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Abstract

Contents

Introduction

Coal mines of Ukraine fulfill stocks at depths which average mark reached 700m. The considerable part of mines fulfills layers lying at a depth more 1000ì. At such depths, level of mountain pressure is very high. The vertical component of tension in the untouched massif outside influence of clearing works exceeds 25mkPà. At working off of suite of the pulled together layers there are zones of imposing of PGD in which the massif of rocks possesses the increased tendency to a vybrosoopasnost. In this regard researches of such zones is an actual task.

Work purpose. Therefore the purpose of this work is specification of parameters of borders of zones of the increased mountain pressure at a different configuration of the developed spaces in the course of working off of suite of the pulled together layers and improvement of ways of fight against the gasdynamic phenomena and their forecast, utochny justifications of actions for prevention of the gasdynamic phenomena.

The scientific task consists in increase of safety of conducting mining operations, at the expense of increase in reliability of the forecast of zones of the increased mountain pressure by means of determination of initial speed of gas emission.

Scientific provisions, scientific novelty. Coefficients of concentration of tension will be specified when forming öåëèêîâ at the developed spaces fulfilled on adjacent layers.Áóäóò the new principles of the forecast of the gasdynamic phenomenon are proved.

 

1. Survey information

1.1. The review of researches on a subject in DONNTU

The institute of mining and geology of Donetsk national technical university is one of the leading scientific organizations who deals with issues of mountain pressure in the massif of rocks when conducting extraction works.

The chair of surveying business traditionally deals with issues of redistribution of displacement of tension at development of mining operations in suite of the pulled together layers.

1.2. The review of researches on a subject in Ukraine

In the territory of Ukraine researches by questions of redistribution of displacement of tension at development of mining operations in suite of the pulled together layers

the chair of surveying business of the Dnepropetrovsk National Mining University and department of mountain pressure of UKRNIMI of NAN of Ukraine is engaged.

1.3. The review of researches on a subject in the world

Many scientists from the Russian Federation are engaged in questions of displacement and deformations of a terrestrial surface.

– St. Petersburg state mining institute of a name of G. V. Plekhanov;

– Southern Russian state technical university (Novocherkassk polytechnical institute);

– Moscow state Mining University.

 

2 . Main content of work

Standard branch techniques allow to determine zone PGD width, being based on empirical approach through calculation of length of a zone of basic pressure from a single lava. Such simplified approach leads to that the expected sizes of zones PGD differ from actual several times. Information on the size of concentration of mountain pressure in zones PGD, has big practical advantage. This parameter is used at an assessment of stability of preparatory and clearing developments, the forecast the gasdynamic phenomena. However such parameter can be determined only by numerical methods. Besides, only three-dimensional numerical models are capable to consider spatial effect at distribution of mountain pressure in a vicinity of the developed space of a difficult form. Especially it is actual at simultaneous development of suite of the pulled together layers. In this article one of possible approaches at calculation of the sizes and sizes of concentration of tension in zones PGD taking into account spatial nature of redistribution of tension in development of clearing works in suite of the pulled together coal layers is stated.

The geomechanical model for calculation of three-dimensional distribution of tension in the massif is constructed as follows. Intense the deformed condition it was investigated regularities of redistribution by means of computer modeling.

Let's present thickness of rocks, as the thick plate leaning on the non-uniform basis of 3 and caving in under a body weight of q (fig. 1).

The plate leans on the massif which rigidity 3 depends on existence of the developed spaces and the taken-out power of m of layers. By positions 1 and 2 are specified earlier developed space and what is formed by an adjoining operating lava.

On a terrestrial surface in the course of working off of lavas 4 it is formed a cartoon of displacement 5. Distribution of tension and deformations in a thick plate is defined by means of three-dimensional models. Having replaced a thick plate thin, it is possible to pick up such equivalent sizes of rigidity of the basis and deformation parameters of a plate at which some parameters intense the deformed condition will correspond to the actual.

By means of such model it is possible to predict with high reliability deflections, tension and spatial distribution of mountain pressure in pedigree layers within height of the earned additionally thickness equal to 150 m.


Fig. 1. The settlement scheme for definition of the naprya-zhenno-deformed condition of earned additionally thickness of rocks
1 – earlier developed space
2 – operating lava

 

The problem about a plate layer deflection over the developed spaces is solved by numerical differentiation of the equation in private derivatives by a method of final differences.

(1)

Where

ω – deflections of points of a plate;

q – normal to the median plane and distributed on a plate surface

K – coefficient of rigidity of the basis, changing depending on existence or lack of the developed space;

D – cylindrical rigidity of a plate;

(2)

where

h – plate capacity;

E – the given module of deformation of the layered massif;

μ – Poisson's coefficient of containing breeds.

As a result receive lowerings of the earned additionally thickness at the level of the upper bound of the main roof of layer.

For the accounting of mechanical properties of all layers making thickness, their sizes were given to the median plane of a plate layer on the following dependence:

(3)


where

Ei – the module of deformation of i-go of a layer;

pi – the weight of influence of i-go of a layer which is on a formula

(4)


where

hi – the capacity of i-go of a layer;

yi – distance from the center of gravity of i–go of a layer to the median plane.

The dependence mentioned above, allowed to consider properties of all layers of the earned additionally thickness. This model considers also a relaxation of tension and creep of the breeds composing the earned additionally massif. It is essential advantage of the chosen model as dynamic processes of manifestations of displacement of rocks are the expressed nonequilibrium physical processes and significantly depend on time.

The example of calculation of parameters of zones PGD is given for a case of simultaneous development of four pulled together layers by two next mines. The mine of Zasyadko develops three coal layers at eastern frontier of the field: k8, m3 and l1. There is a considerable probability of that the field of tension round the developed spaces created by mine of Zasyadko is indignant with clearing works as the next extinguished Krasnogvardeyskaya mine.

In figure 2 the combined plan of excavations on two next mines is shown.

All developed spaces created on all four coal layers, were grouped so that to bring together them on the working off periods. So, the first group of the developed spaces is collected from what are fulfilled in the seventies, the second in the first half of the 80th and so on, up to the present moment. The closer to the current date, the developed spaces are more precisely grouped. It means that the last developed spaces are entered from each lava fulfilled during 2005-2007. All developed spaces are collected in 11 groups including 23 lavas. These groups were entered into the settlement scheme in a retrospective order, that is in that order in which they were fulfilled in reality. Thus, the real sequence of working off of all lavas that gave the chance to describe adequately a difficult configuration of the developed space formed on all pulled together layers was modelled.

 

Fig. 2. The scheme of the combined plan of excavations

 

Known approach at which the size of concentration of tension in zones PGD was compared to convergence speed on a contour of preparatory developments was applied to check of reliability of the received results. Results of monitoring of convergence on a contour of the preparatory developments passed on l1 layer in a vicinity of the 12th east lava were for this purpose used. It were conveyor, biases and arrivals on the specified developments. For comparability of results of tool supervision all zamerny stations were given to identical conditions on durability of containing breeds. The stations put in sheeted developments were accepted to a standard. The results of supervision executed in field developments, were corrected by multiplication of coefficient of the similarity equal to a ratio of the average durability of containing breeds. So, for example, at increase in durability of lateral breeds in field arrival by 2,5 times in comparison with durability of lateral breeds sheeted conveyor øòðåêà, the speed of convergence of lateral walls of development increased in the corresponding quantity of times. It gave the chance to compare results of computer modeling with data of mine tool supervision.


Nature of modification of zones PGD in development of clearing works in the pulled together layers (4 slides, 7 repetitions, 199 kb)

In table 1 results of comparison of size of concentration of mountain pressure and speed of convergence of lateral walls of developments are given in the corresponding points. All developments were approximately at one depth around the 12th east lava that gave the chance to compare data of measurements and modeling.

 

Table 1 – Results of comparison of settlement concentration of mountain pressure and the measured speed of convergence on a contour of preparatory developments

Stage of development of clearing works

Concentration of mountain pressure in zone PGD

The specified speed of convergence, mm/days

Ratio concentration/speed

9

0,27

0,2

1,35

10

1,84

1,1

1,67

11

1,59

0,7

2,27

11

2,33

1,9

1,23

 

The average size of a ratio of size of concentration to the speed of convergence made 1,63±0,47. It means that the coefficient of a variation of results of comparison is equal 28% that it is possible to consider quite accepted. It testifies to reliability of results of modeling and reliability of the drawn conclusions.

 

CONCLUSIONS

Thus, the executed researches allowed to determine a certain consistent pattern of inheritance in evolution of zones PGD at development of clearing works in suite of the pulled together layers. This inheritance is shown that at over – and a side job of places of high concentration of tension (more than 2,5) in the developed space under – or a nadrabatyvayushchy lava there is a zone which keeps a configuration of the former zone PGD and in which mountain pressure is close to geostatic level. If earlier existing zones PGD on own or adjacent pulled together layer don't get under the plane or over the plane of a projection of the new developed space, concentration increases in the specified zones by 1,1-2,1 times after formation of the new developed space.

 

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