Educational film for students of mining technical schools. Methods of managing the roof of mine workings during coal and ore mining are examined in detail.
Industrial landscape.
Slag heap.
Cartoon explaining the pressure in the ground above mine workings.
When driving workings, supporting pressures arise in front of the face, a collapse zone and a subsidence zone in the roof layers, a heaving zone in the soil layers.
Manifestations of rock pressure.
Cartoon explaining methods of combating these manifestations.
The squeezing of coal caused by the supporting pressure facilitates mining.
Work of a combine.
To relieve the supporting pressure of the roof rocks on the face, the overhanging layers of the roof in the mined-out space are collapsed.
Miners leave the face to allow such a collapse.
The support reliably protects the space along the face from collapse for the safe passage of people and ensures the operation of mining machinery.
Miners regulate the movement of rocks lying in the roof, supporting it in one place and deliberately collapsing it where there is no need to preserve the workings.
This is roof management.
Three types of roof.
Cartoon explaining each type.
The false roof collapses simultaneously with the development of coal.
The immediate roof collapses after the removal of the lining.
The main roof collapses after exposure over a large area.
The pressure on the lining increases.
It happens that when the immediate roof collapses, the entire space from the soil to the main roof is filled.
In such cases, the collapse of the main roof is weak.
Cartoon explaining the concept of a flat and inclined seam.
The choice of roof management method in flat and inclined seams depends on the thickness of the seam and the immediate roof.
In the first class, the thickness of the immediate roof is equal to and exceeds six times the thickness of the seam being developed.
In this case, complete destruction is used.
In the second class, the thickness of the immediate roof is less than 6-8 times the thickness of the seam, so the collapsed rock of the immediate roof is not enough to fill the mined space.
Then dangerous manifestations of secondary settlements are possible.
This danger is prevented by laying rubble strips.
With the width of rubble strips of 5-6 m and intervals of 8-16 m, roof management is carried out by the method of partial caving.
A smaller distance is also left between rubble strips, 3-4 m.
Such roof management is called partial backfill.
The roof descends freely without caving.
With the third class, the roof is almost absent.
The roof is also controlled by the method of partial backfill.
A coal mining combine is in operation.
Modern mechanized metal supports have changed the technology of roof management on flat seams.
Such supports allow the use of complete caving of roof rocks not only of the first, but also of the second and third classes.
The last, fourth class includes roof rocks that descend smoothly, without caving.
Wooden supports.
Roof management passport.
The passport provides a technical solution for roof management.
Coal mining, Fortification, Coal seams, Roof of the workings
A fragment of a specific roof management passport is considered.
The caving step in this longwall is equal to two shearer grips.
After removing the second chip, the OKU pedestals are moved to the caving step, the metal support in the caving zone is removed, and the roof collapses.
Longwall 55 of the Cherkenskaya Yuzhnaya mine of the Kuzbassugol combine.
The shearer is moved to a new grip.
The conveyor is moved.
The miners strengthen the longwall with metal posts and tops, hingedly connected to the tops of the previous grip.
To prevent rock falls, the roof is tightened with slabs.
The shift supervisor and the mining foreman constantly monitor compliance with the technical conditions for securing the longwall.
In addition to the metal support, wooden control posts are installed in the longwall.
Conveyor with coal.
The roof setting process usually begins with removing the face support and moving it behind the new caving line.
If the roof rocks of the longwall face are of the first class, the roof is controlled by collapsing the OKU pedestals onto the landing legs.
A hand winch is used to move the landing legs.
After lifting the main screw and securing it with a wedge, the initial thrust of the leg between the roof and the soil is created with the adjusting screw.
The roof rocks in the longwall face are strong, and if a large area of exposure is allowed, the collapse may be caused by an air strike.
To avoid this, the control legs remaining in the collapse zone are blown up with special spark-proof cartridges.
Explosion and collapse of the roof.
After the explosion, the face is ventilated and after 30 minutes the miners begin mining coal.
The choice of roof control method on steep seams, the angle of incidence of which is from 45 to 90 degrees, also depends on the stability of the soil.
Cartoon showing the collapse of the roof in steep seams and the sliding of the soil in the near-face space.
Particular attention is paid to the reinforcement of the developed space.
The working faces are secured with rows of posts located strictly according to the dip, and fire support.
The posts are never knocked out, and fire support can be moved.
Complete caving is used in the case of an easily collapsing roof, exceeding five times the seam thickness.
The soil should consist of stable rocks, not prone to sliding.
Longwall.
Mechanized knocking out of supports.
Complete caving is safer and more economical on steep seams, where shield support is used.
The shield reliably protects the longwall from collapsed wall rocks.
On thin steep seams with elastic roof and soil rocks, the previous method is used - smooth lowering.
If the wall rocks of the seams are unstable, then it is preferable to hold the roof on fires.
Miners disassemble the material to build fires.
The material is fed into the longwall.
The miner works in the middle of the fire support.
In case of unstable wall rocks, as well as to reduce coal losses and decrease the risk of spontaneous coal combustion, roof management is used by completely filling the mined-out space.
Coal mining, Fortification, Coal seams, Roof of the workings
Kuzbass
Lava 55 of the Cherkenskaya Southern mine of the Kuzbassugol plant.
Backfilling of mined-out spaces.
Sand, gravel and crushed rock are used as backfill materials.
Crushed rock is obtained by blasting.
A quarry for mining backfill materials.
The rock is delivered to the crushing plant in wagons.
Depending on the backfill conditions and the nature of the rock itself, it is crushed into pieces of a certain size.
Shield crusher.
Screening process.
Small and large fractions are sifted out.
Large fractions undergo additional crushing.
The finished backfill material is sent for loading.
Depending on the method of transporting and placing materials in mined-out spaces, the following types of backfilling are distinguished.
Hydraulic backfilling.
Wagons with backfill are delivered to the mine and unloaded into the underground bunker of the backfilling complex.
The command to the face about readiness.
Conveyor with backfill material.
The sifted material is washed away with water and flows down the concrete floor of the mixing bin into the loading funnel of the pipeline.
The pulp is directed to the filling mass.
A cartoon showing the hydraulic filling process.
Gravity filling.
The material is delivered to the mine in wagons and poured into the bunker.
A cartoon showing the gravity filling process.
The massif shrinks greatly during gravity filling.
During pneumatic filling, the rock is fed by a conveyor to the filling machine, which uses compressed air to feed the filling material into the pipeline.
A cartoon explaining pneumatic filling.
Roof control during ore mining is carried out in the same ways as during coal mining.
However, other methods are also used in mines.
A cartoon explaining the use of spacer lining in steep, low-power deposits with stable wall rocks.
A cartoon explaining the use of reinforced spacer lining.
A cartoon explaining the use of shrinkage.
A cartoon explaining the use of sublevel forced caving.
A cartoon explaining the use of a room and pillar system.
This system makes it possible to use powerful self-propelled equipment with high productivity.
Bookmarking of mined-out space, Bookmark material, Mines