Theme of master's work: «Justification of method parameters of stress and strain of rock mass based on the use unexplosive destroying materials».
Speciality: «Research in deformation of rocks containing mining workings in their unexplosive static load».
The analysis of mine's condition shows that loss of the area of cross-section for preparatory mine out of zone influence of clearing works exceeds 30-40 %, and with connection of clearing face – reaches 50-70 % that leads to necessity of their refastening and repair. Application of more metal-consuming timbering does not allow to solve the specified problem. It is explained with complexity of prevention and restraint of development round developments modern depths of a zone of the destroyed breeds (ZDB).
For preservation of rocks stability within ZDB there was suggested a way based on compression of destroyed rocks with a help of self-extending structures [1] . Key parameter of an offered way of maintenance of mine’s stability is the distance between cords with spacer elements. As a resource of thrust creation it is offered to use unexploited destroying material NRW-80, which researches characteristics [2, 3] allow to define the pressure developed by given structure at various volume deformations.
There is an analytical decision of a similar problem for research of action of explosion in a ground [4], however its application for a considered case, in our opinion, it is not absolutely correct that is connected with the different mechanism of influence on a file, and, accordingly, different sources of rupture of breeds.
For comparison of explosive and not explosive ways of stressing the rocks some experiences have been spent. In scale 1:5 the file of rocks contained a cord with diameter of 43mm, a cartridge containing at the first stage with , on the second – an unexploited destroying material was modelled. In the first series of experiences of research were spent on plaster plates in the sizes 240х240х60 mm with durability on одноосное compression 1,8 МПа. The General view of plates after test is resulted on drawing 1.
Drawing 1 - Results of fracture plates made of gypsum
a) by means of explosives;
b) using the NRW-80.
The analysis of a condition of cords’ surfaces, after carrying out the experiments, has shown that at explosive destruction of a wall cord is crossed by system of radial cracks, and at not explosive – walls are left almost smooth. Thus, despite presence of three open surfaces for tested plates, it is obvious owing to dynamic influence of explosion, near cording area collapses; while at gradual stressing walls of the cord remain indestructible. The condition of cord’s walls after destruction of samples is illustrated on drawing 2.
In the second series of experiments the researches were based on samples made of clay, placed in plastic cylinders. Humidity of clay totalled 26 %. Diameter of plastic cylinders was 70 mm for the first experiment and 175 mm for the second experiment. General view of samples’ first and second carried out experiments is illustrated on drawing 3 and 4 accordingly.
Drawing 2 - The walls of blast-holes after fracture
a) by means of explosives;
b) using the NRW-80.
Drawing 3 - General view of the samples after loading (external diameter 70mm)
a) using the NRW-80,
b) using explosives.
Drawing 4 - The general appearance of the samples after loading (external diameter 175mm)
a) using the NRW-80;
b) using explosives.
The analysis of the figures shows that as a result of blasting explosive charge in the clay formed a cylindrical cavity with a diameter 3,0-3,30 diameter hole, outside the cavity of continuity of specimens is not broken, then there is a zone sealing material diameter 4,7-4, 9 hole diameter, ie, it can be argued that the zone of influence of an explosion limited to 5 hole diameters. The simulation results agree well with data obtained by blasting contained and charges in the clay [5]. The result of non-explosive material is also a destructive cavitation diameter 2,8-3,2-diameter hole, but outside the cavity of the samples are divided by radial cracks in diameter 6,2-8,0-diameter hole, and the zone of intense compression is not visually observed.
Studies have shown that the explosive and non-explosive impact, even with the same result, has a different nature and character. The explosion instantly frees large amounts of energy, which leads to impulsive action on a rock, causing rock loop hole located at the front of the shock wave, destroying the instantaneous action of compressive stresses do not have time to redistribute pressure from the expanding explosive gases deep into the array, and the region the influence of a small explosion, as there is intense attenuation of the shock wave.
Transmission of pressure from self-expanding material capable of holding the array is carried out gradually: in the array redistribution of stresses, and the loop hole has time to be unloaded from the high compressive stress, resulting in the walls of the hole remain essentially undisturbed, but around the hole formed shear cracks.
Thus, it can be concluded that the deformation processes occurring in the array with the expansion of non-explosive depleting substances have different mechanisms and their characteristics, as compared with the processes caused by the explosion, which defines a different area of influence of blast holes, containing a cartridge with explosive and non-explosive blasting material. From this it follows that the problem of determining the characteristics of transmission of pressure from the walls of the hole, enclosing self-expanding material, deep rock mass is relevant and must be addressed.
The object of work - determine the zone of influence of one element of the spacer and the study of patterns of pressure transfer from the walls of the hole containing a self-expanding material deep into the rock mass
The idea of work - is to use the features of non-explosive loading of rocks in order to ensure their sustainability.
The problems solved in the master's work:
1. Establish patterns for pressure from the walls of the hole containing DMI deep array
2. Justification of rational parameters of the proposed method of ensuring the sustainability of developments.
The object of study - structurally inhomogeneous rock mass.
Subject of research - the deformation processes in rock mass due to static loading.
Research Methods - ordering, analytical method for physical simulation, bench tests, the method of statistical data processing.
Scientific novelty of the work is as follows:
- The peculiarities of transmission of pressure self-broadening from the walls of the hole deep into the array of continuous and discrete environment;
- The correlation coefficient for pressure deep into the array of mining and geological conditions.
The practical value of the work is to justify how the parameters of sustainability workings based on the application of DMI.
The theoretical rationale for the changes of stresses in the material for such a task given Lame for infinitely thick-walled cylinder. However, the solution of this problem is given in an elastic formulation, this gives a significant error in calculations, due to the anisotropy of the rock mass. Also, the task of transferring the pressure from the walls of the hole deep into the array for different conditions studied in sufficient detail in the physics of the explosion. However, the pulsed load application in this case leads to the different nature of loading material and consequently the error of the proposed settlement.
The material used for the realization method in recent years is widely used in world practice. Materials based on non-explosive depleting substances (NRW) is currently used in engineering construction for the destruction of foundations and other building structures. In mining, these substances are used for the destruction of strong brittle rocks, crushing oversized blocks the extraction of rocks open way, breaking gem raw materials and other cases, instead of conventional explosives (GOST 9479-84). This is due to high safety performance of the works are absent seismic effect and explosive gases.
As the technical means to create destructive tensions in the expected use of non-explosive destructive means NRW-80 (DSTU BV.2.7-75-98), produced in Ukraine is currently undergoing scientific developments to create a directional rock disintegration using the HPM in the world had not been maintained.
The main prospect research is the ability to utilize the work in the coal industry in Ukraine.
The results of the master's work will serve as a basis for further research.
At present the work for the magister degree is being carried out, in January 2011. For farther information ask the author Volodkov Andrey and teacher Sakhno Ivan
1. Сахно И.Г., Петренко Ю.А., Овчаренко Н.А. Лабораторные исследования особенностей работы разрушенных горных пород при формировании из них несущей конструкции / Проблеми гірського тиску 2008, №16- С 70-81
2. Касьян Н.Н., Овчаренко Н.А., Сахно И.Г., Петренко Ю.А., Самусь О.Л. Лабораторные исследования работы невзрывчатых разрушающих веществ при упрочнении массивов разрушенных горных пород // Науковий вісник НГУ. 2008. - №8. - С. 50-52.
3. Касьян Н.Н., Сахно И.Г. Лабораторные исследование влияния компонентного состава НРВ-80 на его рабочую характеристику при укреплении вмещающего горные выработки массива // Вісник Криворізького технічного університету. 2009. - №23. - С. 31-34.
4. Физика взрыва / Ф.А. Баум, Л.П. Орленко, К.П. Станюкович и др. М.: Наука, 1975.
5. Сонин С.Д., Шейхет М.Н., Черняк И.Л. Борьба с пучением почвы горных выработок взрыванием камуфлетных зарядов // Шахтное строительство. - 1961. - №3. - С. 8-10.
6. Литвинский Г.Г. Монолитная оболочка из разрушенных и упрочненных пород // Шахтное строительство, №12, 1981. - 18-20 с.
7.Упрочнение пород в подготовительных выработках / И. Л. Черняк - М.: Недра, 1993. - 256 с.