Development of explosion cavities in sandy soils

Kolkov, O. S.; Tikhomirov, A. M.; Shatsukevich, A. F.

doi:10.1007/bf00741685

Cited by 3 publications

(4 citation statements)

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“…This agrees with the experimental data on the advantages of coarsegrained stemming [3,4]. From the viewpoint of maximum utilization of the explosion energy and of safety of blasting at sites hazardous because of gas and dust, the most effective stemming is a water-filled capsule with the borehole mount sealed with a sand-clay stemming.…”

Section: Resultssupporting

confidence: 84%

“…The law of variation of a(t) agrees fairly well with the data in [4] (a = 17.9t ~ when recalculated for Q = 300 g). The difference in the coefficient may be due to the type of explosive (PETN) used in [4], to the medium (sand), and to the spherical symmetry of the explosion.…”

Section: Resultssupporting

confidence: 68%

“…To record the development of the radius a of the cavity due to the explosion we used an experimental method similar to that described in [4]. Several transducers, connected as the inductance in a resonant circuit, were placed at various distances from the axis of the charge and were rigidly fixed.…”

Section: Resultsmentioning

confidence: 99%

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The optimum depth for long cylindrical explosive charges

Stepanov¹,

Demchuk²

1975

Soviet Mining Science

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By the optimum depth for a long vertical cylindrical explosive charge, h,, we mean the length of the monolithic stemming of homogeneous material which, under given explosion conditions (given mechanical properties of the rock and stemming, natural parting of the rock, quantity and properties of the explosives, presence or absence of air gaps between the charge and the borehole walls, and direct or reverse initiation), will give the maximum utilization of the energy of the explosion in terms of newly formed free surface (crushing) and the total crushed volume.We will consider hz from two points of view.First we calculate the optimum maximum depth hz = h+, which we find by means of the phenomenological theory of puncturing of a barrier Of finite thickness, as developed in [I, 2]. Then we will use another criterion for hl --simultaneity of ejection of the stemming and emergence of the explosion products at the free surface through the clefts in the surrounding rock [3]. The two approaches will be compared by means of an illustrative example. Experimental ResultsWe investigated the commonest stemming materials (sand, gravel, clay, and water) with charges of Ammonite 6ZhV weighing Q = 300 g, with diameter do = 4.2 cm, length ~o = 22 cm, in 1 m boreholes in a granite quarry in the region of the "Kuznechnoe" station of the Leningrad region and in the Bugaevskii sandstone quarry in the Voroshilovgrad region.To record the motion of the stemming and its time of flight from the borehole we constructed a special apparatus, based on recording the changes of inductance in a coil 2 m in diameter in which a magnetic field from ferrite rings pressed into the stemming at distances of 60, 40, and 20 cm from the borehole mouth moved.The coil was placed around the borehole. The emf induced in the transducers was recorded with an oscillograph.The velocities of the transducers were equated with the velocity of the corresponding layers of stemming.The time marks were made with an ionization gage at the opposite end of the cartridge from the detonator. The resulting oscillograms were processed in conformity with calibration graphs taken before the explosion after warming up the apparatus and balancing the measurement bridge.The start of motion of the stemming was monitored with an SKS-IM instrument. *Deceased. All-Union Scientific-Research Institue of Natural Gas.

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Section: Resultssupporting

confidence: 84%

Section: Resultssupporting

confidence: 68%

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The optimum depth for long cylindrical explosive charges

Stepanov¹,

Demchuk²

1975

Soviet Mining Science

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“…Kolkov et al [6] showed that in the explosion of an ordinary charge the kinetic energy of the ground in the compression wave at distances R/C I/~ > i is about 2-3% of the total energy of the explosion, and the energy of the explosion products in the cavity at the moment of its maximum expansion is about 3-4%.…”

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confidence: 99%

The effect of an air cavity on the motion of the ground during ejection blasting

Mel'nikov¹,

Marchenko²,

Zharikov³

1976

Soviet Mining Science

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The increasing scale of utilization of blasting in mining and construction is using up a huge quantity of explosives.It is therefore important to study the problem of increasing the useful expenditure of blasting energy and reducing the specific consumption of explosives.It has been found [I] that the use of alr-cavlty charges is one of the most effective methods of controlling the processes of ejection of the ground, and can significantly increase the useful work of a blast.The motion of the ground in ejection blasting qualitatively characterizes the mechanism of transfer of energy to the surrounding medium.Consequently, by considering the motion of the ground at various stages in the action of the blast, we can establish the character of conversion of the energy of the detonation products of the charge to kinetic energy of motion of the ground.In this article we will try to adopt a unified point of view in considering all three maln stages in the ejection process In order to make a more detailed investigation of the mechanism of transfer of energy of the blast to the surrounding medium during the action of air-cavity charges.In the first stage, before the compression wave reaches the free surface, the motion of the medium will be similar to the motion in camouflet blasting, both from the viewpoint of central symmetry and of energy consumption.In the second stage, after the reflected decompression wave from the free surface arrives, the central symmetry of the development of the cavity is lost. This stage in the blasting of ground is characterized by a pfston-llke action of the gaseous explosion products, the energy of which is expended on additional acceleration of the ground in the direction toward the free surface.The second stage is apparently basic in the process of execution of mechanical work, and reflects the kinematics of development of the ejection blast in which the expanding gaseous explosion products "push out" the ground beyond the edge of the crater.The ejection process is completed by halllstic flight of the ground.In this stage the most important feature is the direction and magnitude of the velocity vector, which determines the range of flight of the ground and the possibility that it may fall back into the crater.To investigate the mechanism of transfer of the energy of the blast to a solid medium in the first stage of development of the blasting process, we made comparative investigations of the action of ordinary spherical charges and of alr-cavity charges in blasting in elasticoplastic (Plexiglas) and brittle (sodium thiosulfate) media.As a dimensionless geometrical parameter modeling the load on the sides of the cavity we took the charge cavity index n, equal to the ratio of the radius of the cavity to the radius of the charge.The parameters of the compression wave were measured by electroInstitute of Geophysics, Academy of Sciences of the USSR, Moscow.

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