Auger Boring Machine

Simple basic principle, efficient tunnelling technology

Auger boring machines work on the principle of screw conveying. They achieve high advance rates in displaceable, dry, loose soils. With the front steer technology with down-the-hole hammer, controlled drilling from Ø 324 mm is also possible in consolidated rock up to 250 MPa. The principle is as clever as it is simple: an auger inside a protective steel casing transfers the torque from the drive to the cutterhead. At the same time, it transports the excavated material from the face to the launch shaft. In this way, the borehole is driven into the ground pipe by pipe. In the target shaft, the individual jacking pipes are recovered, and the product pipes are pushed after them.

Control as required

The choice of control method depends largely on the drive length and the required drilling precision. For very short drilling distances, unguided machines are used. The rule of thumb here is: the longer the pipe sections used, the more precise the drilling. For longer drives with great precision, a controlled, soil-displacing pilot borehole is first drilled to the target shaft. The direction and inclination of the pilot bore are monitored precisely and continuously using an optical surveying system. Depending on the diameter, various methods are then available for reaming. Front steer technology is used for non-displaceable soils and consolidated rock.

The right technology for every application

Compact machines are used in inner-city areas and in confined jobsite conditions. If the space available on site is of secondary importance, so-called long frame machines are the ideal choice. Thanks to the modularly extendable frame, they allow the jacking of steel pipes up to 18 meters in length.

Special developments for new applications

Controlled pilot drilling is not possible in non-displaceable soils or in rock. For this special requirement, in partnership with Herrenknecht, Bohrtec developed the patented front steer technology. A cutting disc excavates the soil or rock up to a strength of 30 megapascals. The material is transported to the launch shaft by means of hollow stem augers with a continuous path for the optical surveying system. This enables drilling with millimeter precision even in harder geologies. Customer and project-specific solutions round off the range and the possible applications of the technology. Examples include the groundwater auger for drilling up to 3 meters below the groundwater table, the down-the-hole hammer for guided drilling in consolidated rock up to 250 MPa, the retractable double-wall rod for blind holes for installing drainage pipes and the Hole Opener for pulling in plastic pipes.