Vladimir ARTAMONOV,
Yevgeny NIKOLAYEV

Source: Collection of reasons of the Ostrava technical university, 2006. – P. 24-29.

Introduction

Mining operations imply a wide use of blasting operations while developing preparatory excavations and forming of niches in breakage face in the final sections of faces. More than a half of breakage faces of "Donetskugol" prepare niches using DBO (drilling and blasting operations).

Dust which is formed in the result of coal deformation is of high dispersive quality and consequently the danger of pneumoconiosis is very high, it is difficult to be watered and neutralized. Aggressive influence of such kind of dust on respiratory system of a human being is intensified by adsoption of poisonous gaseous blast products on its surface. This leads to high fibrohenic activity and causes pheumoconiosis among mining workers. The consequent poisonous gases outlet can cause intoxication among miners [1].

The real state of the problem

Analysis of applied methods has shown that in sprite of hydroblasting technologies improvement, effeciency of a single method of dust and gas suppression does not allow to descrease residual dust contents of air and gas release from cut coal according to demanded standards.

To fight against coal dust formation and adsorption of poisonous gases is necessary to carry out some efficient measures on prevention of harmful effects of poisonous gases and dust appearance which occur while carrying out blasting operations. It is simpler, cheaper and more efficient to prevent dangerous and harmful phenomena than to elliminate its results.

One of the methods of dust and gas formation can be hydroprocessing of edge parts of coal layers by water solution of active surface substances. Moisturized zones of the layer are formed in these substances changing physical and mechanical coal properties. Being combined with applied method and measures on dust and gas forming decrease while carrying out blast operations it will allow to create local zones on workplaces of face final sections in which concentration level of dust and gas contents is not higher than the maximum possible concentration [2].

Both coal destruction mechanism and processes of dust formation are changed while carrying out blasting operations in a moisturized zone of a coal layer.

The theoretical ground of the researches

It is known that energy contents of destruction depends on both a kind of load application and physical and mechanical properties of the surroundings. Changing these properties leads to certain changes of energy indicators of destruction. When coal porosity is increased, steady increase of specific dust release is observed.

Functional dependence of specific dust formation on energy destruction has been calculated [3,4]:

(1)

where
B – an indicator that features coal massif according its ability to crush;
H_w – specific energy of destruction.

(2)

Where

(3)

a_i – arithmetic mean of release of particles with size less than d, %
d_i – size of holes of sieve i, mm; n – the amount of sieves.

Researches show that summarized release of dust particles is proportional to work spent on coal destruction. Meanwhile the layer's properties effect dust contents in destroyed coal more than its destruction regime.

The change of properties of a layer by hydro effect leads to change of coal crush degree, i.e. it leads to change of its surface destruction. Area of dust surface F specific, which is formed when coal destruction occurs, is one of the main indicator of sorbing quantity of poisonous gases. These gases come into excavation atmosphere later. Specific energy of destruction H_wof both dry and moisturized coal is changed proportionally to the area of surface of their destruction depending on the degree of moisturizing.

The experiments in real conditions

The whole range of laboratory and real researches were held. In order to establish effect of low pressure of moisturizing on deformation coal features, its destructive and dust formation abilities. Coal of K_в layer of "Lidiyevka" mine SE "Donetskugol" was chosen to be tested because of coal high hardness (f = 1,5) and its destruction energy capacity require use of DBO while preparing niches.

The moisturized zone of the layer has been formed on section 7 of western face from the side of haulage drift in the distance of 25-50 mm. from the lower niche. From this niche sampling cut coal was done in order to establish granulometric contents of cut coal. The same kind of sampling has been done in the zone of upper niche which wasn't moisturized.

Conclusion

The effect of extra preliminary hydro treatment of a coal layer in the potential drilling and blasting operations (DBO) zone gives the opportunity to reduce dust and harmful gas release from the cut coal into the mine atmosphere. It helps to create safe conditions of blasting operations.

References

1. Professional illnesses of coal mine workers guide / Edited by G. A. Kobets – K.: Zdorovye, 1992. – 232p.

2. Artamonov, V. N., Nikolayev, E. B.: Preliminary moisturizing as a complex method of more effective and safe mining // Geotechnologies in the 21st centure. Donetsk, DUNPGO, 2001 – t.1, P. 124-129.

3. Ishchuck, I. G., Pozdnyakov G. A.: Methods of complex dedust formation in mines. Reference book - M: Nyedra, 1991. – 253p.

4. Dust control in coal mines guide: the 2nd ed. M: Nyedra, 1979. – P. 29-33.