Explosive Charge Research Articles

IMPROVING THE BLASTING TECHNOLOGY AT THE DEVELOPMENT OF NON-HOMOGENEOUS ROCKS IN AN OPEN PIT

One of the main indicators that determine the effectiveness of blasting in open pits is the degree of crushing of the blasted mass. It is accepted that with an increase in the mass of the explosive charge by thickening the grid of holes, the quality of crushing the blasted rock mass improves. However, this approach leads to an increase in the amount of drilling work and an increase in the cost of explosives. In its turn, the method leads to an increase in the size of the violation of the natural structure behind the contour of the blasted block, which is the focus of oversized output. It should be noted that with an increase in the amount of explosion energy, it is possible to regulate the degree of crushing of the exploded mass, but only when blasting in an extremely large-block (relatively monolithic) array, and with an increase in the number of explosives, the quality of the explosion partially improves. It has been established that in medium and large-block rocks, the main carrier of the explosion energy is considered to be the heterogeneity of the massif. The paper proposes a new technology for blasting operations on ledges of heterogeneous, layered structures. The proposed breaking method makes it possible to increase the useful effect of the explosion energy on crushing, reduce the cost of explosives, and obtain the collapse of the exploded mass of the given parameters.

Experimental Study on the Cumulative Damage of Shipboard Structure Subject to Near-field Underwater Explosions

To explore the cumulative damage law of near-field underwater explosions on the side of the ship structure, the multi-cabin model of the shipboard local structure is designed and applied to close-in underwater explosion experiments with different explosive masses and model conditions. The pressure load of the explosion shock wave near the water surface is obtained and analyzed. The damage results, such as the damage pattern of the model and the damage range of cabins, are acquired. The comprehensive comparison shows that: the secondary explosion on the side has a significant cumulative damage effect; the damage pattern of the structure is closely related to the proportional distance of the explosion. The damaged power of a single large charge explosion on the shipboard is bigger than the cumulative damage caused by two small explosions. The results of this study can provide a reference for the research on the damage and protection of the ship.

Experimental Studies on Post-Explosion Lesions in a Model of Human Soft Tissues

Descriptions of blast-related injuries have long been established in the textbooks. Since, for obvious reasons, it is difficult to perform ballistic studies on human tissues, such research is usually conducted on appropriate models, i.e., gelatin blocks and soap blocks – each of these materials has distinctive properties, which make them suitable for unique applications. The work aims to present the possibilities for analyzing the effects of explosion on the human body using a ballistic soap model. The tests performed allow to conclude that a shock wave affects the surface of the ballistic soap block, generating hemispherical craters, which begin to overlap when the distance between the explosive charge and block is reduced, until they form one semi-cylindrical hollow (when linear charge is used), which represents a temporary cavity. The results obtained allow for an assessment of the extent of post-explosion lesions.

Physical and simulation modelling of solid media fracturing by means of explosive charges of different cross-sectional shapes

Purpose is to evaluate experimentally and theoretically a mechanism of solid media fracturing by means of explosive charges varying in their cross-sectional shapes. Methods. The Mohr-Coulomb strength condition has been applied to describe rock transition to the disturbed state. The condition has become a basis to develop a mathematical model of explosion (i.e. shock and detonation wave) of the concentrated borehole charges. The simulation explosion was modelled while adequate load applying at the points belonging to the outline of both cylindrical charge and at the charging angles in the shapes of triangular and square prisms. The evaluation mechanism of solid media fracturing by means of explosive charges, varying in their shapes, used the models made of optically active materials. A method of high-speed photorecording of the process was involved; the method was combined with the photoelastic technique of stress analysis. Findings. Taking into consideration rock transition to the disturbed state, the Mohr-Coulomb strength condition was applied with the possibility to simulate failures resulting from shear as well as from separation according to the developed mathematical model. The calculation results have helped identify distribution of a geomechanical parameter (Q) at different time points (time iterations). Dependencies of changes in the maximum component of the main stress tensor σ1 / γН along the axis passing through the charge centres perpendicularly to its flat surface for different time iterations have been developed. It has been defined that the maximal stresses are concentrated on the top of both triangular and square prisms helping shape a denser crack network within the zones. Originality. It has been identified that at the initial explosion stage, the maximum values of the main stress tensor component σ1 / γН along the axis passing through the charge centre perpendicularly to its flat surface, experience certain change depending upon a power law with the increasing distance to the charge outline. At the same time, if the charge is of a square prism shape then time iteration being i = 5 makes the main stress decrease according to a linear dependence. Practical implications. The research may be used as the basis for the development of rational parameters of the resource-saving methods applied to separate hard complex rocks in terms of open pits where building materials are mined.

Application Software Developed for the Determination of Expansion Volume in Clay Soil Generated by the Detonation of an Explosive Charge

Blasting in clay soil in the field of anchoring and foundation of objects and structures has its benefits in construction and geotechnical practice. The foundations of the method lay in the fact that a shock wave is generated when the explosive charge is detonated. The shock wave, with high pressure at the wavefront, causes the natural structure of the clay soil to be destroyed, and a spherical expansion in the clay mass is formed. The presented research is focused on determining the shape and volume of the resulting expansion in test blasts performed with several types of explosives. An application named Borehole was developed to determine the resulting spherical expansion formed after the detonation of an explosive charge with the integration of the GNSS method of measurement, depth camera, and laser. The application Borehole calculates expansion volume based on the coordinates obtained with the GNSS and the laser-obtained distance of the formed expansion and provides a graphical interpretation in 2D and 3D views. Additionally, when developing the application Borehole, compatibility with CAD tools was considered, primarily for better verification and a more detailed graphical interpretation of 3D views. The developed method allows for simple determination of the volume and dimension of the spherical expansion in clay soil with acceptable accuracy for the design and building of geotechnical structures constructed above and underground.

Experiments and Fluent–Engineering Discrete Element Method-Based Numerical Analysis of Block Motion in Underwater Rock-Plug Blasting

Underwater rock-plug blasting is a special blasting technique for excavating underwater inlets. In the process of rock-plug blasting excavation, the blasting-block movement from the difference in water pressure inside and outside the tunnel is one of the key factors for successful construction. Laboratory underwater rock-plug blasting experiments were conducted using small explosive charges, and a high-speed camera was adopted to observe and study block motion. Then, numerical simulations were conducted for the model experiment based on the Fluent and Engineering Discrete Element Method (EDEM) coupling program developed using the user-defined function (UDF) interface to reveal the mechanism underpinning the penetration of underwater rock-plug blasting. The results showed that the process of block motion in underwater rock-plug blasting can be divided into two stages. In the first stage, broken blocks move to two sides along the axis of the rock plug under the blast load. A blasting crater is formed on the downstream end face of the rock plug under the effects of the free face, while the upstream end face is loosened, or blocks are ejected under the influence of the water pressure. In the second stage, blocks flow to the broken-rock pit under the effects of water scouring and gravity, and, finally, the rock plug is penetrated. The larger the head of water and the opening angle of the rock plug are, the better the penetration effect for the rock plug is. The Fluent–EDEM coupling algorithm was in good agreement with the experimental results in terms of the rock-plug blasting effect and the velocity curve of the blocks, indicating that the coupling method had a favorable effect in simulating the interaction of blocks and water during underwater rock-plug blasting. The findings are expected to promote the application and popularization of the rock-plug blasting technique and can provide a reference for rock-plug blasting in water-intake and water-diversion projects.

Numerical Study of the Layered Blasting Effect on a Cemented Backfill Stope

The sublevel open stoping with backfill method has recently been widely used in underground metal mines. The primary CPB stope is frequently affected by blasting in the secondary ore stope, leading to stope collapse and ore dilution, which has become a common problem and has received widespread attention. Numerical simulations are carried out in the present work, and a 1/4 numeral model consisting of a primary CPB stope and a secondary ore stope is built. The secondary ore stope is divided into four layers on average in the simulation model, and the incident stress induced by each blasting at the interface of the CPB and ore is simulated. The results show that the CPB stope in the range within the height of the explosive charge induced horizontal compressive stress and tensile stress induced from the explosive charge height, while the mined section under the charge height has no obvious blasting impact. The maximum incident compressive stress is close to 1.2 MPa and occurs in the area closest to the blast hole The maximum induced tensile stress occurs in the range above the charge height, which is about 0.2 MPa. The stress ratios of the four-layered lift blasts are 3.6%, 3.8%, 4.0%, and 4.8%, respectively, showing a slight cumulative effect of layered blasting. In addition, the positive correlation between incident stress and the stress ratio is studied in the present work, and the results show that the greater the incident stress is, the greater the incident ratio is.

Quantitative evaluation method of human comfort under the influence of blast vibration based on human physiological indexes and its application

To reasonably assess the impact of blasting disturbance on personnel in the adjacent area and to protect the safety and physical and mental health of personnel, it is the key to construct a human comfort evaluation system under the impact of blasting vibration. In view of the uncertainty of human subjective feelings in the existing evaluation system of human comfort under the influence of blasting vibration, the human vibration response experiment is carried out by simulating blasting vibration through a shaking table, and the quantitative relationship between blasting vibration parameters, ECG indicators, and human subjective feelings is analyzed by combining with human ECG indicators to construct the evaluation system of human comfort under the influence of blasting vibration. At the same time, the evaluation system is applied to the actual project with Wuhan Metro Line 5 as the engineering background by combining numerical calculation methods. The results show that: the vertical direction is the main vibration direction affecting human comfort, and the impact of vibration on the human body is related to the main vibration sensation parts of the human body, and the degree of impact gradually increases when the main vibration sensation parts moves up from the feet to the head; There is a quantitative relationship between the decreased ratio of human ECG index RMSSD and blasting vibration parameters as well as human subjective feelings, when the decrease ratio of human RMSSD is >0.28, the extent to which the human feels the degree of annoyance cannot be ignored, and the vibration velocity and frequency (0.7 cm/s, 80 Hz) in the vertical direction of the ground surface at this time can be used as the control threshold of blasting works in the adjacent densely populated areas. It is recommended that the maximum explosive charge in the single delay of the subway tunnel blasting excavation does not exceed 0.32 kg.

Dynamic Performance Enhancement of One-way Reinforced Concrete Slabs by Fiber-reinforced Polymer Re-bars and Aluminum Foam under Air-blast Loading

In the present study, finite element (FE) simulations are performed using the high fidelity physics-based finite element program, ABAQUS/CAE on the models of the one-way normal strength concrete slab, reinforced with the High Yield Strength Deformed (HYSD) steel re-bars, subjected to air-blast loading. The FE models are developed and subjected to different quantities of the TNT explosive charges at different scaled distances (between 0.75 and 3.0 m/kg1/3) in free air. There exists a good correlation between available experimental values/observations and the results obtained analytically. Analyses have been extended replacing the conventional steel re-bars with the re-bars of the fiber-reinforced polymers namely; aramid, basalt, carbon, and glass, of equivalent strength on the tension side, impact side only, and both the sides of the slab. The replacement has been considered to improve the blast resistance of the slab. The damage in the slabs has been simulated using the available sophisticated material model to evaluate geometric parameters of cracks. FE simulation results for the considered combinations of the reinforcement have been compared to arrive at the best reinforcement combination in the slab. To further enhance the blast performance of this slab, single and double layers of the aluminum foam has also been considered on the impact face. Application of the aluminum foam is found to be effective in reducing the mid-span deflection, damage dissipation energy, and depth of transverse flexural cracks.

Effect of Skew Angle on the Dynamic Response of a Reinforced Concrete Bridge under Blast Loading

Accidental explosions and subversive blasts are on rise. The recent devastating Beirut explosion witnesses this fact. Performance of the structures such as bridges in cities and strategic boarder areas is of paramount importance. With this concern the effect of skew angle on the performance of a single span reinforced concrete (RC) bridge deck supported on three symmetrically placed RC girders under blast loading generated by1000kgTNT charge located above and below the mid-section of the central girder at a standoff distance of 0.5 m has been investigated using ABAQUS/CAE. Analyses have been performed at different skew angles i.e. 0º, 10º, 20º, 30º, 40º, and 50º. Several empirical relations from the literature have been used to estimate the blast parameters such as peak overpressure, positive phase duration, the arrival time of blast wave, and decay coefficient. Blast pressure P(t), has been modeled using modified Friedlander’s equation. Distributions of damages have been evaluated with a mesh size of 300 mm using concrete damage plasticity (CDP) model. Maximum displacements have been computed and are compared with those obtained from the provisions of AASHTO: Load Resistance and Factor Design (LRFD) - Bridge Design Specifications (2014). It has been found that the midspan displacement and the stresses of the deck increase for 10º skew angle but decrease for subsequent increase in skew angle for the explosive charge loaded above the mid-section of the central girder. However, tensile as well as compressive damages in girders increase with increase of skew angle irrespective of the location of the blast. Side girders suffer more damage with increase in skew angle than uniform damage for ‘under the deck’ location of explosive charge.

Experimental and numerical investigation of blast loads induced by moving charge explosion

With the development of high-speed weapons, moving charge explosions frequently occur in industry and military activities, which will lead to significant damage to structures. In order to investigate the blast loads induced by moving charge explosion, explosion experiments are carried out. The pressure curves and blast load parameters are analyzed. Results indicate that the blast load distribution is directional in moving charge explosion, and the blast load parameters are influenced by distance and direction. Numerical simulation investigation is conducted to further study the effect of charge shape and velocity on blast loads induced by moving charge explosion. The numerical model is developed and verified with experiment data, which indicates that the numerical method is sufficiently accurate for moving charge explosion investigation. The numerical study characterizes the influence of charge shape and charge velocity on blast loads in different directions. The shape factors of cylindrical charge and the velocity factors of 580 m/s, 700 m/s, 900 m/s and 1200 m/s in moving charge explosion are analyzed. The results indicate that the charge shape effect must be considered in the near-field and the charge velocity effect must be considered in different directions, especially in directions with angles less than 90°. This research will contribute to combatant power evaluation, structural engineering and structural design.

Blast resistance of RC tubular structure under internal ANFO explosion

The degree of structural damage is significantly more severe when a blast occurs inside than outside of a structure. However, existing designs for RC structures such as reinforced concrete containment vessels (RCCV) do not include design features to protect the structure for internal blast. Therefore, the internal blast resistance capacity of RC structures is evaluated by performing internal blast tests on RC tubular structures. The main objective of the study was to observe and document the basic structural behavior data obtained from internal detonation tests. ANFO explosive charge weights of 15.88, 20.41, 22.68 and 24.95 kg were selected for a charge detonating at a cross section center of the mid-span of the specimen, giving a standoff distance to the inner wall surface of 1000 mm. The data acquisitions include blast pressure, deflection, strain, and crack pattern. When the explosive charge weight increased from 15.88 to 24.95 kg, the peak incident pressure and time duration increased from 0.1718 to 0.3394 MPa and from 5.856 to 5.981 ms, respectively. Then, the test data were used to predict the internal charge weight required to fail a real scale RCCV using simple assumptions and the test data. The results of the study are discussed in detail in the paper.

Assessment of the Sympathetic Detonation of Blasting Caps

The neutralization of improvised explosive devices (IEDs) involves the use of disrupting agents propelled explosively. Due to the special nature of such materials, a proper investigation of the parts most susceptible to sympathetic detonation is in order. The initiation of IEDs is caused by detonation products, shock waves, and propelled disruptive agents. In this paper, initiation of IED composition (acceptor charge) due to the neutralization system’s (donor charge’s) explosive charge detonation is evaluated based on the influence of the first two of the three above-mentioned factors. One of the most susceptible components of IEDs to sympathetic initiation is the blasting cap. Based on an experimental and numerical mix approach, blasting cap tendency to sympathetic detonation in open field had been investigated. The suitability of critical energy fluence and Chapman–Jouguet threshold criteria to the sympathetic detonation tendency of blasting caps was investigated. Experimental and numerical/analytical results describing the phenomenon are in agreement.

On Eulerian-Lagrangian methods to investigate the blast response of composite plates

The blast-resistant design of engineering structures has recently been supported by numerical approaches. This solution has allowed expanding the design space to complex materials and structures, which could not be properly addressed through available empirical and analytical methods. At the same time, numerical approaches have opened up the possibility of studying in more detail the physics of fluid-structure interaction (FSI) effects, which are particularly relevant in case of lightweight structures. However, reliable simulations accounting for FSI effects on complex structures have not been properly addressed yet in the literature. Hence, leveraging the potentialities of state-of-the-art numerical methods, in this work a framework was set up to describe the response of blast loaded composite plates through high-fidelity coupled and uncoupled simulations. The framework was validated against experimental data, and numerical simulations were used to identify and describe FSI effects. The flexibility of the framework also allowed (i) studying the influence of boundary conditions on the structural dynamics, which was accounted for by explicitly modelling the clamping assembly, and (ii) investigating the influence of explosive charge parameters on blast waves properties. Results showed that FSI effects strongly influence the response of blast loaded composite plates even in scenarios where metal plates would not undergo any FSI effects.

Influence of underground mining with explosives on a hibernating bat population

AbstractBats arouse from hibernation both naturally and in response to disturbances. Frequent bat arousals can decrease survival due to increased energetic costs. An active sand mine in west‐central Wisconsin hosted over 52,000 hibernating bats of 4 species in inactive tunnels, and regularly blasted with explosives to remove sand. We collected environmental and acoustic data at this mine during two hibernation seasons (November 1 through February 28 in 2013–2014 and 2014–2015) to examine the effect of blasting on echolocation calls (bat activity), a measure of bat arousal from hibernation. We used total bat activity recorded 7 h before and 7 h after blast time as the response variable, assigned it to a binary category and used that as a fixed effect. We used explosive charge per delay (kg), number of blasts per day, number of consecutive blast days, barometric pressure, temperature, and hibernation season as fixed effects. We used generalized linear mixed models with a negative binomial distribution and Bayesian information criterion (BIC) for model selection. The BIC‐optimal model did not include any of the variables associated with blasting, but included activity timing, temperature, barometric pressure, and season as fixed effects, of which all were significant. Blasting did not influence bat activity significantly in this mine.

ON THE DESTRUCTION AND PREFRACTURING OF SOLID ROCKS UNDER BLASTING IN FORMATION CONDITIONS

Purpose and task. Analysis and specification of mechanisms of softening and change of structure of monolithic and low-fractured rocks under blasting of single and dispersed charges, definition of the reasons and model of their evolution in a formation. To solve this goal, the followingscientific tasks were set in the work:1. Estimation of force factors of external action on rock.2. Thermodynamic analysis and detection of mechanisms of structural changes in rocks at a considerable distance from the well, which provide a change in its productivity.Research methods. To solve the set tasks, the following were performed: calculations of the attenuation of shock wave amplitudes generated during the explosion of spherical and elongated charges; analysis of the results of explosive treatments of oil and gas wells; energy analysis of processes and mechanisms of changes that occur around the well in the reservoir.The main results. Studies have shown that structural changes in rocks during low-energy explosions, as well as other low-energy methods of external action on the reservoir occur in the form of increased cracking of rocks at micro and macro levels due to cooperative effects of external action, internal reservoir energy and physico-chemical effects of reservoir fluids.The main results. The mechanisms of decompaction of the rocks in rock formation conditions in the presence of rock and reservoir pressure at low-energy external actions are considered. Experiments on the operation of oil, oil and gas and gas wells show that the transition of the system "well - formation" from one thermodynamic state to another occurs in a time that depends on the internal energy of the formation. The transition is the result of the cooperative effects of the combined action of external influences, the internal energy of the formation and rock pressure. For gas wells this time does not exceed a few hours or days, for oil and oil and gas with depths of 3000… 4000 m the typical time of the well to reach maximum productivity is ≈ (30 - 90) days.Conclusions and practical significance. The analysis of the results of industrial tests of explosive intensification technology and calculations of attenuation of compression wave amplitudes show that under rock pressure conditions structural changes in rock after explosions of several charges occur at distances up to ≈ (80… 100) R0. Under reservoir conditions, the main reasons for the appearance of such long zones of increased permeability around the well are the cooperativeeffects of the combined action of blast waves, reservoir gases (methane, carbon dioxide, helium and possibly hydrogen), as well as changes in rock pressure in the process of its development. Of practical importance is to understand the sequence of technological operations in the work tointensify the inflow of oil and gas.

The influence of fracture energy on wooden structural members due to contact explosion

In military operations, sappers must often breach wooden structures. The formulas for determining the destructive explosive loads available in instructions and manuals used by sappers are simplified because they consider only a few variables, such as structure member diameter, whether the wood is dry or damp, or the wood species of the structure. In this study, the destructive explosive loads needed to breach pine, birch and oak members were computed via the finite element method. Static compression tests in three directions were conducted to define the orthotropic constitutive models of those wood species, and the results were used as an input to the numerical models. The damage model for wood considered different levels of energy criteria. The finite element analyses of contact explosion of TNT charges against cylindrical log beams were conducted for selected wood species, and destructive explosive loads were computed for different log diameters. Assuming different energy criteria, the results showed that the traditional approach in military instructions and manuals is higher than the values obtained from the numerical approach, i.e., standard manuals suggest using more explosive than may be needed.

The dynamic response and damage models of rebar reinforced polymer slabs subjected to contact and near-field explosions

Non aqueous reactive polymer materials produced by the reaction of isocyanate and polyol have been widely used in infrastructure construction, which may be subjected to explosion loads during complex service conditions. The blast response of composite materials is a crucial aspect for applications in engineering structures potentially subjected to extreme loadings. In this work, damage caused to rebar reinforced polymer slabs by surface explosive charges was studied experimentally and numerically. A total of 6 field tests were carried out to investigate the performances of the failure modes of rebar reinforced polymer slabs under contact and near-field explosions. The influence of explosive quantity (10–40 g) and stand-off distances (0–20 cm) at the damage modes were studied. The results show that the failure modes of rebar reinforced polymer slabs under near-field explosion mainly were bending and surface spalling, while under the impact of contact explosion, the failure modes were craters of the top surface, spalling of the bottom surface, and middle perforation. Furthermore, a detailed fully coupled model was developed and validated with the test data. The influences of explosive quantity and slab thickness on rebar reinforced polymer slabs under contact explosion were studied. Based on this, the calculation formula between breach diameter, explosive quantity, and slab thickness is fitted.

Analysis of explosive energy distribution at Pit 7 West PT. Makmur Mandiri Utama Binungan Suaran - Berau, East Kalimantan Province

Blasting geometry and blasting material filling are closely related to the rock mass characteristics and the geological conditions to obtain ideal fragmentation. Blastability Index analysis, including Description of Rock Mass, Combined Plane Spacing, Combined Plane Orientation, Specific Gravity Influencey, and Hardness, are the alternative geometry experiment conducted to overcome the problem of rock fragmentation so that the speed of excavation equipment can increase according to the productivity of Komatsu PC2000 plan at PT. BUMA Jobsite BINSUA. Furthermore, the actual rock values obtained from blasting location and alternative geometry recommendations using R.L.Ash theory combined with Vertical Energy Distribution theory. In the C2 layer with a rock factor value of 5.95, the recommended load is 7.2 m, space is 8.3 m, and the VED explosive power is 48%. In layer D2 the rock factor value is 6.89 with a load of 7.5 m, space of 8.3 m, and 55% VED explosive charge. While in the DU layer, the rock factor value is 6.39 with a load of 7.3 m, 8.4 m space, and 51% VED filling of explosives. Prediction of blasting fragmentation analysis using Kuz-ram theory obtained fragmentation > 100 cm, namely 14.99% for the C2 layer, 14.84% for the D2 layer, and 14.82% for the DU layer.

Prediction of Blast-Induced Structural Response and Associated Damage Using Machine Learning

Terrorist bombing-induced casualties are not only related to immediate fatalities but also to structural deterioration, damage, or even collapse that might occur and may lead to tremendous loss of life. Efficient assessment of blast-induced structural damage following explosion events is becoming a growing problem in modern societies. An attempt based on machine learning is made in this study to anticipate structures’ responses and the associated structural damage to reinforced concrete (RC) buildings exposed to extremely short-duration explosive loads. A program is developed to generate a set of analytically derived data for nonlinear building models subjected to explosive loads. Common machine learning models and Python libraries were utilized during the development of our program implementation to learn from a dataset. The latter has different features or input parameters, such as the amount of explosive charge, the distance from the building, fundamental period, and the building’s mass and rigidity, as well as the soil type. Our database is thus used, along with our regression-and-classification based implementations, to generate an output index that estimates and categorizes the state of damage based on the several most-important parameters of the explosion exposure. In the input database, the state of damage, based on the values of captured damage indices, is classified into one of four cases. Our code efficiently predicts those cases using a model that learns from the database. The prediction rates of the presented model reach an overall high accuracy. Therefore, the proposed model provides an accurate prediction of the level of structural damage by using the computed damage indices.