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Buderus Manual on Trenchless Installation of Ductile Cast ... - Duktus

Buderus Manual on Trenchless Installation of Ductile Cast ... - Duktus

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8. Installati<strong>on</strong> with steered pilot bore<br />

An interesting variant technique for the trenchless installati<strong>on</strong> <strong>of</strong> new ductile cast ir<strong>on</strong><br />

pipelines was seen for the first time in 200 at the Berlin Water Exhibiti<strong>on</strong> [8.1]: a steered<br />

pilot bore was run to the arrival pit over a distance <strong>of</strong> approximately 70 metres using a<br />

tunnelling machine for microtunneling. As a sec<strong>on</strong>d step, this pilot bore was upsized to a<br />

diameter <strong>of</strong> 80 millimetres by soil removal through auxiliary pipes c<strong>on</strong>taining an auger<br />

feeder. The third step was to withdraw the auxiliary pipes while at the same time pulling<br />

in individual ductile cast ir<strong>on</strong> pipes. The accuracy which can be achieved with this variant<br />

technique is so great that even the stringent requirements <strong>of</strong> draft DWA Arbeitsblatt A<br />

12 [8.2] for gravity pipes can be met.<br />

8.2 A descripti<strong>on</strong> <strong>of</strong> the technique<br />

The first step is to make the pilot bore. Starting from the launch pit, the pilot pipe is<br />

pressed through the displaceable soil to the arrival pit. An optical system, a steering<br />

head, a theodolite fitted with a CCD camera and a display are used to enable the target<br />

point to be homed in <strong>on</strong> exactly while directi<strong>on</strong> and inclinati<strong>on</strong> are c<strong>on</strong>stantly m<strong>on</strong>itored<br />

(Fig. 8.1).<br />

Fig 8.1 Step 1: Pilot bore<br />

8<br />

The steered pilot bore technique<br />

8.1 General<br />

1. Pilot bore<br />

Bohrtec<br />

BM 00<br />

Launch pit<br />

Surface <strong>of</strong> ground<br />

Drive <strong>of</strong> pilot bore<br />

Arrival pit

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