Mass Blasting Research Articles

Numerical simulation of blasting behavior of rock mass with cavity under high in-situ stress

With the shift of coal seam mining to the deep, the in-situ stress of coal and rock mass increases gradually. High ground stress can limit the generation of rock cracks caused by blasting, and blasting usually shows different crushing states than low stress conditions. In order to study the blasting expansion rule of rock mass with cavity under high ground stress and the rock mass fracture state under different side stress coefficients. In this paper, the effective range of blasting and the stress distribution under blasting load are analyzed theoretically. The RHT (Riedel-Hiermaier-Thoma) model is used to numerically simulate the blasting process of rock mass with cavity under different ground stress, and the influence of ground stress and lateral pressure coefficient on the crack growth of rock mass is studied. The results show that when there is no ground stress, the damage cracks in rock mass are more concentrated in the horizontal direction and the fracture development tends to the direction where the holes are located, which confirms the guiding effect and stress concentration effect of the holes in rock mass, which helps to promote the crack penetration between the hole and the hole. The length difference of horizontal and vertical damage cracks in rock mass increases with the increase of horizontal and vertical stress difference. Under the same lateral stress coefficient, the larger the horizontal and vertical stress difference is, the stronger the inhibition effect on crack formation is. For blasting of rock mass with high ground stress, the crack formation length between gun holes decreases with the increase of stress level, and the crack extends preferentially in the direction of higher stress. Therefore, the placement of gun holes along the direction of greater stress and the shortening of hole spacing are conducive to the penetration of cracks between gun holes and empty holes. The research can provide reference for rock breaking behavior of deep rock mass blasting.

Study on Blasting Effect Optimization to Promote Sustainable Mining under Frozen Conditions

In order to respond to the theme of national green and healthy sustainable development and in response to the problems of large block rates and pollution of the environment after the blast mining of underground rocks in alpine areas, we conducted research on the joints of underground rocks and the blastability of frozen rocks. According to the actual geological conditions of an underground mine blasting in Heilongjiang Province, three kinds of joint blasting geometric models were established. The rock mass blasting process of different types of joints was simulated by LS-DYNA software and the influence law of joints on rock mass blasting was summarized. The blasting crater test and the triaxial compression test of frozen rock were carried out. Combined with the blasting fragmentation characterization function (R-R and G-G-S), the blasting fragmentation, strength and stiffness of frozen rock at different temperatures were obtained. Based on the above, the blasting parameters of a multi-joint underground rock mass in an alpine region were optimized: hole spacing 4.0 m, row spacing 2.5 m, hole depth 11.5 m, V-type initiation network. The optimized blasting parameters significantly improved the mining efficiency and reduced the large lump rate to 3.1%. In order to promote the sustainable exploitation of resources in alpine regions, this study optimized the blasting technology of underground rock mass.

Study on Blasting Technology for Open-Pit Layering of Complex Mine Adjacent to High and Steep Slope

In China, mining blasting vibration has seriously threatened the safety and stability of high and steep rock slopes. In this paper, taking the east mining area of Jianshan Phosphorus Mine as the research background, combined with field survey, field blasting test, numerical simulation and theoretical analysis, we systematically studied the adjacent high-steep rock slope and the layered blasting technology of complex ore. Based on wide hole spacing blasting numerical simulation and field tests, the use of 8 × 4 m hole network parameters, oblique line hole-by-hole initiation method, detonator delay using 35 ms between holes, 65 ms between rows and 500 ms within the holes, the rock mass rate was reduced and the drilling workload was decreased. In addition, regression analysis was carried out on a large amount of vibration test data, and the attenuation law and propagation law of blasting vibration of adjacent high and steep slopes were predicted, which provided a reference for mine production blasting. By establishing a mathematical model of cumulative damage of rock mass blasting, it shows that the depth of impact of mining blasting on the slope of Jianshan open-pit was 0–3.6m, but the blasting did not cause overall damage to the adjacent high and steep slopes. In the future, this model can be used to predict rock damage caused by subsequent blasting.

Study on Numerical Simulation of Geometric Elements of Blasting Funnel Based on PFC5.0

Based on the particle flow code (PFC2D) within the discrete element method (DEM), the rock mass model was established according to the site rock conditions and the rock mass blasting was simulated by the explosive particle expansion method. The influence of various parameters (the peak pressure action coefficient of the borehole wall, explosive particle buried depth, and charge mode) in the explosive particle expansion method on blasting effect was investigated. Furthermore, the relationship between the various parameters and the geometry size of the blasting crater was obtained. By comparing the size of blasting crater in the field blasting test and numerical simulation example, the reliability of rock mass blasting simulated by the explosive particle expansion method using PFC is verified. The result shows that this paper provides a reliable new numerical simulation method for rock mass blasting and can be used to guide field blasting.

Research on the Seam Formation Mechanism of Elliptical Bipolar Linear Directional Blasting Based on the SPH‐FEM Coupling Method

Rock mass blasting is a complex process that involves the coupling of both discontinuous and continuous media. This paper aims to reveal the dynamic failure process between adjacent boreholes under an elliptical bipolar linear charge structure using the SPH‐FEM (smooth particle hydrodynamics and finite‐element method) coupling algorithm numerical simulation method. The numerical simulation results are compared with the existing experimental results, which proves the rationality of the algorithm. According to the numerical simulation results, the shaped jet will first shock the hole wall and form a stress concentration zone that will guide the formation of cracks during the stress wave propagation process. In the case of double‐hole blast loading, there is a tendency for cracks coalescence to develop between adjacent boreholes due to the superposition of stresses between the double holes and the increase in damage and plastic strain. The best blasting results will be achieved with this structure when the distance between adjacent holes is 110 cm. Finally, the superiority of elliptical bipolar linear blasting in engineering blasting was verified through field experiments. The results of this study provide a reference for subsequent applications of elliptical bipolar structures in the field of rock blasting.

Effect of an eccentric decoupled charge on rock mass blasting

Experimental and numerical analyses were conducted to investigate the effect of an eccentric loaded contour hole on a rock mass. In the concrete blocks used for the analyses, detonating cords were placed at the centre of the blast hole and eccentrically against the wall of the blast hole. PFC2D and AUTODYN were used for the numerical analyses, and the results of these software showed that an eccentric decoupled charge can result in the directional development of fractures, thereby enabling the control of cracks in the opposite direction. Even though both types of blasting have identical decoupling indexes, the crack and fracture patterns were affected by the location of the explosive, tamping, and other conditions. The results showed that an eccentric charge holder can be applicable to control the fracture direction and the damaged zone. For an eccentric charge, the initial crack was generated at 0.01 ms and expanded in the intended direction. For the eccentric charge, the maximum pressure at the area in contact with the blast hole wall exceeded that for the central decoupled charge by a factor of 5.5. Furthermore, the pressure in the intended direction was twice of that in the opposite direction.

Numerical simulation of rock mass blasting using particle flow code and particle expansion loading algorithm

Numerical simulation of limestone rock mass blasting was carried out using the two-dimensional particle flow code (PFC2D) within the discrete element modeling framework, and the explosion load was loaded using the particle expansion algorithm. A field experiment of rock blasting was also carried out from which the size of the blasting funnel and the maximum blasting vibration velocity were recorded. The simulation results were compared with the experimental results in two aspects: the blasting result and the post-explosion effect. From the comparison, it has been observed that the size of the blasting funnel obtained from the numerical simulation shows a good agreement with the field experiment. However, in the case of the post-explosion effect (the blasting vibration velocity), the results of the numerical simulation and the vibration velocity curve obtained from the field test show disagreement to a certain extent. This demonstrates that the particle expansion loading algorithm is reliable in simulating the rock blasting process. The results of this research serve as a reference for subsequent applications of the PFC method in the field of rock blasting.

The Study of Parameters of Quarry Faces in Muruntau and Myutenbai Open Pits in Case of Applying Major Blasts

The paper presents process layouts for excavation of zones near pit envelope based on the analysis of findings of the ore loss study in case of open-pit mining, as well as the results of field measurements in the quarry faces in Muruntau and Myutenbai open pits. In the course of the field measurements, parameters of the quarry faces at Muruntau and Myutenbai open pits were determined under the following working conditions of an excavator: at full bench with shotpile height of 19–21 m; at full bench with shotpile height of 12–14 m at excavation of the “blast cap”; at heading face and taking ramp material. In all the above-listed quarry faces, the slope angles and the ore mass shotpile height when excavating were measured. Besides, the used excavator type (dragline or hydraulic) was taken into account. For each face, 2–3 measurements were performed, and the average slope angle at the ore mass excavation was determined for each type of excavator. At the next stage of the field measurements, the bench height in the rock mass and the shotpile parameters were measured before and after blasting operations under the following arrangements for preparing the rock mass for excavation: a) under normal conditions, when the ore mass blasting is performed for the selected face or relieving wall of the required thickness; b) in compression with a “blast cap” formation; c) in the marginal parts of the bench. Based on the results of the actual bench height and the blasted rock shotpile parameter field measurements, the following conclusions were drawn: a) the actual slope angles of the quarry faces were 49° when excavating the “blast cap” using dragline excavators, and 53° when excavating the ore mass at full bench regardless of the excavator type used; the slope angles of 49° for the dragline excavator and 53° for the hydraulic excavators were taken for further calculations; b) the width of the marginal (near-envelope) zone, where losses and dilution of balance ore are generated, increased from 7 to 13.0 m (at 49°) and from 7 to 11.3 m (at 53°); as a result, the areas of loss and dilution triangles have increased; c) when blasting in compression conditions, in the upper part of the shotpile, intense mixing of the involved rock and all ore grades occurs, therefore, when excavating the “blast cap”, bulk ore mass mining is only possible. The lower part of the blasted bench preserves the geological structure of the rock mass to a greater degree and can be selectively excavated with separation of the ore mass by grade; d) when blasting the rock mass, to maintain the required pulse direction and the blasting sequence, barren boreholes are included in the breaking outline, which increase the balance ore dilution, and structural dilution arises, which should be taken into account when drawing up the "Methods for determining, limitation and accounting for ore losses and dilution in the course of the Muruntau and Myutenbai (the fifth stage) open-pit mining"; e) when compiling the "Methods ...", the option of dividing a bench of 15 m high into two sub-benches of 7.5 m should be considered.

Models of Determining the Parameters of Rock Mass Oscillation Equation with Experimental and Mass Blastings

The explosion caused by detonation of explosive materials is followed by release of a large amount of energy. Whereby, a greater part of energy is used for rock destruction, and part of energy, in the form of seismic wave, is lost in the rock mass causing rock mass oscillation. Investigations of the character and behavior of the pattern of seismic wave indicate that the intensity and nature of the seismic wave are influenced by rock mass properties, and by blasting conditions. For evaluation and control of the seismic effect of blasting operations, the most commonly used equation is that of M.A. Sadovskii. Sadovskii’s equation defines the alteration in the velocity of rock mass oscillation depending on the distance, the quantity of explosives, blasting conditions and geological characteristics of the rock mass, and it is determined based on trial blasting for a specific work environment. Thus, this paper offers analysis of the method for determination of parameters of the rock mass oscillation equation, which are conditioned by rock mass properties and blasting conditions. Practical part of this paper includes the experimental research carried out at Majdanpek open pit, located in the northern part of eastern Serbia and the investigations carried out during mass blasting at Nepričava open pit, located in central Serbia. In this paper, parameters n and K from Sadovskii’s equation were determined in three ways—models in the given work environment. It was noted that, in practice, all three models can be successfully used to calculate the oscillation velocity of the rock masses.

Physical and technological factors of the formation of detonation capacity of blasthole charges of emulsion explosives

Modern conditions of mining are characterized by a constant increase in the depth of the pit, as a result of this there is a change in the geological and mining conditions. The obtaining of the mined rock is provided by using the drilling-and-blasting method as the main process that influences the technical and economic indicators of the next processes and enterprises in general. The effectiveness of the explosion in rocks depends on the technology of blasting.In scientific and technical literature the influence of various natural and technological factors on the process of the explosion has been studied in detail. We developed methods and recommendations for calculating the parameters of mass blasting used in common projects in the blasting operation and ensure their implementation of getting the rock mass of different coarseness of grading. However, these methods are based on traditional formulas and empirical dependencies, according to which the parameters of location and charge blasting accepted as the same, despite the fact that the blocks that blasted may include different types of rocks, and this, in turn, causes predatory yield of sub-standard fractions.Therefore, the implementation of the design parameters of the blasting should be based on modern scientific achievements, interrelationships of geological and technological indicators and parameters with the least expenditure of labor and time in the design process.The article analyzes the impact of the physical condition and the composition of emulsion explosive, geometric parameters and conditions of charge blasting, characteristics of dynamic processes in the charge and the decomposed array for the manifestation of the phenomenon of desensibilization emulsion explosives.

Numerical simulation of the complete rock blasting response by SPH–DAM–FEM approach

Rock mass blasting is a complex process which involves the coupling of both discontinuous and continuous media. This paper aims to provide a numerical simulator capable of reproducing the complete blasting response in rock mass by incorporating large deformations, damage distribution and blasting vibration with a single numerical model. A Smooth Particle Hydrodynamics (SPH) algorithm and a modified blasting damage model were introduced into the explicit finite element code LS-DYNA with a subroutine interface in order to develop the coupled SPH–DAM–FEM numerical simulator. The coupled SPH technology with the modified Damage model is used to simulate the near zone in the blasting process and the FEM to capture the far field response of the rock. The complete dynamic response of a presplit blast and a bench blast was investigated with the developed coupled model in two case studies regarding a blasting excavation of high rock slopes in China. The discontinuous characteristic of the blast process, large deformations and damage were analyzed carefully. The reproduction of the damage contour and vibration was compared with site measurements. From the analysis conducted, it is shown that the results produced by the developed coupled model match quite well with field observations. This demonstrates the capability of the proposed coupled model. To complete the analysis, a sensitivity analysis of the main SPH parameters was studied parametrically to obtain a better understanding and expose more capabilities and applications of the proposed coupled approach.

Parameter determination of soil oscillation law using quotient of the relative growth increments of oscillation velocity and reduced distances at 'Nepričava' Open Pit Mine

During blasting operations, the potential energy of explosive materials is transformed into a mechanical work. That energy, in the vicinity of blasting location, destructs and crushes rock mass, a bit further creates cracks and permanent deformations in the rock mass, and even further it is being transformed into elastic deformations. The effect of elastic seismic wave is movement of particles of the rock mass from its equilibrium position. Such oscillation of the rock mass particles is manifested as a shock and represents one of the negative effects of blasting. In order both to evaluate and control the seismic effect of blasting, as well as to plan it, the determination of soil oscillation law is required, with the strike: mine field - facilities to be protected. One of the most commonly used equations is that of M. A. Sadovski defining the law of alteration in the oscillation velocity of the soil depending on the distance, the explosive amount, and conditions of blasting and geologic characteristics of the soil, being determined on the basis of test blasting for the specific work environment. In this paper, an analysis of the method for the determination of soil oscillation law parameters has been conducted, suggested by Professor M. A. Sadovski. The applicability of this law was analyzed on examples of mass blasting in the 'Nepricava' Open Pit Mine being carried out in order to exploit the deposit. To determine parameters in the equation of Sadovski, in addition to the common method of least squares, another model was applied. Thereby, it has been stated that both models can be used to calculate the oscillation velocity of the rock mass.

Research on Rock Mass Blasting of Weak Plane by High Dynamic Strain Test

when explosive blasts in the rock, the stress wave of impact produced appears all kinds of phenomena, such as reflection, refraction, and transmission in the process of transmission on the joint surface because of discontinuity, heterogeneity and anisotropy of rock mass of weak plane in physics, which lead to extremely complex on rock blasting process. Through conducting on high dynamic strain test of blasting process on joint rock mass model, it researches dynamic load characteristics of joint rock mass and joint-planes effect on extension of critical raw crack and attenuation law of stress wave, analyzes the strain waveform of strain gages which locate in the different direction between initial crack of blasting and joint, and figures out the impact of joint plane on the stress wave transmission, which provide an important theoretical basis on the relevant parameters design in the process of blasting engineering of joint mass existing in actual.

Properties of nano- and microparticles emitted into the environment from open-pit mining of iron deposits

The properties of nano- and microparticles (60 nm-200 μm) of the dust formed by mass blasting in the iron ore open pit of the Lebedinsky Mining and Concentrating Combine have been studied. Data on the morphology of particles, their magnetic properties, mineralogy, and dimensions have been obtained. Quartz, magnetite, and mica were identified among these particles. The dust mostly consisted of fragmented iron ore formation from the rock massif involved in the blasting.

Evaluation of the Part of Blasting Energy Used for Rock Mass Fragmentation

In the literature, the results of numerous studies were used to propose predictive tools for the evaluation of fragmentation efficiency in rock mass blasting. The methodology developed during several years at the Centre de Geologie de l’Ingenieur is based on the comparison of rock mass and corresponding muck piles block size distributions [1–4]. This paper introduces a new approach of the evaluation of the part of blasting energy used in fragmentation, based on the assessment of the energy devoted to the formation of crack surface. The fundamental assumptions of this method will be exposed and discussed in detail. The method is then applied to blasts performed in two Spanish mines in different geological contexts. The corresponding results are presented and the influence of some blast parameters (such as geological rock mass structure, specific energy and time delays) is discussed.

Pre- and post-failure ground behaviour: case studies of surface crown pillar collapse

Five case studies of collapse of surface crown pillars from Western Australia and the Northern Territory were analysed. It was found that there was a pattern in the geotechnical behaviour of the rock mass prior and after the collapse. The pattern indicated that the hangingwall was deteriorating years or months prior to collapse. Weeks before, level pillars were collapsing and broken rock rilled down the stopes. Within days or even hours before the collapse, rock noises and rock falls were reported in various parts of the mines. To monitor different behaviour of the rock mass it is recommended that appropriate geotechnical instrumentation and monitoring be used. Deterioration in ground conditions can be triggered by external sources like mass blasting or a seismic event. After the collapse, the postfailure behaviour in a from of further ground collapse and gradual movement continued for a number of years.

Mass blast computer design, analysis and monitoring—a case study

Abstract In underground operations, the controlled recovery of large quantities of valuable ore in the form of stopes and/or remnant pillars has involved the application of mass blasting techniques. An underground mass blast may be defined as an approach, which requires the design and implementation of a large number of drilling patterns; charging and sequencing strategies with the aim to extract a large section of ore. In the context of underground mining and productivity, mass blasts may vary in size and can typically range from the planned ore recovery of 100,0001 to in excess of 1,000,000 t. The recovery of such amount of material presents a particular challenge to the blasting engineer from design through to the implementation stages. This paper aims to provide engineers with some background and guidelines for the design, analysis and monitoring of underground mass blasts, thus further facilitating the transition from design to implementation. With reference to a particular case study, computer aided design tools are described and used in both the design and analysis process. A blast monitoring strategy was carried out in this study with the view to assess and describe the performance of the blast. Monitoring was also carried out to detect seismic activity associated with the redistribution of stresses. The use of the computer software tools proved to be essential in the design and post-blast analysis stages of the mass blast. Computer simulations justified the inclusion of re-drills and additional rings to ensure a more efficient explosive energy distribution, simulations also provided a full 3D visualisation of the blast sequence, allowing engineers to make final design adjustments.

Measurement of the fragmentation efficiency of rock mass blasting and its mining applications: J. Aler, J. Du Mouza & M. Arnould, International Journal of Rock Mechanics & Mining Sciences, 33(2), 1996, pp 125–139

Measurement of the fragmentation efficiency of rock mass blasting and its mining applications: J. Aler, J. Du Mouza & M. Arnould, International Journal of Rock Mechanics & Mining Sciences, 33(2), 1996, pp 125–139

The Kostanjek landslide in Zagreb

The large landslide, Kostanjek, on the southern slopes of the mountain, Zagrebacˇka Gora, in the western suburb of Zagreb was activated in 1963 after some 2.1 × 10 6 m 3 of marl for the cement factory, Croatia, was excavated at the foot of the slope. The geological features (sinclinal structure, faults, hydrogeological conditions, extension of the “Tripoli” marl strata) which had an important role in the formation of the slide, as well as the means of marl exploitation by means of mass blasting, are presented in the paper. The Kostanjek slide involves an urbanized area of some 100 ha. It is estimated that a sliding mass of some 32 × 10 6 m 3 is involved, with a maximum depth of 90 m. Sliding occurs in three levels. The displacements of the surface are 3–6 m. The excavation of marl was stopped in 1988, when a total of 5.3 × 10 6 m 3 of material was excavated. Since then the magnitude of surface displacement per year has decreased. The Kostanjek slide is still active. It is estimated that natural stabilization will take a long time, probably decades. Analyses of possible measures for the stabilization of movements suggested that preventive drainage with continuous observation of the slide is most suitable.

Measurement of the fragmentation efficiency of rock mass blasting and its mining applications

A new approach in evaluating the fragmentation efficiency of rock mass blasting is presented. It differs from most of the methods as it is predicated on a pre-existing in situ block size distribution in the rock mass as defined by the natural discontinuity network. Blasting therefore accomplishes the supplementary fragmentation of the already fragmented rock mass, the efficiency of which depends on the blasting parameters employed. The blasting efficiency is evaluated through comparison of the block size distributions of the rock mass and the corresponding muck pile. The estimate of the former is achieved by discontinuity network modelling in three dimensions with the aim of identifying the in situ blocks formed and measuring their volumes. For the muck pile, image analysis techniques applied to “randomly-taken” photos are used to derive the resulting block size distribution. Validation of the proposed method on various mines is presented as well as its significant and practical mining applications.