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Jul 01, 2021 Micro tunnelling refers to unmanned, remote-controlled methods for jacking pipes.
This module covers the various methods, in particular, micro tunnelling with hydraulic, pneumatic, auger and scraper conveyance and soil displacement. The focus is on removal and processing the spoil, drive variants of the cutting head, cutting head design, application in groundwater, measures to reduce jacking forces and measures to remove obstacles.
After completion of this module, you will have a sound knowledge of:
- cutting head design;
- processing of the spoil in separation plants;
- measures to reduce jacking resistance; and
- dealing with obstacles.
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Today, supply and discharge lines are still predominantly installed by using the open-cut method: a trench is dug, the lines are installed. Under the protection of an embankment or sheeting and the trench is filled afterwards. In the face of the numerous disadvantages as well as the citizens' growing environmental consciousness in the future it is urgently necessary to take trenchless technology into account much stronger than until today as an alternative … |
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(Image: Steering of a jacking) Functions of the jacking steering:
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(Video: Displacement- and steering principle of the ACEMOLE PL 30) Video: Steering of the shield machine by means of steering cylinders [Image: S&P GmbH]. This interactive object is only visible online. |
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Steering cylinder: By extending/drawing in single steering cylinders, the shield machine is steered out of the direction of the jacking pipes. (Video: Steering of the shield machine by means of steering cylinders) |
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During the steering itself, it must be taken into account that after the introduction of the steering process, the boring or displacement head or the microtunnelling or shield machine will still cover a certain distance in the old (incorrect) direction before the directional correction comes into effect. This means that the required countersteering must be introduced already before reaching the prescribed design path. (Image: Principle of the series … |
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"A gyroscope can be generally designated as a rigid body that carries out a desired rotational movement. Fundamental features are its steady state capacity (inertia) and its precession (advertence due to external moments acting on its axis of rotation). With respect to its ability to move in all three axes, about two axes or about a single axis, one differentiates gyroscopes with three or two degrees of freedom or a single degree of freedom" [Deuml80]. |
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The principle of measurement is based on the physical property of fluids in connected containers of any cross section always to find the same level (communicating pipes). In practice, electronic levelling units are used exclusively in measurements in most trenchless installations. During the whole of the jacking course, the electronic levelling unit determines the MSL height of the machine. (Image: Functional principle of a hose water level) |
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(Image: Hose of the hose water level (green) within the pipe string) (Image: Determination of position and direction) (Image: Position determination - Reference module of the hose level (height level always above the level of the tunnelling machine)) The electronic levelling unit consists of three modules [FI-Bodenb]:
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Mechanical pendulums can be used for jacking methods with an illuminated target board and picture transmission by a video camera. The required angle is read off using the monitor; an electrical signal that can be evaluated for automatic steering is not received. (Image: Mechanical pendulum for measuring changes in the angle of inclination [Stein87g]) |
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