HDD drilling with the fluid assisted GRUNDODRILL HDD rigs

With fluid-assisted drilling (HDD drilling), the directional GRUNDODRILL rig first creates a pilot drilling along a flexible bore path using a steerable drilling head. When the drill rods are pulled back, the borehole is upsized by an expanding head and the attached pipe is pulled into the bore path. That way, longitudinal bores, crossings underneath of waters and other traffic ways can be carried out even in rocky ground. The drilling fluid consisting of water and the clay mineral Bentonite makes a major contribution to the successful execution of the pilot bore. It supports the excavation of the soil, removes the cuttings, stabilizes the bore channel and reduces the casing friction of the pipe to be installed.

Application of the GRUNDODRILL during the HDD drilling process

The application range of the GRUNDODRILL HDD rigs covers all pipe construction measures for gas, district heating and drinking water supply, the installation of sewage pressure pipes and cable protection pipes for broadband supply, telecommunications, e-mobility and wind power. The GRUNDODRILL HDD rigs are also applicable for further innovative HDD drilling applications in drainage and well construction as well as geotechnics.

Application range

• Undercrossings
• Longitudinal bores
• Installation of protection pipes
• Rock drilling

Special applications

• Horizontal drinking water wells
• Irrigation and drainage
• Geotechnical applications
• And much more (unique customized applications)

HDD drilling method for trenchless pipe laying and pipe renewal

Horizontal directional drilling (HDD drilling) is a method of installing underground pipelines, cables and service conduit through trenchless techniques. A HDD rig is used here and the HDD drilling process can be divided into three stages.

HDD drilling – how does it work?

Pilot hole

In the HDD drilling process, a pilot hole is first drilled with the diameter of the drill lance. This pilot bore ends at a predetermined target. The soil is crushed by the drill bit and the drilling fluid, which is pumped forward by the drill pipe. The drilling fluid transports the excavated material back to the surface at the entrance pit. There are several ways to control the pilot drilling. These depend on the size and complexity of the drilling. For smaller holes, a guide system running above it is used. For larger holes, a magnet system is used.

Pre-reaming

In the next step of the HDD drill progress the pilot hole is widened to the size required to lay the product pipes. A reamer is used, which is retracted and rotated. The drilling speed depends on the soil conditions. Bentonite is used to ensure a stable drill hole. This forms a layer around the outside of the hole, which increases stability and reduces fluid loss.

Pipe pullback

The last step in the HDD drilling process is to pull the installation pipe back inside the driven hole. To prevent torsional stress from being transferred to the pipe, the drill pipe and reamer are fixed to a swivel. While the actual pipe is pulled into the drill hole, drilling fluid is pumped in for lubrication. Image available?

What are the benefits of the HDD drilling method?

• Minimal surface damage
• No / minimal impact on traffic or residents
• Difficult areas can be passed under (lakes, rivers, roads, buildings, gardens)
• Environmentally friendly and largely weather-independent process
• Obstacles can be avoided by the controlled HDD drilling
• Rock drillings are possible
• Underpassing of very large distances possible