Iron ore mine Konrad
| Konrad mine | |||
|---|---|---|---|
| General information about the mine | |||
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| other names | Konrad shaft | ||
| Mining technology | Underground mining | ||
| Funding / year | up to 700,000 t | ||
| Funding / total | 6.72 million tons of iron ore | ||
| Information about the mining company | |||
| Operating company | Ore mining Salzgitter AG | ||
| Employees | to 368 | ||
| Start of operation | 1957 | ||
| End of operation | 1976 | ||
| Successor use | Repository for low level radioactive waste | ||
| Funded raw materials | |||
| Degradation of | Brown iron / brown iron | ||
| Brown iron | |||
| upper camp | |||
| Mightiness | 0-10 | ||
| Raw material content | 30-34% | ||
| Greatest depth | 1,232.5 m | ||
| Brown iron | |||
| Degradation of | Brown iron | ||
| lower camp | |||
| Mightiness | 8-20 | ||
| Raw material content | 30-34% | ||
| Geographical location | |||
| Coordinates | 52 ° 11 '1.2 " N , 10 ° 24' 10.7" E | ||
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| Location | Bleckenstedt | ||
| local community | Salzgitter | ||
| Independent city ( NUTS3 ) | Salzgitter | ||
| country | State of Lower Saxony | ||
| Country | Germany | ||
| District | Peine-Salzgitter area | ||
The iron ore mine Konrad , today also Konrad called, is a former iron ore - mine in the north of the city of Salzgitter near the district Bleckenstedt . The ore deposit was discovered in 1933 during test drilling for oil in the Gifhorn area. Construction of the mine with two day shafts began at the end of 1957 and the ore was mined until 1976. Afterwards, the mine was examined for its usability for the emplacement of low-level radioactive waste and in 1982 it was found suitable. The mine has been converted into a repository since 2007 .
Deposit
The ore deposit in the Konrad mine is part of the Gifhorner Trough , which is 60 km long and 8 to 15 km wide and begins at Vorhop (district of Wittingen ) and ends in the Salzgitter-Hallendorf area . The Bleckenstedter special trough, which forms the actual ore deposit of the mine, is located at the southern end of this trough and begins around the Mittelland Canal . The ore deposit begins at a depth of 700 to 800 meters, dips to the west at approx. 20 ° and extends to a depth of 1400 meters. The thickness of the ore deposit is 4–6 m in the south and 18 m in the north, in the area of the pit it is between 12 and 18 m.
The ore deposit consists of oolithic brown iron from the Upper Jura and, at 150 million years old, is the oldest of the three ore deposits in the Salzgitter district. Bit younger, namely 120 million years old, the ore deposits at Salzgitter Hills are (pits Finke Kuhle , Haverlahwiese and Hannoversche loyalty ), the striping Heimer well ( mine grid-Georg ) and the ore deposits between Flachstöckheim and Hornburg with the pit Worthlah-Ohlendorf , the together form the actual Salzgitter ore . The youngest ore deposit contains Upper Cretaceous ores that were formed around 80–90 million years ago, such as those found in B. in the area of Peine , Ilsede and Lengede . These three ore deposits in the Salzgitter district are not connected to one another.
The iron content of the ore mined on Konrad is 30–34% Fe, the basicity is balanced with 12–16% SiO₂ and CaO each . The ore also contains an average of 5% alumina (Al₂O₃), 1.2% MgO , 0.39% phosphorus and 0.18% manganese . The raw ore was not suitable for wet mechanical processing , for further processing it was mechanically crushed and added directly to the blast furnace sinter.
Reservoir exposure
Since the camp, unlike the other deposits in the Salzgitter district, does not come to light, it was discovered very late. For the first time in 1933 a drilling for crude oil near the town of Calberlah in the district of Gifhorn produced evidence of iron ore, which was detected in depths of 661 to 666 m and 676-678 m. South of the Mittelland Canal, the camp was first detected in 1934 by the Bortfeld 1 borehole , here at a depth between 1172.6 and 1186.8 m. Further successful test wells on iron ore followed until 1936, such as Wendezelle 4 , Siegfried-Hillerse 9 and Vechelde 1 . The first small speculations on the iron ore finds were made in 1937/38 by the Reichswerke and the Ilseder Hütte . Extensive explorations for iron ore were carried out between 1938 and 1943 as part of the " Reichsbohrprogramm ", as a result of which 27 fields were muted and awarded to the Society for Practical Deposit Research (at that time a subsidiary of the Reichswerke, later PRAKLA ). In the autumn of 1943, the most important ore deposit to date was found near Bleckenstedt in the immediate vicinity of the Reichswerke ironworks at a depth of 967.9 to 986.7 m.
In the early 1950s, exploration of the deposit was intensified. In addition to Bergbau- und Hüttenbetriebe AG (successor company of the Reichswerke), Ilseder Hütte, Harz-Lahn-Bergbau AG and Barbara Erzbergbau AG also took part in the search for deposits. The Salzgitter AG and Ilseder hut founded in December 1954, the union Konrad , were involved in the two companies in half. The union was named after Konrad Ende , then Chairman of the Supervisory Board of Salzgitter AG. In order to avoid conflicts of interest between the ore-seeking companies, an agreement was reached on the Hanover-Wolfsburg railway line as the border; the area south of this line was awarded to the Konrad union. By the end of 1955, the Konrad union, which had its headquarters in Groß Bülten , had transferred 60 fields from Ilseder Hütte and 37 fields from Salzgitter Erzbergbau AG; these mine fields covered an area of around 160 km². From the start of the investigations in 1933 to the end of 1957, a total of 90 boreholes totaling 85.9 kilometers had been carried out.
Construction of the mine
On July 5, 1956, Salzgitter AG announced its decision to open up the ore deposit for mining . For this purpose, Salzgitter Erzbergbau AG leased the eight southernmost mine fields from the Konrad union. Specifically, these were the fields Bleckenstedt 2 , Hallendorf 1 , Engelnstedt 1 , Albert 1 , Hüttenberg 1 , Alvesse 1 and Üfingen 1 and 2 , these covered an area of 19.8 km².
The plans envisaged the construction of two day shafts designed for a daily production of 3000 to 5000 tons of raw ore. The mined ore should be added to the mixed sinter after being crushed in the sintering plant of the steelworks and fed from here to the blast furnaces .
Konrad shaft 1
The construction work for shaft 1 began on September 18, 1957 with the construction of a fore shaft with a diameter of 12 m. The shaft starting point was about 500 m northwest of the village of Bleckenstedt at a height of 98.5 m above sea level. NN . After the sinking structure had been set up, the actual sinking of the shaft began on May 3, 1958 . The work was carried out under the leadership of Vereinigte Untertag- und Schachtausbau (Veruschacht) GmbH and the participation of the Walter union from Essen (today Deilmann-Haniel Shaftsinking GmbH ). The shaft was designed for a clear width of 7 m, including the wall ring, the diameter of the excavation was 8.4 m. The lining of the shaft with concrete blocks was always continued when, depending on the strength of the mountains, about 18-25 m shaft tubes had been driven. For this work, a platform was carried in the shaft, which could be raised and lowered by a cable winch standing above and which was anchored to the masonry to secure it. To promote in the sinking work on the shaft bottom incurred mountains in the wall stage two closable stage openings were fitted through the mountains bucket could be brought to light.
During the sinking, the filling points of the 3rd, 4th and 5th levels were exposed at 1000, 1100 and 1200 m . On January 31, 1960, the final depth of 1232.5 m was reached. In the area of the shaft the ore was encountered between 1150.5 and 1184.9 m. Construction of the headframe began on November 23, 1959. The remaining manhole installations were completed by March 1960, after which the frame conveyor system for cable travel and ore extraction was installed. The conveyor baskets of the northern conveyor system of the double gantry frame received three support floors, each of which could hold 20 men or two small or one large conveyor wagons . A total of 18 tons could be conveyed per conveyor cycle. In the southern strand, a smaller rack conveyor system with a payload of 4.6 t load capacity was installed for goods transport and cable travel.
Konrad shaft 2
The starting point of the second shaft ( location map ) was determined on the site of the ironworks, between the areas of slag utilization and tar utilization. The shaft mouth was about 90.2 m above sea level. NN , this shaft was also given a clear width of 7 m. Test boreholes sunk between the end of 1959 and January 1960 showed loose mountains for the first 33 meters depth. It was therefore not possible to simply drill through this area as in shaft 1, because this would have lowered the groundwater level in the steelworks. The company Weyss and Freytag was therefore commissioned to sink this upper section using the “ sump shaft method with overpressure” ( caisson method) in order to prevent the groundwater from penetrating the shaft. This work began on March 1, 1960, and the permanent area was reached on July 29, 1960. On November 14, 1960, the working group of Veruschacht GmbH and the Walter union , which had also sunk shaft 1, took over the further sinking work , this time the Walter union was in charge . The work was completed on October 31, 1962 at a depth of 999 meters. This is where the third level was set.
In the mine building , shaft 2 had the function of an extending weather shaft . The shaft was also used for rope travel and was equipped with a single-section frame conveyor with counterweight that could accommodate 20 people or 2 cars each on two supporting floors. The shaft also served as a flushing shaft, through which the backfill material was brought in to fill the excavated excavation chambers.
Ventilation
In order to enable weather management to be carried out on site, an accompanying section with a smaller diameter was carried along when driving the main invert sections parallel to the straightening section and above the roof . The fresh weather was supplied via the straightening section, the used weather was discharged via the accompanying section. Furthermore, the shaft was provided with a weather separator along its entire length , through which the fresh and waste weather were separated from each other. Only in this way was it possible to provide adequate cooling on site, where the mountain temperature was 40 to 50 ° C. Because in spite of weathering and high temperatures locally was during for tunneling four-shift operation (working six hours each) worked in.
Alignment of the mine building
The horizontal alignment of the mine building began at the same time as the sinking work. Starting from shaft 1, the 3rd level (1000 m) was set in September 1959, the 4th level in October / November 1959 and the 5th level in January 1960. The work was accompanied by extensive sampling in order to gain further knowledge about the deposit and to plan ore mining. On the 5th level, around 1,500 analysis samples were taken from core drillings and channel samples, on the 4th level the sampling points were a little closer, so that around 2,000 analysis samples were obtained here. 2450 analyzes are available for the third level. The connection between the two shafts took place on the 3rd level, the section driven by shaft 2 broke through on January 24, 1963 with a cross passage driven from shaft 1 . This resulted in a significant improvement in weather management across the entire mine. In order to connect the lower-lying soles to the ventilation system, they were connected to the third level by several knocks .
For further investigation of the ore deposit, a second level was driven from shaft 2 at a depth of 900 m in 1963, which was connected to the rest of the mine building by hewing the third level.
Dismantling process
In roadway support steel arches were used to hedge initially. For cost reasons, it was soon decided to secure the routes with mountain anchors . At first, welded wire mesh was used, which were secured with adhesive or concrete anchors. From the 1970s the “anchor-wire mesh composite construction” was used, a combination of expanding sleeve anchors with wire mesh.
In order to backfill the cavities created by the ore mining, a gravel / sand mixture was used as backfill. The backfill material was extracted from a sand pit near Üfingen that was built for this purpose and temporarily stored on the site of shaft 2 on a dump with a capacity of 40,000 to 80,000 m³. From there it was brought into shaft 2 via drop platforms. At a level of 667 m, a water supply section for 3200 m³ of rinsing water was excavated, here the material was mixed with water and then piped to the former mining areas. The water was then collected in a swamp section of the 1100 m level and pumped back into the storage section for reuse.
Operation of the mine
To a small extent, ore mining began as early as December 1960 while the route was being driven. In the years that followed, ore was also mined alongside the layout and fixture work; by 1964, the ore production had increased from 75,300 t in 1961 to 235,263 tonnes per year. This was only possible by increasing the workforce, which had grown from 130 to 319 between 1960 and 1964. Most of the newly hired miners had previously been employed in other iron ore mines of Salzgitter-Erzbergbau AG and were laid off in their previous operations due to falling sales.
The choice of the mining method was based on the nearby Peine mine , as there z. T. comparable conditions existed. The procedure of the "floating chamber expansion building " was applied to Konrad . The actual mining started in 1965 on the 1000 and 1100 m levels. In 1966, the first year with continuous ore mining, production amounted to 472,237 t of ore. B. in the shooting process , through the use of more powerful crushers and the securing of the expansion exclusively by means of the anchor wire netting composite expansion, the conveying capacity could be increased to 669,214 t of ore by 1969 with almost the same number of employees (1965: 333 men, 1969: 317 men). With the introduction of loaders, the switch to trackless, rubber-tired vehicles at the beginning of the 1970s brought further improvements in conveyance . To increase the mobility of the machines, ramps and spirals were installed, through which the vehicles could change independently between different levels. Despite a decreasing workforce, in 1972 only 277 men were employed, the production could be increased slightly and this year reached 698,966 t.
Starting in 1974, the mining process was switched to the painting chamber construction . The dismantled cavities were no longer filled with an offset; instead, supporting pillars were left to secure . Compared to the previous conventional mining method, the moving times could be reduced to a third and the output increased from around 12 t to 19-20 t / man shift. The highest production of the Konrad mine was achieved in 1973 with 706,960 tons of ore despite the reduction in the workforce to 241 men.
After first attempts at the beginning of the 1970s, in 1976, before ore mining was discontinued, " cutting ore mining ", a process that was already successfully used at the Haverlahwiese mine . Instead of just common herauszusprengen the upcoming ore, it was now heading machines cut and then added with loaders and ore pass transported ( load-haul-dump process, LHD) from where it was conveyed to the shaft and day.
At the end of 1973 the economic situation for ore mining deteriorated. The consequences were a major downsizing - in 1975 only 119 people were employed - and a reduction in production, which sank by more than half by 1975 and this year was only around 283,000 t. In November 1974 the board of directors of Salzgitter AG had already suggested a possible closure of the mine. After the production had fallen again until August 1976, the ore mining was stopped on September 30, 1976. Since mining began in December 1960, 6.72 million tons of iron ore had been extracted from the Konrad mine.
Successor use
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In order to prevent the pit from being closed, Salzgitter AG had already started thinking in 1974 about using the pit as an underground landfill for waste after ore mining had ceased. At this time, the search for a suitable underground dump for radioactive waste began nationwide . In 1975 the Society for Radiation and Environmental Research (GSF) - today the Helmholtz Zentrum München - carried out initial investigations on Konrad, as a result of which the possible use of the pit as a dump for radioactive waste was considered.
After the ore mining stopped, the GSF, in cooperation with the Karlsruhe Nuclear Research Center, on behalf of the then Federal Ministry for Research and Technology (now the Federal Ministry for Education and Research ) started further investigations, which mainly dealt with the geological and mining conditions of the mine. The final report presented in July 1982 came to the following conclusion:
"At the end of the suitability tests, the Society for Radiation and Environmental Research concludes that the suitability of the Konrad mine for the final storage of low-level radioactive waste and decommissioning waste has been proven by the available results and the nuclear safety of the operation has been proven."
On the basis of this positive result, the Physikalisch-Technische Bundesanstalt (PTB), as the federal authority responsible for final disposal at the time, applied on August 31, 1982 to initiate the plan approval procedure prescribed by the Atomic Energy Act . To supplement the planning data obtained so far, an expanded site exploration program was started in 1982. In 1992 the mine became the property of the federal government, and the management was taken over by the German Society for the Construction and Operation of Repositories for Waste (DBE) . In 2007, the retrofitting work for the construction of the repository began. Since the concept provided for the delivery and storage of waste via shaft 2, the headframe and daytime facilities of shaft 2 were demolished and will be rebuilt. A temporary conveyor system was built at the beginning of 2008 to keep operations going. As far as we know today (2018), the repository will not be operational until 2027 at the earliest.
literature
- Heinz Kolbe: The history of iron ore mining in Salzgitter: Revealing history of the Konrad mine near SZ-Bleckenstedt . In: Geschichtsverein Salzgitter eV (Ed.): Salzgitter yearbook 1983 . tape 5 . Salzgitter 1983, p. 77-91 .
- Mining in Salzgitter . The history of mining and the life of miners from the beginning to the present. In: Office for History, Culture and Homeland Preservation of the City of Salzgitter, Editing: Heinrich Korthöber, Jörg Leuschner, Reinhard Försterling and Sigrid Lux (eds.): Contributions to city history . 1st edition. tape 13 . Appelhans, Salzgitter 1997, ISBN 3-930292-05-X , p. 238-258 .
- Ernst-Rüdiger Look : Geology, Mining and Prehistory in the Braunschweiger Land (= Geological Yearbook . Issue 88). Hanover 1985, p. 175-180 and 237 ff .
- Gesellschaft für Strahlen- und Umweltforschung mbH - Institute for Deep Storage - in cooperation with Kernforschungszentrum Karlsruhe GmbH - Institute for Nuclear Waste Management (Ed.): Suitability test of the Konrad mine for the final disposal of radioactive waste - final report . Munich 1982, deposit exploration and mine history Konrad , p. A1-1 through A1-39 .
- Federal Office for Radiation Protection (Ed.): Konrad repository. Knowledge creates trust . Salzgitter 2009, daily systems: figures, data and facts , p. 17-25 .
Web links
Individual evidence
- ↑ a b c d e Suitability test of the Konrad mine - final report 1982
- ↑ a b c d e f Mining in Salzgitter , pp. 238–258
- ^ Ernst-Rüdiger Look: Geology in the Braunschweiger Land , p. 237ff
- ↑ a b c d e f Heinz Kolbe: History of the exploration of the Konrad mine
- ↑ Chronicle of the renovation ( Memento from March 10, 2018 in the Internet Archive )
- ↑ Completion of the Konrad repository is delayed , Bundesgesellschaft für Finallagerung (BGE), March 8, 2018
