The techniques of unmanned, steerable pilot pipe jacking, also known in the literature as guided boring [Stein89g] [Stein85e] [Stein82d], is based on the principle of soil removal [DINEN12889:2000] [ATVA125:1996] (Tabelle 7.1), with two exceptions (Abschnitt 7.2.1) (Abschnitt 7.3.1).

Phase 1: Pilot boring

After installation of the jacking station in the starting shaft, the pilot bore is created in the first phase (Bild 7.2.1.1) (Bild 7.2.1.1) (Bild 7.2.1.1) (Bild 7.2.1.1). The pilot drill string consists of the pilot drill rod string and a hydraulically extending displacement and steering head (Bild 7.2.1.1) (Bild 7.2.1.1) (Bild 7.2.1.1) (Bild 7.2.1.1).

(Image: ACEMOLE PC 10 with expander [FI-NTTa])

The ACEMOLE PC 10 MP [FI-NTTa] (Bild 7.2.1) is a two-phase method (Abschnitt 3). Its features are that in pilot boring as well as during the subsequent expansion boring, it works according to the principle of soil displacement (Abschnitt 6) (Tabelle 7.2).

(Image: IRONMOLE TP80-2 method [FI-Komat])

The IRONMOLE TP80-2 method [FI-Komat] (Bild 7.2.2.1) is a two-phase method (Abschnitt 3). Its features are that in the pilot boring it works according to the soil displacement as well as the soil removal principle and, during the subsequent reaming boring, it works according to the soil removal principle (Tabelle 7.2).

Phase 1: Pilot boring
In the first phase, the steered boring is first established from the …

According to the manufacturer's information [FI-Komat], the IRONMOLE TP80-2 method can be used in the nominal pipe size range DN/ID 150 to DN/ID 900 (DN/OD 232 to DN/OD 1100) with jacking lengths to 50 m.

Because of the different possibilities of combinations of the pilot bore heads as well as reamers, there are a total of five method variations (Tabelle 7.2.2.3) of the IRONMOLE TP80-2 for applications in cohesive and non-cohesive soils with N-values …

The concept and method of operation of the EARTH ARROW method [FI-Nitto] correspond in principle …

(Image: Areas of application of the EARTH ARROW method [FI-Nitto])

The EARTH ARROW method is designed for jacking pipes of DN/ID 150 to DN/ID 700 and jacking lengths up to 50 m with a directional accuracy of ± 20 mm.

The areas of application, dependent on the subsoil conditions and the associated N-values, are shown in Bild 7.2.3.2. Utilization in groundwater is only possible to a limited extent with the help of special measures.

(Image: Overview of the machine equipment for the EARTH ARROW [FI-Nitto])

The EARTH ARROW method [FI-Nitto] (Bild 7.2.3) is a two-phase method (Abschnitt 3). Like the IRONMOLE TP80-2 (Abschnitt 7.2.2.1), the pilot bore can use the soil displacement as well as the soil removal principle and the subsequent reaming boring is carried out according to the soil removal principle (Tabelle 7.2).

The BM 500 method [FI-Bohrt] is a two-phase method (Abschnitt 3). The pilot bore (diameter 420 mm) (Bild …

In two-phase jacking (Bild 7.2.5.1) (Bild 7.2.5.1), in the second phase, the spiral conveyors is placed in so-called spiral conveyor guide pipes of steel in the jacking piping (Bild 7.2.5.1) and, in the installation of a new pipe, is tightly connected to the upstream spiral conveyor guide pipe.

Because of the relatively small outside diameter of the pilot bore string (82.5 mm to 115 mm, depending on the manufacturer), the pilot boring can be carried out in all displaceable (i.e. soils with a number of blows of N₁₀ ≤ 50 with the light dynamic probe DPL-5) (Abschnitt 4.5.2.2) homogeneous cohesive and non-cohesive soils. If the surrounding soil permits, individual cobble inclusions with a particle diameter ≤ 80 mm can be displaced in the 1…

The application of the pilot pipe jacking method in saturated soil is only possible with the aid of additional measures or by means of machine modifications because of the spiral conveyor or auger transport in the reaming phase (Abschnitt 8.2).

In the BM 300 method, the utilization in saturated soil with water levels up to a maximum of 3 m above the pipe invert is made possible by means of a specially designed spiral conveyor lock immediately behind …

In these methods, a pilot bore is always created in the first phase. Subsequently, in two-phase jacking, a jacking station is used to press or jack the piping through the subsoil at the same time as the expansion or reaming of the boring.

In three-phase jacking, the jacking station is used to push in the piping simultaneously with the pushing out of an temporary pipe. In exceptional cases, this phase is also combined with the additional expansion …

The method of operation of the ACEMOLE PC 10 (PC = Press-in Compact) from NT Access Network Systems Laboratories (Bild 7.3.1) is similar in principle to the horizontal jacking with expander (Abschnitt 5.1.3) with the exception that the soil displacing pilot bore is steerable. In the second phase, the pilot bore string (Ø 100 mm) is pulled back to the starting shaft in the soil displacement method. At the same time, a pipe with a maximum DN/OD 300, …

The special features of the two-phase hydros^®STAR method [FI-Weiss] is the pulling-in of piping in the second phase with …

(Image: Working principle in the FRONT JACKING method with reference to [Stein89g] [Image: S&P GmbH])

The FRONT JACKING method [FI-Kogan] corresponds in principle to that of the hydros^®STAR method (Abschnitt 7.3.2). In place of the anchor pulling string, a chain or a winch cable is used and the pulling-in of the line(s) is carried out from the target shaft with the help of a hydraulic pulling arrangement (Bild 7.3.3) [Stein89g].

The expansion or reaming …

Pilot pipe jacking in combination with the pulling-in of the piping in the second phase (also called "front jacking" [Stein89g]) is not mentioned in EN 12889 [DINEN12889:2000] as a variant method.

In the case of trenchless installation, this term will be understood to refer to methods in which, in the first phase, a pilot bore is established and, in the second phase, the line(s) is (are) pulled in with the aid of pulling forces at the same time as …

(Image: Sketch of the principle of microtunnelling (here with hydraulic spoil removal))

The term microtunnelling is used in this text to describe unmanned, remote controlled methods for jacking pipes with a clear diameter less than 1200 mm [ATVA125:1996] (not to be confused with DN/ID (Abschnitt 3), in which, for mechanical reasons and work and health protection, the presence of personnel at the working face during jacking or for elimination of interferences …