Blast Parameters Research Articles

Theoretical and Experimental Studies on Blast Wave Propagation in Air

AbstractHigh pressure and temperature are produced when high explosives are detonated in open air. The heat of detonation of the explosive compound, peak pressure, and temperature of the blast wave are important blast parameters. A blast wave generated due to explosion propagates into the air medium at supersonic speed until the pressure in the blast zone is released completely. The intensity of the impact by the blast wave on any intervening solid object depends on the blast parameters and the speed of propagation of the blast wave. A theoretical analysis is carried out to predict the pressure produced in the expanding blast zone as function of distance and time by analytically solving the governing equations. The initial peak pressure and temperature of blast wave, which are required in the theoretical analysis, were calculated making use of the blast wave theory. For comparison, experiments were conducted by detonating different weights of high explosives, and pressures were recorded at various distances from the blast point. The high explosives used in the experiments were TNT (0.045, 0.5, 1, 15, and 40 kg) and Composition B (0.045, 0.5, 1, and 15 kg). The theoretical results are validated by comparison with the experimental data and empirical equations available in literature.

Study on Parameters of Deep-Hole Loose Blasting under the Condition of High Stress

The hole wall crushed and fractured zones length has been derived theoretically,and put forward the calculation formula of blasting crushing circle and radius of the corresponding fracture zone.Corresponding to the deep rock blasting parameters design on the basis of theoretical analysis,then lead to the reasonable parameters.These can provide certain reference design work for coal mine deep rock blasting parameters.

Numerical modelling of water-coupling cutting blasting in granite quarry

To achieve a smooth fracture plane with minimal damage to a rock block or remaining rock mass, a water-coupling cutting blasting technique was applied in a granite quarry. The mechanism of water-coupling cutting blasting is demonstrated with the specification of prerequisites for crack growing and arresting. Using the LS-DYNA program, the maximum principal stress distribution and rock damage evolution process were observed, and the validity of crack extension till coalescence was verified by comparing the calculated and theoretical water pressure needed to induce fracture. The optimum blasting parameters for achieving the best cutting blasting performance were obtained by simulations under different coupling ratios and blasthole spacings. The successful water-coupling cutting blasting practice in the granite quarry has great potential to be applied in other similar engineering.

Isolated Primary Blast Alters Neuronal Function with Minimal Cell Death in Organotypic Hippocampal Slice Cultures

An increasing number of U.S. soldiers are diagnosed with traumatic brain injury (TBI) subsequent to exposure to blast. In the field, blast injury biomechanics are highly complex and multi-phasic. The pathobiology caused by exposure to some of these phases in isolation, such as penetrating or inertially driven injuries, has been investigated extensively. However, it is unclear whether the primary component of blast, a shock wave, is capable of causing pathology on its own. Previous in vivo studies in the rodent and pig have demonstrated that it is difficult to deliver a primary blast (i.e., shock wave only) without rapid head accelerations and potentially confounding effects of inertially driven TBI. We have previously developed a well-characterized shock tube and custom in vitro receiver for exposing organotypic hippocampal slice cultures to pure primary blast. In this study, isolated primary blast induced minimal hippocampal cell death (on average, below 14% in any region of interest), even for the most severe blasts tested (424 kPa peak pressure, 2.3 ms overpressure duration, and 248 kPa*ms impulse). In contrast, measures of neuronal function were significantly altered at much lower exposures (336 kPa, 0.84 ms, and 86.5 kPa*ms), indicating that functional changes occur at exposures below the threshold for cell death. This is the first study to investigate a tolerance for primary blast-induced brain cell death in response to a range of blast parameters and demonstrate functional deficits at subthreshold exposures for cell death.

Anatomical Manifestations of Primary Blast Ocular Trauma Observed in a Postmortem Porcine Model

We qualitatively describe the anatomic features of primary blast ocular injury observed using a postmortem porcine eye model. Porcine eyes were exposed to various levels of blast energy to determine the optimal conditions for future testing. We studied 53 enucleated porcine eyes: 13 controls and 40 exposed to a range of primary blast energy levels. Eyes were preassessed with B-scan and ultrasound biomicroscopy (UBM) ultrasonography, photographed, mounted in gelatin within acrylic orbits, and monitored with high-speed videography during blast-tube impulse exposure. Postimpact photography, ultrasonography, and histopathology were performed, and ocular damage was assessed. Evidence for primary blast injury was obtained. While some of the same damage was observed in the control eyes, the incidence and severity of this damage in exposed eyes increased with impulse and peak pressure, suggesting that primary blast exacerbated these injuries. Common findings included angle recession, internal scleral delamination, cyclodialysis, peripheral chorioretinal detachments, and radial peripapillary retinal detachments. No full-thickness openings of the eyewall were observed in any of the eyes tested. Scleral damage demonstrated the strongest associative tendency for increasing likelihood of injury with increased overpressure. These data provide evidence that primary blast alone (in the absence of particle impact) can produce clinically relevant ocular damage in a postmortem model. The blast parameters derived from this study are being used currently in an in vivo model. We also propose a new Cumulative Injury Score indicating the clinical relevance of observed injuries.

Improving the Charging and Blast Regimes on Blast Furnaces at the Azovstal Metallurgical Combine

An examination is made of the main problems and methods of optimizing the gasdynamic regime of blast furnaces. The gasdynamic regime depends mainly on the distribution of materials in the top of the furnace. The interactive system CHARGING – which models charging by a bell-less charging apparatus – is used to determine the configuration of the layers of charge materials and calculate the distribution of burden coke along the radius of the top. Improvements were made to the charging regimes on blast furnaces Nos. 3 and 4 at the Azovstal Metallurgical Combine. The blast parameters of the furnaces at the combine were optimized by using the interactive BLAST system. This system used the parameters specified for the blast to calculate generalizing characteristics of the blast regime and correct the blast parameters as needed in order to keep the generalizing characteristics at their optimum levels.

Collection, characterization, conservation and utilization of traditional rice varieties of Karnataka

Traditional rice varieties (TRVs) collected from different locations of Karnataka were evaluated for grain yield, its attributes, reaction to blast, grain quality and cooking parameters (protein, amylose, iron and zinc content using NIR) by adopting standard procedures. Analysis of grain nutrient contents such as protein, amylose, iron and zinc revealed wide variation for the grain protein content (5.5714.96%), amylose (17.25–44.42%), iron (9.17–15.72 mg/kg) and zinc (10.24–33.40 mg/kg). Physical, physico-chemical and cooking quality parameters estimated for the selected 49 TRVs also indicated significant difference for water uptake ratio suggesting variation for kernel texture, surface area and amylose content. Screening of the TRVs for field resistance against leaf blast disease revealed that 11 out of 324 TRVs were found resistant at both Mandya and Ponnampet. Molecular validation for leaf blast disease resistance for selected TRVs revealed that, Pi 9 resistance type allele present in 48 TRVs; Pish in 42; Pi38 in 46; Pib in 28; Pi 20(t) in 26 and PiK in 21 TRVs.

Selection of Coal Gasification Parameters for Injection of Gasification Products Into a Blast Furnace

An analytical study was performed on the influence of blast parameters on the course of the processes in the volume of a blast furnace and smelting rates by injection of low-grade coal gasification products. It was found that the use of hot reducing gases produced by an atmospheric blast with the highest possible temperature is more effective for injection into the blast furnace.

Secondary shock features for large surface explosions: results from the Sayarim Military Range, Israel and other experiments

A series of surface explosions was designed and conducted by the Geophysical Institute of Israel at the Sayarim Military Range in the Negev desert, including two large-scale explosions: approx. 82 tons of high explosives in 2009, and approx. 100 tons of low-grade ANFO explosives in 2011. The main goal of the explosions was to provide large controlled sources for calibration of global infrasound stations designated for monitoring nuclear tests; however, the geophysical experiment also provided valuable observations for shock wave research. High-pressure gauges were deployed at distances between 100 and 600 m to record air blast properties and to provide reliable estimation of the true charge yield compared to the design value. Secondary shock phenomena were clearly observed at all near-source gauges as characteristic shock wave shapes. Secondary shocks were also observed at numerous seismic and acoustic sensors deployed in the range 0.3–20 km as acoustic phases. Empirical relationships for standard air blast parameters (peak pressure and impulse) and for a new parameter called secondary shock time delay, as a function of distance, were established and analyzed. The standard parameters, scaled by the cubic root of the estimated TNT yield, were found to be consistent for all analyzed explosions. However, the scaled secondary shock delays were clearly separated for the 2009 and 2011 explosions, thus demonstrating dependence on the explosive type. Additionally, air blast records from other experiments were used to extend the charge and distance ranges for the secondary shock observation, and showed consistency with the Sayarim data. Analysis and interpretation of observed features of the secondary shock phenomenon are proposed and a new empirical relationship of scaled secondary shock delay versus scaled distance is established. The results suggest that the secondary shock delay can be used as a new additional waveform feature for simple and cost-effective explosive yield estimation.

Predictions of Experimentally Observed Stochastic Ground Vibrations Induced by Blasting

In the present paper, we investigate the blast induced ground motion recorded at the limestone quarry “Suva Vrela” near Kosjerić, which is located in the western part of Serbia. We examine the recorded signals by means of surrogate data methods and a determinism test, in order to determine whether the recorded ground velocity is stochastic or deterministic in nature. Longitudinal, transversal and the vertical ground motion component are analyzed at three monitoring points that are located at different distances from the blasting source. The analysis reveals that the recordings belong to a class of stationary linear stochastic processes with Gaussian inputs, which could be distorted by a monotonic, instantaneous, time-independent nonlinear function. Low determinism factors obtained with the determinism test further confirm the stochastic nature of the recordings. Guided by the outcome of time series analysis, we propose an improved prediction model for the peak particle velocity based on a neural network. We show that, while conventional predictors fail to provide acceptable prediction accuracy, the neural network model with four main blast parameters as input, namely total charge, maximum charge per delay, distance from the blasting source to the measuring point, and hole depth, delivers significantly more accurate predictions that may be applicable on site. We also perform a sensitivity analysis, which reveals that the distance from the blasting source has the strongest influence on the final value of the peak particle velocity. This is in full agreement with previous observations and theory, thus additionally validating our methodology and main conclusions.

Application of Loose Blasting in Fully-Mechanized Coal Face Crossing Faults

Loose blasting technology is applied to the problem of fully mechanized coal face passing through fault. The paper gets safe and practical loose blasting parameters and blasting process, achieves no re-open-off cut for the fully mechanized coal face, reduces loss of coal pillars for faults and improves the coal recovery rate. At last, the goal of high yield, steady yield, and increasing yield for fully mechanized mining face is realized.

Deep-hole pre-split blasting mechanism and its application for controlled roof caving in shallow depth seams

The shallow depth coal seams mined in the Shendong Mining Area has led to large area roof weighting frequently due to large thickness, high tensile strength and small overlying load of the main roof. As a result, many accidents have happened including hydraulic support being iron-bound, water inrush through the penetrating cracks along coal wall, and potentially induce large area residual pillars instability and even wind blast damage particularly in the conditions beneath a room mining goaf. To prevent the large area roof weighting accidents, deep-hole pre-split blasting technology for controlled roof caving is a suitable method and has been widely applied in the mines, and many in situ trials have already achieved a sound performance. According to the field conditions of the shallow depth coal seams, this paper employs cylindrical cavity expansion theory to calculate the three blasting-induced divisions including break zone, fracture zone and elastic vibration zone. The software of LS-DYNA3D was applied to establish a deep-hole pre-split blasting model, which presented the rock stress field and the break scope affected by the high energy explosion stress wave. The simulation results revealed the blasting for controlled roof caving mechanism and also optimized the blasting parameters. The field observations showed that, with the application of deep-hole pre-split blasting technology in Shigetai Mine, Shendong Mining Area, the first main roof weighting length was about 17.4m, and neither a hydraulic support being iron-bound nor a serious roof subsidence in the form of step convergence in the mining face happened during the first weighting period. The field application of deep-hole pre-split blasting for controlled roof caving has achieved the expected effects.

Substitution of Coke and Energy Saving in Blast Furnaces. Part 2. Study of influence on the Processes of Individual Charge Parameters

The system of discrete material and thermal balances in the radial annular cross-sections for 12 vertical and 10 radial ring zones is used to describe the heat and mass transfer processes of iron ore reduction and melting in blast furnace with respect to the various degree of preliminary metallization of the metallic burden. It was found that with increase in preliminary metallization degree the heat demand on direct reduction and the ratio between material and gas flow heat capacities are reduced which leads to the decrease in intensity of a heat transfer in the bottom zones of the furnace. As a result, the height of the bottom zones of blast furnace is increased, while the height of the upper zones is decreased. The gas isotherms move upwards, increasing heat losses through the furnace top. The cohesive zone also moves up and increases in size. The influence of material distribution at the furnace top on parameters of blast furnace operation becomes weaker. Because of decrease in extend of direct reduction the effect of natural gas injection on coke rate is also reduced. As a result the reduction in coke rate associated with the preliminary metallization of the metallic burden could not be fully realized if the burden metallization degree is grater than 20%. The model makes it possible to determine the relationships that exist between processes which take place in the furnace and which affect the character of the smelting regimes and the final results.

Rat Injury Model under Controlled Field-Relevant Primary Blast Conditions: Acute Response to a Wide Range of Peak Overpressures

We evaluated the acute (up to 24 h) pathophysiological response to primary blast using a rat model and helium driven shock tube. The shock tube generates animal loadings with controlled pure primary blast parameters over a wide range and field-relevant conditions. We studied the biomechanical loading with a set of pressure gauges mounted on the surface of the nose, in the cranial space, and in the thoracic cavity of cadaver rats. Anesthetized rats were exposed to a single blast at precisely controlled five peak overpressures over a wide range (130, 190, 230, 250, and 290 kPa). We observed 0% mortality rates in 130 and 230 kPa groups, and 30%, 24%, and 100% mortality rates in 190, 250, and 290 kPa groups, respectively. The body weight loss was statistically significant in 190 and 250 kPa groups 24 h after exposure. The data analysis showed the magnitude of peak-to-peak amplitude of intracranial pressure (ICP) fluctuations correlates well with mortality rates. The ICP oscillations recorded for 190, 250, and 290 kPa are characterized by higher frequency (10-20 kHz) than in other two groups (7-8 kHz). We noted acute bradycardia and lung hemorrhage in all groups of rats subjected to the blast. We established the onset of both corresponds to 110 kPa peak overpressure. The immunostaining against immunoglobulin G (IgG) of brain sections of rats sacrificed 24-h post-exposure indicated the diffuse blood-brain barrier breakdown in the brain parenchyma. At high blast intensities (peak overpressure of 190 kPa or more), the IgG uptake by neurons was evident, but there was no evidence of neurodegeneration after 24 h post-exposure, as indicated by cupric silver staining. We observed that the acute response as well as mortality is a non-linear function over the peak overpressure and impulse ranges explored in this work.

Impulsive loading on reinforced concrete wall

This paper deals with the air blast and ground shock parameters for reinforced concrete wall panels. In this investigation peak pressure, pressure wave front arrival time, rising time, decreasing time and duration of the positive pressure phase of air blast time history parameters, and peak particle acceleration, arrival time, shock wave duration and time lag between ground shock and air blast pressure arrival at structures of ground shock owing to air blast were determined experimentally. Empirical relationships have been developed between different parameters. Typical values measured due to various charge weights have been compared with results of previous researchers and Conwep. The SAP2000 was used for stress analysis of wall panels using experimental results. The methodology outlined can be used to estimate the blast response of reinforced concrete walls. It is concluded that an accurate analysis of structure response and damage of structures caused by a nearby surface explosion requires simultaneous consideration of ground shock and air blast pressure.

Effects of Sand Blasting on the TBCs Fabrication Quality

CoCrAlY bond coat(BC) and top ceramic coating(TCC) were fabricated on the GH99 super alloy by air plasma spray(APS), before TCC fabrication, BC was treated by sand blasting with different blasting parameters (blasting pressure, blasting speed). The roughness Ra of BC surface was obtained by orthogonal experiment design. Then, cross section morphology of TCC/BC interface were investigated by scanning electron micrograph(SEM), meanwhile TCC/BC interface stresses were analyzed based upon ABAQUS software using finite element method (FEM). The results show that, the roughness of bond coat surface increase first with increasing blasting pressure and speed, then decrease finally becomes stable. Both maximum tensile stress and compressive stress appear in TCC/BC interface area which is bigger in BC layer than that in TCC layer; With the increase of amplitude of interface triangle, the TCC/BC interface stress increase first then decrease until 7μm amplitude, then there appears a decrease of the interface stress.

Optimization and application of blasting parameters based on the “pushing-wall” mechanism

The large structure parameter of a sublevel caving method was used in Beiminghe iron mine. The ores were generally lower than the medium hardness and easy to be drilled and blasted. However, the questions of boulder yield, “pushing-wall” accident rate, and brow damage rate were not effectively controlled in practical blasting. The model test of a similar material shows that the charge concentration of bottom blastholes in the sector is too high; the pushing wall is the fundamental reason for the poor blasting effect. One of the main methods to adjust the explosive distribution is to increase the length of charged blastholes. Therefore, the field tests with respect to increasing the length of uncharged blastholes were made in 12# stope of −95 subsection and 6# stope of Beiminghe iron mine. This paper took the test result of 12# stope as an example to analyze the impact of charge structure on blasting effect and design an appropriate blasting parameter that is to similar to No.12 stope.

Blast wave mitigation by dry aqueous foams

This paper presents results of experiments and numerical modeling on the mitigation of blast waves using dry aqueous foams. The multiphase formalism is used to model the dry aqueous foam as a dense non-equilibrium two-phase medium as well as its interaction with the high explosion detonation products. New experiments have been performed to study the mass scaling effects. The experimental as well as the numerical results, which are in good agreement, show that more than an order of magnitude reduction in the peak overpressure ratio can be achieved. The positive impulse reduction is less marked than the overpressures. The Hopkinson scaling is also found to hold particularly at larger scales for these two blast parameters. Furthermore, momentum and heat transfers, which have the main dominant role in the mitigation process, are shown to modify significantly the classical blast wave profile and thereafter to disperse the energy from the peak overpressure due to the induced relaxation zone. In addition, the velocity of the fireball, which acts as a piston on its environment, is smaller than in air. Moreover, the greater inertia of the liquid phase tends to project the aqueous foam far from the fireball. The created gap tempers the amplitude of the transmitted shock wave to the aqueous foam. As a consequence, this results in a lowering of blast wave parameters of the two-phase spherical decaying shock wave.

Study and Application on Cutting Technology of Underground Drifting Blasting

Because of the weak borehole sealing and inadequate use of the initial free face, the higher investment and unsatisfactory blasting effect still exist in the mine tunnel excavation blasting. In order to improve the blasting effect of drifting, on the basis of a discussion on blasting mechanisms, the author take Xinhong Mine fine sandstone roadway for example, select reasonable blasting parameters and determine the proper cutting form. So that the efficiencies of blasting and excavation have been increased greatly, and good economic results has been achieved.

Experimental Research on Technology of Medium Deep Hole Blasting in Large Inclination Rock Diphead Roadway

For improve the efficiency of large inclination diphead excavation, according to the actual construction of field, rock and explosives properties, parameters of smoothing blasting technology for medium deep hole blasting in large inclination rock diphead tunnel is researched, especially improved the blasting parameters of bottom hole and construction technology, present technologies of double bottom hole and casing for disblocking. Experimental study has obtained the good blasting effect, utilization ratio of blasting hole achieved 89.0% on average.