With the increase of the depth of extraction the conditions of excavations maintenance become worse.
The problem of firmness maintenance and increase behind a production face is topical not only from the position of
their re-use but also for providing uniflow ventilation, because reverse-flow ventilation does not allow to create
high load on a longwall in terms of gas factor.
In difficult mining-geological conditions the expenses on excavations maintenance increase,
nevertheless many of them are in a satisfactory conditions. Upheaval and not satisfactory carrying capacity of
frame metal structures result in often repairing works with the face maintenance, decrease of labour efficiency,
increase of coal cost price and decrease of labour safety. That is why it is necessary to research this problem in
order to use more efficient ways of mine workings protection, as well as methods of the rock massif management,
which would be economically efficient and competitive for particular mining and geological conditions of the seam k8
of Zasyadko mine.
Stratigraphic record of the seam is given in picture 1.
Picture 1 - Stratigraphic record of seam k8 and bearing strata.
Protection of a conveyorway at the mine is accomplished with the help of 3 lines of BGBT (picture 2).
Picture 2 - Protection of the re-used mine way BGBT.
Let's consider the application of different protection methods of extraction workings in the conditions similar to seam k8 of Zasyadko mine.
At the mine named after Bazhanov of the association "Makeyevugol" the longwall was worked according to allwork development system
The distance between lining frames was 1 m. extraction was done by combine 4PP-2 together with scraper ZU to put rock into packs [1].
Workings developed behind the production face were in good condition and were successfully re-used.
On the basis of this experience it is possible to consider allwork behind the production face as environmentally friendly, which allows to solve one of the most important questions - leaving of the rock in the face.
At mine "Sukhovskaya" PA "Torezantratsit" coal pillars were replaced by two continuous
rows of concrete poles which were installed after the conveyor advancing by 1.5 m from the lining base.
Concrete poles were not deformed. Maximum compression of the wooden block filler was 78 mm. pillars that
were installed without wooden fillers were completely demolished. Air leak was the same as with coal pillars.
Displacement was only 200 mm. Maximum speed of the roof displacement was 3.2 mm a day.
At mine ¹12 "Naklonnaya" Donetskugol in seam h4 the working was protected by hard
stripe on the basis of phosphogypsum astringent. The saving rate made 26 roubles (in prices in 1986) per 1 m of
the supported working. Industrial check showed that this method is efficient for production faces support in the
described mining and geological conditions. They can be recommended to the wide use.
"Komsomolets Donbassa" mine of the association "Shakhtyorskantratsit" develops seams l4 and l7. Seams
thickness is 1...1.1 m, angle of dip 5...10?.
Belt headings supported at the border with the developed space were originally protected with the help of artificial
construction - BGBT combined with sheathing [4].
Considerable displacement was in belt headings while supporting them with two rows of BGBT with wooden .
For the conditions when in the bed top there is soft rock workings support with BGBT pillars is not efficient. BGBT pillars are efficient in the conditions when the top and floor of the bed are hard rocks.
With the deepening of the development of the seams at "Sverdlovantratsit" the support of development workings led to increase of coal loss and not always guaranteed their satisfactory condition during a long period of operation [5].
Picture 3 - Development of the working with partial superposition of the coal massif.
During developing second workings at adjacent mining blocks there appears movement of the
earlier developed rock mass. This leads not only to increase of displacement, but also to asymmetrical pressure on the
lining, which results in movement of its vertical axis towards the coal massif or pillars.
Experience at mine "Kuznetskaya" "Kuzbassugol" has shown that with free caving roof it
is possible to support the development workings behind the longwall with the help of pressing lining (Picture 4).
This method was examined at Lenina mine "Voroshilovgradugol". Industrial test showed that with this supporting method
at the experimental part there was ensured overhaul support of the block. Displacement of the working boundary made from
the roof - 350 mm, floor - 300mm, sides - 500mm.
Picture 4 - Conveyor cundy supported by the displaceable lining of GSK-9 pillars.
In the certificate of authorship [7] the following supporting method is suggested - after the seam extraction the thrust lining is constructed at the border of the support stripe, which is characterized by the fact that before the construction of the support stripe with the help of the thrust lining the even indentation of the edge roof rock with the pressure 1500-3000 kH/1m is carried out with the aim of decrease of support expenses and labour safety increase.
Picture 5 - Scheme of the stripe construction with the preliminary thrust.
The suggested method will allow to decrease expenses on the workings support and to increase
labour safety. The application of this method prevents rock foliation, thus decreasing the pressure on the lining
and supporting construction. That is why this supporting method is perspective in Donbass.
Thus, summarizing all the said above we can conclude that for the
conditions of seam k8 the following methods can be applied: pack,BGBT, hard stripe of phosphogypsum astringent, sheaves.
