Explosion Cavity Research Articles

New Steel Fiber Concrete Mechanics Parameters and Contact Explosion Tests

For getting the mechanics and contact explosion capability parameters, some new steel fiber concrete samples with 5% steel fiber were tested, many groups data were obtained with compress strength, shear strength and fracture toughness. The model tests were carried out on the new steel fiber concrete under contact explosion, the coefficient of explosion cavity radius of the material is obtained by above experiments and theory study. The two kinds of experiments above point out, the new steel fiber concrete with steel fiber has very high strength and rupture temper and its capability anti-explosion is about three times than general concrete.

Study on Stress Field Distribution Characteristics under Coal Seam Pre-splitting Blasting

In order to analyze thoroughly cracks characteristics inside coal seam which are most important for improving the effect of methane extraction, according to ventage stress concentration theory and thick cylinder principle, this paper study the characteristics of various stress distribution under pre-splitting blasting in coal seam. The results show that on explosion cavity wall, radial stress of coal particle is equal in value and opposite in direction with blasting gases; tangent stress is related to differ position; cracks extension on explosion cavity wall will start along horizontal direction firstly. Therefore, methane extraction hole must be designed by cracks distribution characteristics so that obtaining most effect.

Anti-strike Capability of Steel-fiber Reactive Powder Concrete

Penetration and contact explosion tests on reactive powder concrete (RPC) containing 5 per cent steel-fiber were carried out to investigate the anti-strike capability of steel-fiber reactive powder concrete (SFRPC). The penetration tests consisted of two sample groups corresponding to hit speeds 308 m/s - 582 m/s and 808 m/s - 887 m/s, respectively. The contact explosion tests were carried out in an explosion test pit using TNT with charges in the range 0.5 kg - 3.0 kg. The tests results show that the anti-strike capability of SFRPC targets is much better than ordinary C30 concrete. The penetration depths of the SFRPC targets were less than half those evaluated values of the C30 concrete targets. The areas of the blasting funnels and the explosion cavity radii in the SFRPC plates are also much less than the calculated results in ordinary C30 concrete, being about one quarter of those of the latter. Defence Science Journal, 2013, 63(4), pp.363 -368 , DOI:http://dx.doi.org/10.14429/dsj.63.2407

The Effect of an Intermediate Inclusion in Soil on a Buried Lined Tunnel Due to a Nearby Explosion

The paper presents the analysis of a buried explosion in the proximity of a tunnel in a soil medium. The soil is modeled as an elastic plastic material with irreversible bulk and deviatoric strains. The tunnel lining is modeled as an elastic plastic Timoshenko shell. An inclusion is placed in soil between the explosion source and the tunnel and its effect on the tunnel response is investigated. A coupled approach is proposed to allow to perform stable calculations of that complex problem and to follow the development of the large deformations and distortions of the tunnel lining's shape, as well as the large deformations of the explosive cavity. The effect of the rigid single inclusion or of the set of rigid inclusions located between the charge and the lined tunnel on the tunnel lining's response has been studied. When the inclusion is relatively distant from the lining, even a small inclusion improves the state of displacement and pressure of the lining, while when the inclusion is placed close to the lining, the lining's displacements increase. When the inclusion is small, its size slightly affects the lining shape while for middle sized inclusion the permanent displacement sharply decreases. Compared to the case of a single inclusion, a set of intermediate inclusions of the same size slightly decrease the peak stress at the front point and more significantly protects the periphery zone. The usage of larger inclusions yields better protection of the lining front part.

Evaluation of the radiation hazard in flooding of the underground nuclear explosion zone in Yunkom mine

The radiation hazard of the Klivazh object (Yunkom mine, Enakievo, Donetsk oblast, Ukraine) was evaluated, alternative ways of the mine decommissioning were considered, and the radiation hazard of the mine flooding was assessed. Specimens simulating the virtified glass-ceramic melt formed by the nuclear explosion were fabricated, and their chemical resistance (solubility) was examined by leaching of U, Cs, and Sr. The U, Cs, and Sr concentrations in water flowing over the explosion cavity were determined. When the tunnels of only two lower horizons (936 and 826 m) will be flooded, the radionuclide concentrations in the mine water will not exceed 10−4 PC C ingest (PC C ingest is the permissible concentration in potable water for population, established in the Ukraine).

Research on Flame Spread of Flying Small Coal Particles Explosion

The explosion cavity, in which nine coal dust explosion tests are made, is made of circular pipe of 0.3m diameter and square pipes of 80mm section side. The analysis of test results shows the flame spread in coal Dust explosion is fast, big change and poor stability; Neither the maximum flame speed nor the spread distance keeps direct proportional to the amount of coal dust. However, there is the optimal coal dust consistency, with which the flame speed can reach its maximum. When the coal dust consistency is bigger than the optimal consistency, the flame speed curve will overall decline. Temporarily "hypoxia" is a very important factor that led to this situation.

Gas Leakage Prediction Model of Large-Scale Explosions in Hard Rock Based on Quantification Theory

The toxic gas produced by the underground large-scale contained explosions have a great impact on the surrounding environment safety of the explosion project, so it is of great significance for the safety protection design to predict the leakage of the explosion gases to the environment. Based on the study of the one-dimensional spherically (axially) symmetric fluid dynamic model for seepage of the underground contained explosion gases, the qualitative and quantitative variables which impact the gas seepage, such as the explosion cavity, the gas pressure in the cavity and the rock mass permeability, among which the qualitative variables can describe the uncertainty of the geological mass, were analyzed. In accordance with the physical significance of variables and the quantification theory, the qualitative variables were quantified and such details as the principle for variable selection, significance assessment and recurrence test to establish a quantification prediction model, etc. were discussed. Based on 15 test samples on the hard rock conditions, we have established a quantification model for prediction of the contained explosion gases leakage at the specific site. The prediction accuracy of this model can meet the requirement of this project, and according to this model, it is known that such qualitative factors as groundwater status and rock properties have significant influence on the gas leakage. In this study, the prediction model is established based on physical analysis so that the quantitative prediction model could have its rationality and effectiveness well ensured, and the research methods and results in this paper could be promoted and applied in the similar engineering practices.

Leaching of radionuclides from products of underground nuclear explosions in granite: Experiments with radioactive samples of melted rock from explosion cavities on Semipalatinsk test site

Leaching of 137Cs, 90Sr, and 239+240Pu from products of underground nuclear explosions in tunnels 504R, 148/5, and 190 of the Semipalatinsk test site was studied. Samples were taken from central zones of the explosions. Sample characteristics are presented. Leaching experiments were performed in the batch and dynamic modes. The degrees and rates of 137Cs, 90Sr, and 239+240Pu leaching with granite aqueous extract were determined. The leach rates determined in batch experiments are in the following ranges: 90Sr 2.3 × 10−6−1.6 × 10−4, 137Cs 5.0 × 10−6−2.5 × 10−4, and 239+240Pu 5.6 × 10−7−2.1 × 10−4 g cm−2 day−1, and those determined in dynamic experiments are in the following ranges: 90Sr 9.2 × 10−10−10−8, 137Cs 1.0 × 10−9−1.6 × 10−7, and 239+240Pu 1.3 × 10−11−2.5 × 10−11 g cm−2 day−1. The values obtained are close to those reported in the literature for vitrified radioactive wastes.

The geoelectric structure at the site of “Crystal” underground nuclear explosion ( Western Yakutia) from TEM data

The resistivity pattern at the site of the “Crystal” underground nuclear explosion (Daldyn–Alakit district of Yakutia) of 1974 which led to an accident has been imaged using TEM data. The local background pattern corresponds to a three-or four-layer earth with a conductor at the base. The uppermost layer, with a resistivity of tens to hundreds of ohm · m, has its bottom at 190–260 m asl and consists of perennially frozen Late Cambrian carbonates. The resistivity structure of shallow subsurface at the blast epicenter remained unperturbed though being subject to mechanic and thermal effects. The bottom of the second layer is at 20 to 190 m below the sealevel and its resistivity is 7–10 ohm · m. It is composed of frost-bound and unfrozen cold rocks that belong to a Late Cambrian water-bearing sequence (an aquifer). The third and fourth layers make up the conducting base of the section (0.2–1.4 ohm · m) while the conductor’s top matches the table of a Middle Cambrian aquifer. Anomalous transient response at the site prompts the existence of a local conductor possibly produced by highly saline waters in the containment cavity and in deformed rocks around it. However, the resistivity is too low (0.02 ohm · m) to be accounted for by any model available at the present state of knowledge. Another problem is to explain how the brines circulating at large depths may have reached the explosion cavity and the surrounding strained zones. The study has provided a first idea of the background resistivity distribution and its UNE-induced changes.

Explosive characteristics of nanometer and micrometer aluminum-powder

The explosive characteristics of aluminum powder have great significance in preventing and controlling aluminum-dust explosion accidents, especially the nano-aluminum powder. The explosion characteristics of 100 nm and 75 μm aluminum powders were investigated by using a 20 L spherical explosion cavity and a horizontal pipe whose cross-section area is 80 mm × 80 mm and length is 8 m. The results show that the maximum explosion pressure and its rising rate of 100 nm aluminum powder gradually increase with increasing concentration of aluminum-powder at the beginning. When aluminum-powder concentration is 1 kg/m 3, the maximum explosion pressure reaches its maximum, and then gradually decreases. While when the concentration is 1.25 kg/m 3, the maximum rate of pressure rise obtains its maximum, and then decreases. After 100 nm aluminum powder is exploded in pipes, the peak overpressure of blast wave first decreases and then increases to the maximum at a distance of 298 cm from the ignition source, and then gradually decreases. The most violent concentration is about 0.4 kg/m 3 which is lower than 0.8 kg/m 3 of 75 μm aluminum powder, so 100 nm aluminum powders are more easily exploded. The change laws of maximum explosion pressure, maximum rate of pressure rise and blast-wave peak overpressure of 100 nm aluminum powders with concentration are similar to those of 75 μm aluminum powders, but these values are much higher than 75 μm aluminum powders under the same concentration, so the aluminum-powders explosion of 100 nm will produce more harms. In the process of production, storage and transportation of aluminum powder, some relevant preventive measures can be taken to reduce the loss caused by aluminum-dust explosion according to nano-aluminum dust.

Target Loading from a Submerged Explosion

The pressure on a flat plate suspended over a submerged detonation is measured and simulated. Calculation and experiment are in relatively good agreement, although there is variation in experimental results and simulations are sensitive, near the centerline, to the computational details. This sensitivity is linked to the instability of the accelerating plume, typical of a Richtmyer-Meshkov instability. The plate loading features an initial force at plate center, followed by an expanding circular loading pattern. The initial load is due to plume impact, while the circular load arises from the impact of water transported up the edges of the explosion cavity.

Target Loading from a Submerged Explosion

The pressure on a flat plate suspended over a submerged detonation is measured and simulated. Calculation and experiment are in relatively good agreement, although there is variation in experimental results and simulations are sensitive, near the centerline, to the computational details. This sensitivity is linked to the instability of the accelerating plume, typical of a Richtmyer-Meshkov instability. The plate loading features an initial force at plate center, followed by an expanding circular loading pattern. The initial load is due to plume impact, while the circular load arises from the impact of water transported up the edges of the explosion cavity.

Underground explosion of a cylindrical charge near a buried wall

The paper investigates the explosion characteristics of a cylindrical explosive that is buried in soil close to a rigid obstacle. The soil is modeled as a bulk compressible elastic plastic medium, including full bulk locking and dependence of the current deviatoric yield stress on the pressure. The Lagrange approach and the modified variational-difference method are used to simulate the process. The pressure distribution along the rigid obstacle has been studied for various stand of distances of the explosive from the obstacle. It was shown that when the explosion is relatively close to the obstacle, the envelope of the pressure distributions (connecting the maximum stress values of all distributions along the wall) shows a maximum value that is located at some distance away from the axis of symmetry and not along the axis as is the case for a distant explosion. It was found that this phenomenon appears when the interaction of the reflected wave with the explosive cavity yields significant deformation of the cavity frontal part that it is sharply deformed and becomes planar. When the explosive stand of distance from the obstacle is moderate or large, the explosion cavity remains cylindrical during all times and the peak pressure is developed along the axis of symmetry. The paper also studies the dependence of maximum stress values of all distributions and their location on the explosive stand of distance and the cavity expansion time history.

Radionuclide release and transport from nuclear underground tests performed at Mururoa and Fangataufa — predictions under uncertainty

In the context of a study by the International Geomechanical Commission (IGC) and the International Atomic Energy Agency (IAEA) on the effects of nuclear tests at the atolls of Mururoa and Fangataufa, release to the biosphere is estimated for 35 radionuclides originating from 147 nuclear underground tests. Based on a qualitatively characterised hydrogeological situation of atolls and relatively scarce site-specific data, a model chain was developed to conservatively estimate the radionuclide fluxes via groundwater, from their sources, the explosion cavities, towards the biosphere, the ocean or lagoon. Finite element hydro-thermal modelling was used to describe water flow. Parameters were calibrated by a very few measured pre-test temperature profiles in bore holes. The impact of the tests on groundwater flow and mechanical impact on rock was considered. Estimates were made to quantify spatial extensions and temporal evolution of impact by using measurements on refilling rate of the cavities. Tests were categorised according to their specific yield and location although detailed data were missing. A base case parameter set was defined for the hydraulic conditions and for the initial radionuclide inventory of individual tests. Models were used to describe the concentration of radionuclides in the cavities as a function of time. Radionuclide transport from the cavities to the biosphere was represented by two different approaches: a double porosity model for the fractured volcanic rock and a single porosity model for the overlaying, highly porous carbonates. Results consist of conservative estimates on radionuclide release into the environment, or concentration in the lagoon or ocean water. Their sensitivity was investigated using different models and parameters. A few measured data (concentrations in a few cavities, in the deep carbonates and in the lagoons for selected radionuclides, such as 3H, 14C, 36Cl, 90Sr, 129I, 137Cs 239, 240Pu and 241Am) were available for a comparison with the calculations. In view of the lack and uncertainty of site-specific data, the agreement is of acceptable quality.

Influence Exerted by Gas Leakages from the Explosion Cavity for a Spherical Charge on Rock Breaking

A calculated scheme is developed for the explosion action of a spherical charge in brittle rock taking account of the ejection of stemming and penetration of gaseous detonation products through the charge borehole into broken rock mass. The influence of stemming parameters on operating efficiency is determined. Estimates are given for the dimensions of breaking zones when the gas finds its way into cracks.

Generation of geomagnetic oscillations in the late stage of a camouflet explosion

Generation of geomagnetic disturbances is studied at the late stage of an underground nuclear explosion, where the originally displaced geomagnetic field penetrates into the explosion cavity again. The strength of the electric field of a geomagnetic disturbance due to oscillations of the magnetic moment is calculated. A method for analyzing records of geomagnetic disturbances is developed that permits one to take into account the character of quasiperiodic oscillations in the signal. The calculations are compared to results of the experiments performed in the state of Nevada in 1958.

Effect of the parameters of the biaxial field of rock pressure on the shape of the fracture zone formed by an explosion of a cylindrical charge in a brittle medium

The effect of the biaxial field of external rock pressure on the deformation of the fracture zone formed by radial cracks in an elastic-brittle medium is studied. We consider cylindrical charges that are rather thin compared to the diameter of the explosive borehole. This allows one to exclude the grinding zone from consideration. At the initial moment of time, the system of emerging cracks originating at the boundary of the circular hole is assumed to be symmetric. To solve the problem, we use singular integral equations and the fracture criterion σϑ. The propagation trajectories of the system cracks are calculated in the quasistatic approximation in a step-by-step manner in relation to the parameters of the external compressive stress field. Two ideal variants of loading of the crack system are analyzed. In the first variant, gaseous detonation products penetrate into cracks, and the pressure in the explosion cavity and the cracks instantaneously equalizes. In the second variant, gases do not penetrate into the cracks of the system. The fracture zone is shown to become an ellipse whose long axis is oriented in the direction of the largest compressive stress in magnitude acting at infinity. The effect of the variants of loading of the crack system on the shape and dimensions of the deformed fracture zone is evaluated.

Modeling fractures in rock blasting

A numerical model based on the discrete element is used to investigate the importance of stress waves on the initiation and propagation of radial fractures during the dynamic loading phase of an explosion. An explosion occurring in a two-dimensional rock plate is simulated and the resulting fracturing process is detailed. First, during the pressure rise of the explosive source, a crushed zone is created in the vicinity of the explosion cavity. Then, because of the tensile tail of the propagating pressure wave, radial fractures propagate from the edge of the crushed zone. Different crack velocities were found which varied with respect to crack length. It was seen that the higher the crack velocity the greater the extent of the radial fractures. Tests with different explosive sources have shown that both the size of the crushed zone and the length of the radial fractures depend on their peak pressure and frequency content. Efficient sources, which generate long radial fractures with a small crushed zone, can be obtained with low peak pressures provided that the frequency content is lowered. Finally, when the plate is subjected to uniaxial compression, the fractures align along the main stress axis. In the light of these results, the method proposed here seems to be appropriate to study complex problems involving the creation and evolution of discontinuities.

Efficiency of pulse gas-dynamic technique of pneumatic transportation of friable materials

transferable over a long distance, but this requires substantial energy and also imposes limits on the particle size, moisture content of the material, and uniformity of physical properties. In this work we have studied a new pulse gas-dynamic technique of friable material transportation, which proposes to eliminate the above-mentioned drawbacks. The essential feature of the technique is cyclic ejections of compressed gas from gas sources lying deep under a friable material bed. The sources are snapped into action in the "travelling wave" mode, in which an ejection cone as well as a camouflet (underground explosion cavity) may be the external manifestation of each pulse [2]. In physical nature, this process is similar to the phenomenon of directed excavating explosion well known in explosion engineering, but in this case the material moves within the confined space of the transport trough. Studies were made earlier to determine the local transportation index for both cone and camouflet formation [2]. The studies were aimed at deciphering the most effective range of parameters, in which the material transportation process, at a fLxed consumption of the energy of the gas, is optimum. It was shown that the most acceptable is that range of parameters on combination of which is formed, in the case of singular actuation of the gas source, a limiting camouflet or a cone with a small ejection activity index fi = 0.4-0.7, fi being the ratio of the cone radius to the source depth. However, previous studies examined actuation of only a pair of sources where symmetric ejection of the first source in a bed of an unagitated friable material is preparatory and the next (directed) one is operating. In real transporting situations, on the other hand, the operating ejection of the preceding source is preparatory, i.e., the physical pattern of development of the phenomenon is different. This necessitates an assessment of the efficiency of the pulse pneumatic transporter and precise determination of the optimal combination of the starting paraxneters. The following should be distinguished as the key factors governing the rate of development of the phenomenon. The energy E of the gas in a pulse, whose scale can be depicted via the full ejection energy, with due regard for the degree of gas expansion [3], is:

A field study of tritium migration in groundwater

A field study of tritium migration from an underground nuclear explosion was carried out for more than 7 years. A series of satellite wells was drilled around the explosion cavity, which is within a nuclear test site water-supply aquifer. Samples from various wells were analysed. In this way, variations in the tritium concentration of water from different wells were determined, and the extent of tritium migration during the 7 years after the detonation was examined. The maximum tritium concentration reached in water from various wells is just 52-times higher than the maximum permissible concentration for drinking water and decreased afterwards. According to the results obtained, the flow rate of groundwater was inferred to be about 91 m per year and the maximum contamination distance of water supplies by the tritium were ≤ 2 km from the explosion cavity.