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At present, the drill-and-blast method is still one of the main construction means in the road tunnel excavation process. When the tunnel penetrates underneath sensitive structures such as high-voltage transmission towers, the blasting and supporting parameters must be strictly controlled to ensure the stability and safety of the surface structures. In this paper, numerical simulations based on a large-section shallow buried tunnel project in Zhuhai are conducted to study the effect of controlled tunnel blast on the dynamic response of transmission towers. The numerical simulation results indicate that the blast vibration velocity of the rock generated by controlled blasting decreases rapidly along the tunnel excavation direction. The blast vibration velocity of the high-voltage transmission tower and its pile foundation gradually increases with the propagation of the blast waves, and the maximum vibration velocity is about 1.24 cm/s. The results indicate that the controlled blasting design of this project can effectively restrain the vibration velocity induced by the blasting load and could ensure the stability and safety of the transmission tower. [ABSTRACT FROM AUTHOR]

The propagation characteristics of blast waves and the prediction accuracy of blast vibration velocities along negative slopes are important because those can be used to guide engineering application and theoretical research. In this paper, the wave theory was applied to better understand the propagation mechanism of blast waves along negative slopes. Regression analysis was used for the Sadovsky and the CRSRI blast vibration velocity prediction models during on-site operations. The magnification of peak blast vibration velocity along a negative slope was introduced to determine the threshold altitude difference for the magnification effect to occur. Based on this parameter, the relative errors between the two prediction models were compared. The obtained results indicate that the superposition of incident and reflected blast waves on a negative slope creates the "slope effect" which locally amplifies the blast vibration velocity. The relative error of the CRSRI prediction model was as small as 17.53%, demonstrating a greater accuracy than Sadovsky's prediction model. The magnification effect of a negative slope was observed at specific altitude differences and was more noticeable in the perpendicular direction. This paper creates a theoretical basis for studying the propagation mechanisms of blast vibration waves along negative slopes as well as predicting the blast vibration velocities. [ABSTRACT FROM AUTHOR]

The blasting vibration has an impact on the rock and soil around the blasting hole and the nearby structures. The vibration-isolating slot is one of the methods to reduce the damage of blasting vibration. In this paper, the influences of the depth and position of the vibration isolation slot on the PPV (peak particle velocity) attenuation characteristics of the ground vibration and blasting vibration damping effect of the vibration isolation slot at different measuring points are studied systematically by LS-DYNA numerical models. The results show that the damping effect of the vibration isolation slot is realized by reflecting the blasting vibration wave and increasing the propagation paths of the blasting vibration wave. When the measuring points are 5 m∼45 m far away from the vibration-isolating slot, the average vibration damping effect of the vibration-isolating slot is more than 30% and the deeper the depth of the vibration isolation slot, the better the vibration damping effect when the measuring points are 5 m∼15 m far away from the vibration isolation slot. However, when the measuring points are 15 m∼45 m far away from the vibration isolation slot, the vibration damping effect is best when the depth of the vibration isolation slot is 15 m. The vibration damping effect of blasting vibration at the same measuring point is different due to different positions of vibration isolation slot. For the measuring points M3 and M5, with the increasing of the distance between the vibration-isolating slot and the explosion source, the vibration damping effect of the vibration-isolating slot shows an increasing-decreasing-increasing trend; however, it shows a decreasing-increasing-decreasing trend for the measuring point M4. [ABSTRACT FROM AUTHOR]

In order to better study the propagation law of tunnel blasting in mountain landforms, taking the excavation blasting project of the Yangliu tunnel along the Yinsong expressway in Guizhou as the research object, the propagation law of vibration waves to tunnel blasting under the mountain tunnel was analyzed based on the ABAQUS finite element software and compared with the field monitoring data. The results show the peak vibration velocity of numerical simulation. Generally, the simulation value is slightly larger than the field monitoring value, but the average error of closing speed is less than 25% and the maximum error is less than 45%. The component velocity of surface peak vibration under blasting to load is the largest in the vertical direction. The "cavity effect" formed by the side-passing tunnel wall has the most significant amplification effect on the peak vibration velocity in the X direction of the rock and soil above it, which is about 1.62∼1.85 times and the resultant velocity is enlarged by 1.27∼1.45 times. Blasting vibration waves spread to the surface in the form of spherical waves inside the mountain, causing the vibration center of the surface to move to the area with lower elevation. The "cavity effect" caused by the side-through tunnel and the shift of the surface diffusion center to the lower part together led to the peak velocity of the lower measuring point of the Yangliu tunnel being much higher than that of the higher measuring point. The research results of this paper have certain reference significance in controlling the influence of underground blasting vibration on residential buildings in mountain areas. [ABSTRACT FROM AUTHOR]

When the effect of combined blast induced shock wave and fragment penetration impact load is sufficiently large enough to induce severe damage in structures compared to individual actions of only-blast and only-impact load, this scenario is called synergetic effect of simultaneous actions. The combined nature of those dual actions aggravates damage and collapses of structures. This paper presented the state-of-the-art review on effect of different parameters, dynamic responses, failure types, and damage mitigation techniques for structures prone to combined actions of blast induced shock wave and fragment impact loads based on findings of experimental, numerical, and analytical research works conducted in previous literature. [ABSTRACT FROM AUTHOR]

This work uses a combination of simulations performed via numerical models and field observations studied the attenuation of deep-hole blasting stress waves and the evolution mechanism of cracks in a jointed rock mass. First, we conclude that the larger the joint angle is, the larger is the transmission coefficient and smaller is the fractal dimension. Second, the time difference between the peak stress difference and the maximum principal stress on both sides of the blasting hole in the horizontal direction of the rock mass with joints is relatively large, but there is no significant difference in the vertical direction. Finally, an unjointed-rock-mass model and multiple parallel joint model are established to explore the attenuation of stress waves and damage effect of multiple joint rock mass, it is concluded that the larger the angle, the smaller is the particle peak velocity and amplitude attenuation, and as the number of stress waves passing through the joints increases, the amplitude gradually decreases and the high-frequency amplitude decreases more significantly than the low-frequency amplitude. The research conclusions of this paper further reveal the damage mechanism induced by a blasting stress wave on jointed rock masses and the law of stress wave propagation and attenuation. [ABSTRACT FROM AUTHOR]

Blast waves generated from the muzzles of weapons may exert negative effects, such as shock waves and impulse noise. If the weapon is fired with a muzzle brake, these effects are recognized to be more severe. This paper discusses the influence of the muzzle brake on certain aeroacoustic noise characteristics based on numerical simulations and a corresponding experiment. The impulse noise, which is induced by complex jet flows discharging from small caliber rifles with muzzle brakes, is focused in this study. Computational fluid dynamics (CFD) and computational aeroacoustics (CAA) are combined to calculate the muzzle flow field and jet noise for cases with and without a muzzle brake, and then the data sets are carefully compared. The simulations indicate that the muzzle brake alters the muzzle flow field and directional distribution of the jet noise compared to a rifle sans muzzle brake. Deviations less than 7.6% between experimental data and simulation results validate the simulation model. The results presented in this paper may provide a workable reference for the prediction of muzzle noise and the optimization of muzzle brake designs. [ABSTRACT FROM AUTHOR]

After an explosion occurs in a tunnel, the blast waves take on diverse forms of attenuation in different regions when it propagates along the tunnel. However, the prediction of the overpressure decay laws proposed in previous studies has not taken into account the influence of the different regions in the tunnel. The present paper uses the example of the Micangshan highway tunnel in China and considers many factors that influence the propagation of the blast waves by dividing the tunnel into four zones. The paper modifies the decay equation proposed by Smith and applies it to the Micangshan highway tunnel in China. The decay equations are different in different zones. Field tests in this tunnel show that the modified equation is more suitable to describe the attenuation of the blast waves in the tunnel than the original equation. [ABSTRACT FROM AUTHOR]

The influence of large-scale congestion on a confined natural gas explosion in a typical Chinese kitchen was studied using the computational fluid dynamics technology. It was found that opening the explosion venting surface promotes the development of turbulence, flame propagation velocity, and multipeak overpressure in the explosion flow field. Large-scale congestion can significantly strengthen the influence of the explosion venting surface on the flow field; the congestion and the explosion venting surface have a synergistic effect on the explosion flow field. At the moment of gas explosion, the flow fields in each area of the kitchen exhibit different distribution characteristics. A flow field near small-scale congestion is more likely to produce greater turbulence, combustion rate, and flame speed. The obstruction effect of large-scale congestion perpendicular to the flame propagation direction is dominant. The indoor flame propagation speed and overpressure development speed increase and the peak combustion rate and indoor peak overpressure decrease with an increase in obstacle blockage. Increases in the large-scale volume congestion rate and volume blockage in the kitchen induce changes in the indoor flame propagation mode and increase the external explosion overpressure. This paper investigated the correlation behavior between large-scale congestion and vent surface in a typical Chinese civil kitchen during natural gas explosion process and provided important support for understanding the mechanism of congestion on gas explosion process and the distribution of explosion hazards in a kitchen. [ABSTRACT FROM AUTHOR]

In the blasting construction of underground engineering in layered rock mass, the mechanism of cut blasting and the propagation law of blasting vibration waves are very complex. In this paper, a new method for predicting the blasting vibration velocity of layered rock mass under multihole cut blasting is proposed. The key steps include determining the equivalent elastic boundary and load, establishing the multidegree freedom model of blasting vibration and its motion differential equation, and solving the motion differential equation by time-history analysis method. Two multihole cut blasting tests of different schemes were carried out in the construction site of layered rock mass, and the measured results of blasting vibration waves were obtained. By comparing the time-history curves of the predicted and measured blasting vibration velocity, it can be seen that the time-history curves predicted by the proposed method can reflect the characteristics and attenuation law of blasting vibration waves, and the predicted waveforms are similar to the measured waveforms. By using the proposed method, the prediction accuracy for the peak velocity of blasting vibration in the two tests is 93% and 94%, respectively, and the prediction accuracy for the dominant frequency of blasting vibration in the two tests is 86% and 94%, respectively. The prediction accuracy of the main characteristic parameters of blasting vibration waves is high. So it can be proved that the prediction method proposed in this paper is feasible in effectiveness and accuracy, which can provide important theoretical guidance for the optimization of blasting design and the control of blasting vibration in underground engineering in layered rock mass. [ABSTRACT FROM AUTHOR]

This paper focuses on the investigation and control of the blasting-induced ground vibration under cold condition. The mechanical performance and wave propagation characteristics of the frozen rock mass are quite different from that of the conventional condition. Laboratory tests were implemented to investigate the wave impedance of rock mass in the frozen, saturated, normal, and drying states. Results reveal the longitudinal wave velocity could be enlarged by 40 percent in the frozen state. Then long-term monitoring of blasting vibration was implemented based on the blasting excavation of the Fengman hydropower station reconstruction project in the north of China. Results demonstrate the PPV and frequency both attenuate much slower when the rock mass is frozen, and the obvious turning points of PPV could be found between different temperatures, where the change of the PPV relationship happens. At last, numerical simulation of the blasting seismic wave attenuation and the response in the protected structure was implemented. The equivalent freezing simulation method was proposed and verified with the site experiment data. Results demonstrate that the attenuation coefficient decreases obviously as the frozen depth of the rock mass increases. The dynamic degree response in structure is much stronger and the maximum charge weight per delay was limited more strictly under the frozen condition. A most adverse frozen depth was determined when the charge weight per delay gets the minimum value. With the above control approaches, a total of 676 blasting was completed in Fengman hydropower station reconstruction and no case of excessive measurement could be found. [ABSTRACT FROM AUTHOR]

In the field of mine blasting practice, accurate prediction of blasting vibration is considered as a critical task. In accordance with the theory of elastic wave, the reflection of blasting vibration wave at the interface of negative elevation is analyzed in this paper. The negative elevation effect exerted by blasting vibration is interpreted considering the mechanism, and the formula of the blasting vibration prediction step (negative) V = K Q 1 / 3 / R α ⋅ 1 / H β is derived, reflecting the negative elevation effect. Besides, the formula accuracy is verified by the measured vibration velocity of the mass in the Jinou coal mine. The step (negative) formula acts as a more feasible candidate for the prediction of step blasting vibration. [ABSTRACT FROM AUTHOR]

Single-degree-of-freedom (SDOF) models are known to represent a valid tool in support of design. Key assumptions of these models, on the other hand, can strongly affect the expected predictions, hence resulting in possible overconservative or misleading estimates for the response of real structural systems under extreme actions. Among others, the description of the input loads can be responsible for major design issues, thus requiring the use of more refined approaches. In this paper, a SDOF model is developed for thin elastic plates under large displacements. Based on the energy approach, careful attention is given for the derivation of the governing linear and nonlinear parameters, under different boundary conditions of technical interest. In doing so, the efforts are dedicated to the description of the incoming blast waves. In place of simplified sinusoidal pressures, the input impulsive loads are described with the support of infinite trigonometric series that are more accurate. The so-developed SDOF model is therefore validated, based on selected literature results, by analyzing the large displacement response of thin elastic plates, under several boundary conditions and real blast pressures. Major advantage for the validation of the proposed SDOF model is obtained from experimental finite element (FE) and finite difference (FD) models of literature, giving evidence of a rather good correlation and confirming the validity of the presented formulation. [ABSTRACT FROM AUTHOR]

Blast events and scenarios, as known, represent extreme phenomena that may result in catastrophic consequences, both for humans and structures. Accordingly, for engineering applications, the reliable description of expected blast waves is a crucial step of the overall design process. Compared to ideal theoretical formulations, however, real explosive events can be strongly sensitive to a multitude of parameters and first of all to the basic features (size, type, shape, etc.) of the charge. In this regard, several advanced computer codes can be used in support of design and research developments. Besides, the input parameters and solving assumptions of refined numerical methods are often available and calibrated in the literature for specific configurations only. In this paper, with the support of the ANSYS Autodyn program, special care is dedicated to the numerical analysis of the blast wave propagation in the air due to several charges. Five different explosives are taken into account in this study, including RDX, DAP-2, DAP-E, Polonit-V, and homemade ANFO. The effects of different mixtures are thus emphasized in terms of the predicted blast wave, as a function of a given control point, direction, explosive mass, and composition. As shown, relatively scattered peak pressure estimates are collected for a given explosive. Comparative results are hence proposed towards selected experimental data of the literature, as well as based on simple analytical predictions. The collected overpressure peak values are thus discussed for the selected explosive charges. [ABSTRACT FROM AUTHOR]

The evaluation of blast effects from malicious or accidental detonation of an explosive device is really challenging especially on large buildings. Indeed, the time and space scales of the explosion together with the chemical reactions and fluid mechanics make the numerical model really difficult to achieve acceptable structural design. Nevertheless, finite element methods and especially Arbitrary Lagrangian Eulerian (ALE) have been extensively used in the past few decades with some simplifications. Among them, the replacement of the explosive event by a compressed balloon of detonation products has been proven useful in numerous different situations. Unfortunately, the ALE algorithm does not achieve a proper energy balance through the numerical integration of the discrete scheme; this important drawback is not compensated by the use of the classical compressed balloon approach. The paper focuses on increasing the radius of the equivalent ideal gas balloon in order to achieve better energy balance and thus better results at later stages of the blast wave propagation. [ABSTRACT FROM AUTHOR]

Effective control of the explosive energy and the propagation direction of blast-induced crack and minimizing damage of remaining rock mass are the main purposes of directional-controlled blasting. In this paper, the experimental test on blast strain fields affected by water jet slot and blasthole wall protection material is conducted. Next, the FEM software ANSYS/LSDYNA is used to simulate the blast‐induced crack propagation and the blast stress wave transmission of different types of blasthole, and the distribution and evolution law of dynamic blast stress are also analyzed. The results indicate that the existence of blasthole wall protection material is not only beneficial to the "guiding effect" of blast‐induced crack propagation of water jet slot but also beneficial to reduce blast-induced damage of remaining rock mass. Besides, the bigger Dm/rb is, the weaker the "guiding effect" and "blasthole wall protection effect" by water jet slot and wall protection material are. [ABSTRACT FROM AUTHOR]

Blast waves generated by cylindrical TNT explosives in partially confined chamber were studied numerically and experimentally. Based on the classical fifth-order weighted essentially nonoscillatory finite difference schemes (fifth-order WENO schemes), the 1D, 2D, and 3D codes for predicting the evolution of shock waves were developed. A variety of benchmark-test problems, including shock tube problem, interacting blast wave, shock entropy wave interaction, and double Mach reflection, were studied. Experimental tests of explosion events in a partially confined chamber were conducted. Then, the 3D code was employed to predict the overpressure-time histories of certain points of chamber walls. Through comparing, a good agreement between numerical prediction and experimental results was achieved. The studies in this paper provide a reliable means to predict the blast load in confined space. [ABSTRACT FROM AUTHOR]

Defects such as voids, pores, and joints will transform into big scale cracks in the rock of tunnel surrounding under dynamic load like blasting and earthquake. In this paper, three kinds of symmetrical cracks were chosen as an example, and experiments and numerical simulations were conducted to study the effect of symmetric cracks on a blast-induced crack. The relationship of main crack propagation characteristic and distribution of symmetrical cracks was investigated. Some circular specimens using two kinds of material, PMMA and sandstone, including a center hole charged with a detonator and pre-existing cracks were used in the experiments. The test system consisted of an oscilloscope and an ultradynamic strain amplifier and crack propagation gauges (CPGs) were employed in monitoring propagation velocity. AUTODYN code was applied in numerical simulation to investigate the propagation behavior of main crack between symmetrical cracks. Linear equation of state and a modified major principal stress failure criterion was utilized to describe the status of rock material. Based on experimental and numerical results, it can be concluded that (1) the pre-existing symmetrical cracks have arrest effect on main crack propagation, (2) compressive stress in y-direction plays very important roles in crack arrest, and (3) the spacing of parallel cracks has a great influence on crack propagation length and velocity. [ABSTRACT FROM AUTHOR]

In order to estimate the stability of slopes with geological defects during blasting excavations, the dynamic responses of a rock slope with a fault subjected to blasting seismic waves are studied. The SV-component of blasting seismic waves is considered and the fault is simplified as a semi-infinite crack in an unbounded space. In the background of an iron mine in central China, the relation between the stress field and the PPV of the incident wave is analyzed and the function of PPV threshold is deduced using both deterministic and probabilistic methods to evaluate the slope stability. Results show that the PPV threshold increases monotonically with the increasing frequency and reaches the lowest point at around γ1 = 14°, which should be proposed as the PPV threshold. The PPV threshold is with an about 50% failure probability when the mean values of mechanical parameters are taken. On the safe side, a more rigorous PPV threshold with only 5% failure probability is determined as 2.25 cm/s for f ≤ 10 Hz, as 2.25 cm/s-5.02 cm/s for 10 Hz < f ≤ 50 Hz, and as 5.02 cm/s-10.05 cm/s for f > 50 Hz. A through structural surface is likely to occur inside the northern slope once the PPV exceeds the proposed threshold. [ABSTRACT FROM AUTHOR]

The impact of blast wave air overpressure (AOp) may cause damage to nearby structures and significant noise pollution. In order to minimize the impact of the blast wave on the buildings around the tunnel, a new wave-blocking trolley (NWBT) was proposed to control the AOp during the construction of the Baitacun tunnel, as the nearby villages were located less than 100 m from the tunnel portal. In the study, the characteristics of the blast wave pressure profiles were studied by field measurements and numerical simulations and the Friedlander equation parameters were obtained. Second, the controlling effect and working mechanism of the NWBT were verified to be effective. The measured peak AOp was weakened from 2.49 kPa to 0.55 kPa with the operating NWBT, which meets the requirements of Chinese specifications. Furthermore, a numerical simulation for the impact process of the NWBT was established using the ANSYS/LS-DYNA software. Finally, it was found that a shorter distance from the NWBT to the source of the blast makes a better contribution to its wave-blocking effect. The waveform characteristics obtained in the study contribute to the design of tunnel surrounding structures; the application of the NWBT is a successful wave-blocking method for tunnels adjacent to environmentally sensitive areas. [ABSTRACT FROM AUTHOR]

With the increase in the depth of large-scale open-pit mining, many mines have to face problems such as what is the effect of open-pit blasting on the rock slope and how to ensure the stability of a high-steep slope. The east slope of the Beizhan iron mine in Hejing County, Xinjiang, belongs to the typical open-pit high and steep slope of mined hanging-wall ore. To study the effect of open-pit blasting vibrations on hanging-wall slope stability, the intelligent blasting vibration detector was used to monitor the open-pit blasting wave of the Beizhan iron mine and the corresponding numerical model was established. We fitted the transmission law of slope blasting vibration by Sodev's regression formula and calculated stress, strain, and vibration velocity of the whole slope by numerical simulation. The result showed that the fitting functional relationship was correct and could be the basic rule of predicting the maximum charge amount per delay interval and minimum safe distance for this area. The estimated open-pit blasting charge weight was reasonable and blasting vibrations would have little effect on the hanging-wall slope. The research method and conclusions in this article have numerous reference values for studying the hanging-wall slope's kinetic stability. [ABSTRACT FROM AUTHOR]

The paper analyzes the structural response of a high-level air blast loaded cable-supported façade. Since the glass panels and the cables present a typical brittle behavior and are subjected to elevated tensile stresses when a high-level explosion occurs, multiple dissipative devices are simultaneously introduced in the conventional glazing system to mitigate the maximum effects of the design blast wave. Dynamic analyses are performed using a sophisticated FE-model to describe accurately the response of the façade equipped by dissipative devices. Based on numerical results of previous contributions, viscoelastic spider connectors (VESCs) are introduced in the points of connection between glass panels and pretensioned cables, to replace "rigid" spider connectors commonly used in practice. At the same time, rigid-plastic frictional devices (RPDs) are installed at the top of the bearing cables to mitigate furthermore the bracing system. As a result, due to the combined use of VESCs and RPDs opportunely calibrated, the maximum tensile stresses in the glass panels and in the cables appear strongly reduced. In addition, the proposed devices do not trouble the aesthetics of such transparent structural systems. At last, simple design rules are presented to predict the response of cablesupported façades subjected to high-level dynamic loads and to preliminary estimate the mechanical parameters of combined VESCs and RPDs. [ABSTRACT FROM AUTHOR]

In order to study the energy characteristics of seismic waves on the liquid CO2 blasting system, the blasting seismic wave signal of liquid CO2 blasting was obtained by on-site microseismic monitoring tests. The adaptive optimal kernel time-frequency analysis method was used to study the basic time-frequency properties of the seismic wave signal. Combining wavelet packet transform decomposition and reconstruction and adaptive optimal kernel time-frequency analysis method, the liquid CO2 energy distribution of the seismic wave signal was further analyzed. And the energy regression model of seismic wave source of liquid CO2 blasting system was discussed. The results show that the vibration velocity is at a low level, and the main frequency range is between 30 and 70 Hz, and the duration is about 20-30 ms. The energy is mainly distributed in 0-125 Hz, which is composed of two main regions. The power function model can be used to describe the attenuation law of the seismic wave energy. The energy conversion coefficient and characteristic coefficient of the source of liquid CO2 blasting system were defined and analyzed. Combined with the empirical formula of the Sadovsky vibration velocity, the energy regression model of the seismic wave source of liquid CO2 blasting system was obtained. [ABSTRACT FROM AUTHOR]

In this study, under the open-close conditions of a roadway outlet, ANSYS/LS-DYNA was used to build models of explosions on roadways with 0° and 90° bending angles, to compare and analyze the shock wave propagation characteristics and variation laws. Combined with the damage degree classification of shock wave overpressure to human body, the destructive effect zoning of explosion in roadway under the condition of opening and closing of roadway entrance was studied. The results showed that as the bending angle increased, the peak overpressure attenuation of the shock waves became prominent, and the arrival time for the same distance increased. The closure of the roadway outlet had a distance effect on the peak overpressure of the shock waves. The explosion shock waves caused the peak overpressure to rise sharply owing to the reflection and stacking effects near the closure. In the far zone of the outlet, the attenuation of the shock waves was too fast and had minimal impact on the peak overpressure. In addition, the existence of the roadway closure increased the damage area and the severity of the blast wave to human body as a whole. With an increase in the bending angle, the damage range and severity decreased. [ABSTRACT FROM AUTHOR]

Transverse momentum spectra of proton, deuteron, and triton in gold-gold (Au-Au) collisions at 54.4 GeV are analyzed in different centrality bins by the blast wave model with Tsallis statistics. The model results are approximately in agreement with the experimental data measured by STAR Collaboration in special transverse momentum ranges. We extracted the kinetic freeze-out temperature, transverse flow velocity, and freeze-out volume from the transverse momentum spectra of the particles. It is observed that the kinetic freeze-out temperature is increasing from the central to peripheral collisions. However, the transverse flow velocity and freeze-out volume decrease from the central to peripheral collisions. The present work reveals the mass dependent kinetic freeze-out scenario and volume differential freeze-out scenario in collisions at STAR Collaboration. In addition, parameter q characterizes the degree of nonequilibrium of the produced system, and it increases from the central to peripheral collisions and increases with mass. [ABSTRACT FROM AUTHOR]

It is pointed out in the literature that the vacuum chamber has the effect of explosion suppression. The effect of explosion suppression depends on the volume of the vacuum chamber, while the vacuum degree has little effect on the performance of explosion suppression. Inspired by this, to explore a new method of gas explosion suppression, a rectangular steel cavity with a wall thickness of 10 mm, a length of 500 mm, a width of 800 mm, and a height of 200 mm was designed. The cavity was installed in a pipeline system to carry out experimental research and to investigate the law of attenuation of gas explosion flames and shock wave overpressure after passing through the cavity. The results show that the single cavity has the function of flame-out and wave attenuation, which attenuates the explosion flame and shock wave overpressure by 42.5% and 11%, respectively, and that the dual cavity further improves the performance of flame-out and wave attenuation, which attenuates flame and shock wave overpressure by 75.4% and 26.7%, respectively. On the basis of the experimental study, a numerical model was established, and a numerical simulation was carried out under the same conditions as the experimental study. The results show that the single cavity inhibits the propagation of the shock wave and attenuates the shock wave overpressure by 10.61%. The dual cavity further improves the suppression performance and attenuates the shock wave overpressure by 28.88%. Finally, by simulating the propagation process of the gas explosion shock wave and flame in the cavity, the mechanism of inhibiting gas explosion propagation by the cavity structure is analyzed. [ABSTRACT FROM AUTHOR]

In the excavation process of a drilling and blasting tunnel, it takes multiple blasting excavations to form, so it is inevitable to produce multiple blasting impact loads, which will cause certain vibration damage to the surrounding rock-support structure. To solve this problem, based on the attenuation formula of blasting vibration wave and considering the cumulative effect of short footage blasting load, the radial displacement formula of surrounding rock particles is derived, and the analytical solution of vibration velocity field is obtained by using the method of separating variables. Then, taking Cuobuling station of Qingdao Metro as the engineering background, the finite element software is used to simulate the tunnel excavation process under the action of short footage multiple blasting. The vibration damage impact of multiple blasting loads on the surrounding rock-supporting structure is analyzed from the accumulated displacement value and vibration velocity cumulative value of the excavation tunnel. The results show that the damage accumulation effect is produced in the surrounding rock of each section during the blasting construction, among which the accumulation is the largest at the arch bottom. With the increase of blasting times, the damage of the surrounding rock is still accumulating gradually. Compared with the first blasting, the peak value of vibration velocity of the second blasting increased by 114%, and with the increase of blasting times, the variation trend of maximum vibration velocity of the measuring point showed an upward trend, but the subsequent vibration acceleration decreased. Under the condition of grade V surrounding rock, when the thickness of the concrete spray layer is 350 mm, the maximum displacement cumulative value of each measuring point in profile 1-1 is reduced by about 50.4% compared with that without support. According to the displacement nephogram of the concrete spray layer, the displacement of the concrete spray layer accumulates after three times of blasting, which affects the stability of the supporting structure. Finally, an example analysis is carried out and compared with the analytical model results to verify the accuracy of the mechanical model. [ABSTRACT FROM AUTHOR]

In order to study the propagation laws of blasting vibration waves in weak rock tunnels, the longitudinal and circumferential blasting vibration tests in Muzhailing Tunnel were carried out, and the measured data were analyzed and studied using the methods of Sadov's nonlinear regression, Fourier transform, and Hilbert–Huang transform (HHT) to provide a reference for the optimization of blasting design of Muzhailing Tunnel or similar weak rock tunnels. The results showed that the tangential main frequency decreases rapidly and the radial main frequency decreases slowly with the increase of proportionate charge quantity. Under a certain charge quantity, as the distance from the explosion source increases, the spectrum width of the blasting vibration frequency becomes narrower, the overall energy is more concentrated, and the vibration frequency tends to be closer to the low frequency. At a certain distance from the explosive source, the frequency of blasting vibration decreases gradually, and the amplitude of low-frequency region increases with the increase of charge quantity. The vibration velocity on the left side of the tunnel is larger than that on the right side, and the vibration velocity at the vault and the arch foot of lower bench decreases rapidly, while the vibration velocity at the arch feet of upper bench and middle bench decreases slowly. The vibration frequencies of the left arch foot of the middle bench and the right arch foot of the upper bench are higher than those of other positions, while the frequencies of the left arch foot of the upper bench are the lowest. During tunnel blasting, the energy input to the strata media is mainly concentrated in the stage of the blasting of the cut hole. The blasting has more energy input to the left arch foot of the upper bench and the tunnel vault, which is consistent with the conclusion of frequency analysis. [ABSTRACT FROM AUTHOR]

By using the method of data-driven reanalysis, the midrapidity transverse momentum p T spectra of charged hadrons ( π + , K + , and p) produced in central and peripheral gold-gold (Au-Au) collisions from the Beam Energy Scan (BES) program at the Relativistic Heavy Ion Collider (RHIC) are fitted by using the blast-wave model with the Boltzmann-Gibbs statistics. The model results are in agreement with the experimental data measured by the STAR Collaboration at the RHIC-BES energies. We observe that the kinetic freeze-out temperature T 0 , transverse flow velocity β T , mean transverse momentum p T , and initial temperature T i increase with collision energy as well as with event centrality. [ABSTRACT FROM AUTHOR]

Presplit blasting can reduce vibration and back impact induced by cast blasting, thus resulting in a smooth bench slope. To design reasonable presplit blasting parameters, this research investigated the formation of presplit faces based on the explosion mechanics and revealed the cracking mechanism of presplit blasting. According to the stress distribution in the vicinity of the blast holes under the action of explosive stress waves and blasting gas, we deduced theoretical formulae for parameters including charge mass in blast holes, hole spacing, and distance from presplit blast holes to cushion holes. On this basis, a method was proposed for the design of large-diameter deep-hole presplit blasting. Field testing was conducted by setting different spacing for presplit blast holes, to monitor the blasting-induced vibration. The results showed that appropriate hole spacing can reduce the particle vibration velocity and the attenuation index of blasting-induced vibration changed slightly while the attenuation coefficient decreased significantly; the formed presplit faces were smooth and had a high half-cast factor. Finally, the reasonable hole spacing for presplit blasting, distance from presplit blast hole to the cushion hole, and the charge mass in blast holes in the Heidaigou open-pit coal mine were determined, respectively. [ABSTRACT FROM AUTHOR]

Results of numerical simulations of explosion events greatly depend on the mesh size. Since these simulations demand large amounts of processing time, it is necessary to identify an optimal mesh size that will speed up the calculation and give adequate results. To obtain optimal mesh sizes for further large-scale numerical simulations of blast wave interactions with overpasses, mesh size convergence tests were conducted for incident and reflected blast waves for close range bursts (up to 5 m). Ansys Autodyn hydrocode software was used for blast modelling in axisymmetric environment for incident pressures and in a 3D environment for reflected pressures. In the axisymmetric environment only the blast wave propagation through the air was considered, and in 3D environment blast wave interaction and reflection of a rigid surface were considered. Analysis showed that numerical results greatly depend on the mesh size and Richardson extrapolation was used for extrapolating optimal mesh size for considered blast scenarios. [ABSTRACT FROM AUTHOR]

In response to the heightened terror threat in recent years, there is an increasing interest in the introduction of access control zones at sites that are characterized by an increased likelihood of being the target of a terrorist attack, as latest data reveal that unprotected areas of mass congregation of people have become attractive to terrorist groups. Such control zones could be located within the building that has to be protected or attached to it. The elevated security needs for these areas call for a design that will consider the risk of internal explosive events. The purpose of this article is to outline a strategy for limiting the consequences of an internal blast, while guaranteeing that the produced blast wave does not propagate into vulnerable areas. In particular, the focus is on the introduction of a protective wall system in the form of a meander that allows unobstructed access of the public and at the same time reduces the possible blast inflow to the building's interior. The performed numerical simulations show that the proposed strategy yields much smaller injury risk areas compared to a design without the addition of protective walls and is recommended for upgrading the security of buildings. [ABSTRACT FROM AUTHOR]