Raise boring

from Wikipedia, the free encyclopedia

Raise boring is a drilling method with which a circular shaft is drilled along a pilot hole from bottom to top . The process is a fully mechanical rod drilling process that is suitable for shaft-like structures with medium depths. Raise boring was developed for ore mining in North America in the 1950s. It is currently the most economical method of building manholes.

equipment

A raise-boring machine is required to produce holes using this method. The raise-boring machine is set up on the upper level. The machine can be equipped with two different drill heads , a smaller drill head for the pilot drilling and the raise drill head. The raise drill head is also known as the reamer. The drill head for the pilot hole has a diameter of up to 311 millimeters. The drill head consists of several roller bits. The raise drill has a diameter of up to six meters and is equipped with multi-stage chisels. Depending on the type of rock, this extension drilling head is equipped with differently designed tapered rollers. In order to be able to correct the direction during the drilling process of the pilot hole, modern drilling machines are equipped with an automatically controlled target drilling system. This target drilling system consists of a target drilling unit located directly behind the drill bit, several transducers for inclination measurement, the control electronics and the control hydraulics. In order to be able to correct the target boring bars in the horizontal plane during the drilling process, the target boring bars have control runners that can be hydraulically extended. To determine the exact direction of the drilling, the target drill rods are equipped with a pulse generator that sends the measurement signals to the machine's control station via the flushing water flow in the drill string. All measured values ​​from the function monitoring are also transmitted wirelessly to the machine's control station. The measuring system of the target boring bar, known as an inclinometer, works with two electronic spirit levels. These spirit levels are arranged crosswise and are used for precise drilling.

Drilling work

Before the actual drilling work can begin, the starting point of the manhole must first be driven under with a pit . This enables access to the later shaft foot. In addition, this creates a reservoir chamber for the cuttings and at the same time an assembly chamber for the raise drill head. The actual drilling process then takes place in two steps, the creation of the pilot hole and then the creation of the expansion hole.

Pilot hole

A precise pilot bore is a prerequisite for the success of the raise bore. This is why the pilot drilling is always a major risk when drilling holes using raise boring. Inhomogeneity and anisotropy of the rock play a major role in the accuracy of the pilot bore . Due to steeply dipping layers with differently hard rock, deviations in the pilot bore can occur. Further influencing factors for the accuracy of the drilling are technical requirements, such as the rigidity of the drill pipe and the diligence of the drilling team. The drill head is pressed into the rock with high pressure while rotating. The pilot hole must be large enough to accommodate the drill pipe for the expansion hole. Through the use of electronics, the drilling process is constantly monitored for directional accuracy and corrected if necessary. When drilling, small pieces of rock are broken out of the rock. The cuttings are flushed with water to the starting point of the borehole and deposited there.

Expansion hole

When the pilot borehole has reached the deeper level, the drill head is removed, a raise drill bit of the desired size is attached and the pilot borehole is drawn from bottom to top and widened accordingly. The expansion drill head is rotated at a low speed , which is up to 15 revolutions per minute with a drill head diameter of 1.52 meters . With a drill head diameter of five meters, the speed is up to four revolutions per minute. It is important that the drill head runs smoothly. The maximum drill head diameter that can ultimately be used depends on the depth of the shaft and the load-bearing capacity of the drill rod. The cuttings do not have to be flushed upwards out of the borehole, but rather fall down and can be conveyed away if necessary . Since the cuttings fall down due to gravity without the addition of water, there is less wear on the drill head when it is pulled up than in the other direction. Nevertheless, tensile forces of over a thousand kilonewtons act on the drill rod when the drill head is pulled up. The drill head and the drill rods are stabilized on the shaft wall by runner stabilizers. This creates a smooth borehole wall in the rock. The shaft lining will be installed after the drilling has been completed. Often no fastening or borehole expansion is required.

application

With the raise boring shafts with a diameter of up to six meters are created. A stable rock is a prerequisite for using this process . The maximum depth with this method is 1200 meters. Application examples are blind shafts that serve as underground connections between two routes in a mine , or connections between a mine and the surface of the earth . The raise-boring procedure was used as one of several variants in the rescue of the accident victims in Chile in 2010.

variants

Based on the basic procedure - pilot drilling, then widening - there are different variants of raise boring, some of which have their own names. In this way, boreholes can be inclined or made almost horizontally, or the pilot borehole can be created from bottom to top and then widened from top to bottom.

Individual evidence

  1. ^ Walter Bischoff , Heinz Bramann, Westfälische Berggewerkschaftskasse Bochum: The small mining dictionary. 7th edition, Verlag Glückauf GmbH, Essen 1988, ISBN 3-7739-0501-7 .
  2. ↑ a b c d e f Peter Schmäh, Benjamin Künstle, Nobert Handke, Erhard Berger: Further development and perspectives of mechanized shaft sinking technology. In: Glückauf 143, trade journal for raw materials, mining and energy. No. 4, VGE Verlag Essen, Essen 2007, ISSN  0340-7896 , pp. 161-172
  3. ↑ a b c d Ernst-Ulrich Reuther: Textbook of mining science. First volume, 12th edition, VGE Verlag GmbH, Essen 2010, ISBN 978-3-86797-076-1 .
  4. ↑ a b c d e f Dimitrios Kolymbas: Geotechnical tunnel construction and tunnel mechanics . 1st edition, Springer-Verlag, Berlin Heidelberg New York 1998, ISBN 3-540-62805-3 .
  5. ↑ a b c d e f g h i Rene 'Dorrer: Successful raise drilling. In: Gasser Felstechnik AG (ed.): Felssplitter, in-house magazine of Gasser Felstechnik AG and Explosiv Service SA, No. 36, Lungern 2010, p. 9.
  6. ↑ a b c d Tulla Puhakka: Underground Drilling and Loading Handbook, Tamrock Corporation, Finland, 1997, pages 186-187.
  7. ↑ a b c d e f g h W. Dachroth: Handbook of building geology and geotechnics. 3rd expanded and revised edition, Springer-Verlag, Berlin Heidelberg New York, ISBN 3-540-41353-7 .
  8. ↑ a b c d Ulrich Smoltczyk : Grundbau-Taschenbuch. 6th edition, Verlag Ernst & Sohn, Berlin 2001, ISBN 3-433-01446-9 .
  9. ↑ Horst Roschlau, Wolfram Heinze: Bergmaschinentechnik . Ed .: SDAG Wismut. 1st edition. German publishing house for basic industry, Leipzig 1976, 10.5.3. Machines for driving vertical and inclined mine structures, p. 206-209 .
  10. ^ The Raise Boring Concept. (PDF) (No longer available online.) Atlas Copco Rock Drills, archived from the original on February 4, 2014 ; accessed on February 10, 2014 .

Web links