The bottom line of microtunnelling comes down to bursting of ground using tunnel boring machines with the strengthening of the walls of the tunnel with concrete or metal rings (tubing).
Microtunnelling is indispensable in the cases when it is necessary to lay a straight road without breaking the surface, for example in dense urban areas. The penetration length without reaching the surface may be up to several kilometers. The accuracy of the output is determined down by a few millimeters.