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26
DOI: http://dx.doi.org/10.20534/AJT-17-1.2-98-101
Ochilov Shuhratulla Atoyevich, Senior Research Fellow - Competitor, Faculty of Engineering Geology and Mining, Tashkent State Technical University E-mail: [email protected]
Nasirov Utkir Fatidinovich, Head of the Department of Mining, Faculty of Engineering Geology and Mining E-mail: [email protected]
Toshniyozov Lazizjon Golib ugli, Master of Mining machinery and equipment, Faculty of Engineering Geology and Mining E-mail: [email protected]
The oretical study of the fracture mechanism of less fissured rocks
Abstract: The article deals with the fracture mechanism of rock in explosion of concentrated deep-hole charges. The factors, causing involvement of environment at explosion in progress were determined and the fracture mechanism of rock under the influence of kinetic energy of wave was found out. Calculations of distance change between deep-hole charges in less fissured rocks are illustrated. It has been determined that at explosion of ideal flat charges fracture of rocks occur under only compressive stress (in a near zone) and slabbing phenomenon (in a remote zone) appearing at reflex ion of a compression wave from a free surface.
Keywords: crushing, cracking, downhole charges, explosives, destruction, rock, wave energy, strain, slabbing phenomenon.
After the detonation of the explosive charge voltage wave propagates in the environment. At distances of several radii of the charge pressure in a wave commensurate with the pressure of the detonation products and the tens of thousands of atmospheric pressure. At this pressure, there is a plastic flow of the medium, so that at the initial moment it is displaced expanding explosion products. As propagation happens, the surrounding is involved in the movement in the radial direction. If an explosion occurs near the free surface, after reflection of stress waves the displacement among the products of the explosion in the upper half.
The explosion energy in the less fissured environment is transmitted through wave and expanding explosion products in the form of elastic and kinetic components. Calculations and direct experimental measurements [1, 25-33] show that the elastic and kinetic components in the same order of magnitude. The experimental and theoretical studies imply that located at a given distance from the center of the charge volume of the rock starts to not break at the time when it spreads
the stress wave. Experiments in optically transparent media and monitoring under production conditions shown [2, 85-96; 3, 77-100], that failure in this volume begins shortly after its passage. This is proved by the fact that the speed ofpropagation offailure cracks in the rock volume is less than the speed of the stress wave. Depending on the physic-mechanical properties of the medium, the crack propagation rate ranges from 30 to 90 % of the acoustic speed.
Environment, located close to the explosion, due to higher pressures (of the order of tens of thousands of atmospherics) behaves like a liquid. Therefore, all three principal stresses 81, S2, and S3 are equal.
According to the energy theory of strength, generally good agreement with experiment, the reason for failure is the potential energy of forming, proportional to the value:
(-S2 )2 + ( -S3 )2 +(3-5, )2
In view of the equality S1 = S2 = S3 have:
U = 0.
(1)
It follows that in the near field by an elastic component of the wave environment and the pressure of the explosion products will not disintegrate.
In the far field given voltage S in wave according
O O np o
to the theory of energy equals strength (1-2^) S (1-^), where: S — pressure in the compression wave, — Pois-son's ratio. Calculations show that S value in the far
np
zone is less than the tensile strength of rocks (at least for the rocks with factor of a fortress f > 5). Consequently, in the far field rock under the action of the elastic component also will not deteriorate.
Going from the free surface of the expansion wave, interacting with the incident (forward) wave is slabbing phenomenon that for environments with a large acoustic stiffness are the main cause of the destruction. Studies have shown [4, 6-11; 5, 103-109; 6, 263-285; 7, 30-31; 8, 34-39; 9, 172-174; 10, 184-196] that the destruction of these environments are on the charge and the amount of destruction created by spall phenomena, is a small part of the total volume of the destroyed environment. With increasing line of least resistance (LLR), the average size of the largest piece of a fragmented masses increases. At the center of the explosion equal relative distances will be the same voltage Spr. For these conditions in a unit volume of rock will be the same elastic component.
When fragmentation covers the entire volume of the medium, the stress wave due to a sharp lag general destruction front leaves to a distance several times the size of the amount of fragmentation. If calculate the elastic component of the wave energy integrated across the blasted volume for that period, the energy of the wave is much less than the kinetic part of the same volume.
To elucidate the fracture mechanism under the influence of a wave kinetic energy we consider symmetric explosion, when a spherical or cylindrical charges are located, respectively, in the center of the spherical or cylindrical volumes of the medium axis.
After the explosion of the charge and the reflection of stress waves on the free surface and the expanding gas cavity is set symmetric quasi-stationary motion of the medium in the direction of the free surface. Elementary protection layer thickness dr at a distance r from the charge will be in the complex stress state, characterized by radial compressive and tensile Sr and St tangential stresses (fig. 1). At the same time it will move from the charge center in the radius direction with a speed 3r and stretch in the perpendicular direction at a rate $ (fig. 2).
As the strain rate increases towards the center of the charge, the considered elementary layer thickness will be subjected to breed uneven stretching: the lower layer of
rock fibers will be stretched upper. This fact leads to the fact that the elementary rock layer is simultaneously subjected to deformation of tensile shear and impact shift.
Impact shift (skew) is manifested in the fact that some mentally leased plane from the position a-a by stretching velocity gradient rotates y to position b-b (fig. 3a).
Fig. 1. Diagram of the complex state of stress of an elementary volume of the medium in the explosion of the explosive charge
Fig. 2. The velocity field, which is formed in a medium with the explosion of the explosive charge
To impact tensile is exposed rock with layer thickness At and length l at a rate ut (fig. 3b). When the shock tension at an average speed ut if A ut / Ar gradient disruption will happen in time Atp p when in elementary layer elongation t reach destructive values £p.
As:
A/ = vAtp l
£P =
2nr
where l — length of circumference of radius r, nematic dependence.
uT = 2nrur,
we get:
u Af
=
(2) given ki-
(3)
(4)
a)
b)
Fig. 3. Types of strain of elementary volume of the medium: a) — a shock shift under the influence of the velocity gradient; b) — uniaxial tension
It is known that:
p E
(5)
At =
(12)
where SB — tensile strength of rock under shock tensile; E — modulus of elasticity. Therefore:
that substituting into (11) we find:
2(1 + ^ dur '
dr
Drinking At : At obtained from the expression (6) and (12):
7VE
Atp . p E u
(6)
At.
n
dvr dr
In the second case, breed destruction will happen when the relative shift of y (the plane of rotation of the position a-a position b-b) reach destructive values yp. From fig. 3, a it follows that:
Au At
Yp =—7— , (7)
Ar
where At — the time during which the elementary layer of rock will collapse under the influence of shear shock. Since shear:
r.=g ■ ®
where: tp — destroying the value of the shear stress; Gc — shear modulus, given the ratio.
G =
(13)
Atc 1 + ^ ur dr The law changes the value Sr with the distance r can be approximated by:
u =u
(14)
where: u0 - the initial velocity of the breed on the border with the gas cavity; n — exponent, depending on the type of symmetry of the explosion and the physical and mechanical properties of the rock; r — charge radius.
Differentiating, we obtain the absolute value: do..
dr
= n
2(1 + ^)
where y — Poissons ratio, we get:
2(1 + ^
At, =
du
_T
dr
Differentiating relationship (3), we find:
du ^ du —^ = 2n—L, dr dr
(9) (10)
(11) (12)
Substituting formula (14) and (15) in relation (13) we finally find:
Af
nw
A 1 (16)
Atc 1 + ^
As a guideline for spherical and cylindrical symmetry, you can take the n values, respectively, equal to 2 and 1. For estimations y value in comparison with unity can be neglected.
Then we find that the ratio At : At for spherical and
p c r
cylindrical explosions, respectively, equal to 2n and n. This shows that the rock is destroyed from the impact of
:
shear strain is several times faster than the tensile strain from the impact.
By simple calculations we can show that at the time of the destruction of shock rock due to the shear deformation ratio of the potential energy to stretch the same energy shift is (1 + ^) / 2 (nn). For a cylindrical (n = 1) and spherical (n = 2), the symmetry ratio is respectively 1.16 and 1.64. Consequently, tensile energy calculations fragmentation can be neglected.
From this it follows that the failure mechanism at the basis of solid rock and concentrated blast hole charges lies shift shock, which is a consequence of the presence of the radial velocity gradient and is shown in misalignment erodible medium volume. For ideal flat charges at steady gradient of quasi-stationary motion is not speed. Consequently, there will be no impact and shear strain. Therefore, the ideal — flat charges as compared to the
focused provide a lesser degree of down hole rock breaking. This, in particular, can be seen in practice, explain the blasting quality deterioration array crushing rocks with decreasing distance between the wells (at a constant value of specific consumption of explosives). In this case, it becomes an ideal flat charge with decreasing distance to the ground a number of borehole charges. With the explosion of charges of ideal flat rock is destroyed by only one compressive, stress (near-field) and slabbing phenomenon (in the far field), arising from the compression wave reflected from the free surface.
Thus, the mechanism of crushing rocks is considered with the explosion of concentrated downhole explosive charges. It is found that the pressure wave is a factor causing the instantaneous movement involving environment. In the presence of the radial velocity the shift shock is generated, which is a major factor in the destruction of rocks.
References:
1.
Hanukaev A. N. Stress wave energy in the destruction of rocks by explosion. - M.: Gosgortekhizdat, 1962. - 200 p.
Gaek E. V., Drukovanny M. F., Nishin V. V. The rate of propagation of cracks in the rocks and solids and methods of measurement. - In the book.: An explosive affair. - № 51/8. - M.:Gosgortekhizdat, 1963. - P. 85-96. Mosinets V. N. Terms of brittle and ductile rock explosion. - Proc.: The destruction of rocks by explosion. -M.: Nedra, 1967. - S. 77-100.
Zverkov S. N. Okunev A. R. Experience in the use of parallel-contiguous wells in quarries GOK Zhdanov. - In the book: The use of parallel-contiguous wells and underground workings. - M.: IGD, 1967. - P. 6-11. Maksimov E. P. Laboratory studies of the characteristics of lumpiness in crushing explosion. - In the book: An explosive affair. - № 47/4. - M.: Gosgortekhizdat, 1962. - P. 103-109.
Baum S. A. The process of destruction of rocks by explosion. - In the book.: An explosive affair. - № 52/9. - M.: Gosgortekhizdat, 1963. - P. 263-285.
Norov Yu. D., Bibik I. P., Norov J. A., Nasirov U. F., Normatova M. J. Production blasting in complex hydrogeo-logical conditions//Mining journal. - 2013. - № 8-1. - P. 30-31.
8. Norov Yu. D., Bibik I. P., Zairov Sh. Sh. Effective management of the drilling and blasting parameters according to the criterion of the quality of blasted rock mass. News of the Higher Institutions//Mining Journal. - 2016. -№ 1. - P. 34-39.
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DOI: http://dx.doi.org/10.20534/AJT-17-1.2-102-104
Khudoyberganov Abrorjon Akbarovich, Bukhara refinery Deputy Chief Engineer for the implementation of innovative projects and technologies in production Bukhara refinery E-mail: [email protected]
Studying of process steaming of kerosene fraction by hydrocarbonic steams
Abstract: In article resulted results of studying process of steaming kerosene fraction are by hydro-carbonic steams.
Keywords: hydrocarbonic, distillation, rectification, water steam, stripping — column, oil, gascondensate.
Introduction
As is known, by distillation of oil and a gas condensate receive hydrocarbonic fractions which are intermediate products for motor TonAHB. Process is carried out in installation of the primary distillation consisting in basic from rectification and the stripping-columns [1; 2; 3].
Under the existing «know-how» at steaming distillate fractions it is used heating water steam. As the steaming agent it is possible to carry to the basic lacks of application of water steam: increase in expenses of thermal energy at process; increase of loading of a column on steam, leading to increase in its diameter; condensate formation, its branch from fuel fractions and clearing of impurity demands additional expenses; strengthening of corrosion of working surfaces of the equipment under the influence of a water condensate, watery mineral oil and their necessity of the subsequent drying, etc. [2; 4].
For these reasons in the technological plan sharp reduction of the expense of water steam on process of distillation of oil is expedient, in particular, at steaming distillates, or carrying out of the given process without its participation. Thus one of technological decisions of a problem, use of steams of the oil fractions leaving from rectification ofa column, as the alternative heat-carrier instead of water steam is [4]. Such technological decision promotes elimination of the above-stated negative phenomena which are taking place at distillation oilgascond-ensate of raw materials with participation of water steam.
The analysis of a condition of process of primary distillation of hydrocarbonic raw materials in oil refining factories shows, that because of not enough effective organisation ofprocesses in rectification to a column the expense of thermal energy for process realisation raises, that is reflected in growth of the cost price of let out production. Therefore perfection of processes of distillation of hydrocarbonic raw materials, working out of
highefficiencies, energo — and resource saver up technological processes and rectification devices corresponds to the basic directions of dynamic development of oil refining branch.
Experiment
Proceeding from the above-stated, we collect the experimental stand for process studying steaming (decontaminations) of the kerosene fraction leaving from difficult rectification of a column of installation of primary distillation Bukhara oil treatment factory (fig. 1). The main objective of experimental researches was definition of quality indicators — fractional structure, density and temperature of flash of the kerosene fraction leaving installation of primary distillation and from the subsequent processing by its hydrocarbonic heat-carrier (the steaming agent).
Object of research is the kerosene fraction received from local oilgascondensate of raw materials (at a parity of 70 % of a gas condensate and 30 % of oil) on Bukhara OTF.
Experimental decontamination device consists of capacity 1 for easy fraction, thermometers 2, 7 and 9, electrotiles 3 and 10, a manometre 4, a sand bath 5, a gas torch 6, flask Angler 8, a refrigerator 11 and flasks for gathering of light fractions 12.
During experiments the capacity 1 is filled with easy fraction and it heats up by means of an electrotile 3. The capacity is supplied by the thermometers established in pockets 2 and manometres 4 for constant control of working temperature and pressure of investigated fraction. The working temperature of the hydrocarbonic heat-carrier in the given capacity is supported in limits from 350 T° to 400 T° by means of the sand bath 5 which are warmed up by a gas torch 6. The temperature of a sand bath is supervised under indications of the thermometer 7. During experiment in a flask 8 with volume three
