The coal industry of Ukraine is the basis of the fuel and energy complex and the basic coal-mining region of the country is Donbass. It is connected by that the Donetsk region is one of the most provided with resources. In its limits the basic reserves coked and hard coals of Donbass are concentrated, and also considerable reserves of salts, numerous deposits of high-quality mineral and construction materials (carbonates, refractories) are considerable[4].

Coal is used in such spheres of the industry as: thermal power, metallurgy, the chemical industry etc.

For development of the coal industry it is necessary: improvement of working conditions of miners, increase of productivity of coal mining complex, a decrease of the cost price of finished goods, and also improvement of quality of coal and increase in volume of its dressing[9].

Aims and purposes

One of the important tasks of the mining complex is the harmonious work of all its parts, and further technical re-equipment and reconstruction of mines of Donbass. One of problems of a mining complex is the hydroprotection system. But the aim of my diploma project is necessity of installation of the given system[3,4].

Problem statement

To develop electronic system of detection of aquifers in the conditions of mine workings.

Actuality

Electric prospecting is an effective method of searches and explorations for minerals, researches of earth crust and an environment, solution of various tasks in several branches of science and technology[3].

Electric prospecting (electromagnetic prospecting is more exact) combines the physical methods of investigation Geospheres Earth, search and exploration of mineral resources.

These methods are based on analysis of electromagnetic fields which exist in the Earth owing to natural space, atmospheric or physical and chemical processes or created artificially[7].

The basic concepts of electric properties of breeds and minerals

Electromagnetic fields can be:

1) established, i.e. existing from above 1 with, constants and variables (harmonious) frequency from 10^-3 to10¹⁵ Hz;

2) unsteady, pulse with duration of impulses from micro seconds about one seconds. Used harmonious fields can be divided on infrasonic, sound, radio wave, studied in electroinvestigation, and microwave on which thermoinvestigation methods are based. Measured parametres of a field are amplitudes and phases electric Å and magnetic Í fields, and at thermoinvestigation-temperature Ò.

Intensity and structure of natural fields are defined by natural factors and electromagnetic properties of rocks. For artificial fields it depends on the same properties of rocks, intensity and a source kind, and also ways of excitation. Artificial fields happen galvanic when a field in the Earth create by means of a current passed through electrodes; inductive when a feeding current, passing on not earthed contour (the loop, a framework), creates in the environment an electromagnetic field at the expense of an induction, and mixed (galvanic and inductive).

Return concern electromagnetic properties of rocks specific electric resistance ρ, size, electrochemical activity α, polarizability η, dielectric ε and magnetic μ permeability, and also piezoelectric modules d. Electromagnetic properties of geological environments and their geometrical parametres define geoelectric cuts. It is accepted to name a geoelectric cut of semispace homogeneous for this or that electromagnetic property normal, and non-uniform - abnormal.

Specific electric resistance

Specific electric resistance (SER) rocks is the parametre of substance characterising its ability to pass an electric current at occurrence of electric field, is measured in Ohms ·m.

1. Specific electric resistance of minerals depends on their intracrystal communications. For minerals-dielektrikov (quartz, micas, field spars, etc.) with mainly communications are characteristic very high resistance (1012-1015 Ohms ·m). Minerals-semiconductors (carbonates, sulphates, haloids, etc.) have ionic communications and differ high resistance (104-108 Ohms ·m). Clay minerals of hydromica, etc.) possess is ionic-kovalentnymi communications and are characterised by low enough resistance (ρ <104 Ohms ·m). Ore minerals (native) with electronic conductivity very well spend a current (ρ <1 Ohms ·m). First two groups of minerals make a «rigid» skeleton of the majority of rocks. Clay minerals create a «plastic» skeleton. It is characteristic, that «plastic» minerals are capable to adsorb the connected water, and breeds with «rigid» minerals can be sated with only free water.

2. Specific electric resistance of free underground waters (gravitational and capillary) changes from shares Ohms ·m at a high general mineralization (> 10 g/l) to 1000 Ohms ·m at a low mineralization (M <0,01 g/l) and the Chemical compound of the salts dissolved in water can be estimated under the formula ρÂ ≈ 8,4/m. does not play an essential role, therefore according to electroinvestigation it is possible to judge only the general mineralization of underground waters. Specific electric resistance of the connected underground waters low also changes from 1 to 10 Ohms ·m, that explain enough their constant mineralization (3-1 g/l), close to an average mineralization of waters of the World ocean.

3. At temperature increase on 40°Ñ resistance decreases approximately in 2 times. It explain increase in mobility of ions. At freezing resistance of rocks increases jump as free water becomes practically an insulator is defined by only connected water which freezes at very low temperatures (more low-50 °Ñ).

4. Depth Positions, the structure and a breed structure also influence its resistance, changing microanisotropy factor n l λ = ρ ρ where ρn, ρl-resistance of breed and along lamination. More often λ changes from 1 to 1,5, reaching 2-3. Despite a wide range of change of specific electric resistance at different breeds, the basic laws are established accurately enough.

The fragile sedimentary breeds, as a rule, have that áîëüøåå resistance, than it is more size of the grains composing breed.

As a result we will draw a conclusion, that SER rocks, basically, depends on following factors:

1. The overwhelming majority of minerals are do not spend an electric current. An exception are continuous of minerals of conductors - native elements, sulphides, but such formations meet seldom.

2. Communication SER of rocks with porosity factor , factor . Water has flooded and electric resistance ïîðîâîé a moisture is obvious: than more than water in

To breed and than more low SER waters - that more low and SER rocks. For example, dry sand will possess higher SER, than damp, and the last higher, than water sated.

3. The more salinity, the more low SER waters. With temperature is even easier: water - a conductor, ice - an insulator.

4. Clay possess very low SER, much more low, than at water. For example, in the Moscow region VES of water - 25-30 Ohms ·m. This effect is connected with difficult capillary processes. The more shaliness of rocks, the more low SER.

For example here SER some rocks:

The rock name	SER min (Ohms ·m)	SER typical (Ohms ·m)	SER max (Ohms ·m)
Clay	5	10	15
Loams	15	30	50
Sypes	30	50	80
Sand Water has flooded	50	80	200
Sand a little Water has flooded	100	150	500
Sand dry	200	500	10000
Ores of minerals of conductors (basically sulphides)	0,001		1-5

As we see values SER for separate kinds of breeds are strongly various, that gives the chance to distinguish various rocks and to solve a various sort of a problem.

At studying water has flooded mountain developments during working out of deposits of firm minerals by the most important practical problem revealing water zones for drilling water has flooded chinks and designing of other drying actions is. Water has flooded zones here have local, irregular character and are dated for increases in a cut of the maintenance of thicknesses of sandy collectors or the karstic water sated cavities zones.

The basic field methods of studying water mountain developments are VES, VES-VP, MRV, and also electroprofilings (EP). The technique of field works is reduced to the vulgar shootings with density of a network of supervision (100-500) \times (100-500) m[6].

MRV (a method of the refracted waves) is a method from seismic prospecting area, therefore we will not consider it.

Let's consider more in detail a method vertical electric sounding

VES (vertical electric sounding) it is a method of a constant field. The method of vertical electric sounding (VES) is one of the oldest methods of electroinvestigation. The first applications of a method concern to 20th of the XX-th century of. Comparative simplicity and presentation VES has led to its wide circulation and development all over the world[8].

For today electric sounding remain one of the most applied electroprospecting methods. On the basis of VES other modern technologies - for example, an electrotomography, based on the same principles, as for classica electric sounding are developed also.

One of the basic requirements to application of geophysical methods is contrast on physical properties of object of studying concerning the containing environment. For electroinvestigation by methods of resistance which concerns VES is means, that the studied object (a body, a layer, a layer and so forth) should considerably (it is desirable several times) to differ on specific electric resistance from containing breeds[2].

Physical bases of method VES

Idea of method VES - on an earth surface collect electroprospecting installation (installations Shlumberje, Weners, dipol axial installations and some other) which, as a rule, consists of two feeding and two reception electrodes (see a Fig. 1, a Fig. 2). As electrodes usually apply metal probes which are hammered into the earth. Feeding electrodes can be designated letters And and In, receptions - M and N.

Fig. 1. The measurement scheme in method VES.

To feeding electrodes connect a current source - for example, the battery. In the earth there is an electric field and, accordingly, an electric current. Force of a current in a feeding line (I_ÀÂ) measure by means of the ampermeter included in chain ÀÂ.

The length of line MN installations Shlumberje remains to a constant, and the distance between feeding electrodes increases in a geometrical progression with factor 1,2 - 1,5. On reception electrodes of M and N there is a difference of electric potentials (ΔU_MN) which is measured by means of the voltmeter.

Fig. 2. Shematic installations Shlumberje of method VES.

By results of measurements it is possible to judge electric properties of rocks on depths of penetration of a current in the earth. Depth of «current immersing» depends, basically, from distance between feeding electrodes And and Century

By results of the executed measurements calculate seeming electric resistance , designated ρ_ê, and measured in Ohms ·m:

(For symmetric installation)

Where, K - geometrical factor (depends on distances between electrodes A, B, M and N), ΔU_MN - a potential difference on reception electrodes M and N, I_AB - force of the current proceeding in the feeding line.

Seeming electric resistance characterises integrated value SER of rocks in the field of research. The research area settles down under the centre of installation and is stretched from a surface to the depths, approximately equal to half of length of installation - ÀÂ/2 (the Fig. 1 see).

If the studied environment is homogeneous - with SER equal ρ_ñðåäû value of the received seeming resistance ρ_ê will be identically equal ρ_ñðåäû:

ρ_ê = ρ_ñðåäû

If the studied environment is non-uniform, i.e. in the field of research rocks with various values SER value of the received seeming resistance ρ_ê will be more than least of SER breeds settle down

_ρmin <ρ_ê <ρ_max

Effect of sounding

Fig. 3. Effect of sounding in method VES.

For sounding performance make a series of measurements, gradually increasing the size of feeding line ÀÂ. The more parametre ÀÂ/2 - the more deeply «plunges a current into the earth» and the more researches (the Fig. 3 see).

Thus each following area of research completely includes the previous.

Values ÀÂ/2 choose depending on demanded researches. As a rule, minimum ÀÂ/2 accept 1-1 metres. Maximum ÀÂ/2 seldom do more first kilometres. Thus, method VES apply to studying of environments to depths no more than hundreds metres.

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Fig. 4. Principle of hollow practice VES

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As a result of the described series of measurements the set of values of the seeming resistance measured at known ÀÂ/2 turns out. In electroinvestigation parametre ÀÂ/2 name a rating of a feeding line (or simply rating).

Fig. 5. Example of curve VES.

For convenient representation of results of supervision build the dependence schedule ρ_k (in Îì·ì) from a rating (in). Such schedule is called as a sounding or curve VES curve (the Fig. 5 see).

Equipment and the equipment of method VES

For performance of supervision by method VES the specialised electroprospecting equipment is applied to excitation weeding (generators) and measurements potential differences (measuring instruments). Now, as a rule, the equipment is applied to a method of resistance on ultralow frequencies (1-10 Hz) or on a direct current. Among applied domestic devices it is possible to name following samples:

· AE-72 - The device of working out of 60th the working on a direct current;

· UNCH-3 - The device of working out of 70-80th the working on an alternating current on frequency of 4.88 Hz;

· Ayr - the device of working out of the end of 80th the working on frequencies 0, 4.88 and 625 Hz;

· ERA - the modern device working on frequencies 0, 4.88, 625, 1250 and 2500 Hz;

· ERP-1 - The modern device working on frequencies 0, 1.22, 2.44 and 4.88Ãö;

· The generator the ASTER and MARY'S measuring instrument - the modern multifrequency devices working on frequencies from 0 to 625 Hz;

· Measuring instrument EIN-204 is intended for field electroprospecting works on an alternating current of low frequency by methods VP, VES, VES-VP. The device Block diagramme is resulted on fig. 5.1.[12]

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Fig. 5.1. The Block diagramme of measuring instrument EIN-204

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Stale-copper wires and cables are applied to installation of feeding and reception lines. As feeding electrodes use the steel pointed probes, for receptions - copper or brass.

Vertical electric sounding by a method of caused polarisation

Vertical electric sounding by a method of caused polarisation (VES-VP) by a technique of works a little than differs from considered above VES and is intended for a partition of cuts on depth not only on change SER, but also polarizability (η) layers. By means of single-channel or multichannel equipment are measured ΔU_MN and I_ÀÂ, that becomes and in method VES, and also U_VP on ÌN through 0,5 with the ambassador of switching-off of a current in ÀÂ. As a result along with ρ_ê seeming polarizability η_k =.

Fig. 6 Curves VES and VEZ-VP with the branches caused dry (I) and water sated (II) sandy loams, spread glin (III)

Further on forms with logarithmic scale on axes of co-ordinates (forms VES) along with curves VES curves VES-VP are under construction: are across postponed ÀÂ / 2, on a vertical - η_k.

It is accepted to apply other method of electroinvestigation to search of local objects - electroprofiling (EP).

The idea of method EP is even easier, than idea of method VES. Measurements are made with the same electroprospecting installation as in method VES, but only at one-two values ÀÂ/2. Profiling installation moves on a profile of supervision with step from 5-10 to 50-100, depending on the sizes of required bodies and demanded detail of shooting.

Actually EP - is «truncated VES TH». The size of rating ÀÂ/2 used at profiling is defined proceeding from demanded depth of researches.

Results of electroprofiling represent in the form of the schedule of seeming resistance along a profile of supervision .

The conclusion

In method VES key parametre RES is distinguished enough and sharply differs at sounding of various breeds and minerals, and is an excellent method for the decision of a problem of detection of contact of the water environment and mountain developments. That is necessary for in time installations of a mining complex water pumping out elements.