Explosive Column Research Articles

Analysis and Research on the crack of a type of pressed PBX column

Abstract In this paper, aiming at the crack found in a type of press loaded PBX column during ammunition charging, in order to reveal the cause of the crack, the industrial CT nondestructive testing technology was used to scan and analyze the column. The results shown that there was a bulge on the column surface in the crack area, and the internal structure of the bulge was a clearance surface parallel to the outer surface of the column; The finite element method was used to simulate the stress distribution in the pressing process of explosives and the stress after the column collides with the rigid plane. The simulation results of the pressing process shown that the stress concentration area and the area with the first plastic deformation were not at the crack position, but at the corner of the central hole; The rigid plane simulation results of column collision shown that the stress wave propagates in the axial and radial direction, which was consistent with the crack morphology and crack propagation direction on the surface of explosive column, and also matches the internal morphology of column crack. Through comprehensive analysis and judgment, the crack of the pressed PBX column was more likely to be caused by external force collision, and the probability of being caused by internal stress was very small.

Geology, Archaeology, and Historical Studies of the Late 16th Century Plinian Eruption of Raung Volcano: A Potential Case for Disaster Geotourism in Ijen UNESCO Global Geopark, East Java, Indonesia

The enigmatic major eruption in the late 16th century, believed to have originated from Raung, the most active stratovolcano in the Ijen UNESCO Global Geopark in East Java, Indonesia, has ignited significant debate among researchers and historians due to its profound impact on the region. This research aims to substantiate Raung as the likely source of the major eruption by integrating geological, archaeological, and historical data. This study synthesizes current findings and explores ongoing debates surrounding historical volcanic activities. Eruption parameters suggest that the late 16th century eruption exhibited a Plinian type, characterized by an explosive eruption column reaching the stratosphere, widespread pumiceous tephra fallout, and pyroclastic density current (PDC). Stratigraphic succession reveals that the eruption occurred in five phases, with deposits from 10 eruptive units. These deposits are mainly concentrated on the northwestern flank of Raung. Archaeological findings, historical records, and local legends converge to pinpoint the occurrence of this catastrophic event in the late 16th century. These diverse sources estimate that the eruption resulted in approximately 10,000 casualties, marking it as one of the most significant volcanic disasters in the past 500 years. The implications of this eruption extend beyond historical documentation, providing a critical case study for advancing disaster mitigation strategies through geotourism in the geopark area. Moreover, the eruption record outcrops identified in this study can be proposed as potential new geosites within the Ijen UNESCO Global Geopark, enhancing its educational and touristic value. We propose the Jebung Kidul, Alas Sumur, and Batu Sappar sites as potential disaster-based geosites, considering that these sites record the eruption process and preserve archaeological structures. This addition would not only commemorate the historical event but also promote awareness and preparedness for future volcanic activities in the region.

Experimental and theoretical analysis of charge length on single-hole vibration amplitude from underground deep-hole blasting

Experimental and theoretical analysis of charge length on single-hole vibration amplitude from underground deep-hole blasting

Study on explosion impact pressure and damage distribution law of rock powder segmented charge

Study on explosion impact pressure and damage distribution law of rock powder segmented charge

A Case Study of Fragmentation Improvement by Primer Placement in Kevitsa Mine

The effect of detonator placement on rock fragmentation by blasting was studied in the Kevitsa open-pit mine. Considering rock mass properties, explosives properties, and blast parameters, a comprehensive analysis of 37 production blasts confirms that the middle detonator yields finer fragmentation than the bottom detonator in the full range of investigated sizes. Meanwhile, using the LS-DYNA code, a bench model with a single blasthole was built in a three-dimensional setting. A single detonator placed at two different positions—the middle and bottom—of the explosive column was analyzed in this study. By analyzing principal stress states on the plane through the blasthole axial and vertical to the bench face, the numerical results show that the middle detonator creates a stress concentration area near the bench face characterized by triaxial tension, while the bottom detonator does not. Furthermore, the middle detonator generates a larger stress concentration area with biaxial tension near the bench face than the bottom detonator. Considering that triaxial and biaxial tensions are more favorable to fragmentation than uniaxial tension, it can be concluded from simulation results that these areas with triaxial tension and biaxial tension in the middle detonator are a significant factor contributing to achieving better fragmentation, compared to the bottom detonator. The middle detonator position has replaced the bottom detonator position in the Kevitsa mine.

DENSITY MONITORING OF BULK EMULSION EXPLOSIVES IN CONFINED BLASTHOLES

Parameter’s control of explosives used in open pit mining operations have become more relevant over the years, bringing a better understanding of detonation performance. Giving into consideration that bulk emulsion density reflects on blasting results due to its importance in product sensitivity and velocity of detonation (VOD), blast designs are conducted assuming that cup density measurements are reliable and explosives gassing agents will perform as per specifications. Nevertheless, confinement conditions in boreholes are often neglected on predictive modelling. This paper describes the assembly of a device equipped with pressure sensors and its utilization in confined boreholes, obtaining in situ monitoring of density variation in explosive columns. The results enabled a comparison between bulk emulsion density variation when acting in different environments, providing detailed insights into how chemically sensitized explosives behave into different circumstances, giving the opportunity to re-evaluate blast design.

Analysis of the Influence of Burden Deviation from the Designed One on the Intensity of the Blast Vibration

This paper presents an analysis of the influence of burden deviation from the designed one on the intensity of blasting vibrations through the use of laboratory and field examinations. By definition, the burden represents the shortest distance from the axis of an explosive column charge to the free surface. It should be measured along the entire hole length, although, in practice, it is often measured only on the bench surface as the shortest distance from the axis of the explosive column charge to the crest. The real surface of the bench slope (free face) can be very irregular and should be considered during every blast. The deviation of burden in the blast pattern represents a serious problem in the field during blasting operation. Burden deviation from the designed one can be greater or lesser, affecting the results of blasting through poor fragmentation and sometimes causes unwanted effects like increased blasting vibrations or fly rock. The influence of burden deviation on the intensity of blasting vibrations was tested on a laboratory model, where 8 mm diameter holes were drilled into blocks with certain dimensions. The small explosive charges placed in blastholes were initiated. The design burden was set at 30 mm, as the distance from blastholes to the free face of the blocks. Any deviation in distance greater than the designed burden was taken as a parameter for comparison. During each initiation, vibrations were measured using a seismic instrument at a distance of 150 mm from the borehole. At the same time, the free face in the front of the blastholes was photographed to create a detailed 3D model of the blasted surface of the blocks for each blasting. Each measurement is presented on a diagram and classified depending on the values of the burden in the cases where the value of the burden is equal to the designed one, as well as any deviation that is smaller or larger than 30 mm. A total of 55 tests were carried out. The results were analyzed, and the model of dependence of each burden deviation from the designed one on the intensity of blasting vibrations was established under laboratory conditions. To verify the model, the same experiments were also applied in the field. The basic parameter of the model, the coefficient K, which represents the ratio of peak particle velocity and the surfaces of the blasted material from laboratory and field testing, indicates that there is a connection between these values. The deviation of the coefficient K, obtained from laboratory and field measurements, was 5.5%.

Propagation of P‐SV waves radiated by explosive columns in jointed rock masses

AbstractWhen an explosive column initiates, it will radiate P‐SV waves. The propagation of P‐SV waves, which carry the majority of the explosion energy, is extremely complex in jointed rock masses. Therefore, studying the propagation of blasting stress waves in jointed rock masses is of great significance for optimizing the parameters of the blastholes and improving the economy and safety of geotechnical engineering construction. In this study, an analytical model of the propagation of P‐SV waves radiated by explosive columns in jointed rock masses is derived. Using this analytical model, the maximum displacement distribution in jointed rock masses with the free surface is analyzed, and the results show: (1) when the stress waves propagate to the free surface, the reflected waves will be generated, which will produce the remarkable superposition effect with the direct waves, while the superposition effect will affect the maximum displacements at the measuring points significantly; (2) the amplitude of transmitted waves generated from the stress waves that propagate through the rock joints is smaller than that of direct waves, thus the maximum displacements at the measuring points are affected by the rock joints within a certain range; (3) the velocity of detonation (VOD) and the length of the explosive column can affect the superposition effect of stress waves, ultimately impacting the maximum displacement distribution in jointed rock masses. Therefore, optimizing the parameters of the blastholes reasonably to achieve the optimal superposition of stress waves is of great significance for improving the construction efficiency of geotechnical engineering.

Effects of debris entrainment and recycling on explosive volcanic eruption jets and columns

Effects of debris entrainment and recycling on explosive volcanic eruption jets and columns

Effect of charge load proportion and blast controllable factor design on blast fragment size distribution

Blasting operation involves the use of a specific explosive quantity, detonated to fragment insitu and oversize rock block for particle reduction. Rock fragmentation size distribution has a direct influence on the proposed costs of mining one ton of the ore and the cost of run-off-mine processing. The focus of this study is on investigating the effect of charge load ratio and blast design parameters such as stiffness ratio, maximum instantaneous charge, and specific charge on rock fragmentation particle size distribution in dolomite quarry located at Akoko Edo state, South-west Nigeria. The 50% passing sizes (X50, m), 80% passing size (X80, m), and characteristic size (Xc, m) of blast results were determined using Wipware software. It was observed that the optimum mean size (X50, m), 80% passing fragment size (X80, m), and characteristic size (Xc, m) of rock depends strongly on the explosive bottom and column loading ratio, stiffness ratio, and specific charge. The regression analysis result reveals that the explosive specific charge and stiffness ratio influence the fragment size distribution with a negative correlation relationship, and the explosive bottom and column loading ratio has a positive correlation relationship with the blast fragmentation. Multivariate Regression (MVR) models were developed for the prediction of blast fragmentation sizes (X80, X50, and Xc) with R2 values of 0.76, 0.52, and 0.63 respectively. Based on the low correlation value obtained from the developed models, the proposed multivariate Regression (MVR) models are less suitable for the prediction of blast fragmentation particle size distribution.

Effect of detonator position on rock fragmentation: Full-scale field tests at Kevitsa open pit mine

The effect of detonator position on rock fragmentation was studied at the Kevitsa open pit mine. Five full-scale field tests were conducted where the blasts were divided into test and reference areas, and compared with each other. In the test areas, the detonators were placed at or near the middle point of the explosive column, and in the reference areas, corresponding to the conventional blasts used in the Kevitsa mine, the detonators were placed about 1–2 m above the bottom of the blast holes. The rock fragment sizes from both test and reference areas were measured and studied using shovel-mounted machine vision cameras and image analysis. Both theoretical and field studies indicated that the detonator position plays an important role in rock fragmentation, and that the detonator position in the middle of the explosive column yielded significant improvement in rock fragmentation. For example, percentages of fragment sizes x20, x50, and x80 are reduced by 10–27%, 11–30%, and 8–31%, respectively; percentage of large size fragments (>1.0 m) is reduced by 29–99%; percentage of small size fragments (<2.5 cm) is increased by 6–49%. • Detonator location was studied for open pit bench blasting. • The best detonator position is the middle of the explosive charge length. • The middle detonator position significantly improved rock fragmentation. • Fragment size x50 was reduced by 11–24% in the field tests.

The Independent Volcanic Eruption Source Parameter Archive (IVESPA, version 1.0): A new observational database to support explosive eruptive column model validation and development

Eruptive column models are powerful tools for investigating the transport of volcanic gas and ash, reconstructing past explosive eruptions, and simulating future hazards. However, the evaluation of these models is challenging as it requires independent estimates of the main model inputs (e.g. mass eruption rate) and outputs (e.g. column height). There exists no database of independently estimated eruption source parameters (ESPs) that is extensive, standardized, maintained, and consensus-based. This paper introduces the Independent Volcanic Eruption Source Parameter Archive (IVESPA, ivespa.co.uk), a community effort endorsed by the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) Commission on Tephra Hazard Modelling. We compiled data for 134 explosive eruptive events, spanning the 1902-2016 period, with independent estimates of: i) total erupted mass of fall deposits; ii) duration; iii) eruption column height; and iv) atmospheric conditions. Crucially, we distinguish plume top versus umbrella spreading height, and the height of ash versus sulphur dioxide injection. All parameter values provided have been vetted independently by at least two experts. Uncertainties are quantified systematically, including flags to describe the degree of interpretation of the literature required for each estimate. IVESPA also includes a range of additional parameters such as total grain size distribution, eruption style, morphology of the plume (weak versus strong), and mass contribution from pyroclastic density currents, where available. We discuss the future developments and potential applications of IVESPA and make recommendations for reporting ESPs to maximize their usability across different applications. IVESPA covers an unprecedented range of ESPs and can therefore be used to evaluate and develop eruptive column models across a wide range of conditions using a standardized dataset.

The Marifil Volcanic Complex at Sierra de Pailemán: implications for the Early Jurassic magmatic evolution of the Eastern North Patagonian Region

ABSTRACT The Sinemurian Marifil Volcanic Complex at Sierra de Pailemán, located in the east part of the North Patagonian Region, Argentina, includes five lithofacies and three volcanic events. The volcanic activity begins with subaerial pyroclastic-fall deposits, massive lapilli tuffs with eutaxitic textures, and subaerial silicic domes’ emplacement. The upper part of the sequence is formed by pyroclastic fall deposits that pass to massive lapilli tuffs and rhyolitic lava flows. These lithofacies indicate the collapse of explosive eruption columns, coeval with small silicic domes’ emplacement, and lava-flows’ eruption. The volcanic episode at Sierra de Pailemán was generated during continuous magmatic activity because no erosional or unconformity surfaces were recognized. The Marifil Volcanic Complex’s age at Sierra de Pailemán is 191.2 ± 1.3 Ma (Sinemurian) and belongs to the V0 phase of volcanism. These rocks are high-K rhyolites, possibly produced by partial melting of the lower crust, promoted by fluids derived from a subducted plate in back-arc settings that change to an intraplate setting. The Lu-Hf isotopes suggest the possibility of magma mixing in the source and recycling or re-melting of a more evolved crust related to subduction zones. The Lower Jurassic magmatic activity in the western North Patagonian Region and the Patagonian Cordillera of Argentina and Chile correspond to continental arcs.

Observation of asymmetric explosive density evolution in the deflagration-to-detonation transition for porous explosives

We report deflagration-to-detonation transition phenomena in cylindrical columns of porous explosives based on octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). The HMX powder and LX-14 (95.5 wt. % HMX and 4.5 wt. % estane polyurethane) prills were observed with high-speed cameras and flash x rays under conditions that allow for precise scaling and registration of the recorded images. These experimental results test the conventional assumption of axisymmetric, effective one-dimensional burning. Polycarbonate confinement tubes allowed this direct imaging with steel spheres employed as radio-opaque fiducials. Spheres embedded in the explosive column revealed the displacement of the explosive prior to deflagration. X-ray and fast camera images show that a dense plug of compact explosive develops ahead of the deflagration front. The internal fiducials register both internal changes in the plug and changes in the position between successive x-ray images. Tantalum witness strips placed on the inner wall of the explosive channel revealed radial expansion of the tube bore at successive x-ray exposures, indicating the internal pressure of about 100 MPa just before detonation. Images indicate that the deflagration is not only asymmetric but also involves newly observed transient phenomena just before detonation. We typically see a brief but continuous increase in deflagration speed and the formation of a deflagration channel that bypasses the plug just prior to detonation. We hypothesize that these phenomena play an important role in the deflagration-to-detonation transition itself.

Probabilistic models for blast parameters and fragility estimates of steel columns subject to blast loads

This paper proposes a probabilistic framework to predict the failure probabilities of steel columns subject to blast loads. The framework considers the uncertainties in the blast phenomenon, the demands imposed on the column, and the capacities of the column for the limit states of flexure, and global buckling. As part of the work, we propose four probabilistic blast load models. For different types of explosives and atmospheric conditions, two models predict the incident and reflected peak pressure generated by the explosion and two models predict the incident and reflected positive time duration of the blast wave. The models are probabilistic to capture the associated uncertainties, including variations in the atmospheric conditions, the inherent variability in the blast load data even for identical experimental conditions, and model error. The blast load models are used to predict the structural demands (maximum internal moment and deflection) imposed by the blast on a column. The demand models are combined with strain-rate dependent capacity models for flexure and global buckling to estimate the conditional probability of failure (or fragility) of a steel column for given scaled distance. As an example, fragility estimates for different columns representative of typical columns in steel frames are developed. The results highlight the importance of the explosive weight and column axial load on the failure probabilities.

Blast vibration dependence on total explosives weight in open-pit blasting

It is well established that the blast design parameters, namely explosives weight per delay, distance between the blast site and monitoring location, delay interval, total explosives detonated in a blasting round, velocity of detonation (VOD) of explosives, burden, spacing, explosive column length, top stemming length, number of decks and their length, transmitting media and its geology, and scattering in the delay time of detonators, influence blast-induced vibrations. A study was conducted to assess the effect of total weight of explosive detonated in the blasting round on the magnitude of blast vibrations at four big coal open-cast mines in India keeping all the parameters constant as stated above. Accordingly, experimental as well as production blasts were conducted at dragline and shovel benches. The results revealed that the magnitude of blast vibrations was influenced by the total amount of explosive detonated in a blasting round at shorter distances regardless of maximum explosives weight per delay. This paper describes the result of a study carried out to investigate these effects at open-cast projects in India. The study involved 60 blasts with varying blast designs and 498 vibration data were recorded.

Air Decks in Surface Blasting Operations

In this study, the best possible location for an air deck in an explosive column during a surface blasting operation for the most efficient rock fragmentation is described. Volumes of air decks are proposed for the optimization. This study aims at helping guide blasting engineers to easily apply an air deck in a surface blasting operation.

Thermal hazards evaluation of insensitive JEOL-1 polymer bonded explosive

Thermal stimuli is one of the major external stiumuli resulting from an overheated explosion of a munition. In order to evaluate the influence of external thermal stiumuli on the thermal hazards of JEOL-1 (32 wt% octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), 32 wt% 3-nitro-1,2,4-triazole-5-one (NTO), 28 wt% Al and 8 wt% binder system) explosive, accelerating rate calorimeter (ARC) is used to study the adiabatic thermal decomposition properties of JEOL-1 molding powders, and the slow cook-off properties of JEOL-1 are studied by experimental test and numerical simulation. The activation energy Ea, pre-exponential factor A, mechanism function f(α) and self-accelerating decomposition temperature (SADT) of adiabatic thermal decomposition of JEOL-1 molding powders are obtained according to ARC results. The response level of JEOL-1 polymer bonded explosive (PBX) columns exposed to an engulfing liquid pool fire is examined by the slow cook-off test. The ignition location, ignition temperature, ignition time and the transient temperature distributions of JEOL-1 PBX columns during the slow cook-off are obtained by numerical simulation. It can be concluded from this study that JEOL-1 is a low vulnerable explosive with high thermal safety.

Influence of Air Gap Volume on Achieving Steady-State Velocity of Detonation

The velocity of detonation (VOD) is a significant property considered when rating an explosive. It may be quantified as a confined or unconfined velocity. The confined velocity is the rate at which the detonation wave propagates through an explosive within a blast hole or any restrained space. The unconfined velocity emanates when an explosive is detonated in the open. However, the confined velocity is more significant as explosives are usually employed under a definite degree of confinement. This paper evaluates the increment of air deck volume and its effect on the VOD. The air gap (air deck) volume is increased stepwise from 10 to 30% of the total blast hole volume by reducing the stemming height in the collar zone. Thereafter, the VOD estimation in the 172-mm-diameter explosive column is conducted using the Dautriche technique. It is observed that the VOD reduced with the increasing air deck volume and detonation failure is high when 30% of the blast hole volume is replaced with air deck. It is deduced that the increment of the air deck volume has an effect on the attenuation of the steady-state VOD.

FIELD INVESTIGATION IN THE DETONATION BEHAVIOR OF EMULSION EXPLOSIVE COLUMN INDUCED WITH AIR GAPS

In blasting of soft to medium hard rock, the problem of high density resulting in excessive utilization of emulsion explosive is well known. The authors have conducted some experimental blasts to delve into the detonation behavior of conventional blasting and various other explosive consumption reduction techniques which induce air gaps using plastic tubes, plastic bottles or plastic balls in the explosive column. Resistance wire technique is used for gauging in-hole continuous velocity of detonation. The VOD varies from 5321.6 m/s to 4544.2 m/s and from 5123.4 m/s to 4274.2 m/s in conventional site mixed emulsion column and distributed spherical air gap column respectively. The detonation behavior is stable and similar in both these cases. While using plastic bottles or plastic tubes as air gaps, the VOD is fluctuating from 4636.3 m/s to 3268.4 m/s and from 4935.9 m/s to 3362.8 m/s respectively with a collapse of about 12 % from the average VOD of conventional SME column. The VOD falls abruptly when the detonation wave encounters large air gaps but it is successfully travelling through the air gaps making the detonation behavior more capricious.