The Kohnstein in Thuringia with its 335 meters has a
turbulent history. The sulphate rock anhydrite has been minded there since
1917. Anhydrite is used, for example, in cement or screed.
Already in the 1930s anhydrite mining was no longer
viable. Mining work continued underground. This was the starting signal for the
widely branched underground mining gallery.
With some interruptions, anhydrite is still extracted
from the Kohnstein.
the Kohnstein – The historical significance of the Second World War
The British Royal Air Force bombed the Peenemünde
Military Research Centre on Usedom under the operational name “Hydra” on the
night of 17.-18. August 1943.
As a result, important parts of the development and research institute were relocated to the underground tunnels of Kohnstein. The weapons V1 (flying bomb Fi 103) and V2 (ballistic missile A4) were manufactured in Kohnstein from now on.
For this purpose, the gallery in Kohnstein was rebuilt
and expanded by prisoners of the nearby Mittelbau-Dora concentration camp. To
deliver individual parts into the tunnels and to remove the finished missiles,
railway tracks were laid inside the mountain.
Area of conflict between industry and monument
The remains of the Mittelwerk (tunnel system and
leftover materials such as rusted missiles parts) are flooded by the
groundwater today. Anhydrite continues to be mined at the Kohnstein. The
tensions between industry and the protection of historical monuments has
already been felt.
In 1992, for example, the mountain was sold to a
mining company, but not the tunnel system, which was classified as a historical
monument. A very difficult constellation.
Efficient monitoring of the mining gallery with IoT
In 2016, UTK Eco Sens installed a measuring system
with 5 measuring points to monitor the flooded parts of the former Mittelwerk.
Anhydrite mining is to be expanded in the coming years and new mining fields
are to be developed. However, the groundwater level is to be kept in order to
preserve the historically valuable area. For this purpose, in an approval
decision defined measured values must be made available to the authorities.
For the engineering office itself, further measured
values are of interest, which allow early intervention.
The lack of infrastructure in the underground mining
gallery is a challenge. For the 5 measuring sites, up to 40 meters were drilled
through the rock into a cavity. The sensors are connected to the GPS module on
the surface and s solar panels for autonomous operation of the measuring
measurement data collected centrally
Devices of the type myDatalogEASY V3 and myDatalogMUC
are used to measure and transmit the data to the central web platform. These
measure the data at defined intervals, store the values intermediately on the
device and send the collected data at regular intervals to the central
platform. An alarm is automatically sent if a value falls below a defined threshold.
The data is made available to various interest groups
via the online platform and FTP. An extensive right management helps to realize
If you know
earlier, you can react earlier
Two of the five measuring points generate officially
relevant data. Only two chambers are affected by the requirements of the
authority and have a minimum water level which is not allowed to be fallen
For example, precipitation events can be detected more
quickly in one of the chambers than in the others. This is due to the different
permeability of the soil material. These values are relevant to identify
potentially critical situations at an early stage and thus increase the scope
The IoT monitoring of the mining gallery in Kohnstein
protects the interests of industry and monument protection. The groundwater
level for the protection of the historically relevant parts of the tunnel is
measured automatically. While the anhydrite extraction area is being
continuously expanded, it is ensured that the extraction has no influence on
the groundwater level.