In the Elbingerode mine, the upper part of the 1/27 mine is to be completely mixed with a GesbergV approved offset building material (dam and backfill material with SR cement in accordance with DIN EN 197-1 and limestone powder in accordance with DIN EN 13139). The required building material is to be delivered dry by silo vehicles, processed into a suspension by a mixing and pumping mobile and pumped into the pit.

Access to the mine's lawn suspension bench is guaranteed via the Fels-Werke plant road. The installation site for the silo vehicles is a place in front of the shaft hall of the central shaft. The delivery must be made with horizontal boiler vehicles. The removal must be through a rear discharge.

Tonnage approx. 27 to/silo train. The unloading time is approximately 1.5 hours per silo train.

1 General basics

The Lusatian and Mitteldeutsche Bergbau-Verwaltungsgesellschaft mbH, potash ore area, intends to carry out another batch section in the Elbingerode mine, the complete custody of the mining in 1/27.

The mentioned mining is a mining cavity that was created in expansion construction. The heavily mineralized areas were recovered from the 1st sole by means of overcutting. By means of magazining, a work plane was created on which it was possible to drill off the ridges. The mining has an average height of 10 m and is expanded to the mineralization limit (lime roof).

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2 situation on the dismantling 1/27

The free height from the floor to the ridge is currently still a maximum of 6 m.

Water containment is still operated, with the level being kept as low as possible.

Nevertheless, at the beginning of further removal, the offset material must be pumped into the accumulated water.

An acidic environment must be taken into account. Analysis of the water still present in the partially offset decomposition showed a minimum pH value of 4. Other parameters include:

• chloride content of approx. 250 mg/l,

• sulfate content of approx. 1,300 mg/l,

• iron content (total) of approx. 50 mg/l,

• Manganese content of approx. 25 mg/l.

These environmental conditions must be taken into account for the material to be delivered and its subsequent properties.

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3 Technology of offset installation

In the first step, a further reflection of the sole is to take place.

As in the previous batch sections, the batch material is delivered on site in a mixed, dry state by means of silo vehicles. Water is added to the dry building material via a mobile mixing and pumping vehicle, mixed and guided to the zero floor level via 63 PE hose lines (internal diameter=50 mm) in the central shaft. On the empty side of the filling location, the hose is guided in the direction of the “Upper Mühlentalstollen” to the belt section and is guided there to the edge of the slope via a travel overhang for removal 1/27. The hose lines are laid vertically for approx. 60 m and then approx. 230 m horizontally.

During the further reflection up to the upper edge of the slope, the offset hose is intercepted on trestles.

Once the offset level of approx. 419 m above sea level has been reached, construction is halted on schedule for approx. 3-4 weeks. In addition to routing the flushing hoses to the high points, branches are also installed, which are required for flushing the inaccessible widening areas.

During storage, the building material must be used with a high density (δ≥1.6 g/cm3). However, the possibilities of the mixing and pumping vehicle must be taken into account.

The offset material must be evenly distributed on the removal floor, and at the same time the added water must be lifted to prevent mixing and separation.

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4 Other aspects

The work must be carried out outside the bat protection period from April to September 2022

With the submission of the offer for its building material, the contractor must attach the approval according to GesbergVO. In addition, the properties of the building material must be verified by at least 3 laboratory tests before starting the batch work.

- uniaxial compressive strength after 3, 7 and 28 days,

- cylinder compressive strength of at least 2 N/mm2 after 28 days,

- water/solids ratio,

- strip-off dimensions,

- Permeability coefficient (CF value) not exceeding 6.5 e-11,

- Non-elutability in pit water provided by the client.

For the verification of the parameters mentioned above, the client will provide preparation water.

The building material must demonstrate high sulfate resistance (according to cement standard EN 197-1).