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  • This is a unique No-Dig technology that allows the laying of flexible pipes underneath roads, railways, rivers etc. without affecting them;
  • This technology allows the rapid, safe and convenient installation of new pipes


The No-Dig installation system, called Horizontal Directional Drilling (HDD), consists in the carrying out of an underground borehole that will represent the installation site of a plastic or a metal pipe that has been previously welded to the ground surface.
The borehole is made in the subsoil by means of a rotating milling machine positioned at the end of a drill rod train. The milling machine can work in dry conditions (also in soil), or with the aid of a drilling fluid.
In the first case, due to the substantial simplification of the drilling operations, there is a greater use of machinery.
In the second case, due to the use of a more complex site system and the time required in order to carry out the boreholes is relatively longer, this means that there is less use of the equipment and greater precision is needed when laying the new pipes.
The installation of new underground pipes by following predefined paths is based on the possibility to steer the trajectory of the drilling head from the surface.
Predetermined routes can be carried out which allow the desired target to be reached with a tolerance of a few centimetres following paths that can exceed 500 linear metres.
Once the reception shaft has been reached, the milling machine is removed from the drill rod train. These are connected to a reamer and the head of the pipe to be laid. During the removal stage of the drill rod train, the reamer widens the size of the bore hole with the aim of creating the installation side of the new pipe to which it is connected.
The laying of new pipes by means of the Horizontal Directional Drilling (HDD) technique must be preceded by an accurate subsoil survey, which has the purpose of identifying any underground services or erratic boulders that may interfere with the drilling track. The Georadar is effectively used for this purpose.

Edilvie S.r.l. uses Horizontal Directional Drilling (H.D.D.GUIDEDDIRECTIONAL DRILLING or as you prefer to call it), a drilling technique which consists of an active trajectory control, for the installation of trenchless underground infrastructures. This technique was first experimented at the beginning of the 1980s in the USA and subsequently its use also spread to Europe. Unfortunately, this technique is still not widely used in our country, it reduces or it even solves the problem of installing underground services, especially when it is necessary to work in urban areas that require the breaking up of the road surface in order to carry out the works.

The Controlled Directional Drilling (CDD) technique is, by now, an integral part of the procedures relating to the installation of underground services, allowing solutions which previously were considered unthought-of. By means of such system, it is possible to install ducts underneath major roads, waterways, sea canals, communication routes such as motorways and railways (in both longitudinal and transverse directions), industrial buildings, homes, natural parks etc. Recently, such technology has allowed works to be successfully and efficiently carried out as regards the recovery of hydrogeological disasters as well as the decontamination of polluted areas. It is therefore indispensable, prior to carrying out any kind of underground operation, to be aware of the nature of the subsoil both as regards its characteristics and the type of soil as well as the dislocation of the existing underground services.


There are three main operational stages relating to the laying of a pipe by using the Controlled Directional Drilling technique: 

  • The carrying out of the pilot bore hole;
  • The back reaming of the bore hole;
  • The pulling back and pipe laying procedures

The carrying out of the pilot bore hole
This is the first and most delicate work stage. The drilling is carried out by means of inserting a series of rods into the soil, the first of which is connected to a swivel head that allows it to be steered, the removal of excess soil is carried out by means of bentonite clay and various polymers which, by passing through the drilling rods and coming out of the headpiece, remove the soil by allowing it to flow backwards along the borehole, right up to the starting shaft in the form of mud. The drilling and mud expulsion system described above cannot be used for drilling procedures to be carried out in extremely compact materials and in all types of rock. In these situations, revolve-vibrating drilling systems are used which consist in the use of special directional down-the-hole pneumatic hammers, powered by compressed air together with fluid foam (biodegradable). However, such system cannot guarantee precise guidance. A more effective and precise solution could be provided by hydro-mechanical drilling with a ‘mud motor’, obtained by means of a special turbine engine, powered by the forced circulation of mud to which a tool is connected that, mechanically and easily cuts the rock. The drilling head is generally controlled by radio waves or by cable by means of a special probe that is housed inside the head and is capable of providing information at any time relating to: 

  • Depth
  • Inclination
  • Direction on a horizontal plane

For this purpose, there is a wide range of tools available for all kinds of drilling procedure depending on the degree of precision needed as well as the clients’ requirements. 

Back reaming of the bore hole
One the pilot bore hole has been performed, regardless of the method used, the drilling head is substituted by particular reamers that are dragged backwards inside the borehole which rotate thanks to the movement transmitted by the rods that carry out a milling and therefore widening action on the bore hole constantly assisted by jets of mud in order to carry out the removal of soil as well as the stabilising of the borehole walls (usually the diameter of the back reaming must be 20-30% larger than the pipe to be laid).

Pulling back and pipe laying procedures
Once the back reaming stage has been completed, the pipe or group of pipes are connected behind the reamer itself by means of a rotating joint in order to avoid that the rotating action is transmitted to the pipe itself and this is towed backwards right up to the starting shaft. Such operations, which are apparently complex and difficult, become easy to perform once mastery and experience have been acquired in using the technology in question.


There are various fields of application for this technique ranging from the simple installation of underground infrastructures, to hydrogeological redevelopment (the installation of drains, the stabilising of landslide slopes and the regulation of the groundwater level), to geo-environmental redevelopment (the recovery of polluted areas as well as the containment and waterproofing of polluted areas).

There are several advantages of using this type of technology compared to traditional drilling methods such as: 

  • The safety with which the drilling operations can be performed
  • The reduction of costs relating to precautionary measures
  • The speed at which the works are carried out
  •  Road surface damage is avoided
  • Damage to the static resistance of the road sub-layer can be avoided or at least minimised
  • The inconveniences, restrictions and the loss of energy caused to the public and especially to the traffic can be limited or even eliminated
  • The operations can be performed regardless of the weather conditions
  • Both noise and air pollution can be reduced
  • The depth of the trench incurs neither a factor of expense nor of risk
  • The almost total elimination of land handling with the consequent depositing of topsoil onto increasingly less available surfaces (the conservation of natural caves and dumps)
  • Pre-existing works are left unaltered


EDILVIE S.R.L. - Strada Dell'Artigianato n° 22 - 01024 CASTIGLIONE IN TEVERINA (VT)
Lazio - Italia

Tel: (+39) 0761 94.70.23
Fax: (+39) 0761 94.92.44

P.IVA: 01605010568


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