The control of the pilot bore along the pre-calculated target axis is done either by an asymmetric design of the drill head or by using a slightly angled drill rod element behind the drill head. Depending on the soil type, either a jet-bit for primarily hydraulic loosening work or a rock-bit with mud-motor for combined hydraulic-mechanical or completely mechanical loosening work is used. The soil is loosened by a drill head located at the front end of the drill string. The pilot drilling is carried out along a two or three dimensionally bended target drill line between an entry point (in front of the drilling rig) and an exit point on the other side of the obstacle. Pullback (Installation of pipe or duct).Pilot Hole drilling (guided bore along given drill path).The standard procedure of a horizontal drilling can be divided into t hree main steps: These include horizontal filter wells, slope drainage, anchor boreholes, dam and dike protection, ridge protection and retrofitting in tunnel construction. In addition there are numerous other areas of application for the HDD process. Typical applications of HDD technology include crossing watercourse, road and rail crossings, slope drilling, rock drilling, inner-city and extra-urban longitudinal laying and house connection drilling. pulling force between 10t (100kN) and 30t (300kN). The most commonly used horizontal directional drilling rigs are rigs with a max. The HDD process is used to lay pipelines for oil and gas transport, cable protection pipes for electricity and telecommunications as well as gas, water, sewage and district heating pipes made of plastic, steel and cast iron. The constantly developing drilling technology already enables the trenchless laying of pipes up to a diameter of 56″ (DN 1400) in almost all ground formations. With the large drilling rigs on the market today, crossing lengths of more than 2 km have already been successfully completed. Pipeline infrastructures are the lifelines of modern society and it is no longer possible to imagine the construction of this infrastructure without trenchless construction methods, in particular horizontal directional drilling. In the nineties, there was a rapid further development with almost worldwide use. In Europe, the method was first used in the mid-eighties. Until 1979, the use of this technique was limited to relatively short crossing lengths and was only applied in the US. The horizontal directional drilling method (HDD) was developed in the US in 1972 and in its early days revolutionised in particular the crossing of larger rivers with supply lines of all kinds.
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