Break of day

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Pinge after the break-in of an old mine tunnel in Herbolzheim (Breisgau)
Eruption of the Elura mine in Australia

A daybreak (also: Tagebruch , Tagbruch ) is a mountain damage that breaks through after fractures in the subsurface to the surface of the earth (called in the miner's language " day " ). There the damage is often visible through cracks or crater-like collapse funnels (" pings ") . Day Breaks usually occur by the collapse of old, not backfilled mine s stollen and - shafts and are therefore particularly common in mining regions.

Basics

Day Breaks very similar to the caused by natural processes in their effects sinkholes . This is due to the fact that both events are based on the same geomechanical laws. However, day breaks are not caused by naturally occurring cavities, but by man-made cavities, such as. B. in mining. Areas in which cavities have emerged or have been created at shallow depths are particularly at risk for daybreak. If there are surface layers above these cavities that are not permanently resistant, the surface of the surface will collapse under certain conditions. This fracture of the surface of the day, the daybreak, represents the end phase of the breaking process known as the high fracture process.

However, not every cavity created by mining inevitably leads to a daybreak. In order for a fracture process to penetrate from the bottom to the top, the overburden on the one hand does not have to be stable enough and on the other hand there must be insufficient cover. An underground expansion that is no longer viable also has a disadvantageous effect . Due to the pressure of the mountains , this expansion will collapse over time.

In near-surface mining, where the surface layer of the mine workings is less than 30 meters, the existing hazard potential is unlimited. In near-surface mining, the surface layer is at least 30 meters. These mine workings remain open for a long time due to the relatively thin cover layer and the resulting low rock pressure, so the potential hazard remains for decades. All mine workings with depths over 100 meters are referred to as deep mining . Here, ground movements can be recognized within 5 to 10 years due to converging mine workings on the surface of the earth due to subsidence .

Development of daily breaks

If an area of ​​the pit that has become unstable collapses as a result of quarrying or weathering, such a collapse can work its way to the surface of the earth over time. This can lead to subsidence, which can be seen on the surface as depressions, for example. These subsidence are up to 15 m in the Ruhr area and can lead to swamping of the landscape, as the surface water can no longer be drained off naturally. In extreme cases, the earth and rock masses break through on the surface and plunge into the underground cavities. A deep crater, a so-called pinge , then forms . Further day breaks can occur if inadequately stored manhole closures fail and the masses above fall into the still open manhole.

The risk of day breaks depends on the following factors:

  • Depth of the cavity
  • Volume of the cavity
  • Strength of the rock, in which the cavity ascended was
  • Thickness, strength and weathering properties of the overburden layers
  • Hydrology
  • Loosening factor of the rock
  • Tectonics of the subsurface

Source:

Day Breaks are mainly in the southern part of the Ruhr area in front where the mining of coal took place near the earth's surface and a massive overburden was missing over the seams. Another and very dangerous type of daybreak is the collapse of a thrown shaft that was insufficiently filled after the end of mining .

Fracture behavior

Depending on the nature of the overburden, day breaks have two different breaking behavior. On the one hand, the break can occur spontaneously, but on the other hand it can also occur with a delay. In most cases, a daybreak happens spontaneously, so that it comes to light in full size in a short time. This makes the hernia funnel immediately visible. In the event of a delayed break in daylight, only a small drop hole appears on the surface of the earth, so that the entire dimensions of the fracture funnel are not visible at the beginning. Only after some time does the loose earth fall back, so that the full damage becomes visible.

Area of ​​action

An area of action is an area on the surface of the surface that has been adversely affected in its properties and functions due to the action of the old mining near the surface. A future impairment cannot be ruled out in the area of ​​influence. Within the area of ​​action, starting from the tunnel axis outwards, the surface of the day is at risk of subsidence, collapse and even collapse. In the 1970s a start was made to examine and evaluate all damage events known up to that point. A calculation method for the size of the impact area was developed from the findings of the evaluations of the damaging events. For the calculation of the dimensions of the area affected by the surface ( EB ), the thickness of the overburden above the route or tunnel floor ( ), the tunnel or route width or length ( ), the strength of the route extension ( A ) and the depth of the rock line ( ), also known as the depth relevant to the action. The depth relevant to the action can be determined with the help of a nomogram created by Messrs. Hollmann and Nürenberg. For the calculation, a critical angle of 50 gon for the overburden and the backfill and 70 gon for the carbon mountains is used, and a safety distance ( S ) of 1.5 meters around the shaft diameter ( ) is taken into account in the calculation . The area of ​​action is calculated according to the formula:

If the tunnel width is just as large or even smaller than the tunnel height in a tunnel excavated in rocks and the rock cover is at least four times the tunnel height, then the area of ​​this tunnel is stable at the surface of the day.

hazards

If the daybreak occurs after a delay, the risk of break-in is very high, as the areas around the break funnel are usually already loosened and sag under load. The greatest dangers of day breaks are that the affected areas usually collapse suddenly. This is particularly dangerous for humans if the daybreak occurs in areas that are inhabited or otherwise used by humans.

Security

When a daybreak occurs, the area is cordoned off by the police as the first security measure. Then, sometimes at the same time, the population is informed of the incident. The danger zone is usually guarded by security personnel until the security measures have been completed in order to prevent so-called disaster tourism.

A team of experts then examines the break in the break and the affected area and assesses the damage. The areas are analyzed and the cavities are geodetically measured. The condition of the supporting structures and the existing cavities are examined with regard to stability and the individual areas are divided into hazard classes. The other security measures are discussed and implemented. As security measures, depending on the damage and local possibilities, tissue support pillars, so-called Bullflex pillars, are introduced and filled with concrete or the cavities are completely filled with so-called lightning dams. These activities are monitored with so-called field spies to monitor any persistent deformations of existing residual pillars . These measuring probes are installed in crevices and crevices and can register even the smallest movements of a few thousandths of a millimeter. This means that further movement activities in the mountains are monitored.

early detection

An abundance of measures is used for the early detection of day breaks. Thus, by the Markscheider old maps and plan works evaluated the mining operator to obtain data about former mines. So-called deposit projections of areas at risk of collapse are created from the collected data. The results of these calculations are forwarded to the responsible mining authorities for further technical evaluation.

The available data is used to better assess existing hazards. Using the statistical analysis of day breaks that have already occurred, empirical models are developed with which day break events can be better assessed. Using these empirical formulas, variables such as the relative probability of breakage at the surface of the day, the diameter of the day break, the break distance and the break time can be better determined. Based on the parameters obtained from the evaluated measurements of the old events and the data, analytical models are set up. These calculation approaches can be used for a practice-oriented risk assessment. This makes it possible to determine the probability of the daybreak occurring and the extent of damage to be expected.

Examples

Some examples of known day breaks:

  • In 1977 an uncontrolled water ingress caused a disused rock salt mine in Wapno (Poland) to collapse. In the daybreak that lasted until 1978, the entire center of Wapno with 53 houses and a railway station sank . 1402 people were left homeless.
  • In 1992, a daybreak occurred in the immediate vicinity of a hospital in the Rhineland, which was so great that the hospital was completely destroyed. The fact that no one was hurt, one is Steiger thanks to the slate quarry. He had heard unusual noises underground and immediately informed the public order office, which ordered the evacuation of the hospital.
  • On July 17, 1998 in Lassing (Styria) a collapse of a mine caused a 50 m wide and 30 m deep break in the day in which a house sank and a lake formed. It was the worst mining accident in Austria in the post-war period. Eleven miners had an accident when the pit collapsed, only one could be rescued after nine days. The pinge was filled in about two years after the accident.
  • On January 2, 2000, the Höntroper Loch opened in the middle of a residential area in Bochum , the possible expansion of which threatened an entire housing estate and an S-Bahn route. Although security measures began immediately and hundreds of cubic meters of concrete were pumped into the hole, some houses had to be abandoned. The cause of the daybreak was an accident a hundred years ago during backfilling work on a former shaft of the Maria-Anna coal mine . A shaft frame had collapsed at the time and got stuck at a depth of about 40 m. As a result, the shaft could not be filled in properly. The event was forgotten and was not taken into account when the housing estate was built. The subsequent backfilling cost approx. 12 million DM.
  • In 2004 day breaks on the Siegener Rosterberg became known nationwide under the name “ Siegener Loch ”. Old cavities and tunnels in the Hohe Grethe mine had collapsed and resulted in four day breaks. The securing work lasted about a year, 22,000 tons of material were pumped into the mountain.
  • Another daybreak was noticed in February 2008 in a vineyard near Herbolzheim (Breisgau). Here a tunnel of a former ore mine had broken through to the surface. Due to the imponderability and the risk of further break-ins, a large area around the break was permanently cordoned off.
  • In 2008, a daybreak occurred on Landstrasse 231 between Wettelrode and Morungen , caused by the collapse of a shaft.
  • An example of a by Subrosion caused or aggravated days fraction is in the landfill Zepzig occurred day break. Here the pits of an old potash mine (Friedenshall / Solvayhall) are further leached by groundwater.

Individual evidence

  1. ↑ Bergstadt Schneeberg: Der Tagbruch ( Memento of the original from April 2, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (last accessed on October 8, 2012). @1@ 2Template: Webachiv / IABot / bergstadt.eu
  2. ↑ a b A.H. Goldreich: The ground movements in the coal field and their influence on the surface of the day. Published by Julius Springer, Berlin 1926.
  3. ^ G. Meier: sinkholes and day breaks - possibilities of numerical modeling. Online (last accessed on October 8, 2012; PDF; 1.4 MB).
  4. ↑ Practical note: Is the subsoil safe? - The old mining situation in North Rhine-Westphalia ( Memento from May 25, 2010 in the Internet Archive ) (accessed on October 8, 2012; PDF; 244 kB)
  5. ^ Helmut Kratzsch: Bergschadenkunde. 5th updated and revised edition, Papierflieger Verlag GmbH, Clausthal-Zellerfeld 2008, ISBN 3-00-001661-9 .
  6. ↑ Fenk, J., A theory on the origin of day breaks over cavities in the Locker Mountains, Dissertation B, Freiberg 1979.
  7. ↑ Fritz Heise, Fritz Herbst: Textbook of mining science with special consideration of hard coal mining. First volume, published by Julius Springer, Berlin 1908.
  8. ↑ a b Michael Clostermann: Old mining and land-use planning: How to deal with the legacies in the past - today - tomorrow ? Geokinematic Day Freiberg 2009.
  9. ↑ a b Dangers from relics of old mining (civil engineering) . Online (last accessed on October 8, 2012; PDF; 20 kB).
  10. ↑ Günter Meier: Recommendation “Geotechnical-mine-separating investigation of old mining” . Online (last accessed on October 8, 2012; PDF; 178 kB).
  11. ↑ Edward Popiołek, Zygmunt Niedojadło: The application of geophysical methods in the solution of old mining problems. Online ( Memento of December 29, 2010 in the Internet Archive ) (last accessed on October 8, 2012; PDF; 441 kB).
  12. ^ Wismut GmbH (Ed.): Environmental Report 2010 . Chemnitz 2010, pp. 10-17.
  13. ↑ State Office for Geosciences and Natural Resources Brandenburg (Ed.): Performance balance 2002. Kleinmachnow 2003.
  14. ↑ Günter Meier: Geotechnical and mining documentation for safety and remedial measures in old mining. Online (last accessed on October 8, 2012; PDF; 2.9 MB).
  15. ↑ Dieter D. Genske: Engineering geology basics and application. Springer Verlag, Berlin Heidelberg 2006, ISBN 978-3-540-25756-1 .
  16. ↑ diepresse.com: Ten years ago the earth opened in Lassing ( Memento from August 30, 2010 in the Internet Archive ).
  17. ↑ Melanie Niese: Dealing with mountain damage in the southern Ruhr area. Dissertation at the Ruhr University, Bielefeld 2010.
  18. ↑ Like a Swiss cheese: mountain damage in South Westphalia Siegerland ( memento from June 29, 2007 in the Internet Archive ) (accessed on October 8, 2012) (last accessed on October 8, 2012)
  19. ↑ Break in the day on the L 231 highway between Morungen and Wettelrode near Sangerhausen ( Memento from September 13, 2012 in the web archive archive.today )
  20. ^ The potash and rock salt pits in Germany. 6.31 HALL OF PEACE (SOLVAYHALL)

Web links

Commons : Daybreak  - collection of pictures, videos and audio files