Blasting Operations Research Articles

Evaluation of blast efficiency in aggregate quarries: facts and fictions

Evaluation of blast efficiency in quarrying of aggregate stones is one of the most important decisions that should be made by quarry operators for productivity assessment. The regulatory authorities also evaluate blast efficiency for environmental safety compliance. In carrying out this task, there is usually a conflict of interests between the quarry operators and the regulatory authorities. The quarry operators wish to blast and deliver the run-off-mine (ROM) to the processing plant at the least minimum cost with little or no boulders. On the other hand, the regulatory authorities want blast operations to be carried out with minimum disturbances to the environment irrespective of their incurred costs, fragmentation distributions, and effects on further quarrying processes. This conflict of interest calls for different approaches for evaluating blast efficiency by the various interest groups. Nevertheless, there must be an established standard that considers both process efficiency and environmental safety and acceptable to all the critical stakeholders in the sector. However, many of the currently available approaches and models for evaluating blast efficiency do not include safety but production efficiency. The chosen method primarily depends on the further use of quarried products. While quarry operators may evaluate blast efficiency by counting of boulders, shovel loading rate, visual observation, fragment size distribution, and cost analysis, the regulatory authorities majorly based their judgment on the level of blast-induced ground vibration by measuring the peak particle velocity of production blasts. This paper attempts to suggest a common ground and wholistic approach for evaluating blast efficiency and make a distinction between blast efficiency and fragmentation efficiency.

Prediction of air-overpressure induced by blasting using an ANFIS-PNN model optimized by GA

Blasting operations typically have several negative impacts upon human beings and constructions in adjacent region. Among all, air-overpressure (AOp) has been persistently attractive to practitioners and researchers. To control the AOp-induced damage, its strength should be predicted before conducting a blasting operation. This paper analyzes the AOp consequences through the use of the Fuzzy Delphi method (FDM). The method was adopted to identify the key variables with the deepest influence on AOp based on the experts’ opinions. Then, the most effective parameters on AOp were selected to be used in developing a new hybrid intelligent technique, i.e., adaptive neuro-fuzzy inference system (ANFIS)-polynomial neural network (PNN) optimized by the genetic algorithm (GA), called ANFIS-PNN-GA. From FDM and experts’ opinions, four parameters, i.e., amount of explosive charge, powder factor, stemming, and distance from the blast-face were identified as the most effective ones on AOp. In fact, in ANFIS-PNN-GA system, GA was used to optimize the ANFIS-PNN structure. The new framework of ANFIS-PNN-GA was developed, trained, and tested on actual datasets collected from a total of 62 blasting events. To show capability of the newly-proposed model, the ANFIS and PNN predictive models were also constructed to estimate AOp, and the performance prediction of the proposed models were evaluated through the use of several performance indices, e.g., correlation coefficient (R) and mean square error (MSE). R values of (0.94, 0.72, and 0.84) and (0.92, 0.58, and 0.77) and MSE values of (0.003, 0.03, and 0.021) and (0.005, 0.066, and 0.05) were obtained for training and testing datasets of ANFIS-PNN-GA, PNN, and ANFIS models, respectively. Accordingly, because of the role of GA as a practical optimization algorithm in improving the efficiency of both PNN and ANFIS models, results obtained by the ANFIS-PNN-GA model are more accurate compared to other implemented methods.

Prospects of Applying MWD Technology for Quality Management of Drilling and Blasting Operations at Mining Enterprises

This paper presents a review of measurement while drilling (MWD) technology as applied to the mining industry, describes its development path, provides a global review of literature on this topic, and outlines further trends of development for research on MWD application in drilling and blasting (D&B) operations at mining enterprises. The current review serves as a starting point for anyone interested in the research or application of MWD technology in Mining and Construction. In the paper, the authors examine major works of researchers in this area, describe current state of the art, and propose a way to improve MWD for drilling equipments. The paper contains examples of technology application in various processes, associated with drilling and mining operations, describes approaches and problems of MWD system utilization, revealed in the course of data collection and analysis of drilling processes. The study also presents a summary of existing approaches in the area of data validation and verification, applied up to the present day to cope with the problems of global MWD use in Mining and Construction. The authors outline future areas of study which are of interest and deserve the attention of the scientific community and researchers working on the development of MWD technology.

A New Technical and Economic Model to Calculate Specific Charge and Specific Drilling Using Hole Diameter, Bench Height, Uniaxial Compressive Strength, and Joint Set Orientation

Calculation of the specific charge and specific drilling before a blasting operation plays a significant role in the design of a blasting pattern and the reduction of the final extraction cost of minerals. In this work, the information from the Sungun, Miduk and Chah-Firouzeh copper mines in Iran was assessed, and it was found that there was a significant relationship between the specific charge and specific drilling and the hole diameter, bench height, uniaxial compressive strength and joint set orientation. After finding a technical and economic model to calculate the specific charge and specific drilling, this model was tested on the Sungun copper mine. Due to the insufficient consideration during the design of a blast pattern and because of the high hardness of the rocks in some parts of the mine, lots of destructive events such as boulders, back break, bench toe, high specific charge and high specific drilling, fly rock, and ground vibration in the blast operations were observed. The specific charge and specific drilling were found to be the most important technical and economic parameters involved in designing a blasting pattern, and they were found to play an important role in reducing the blasting cost. The blasting cost could be largely controlled by the accurate examination and computation of these parameters. An increase in the rock strength and the angle between the bench face and the main joint set would increase the specific charge and specific drilling. On the other hand, a specific charge and a specific drilling would decrease when the hole diameter increased in every range of the uniaxial compressive strength.

Optimization of blasting design in open pit limestone mines with the aim of reducing ground vibration using robust techniques

Blasting operations create significant problems to residential and other structures located in the close proximity of the mines. Blast vibration is one of the most crucial nuisances of blasting, which should be accurately estimated to minimize its effect. In this paper, an attempt has been made to apply various models to predict ground vibrations due to mine blasting. To fulfill this aim, 112 blast operations were precisely measured and collected in one the limestone mines of Iran. These blast operation data were utilized to construct the artificial neural network (ANN) model to predict the peak particle velocity (PPV). The input parameters used in this study were burden, spacing, maximum charge per delay, distance from blast face to monitoring point and rock quality designation and output parameter was the PPV. The conventional empirical predictors and multivariate regression analysis were also performed on the same data sets to study the PPV. Accordingly, it was observed that the ANN model is more accurate as compared to the other employed predictors. Moreover, it was also revealed that the most influential parameters on the ground vibration are distance from the blast and maximum charge per delay, whereas the least effective parameters are burden, spacing and rock quality designation. Finally, in order to minimize PPV, the developed ANN model was used as an objective function for imperialist competitive algorithm (ICA). Eventually, it was found that the ICA algorithm is able to decrease PPV up to 59% by considering burden of 2.9 m, spacing of 4.4 m and charge per delay of 627 Kg.

АВТОМАТИЧНА СИСТЕМА БЕЗПЕРЕРВНОГО КОНТРОЛЮ СТАНУ НАСАДКИ ДОМЕННОГО ПОВІТРОНАГРІВАЧА

The analysis of the existing methods for assessing the hot blast stove state, in particular its checkerwork was carried out. Based on the existing methods, the task of creating an automatic control system of the hot blast stove checkerwork state was set. The main operational parameters of the hot blast stove affecting the efficiency of its operation were selected. The structure of an automatic continuous control system of the hot blast stove state was developed, which includescontinuous monitoring of the differential pressure in the nozzle, the casing temperature various levels, and the composition of the exhaust gases. Selected modern automation equipment. Using adatabase of the values of the main technological parameters of the operation of a real hot blast stoves block, a regression dependence was built, allowing to calculate the efficiency of each of thehot blast stoves. It was found that the regression dependence also shows the "direction" and the degree of influence of each operating parameter on the heat engineering efficiency of the hot blaststove. The calculation of the efficiency for each hot blast stove was performed. A comparative analysis of the calculated efficiency with technological efficiency was carried out. It was shown thatthe calculated value practically coincides with the technological value. With the possibility of obtaining regression dependences of the efficiency and nozzle resistance on the main parameters characterizing the nozzle and blast heating, in real time it is possible to predict the dynamics of the hot blast stove state or to simulate various modes of operation of the unit. According to the results of the research, it is arguable that the developed control system can be successfully implemented and used in the blast furnace process.

Does Exposure to Naturally Occurring Asbestos (NOA) During Dam Construction Increase Mesothelioma Risk?

ABSTRACT The Calaveras Dam Replacement Project, a major construction project completed in 2019, involved hundreds of workers using heavy earth-moving equipment and mining operations, including blasting, drilling, rock crushing, and other operations designed to move millions of cubic yards of earth. Much of the material was composed of serpentinite, blueschist, and other rocks that contain chrysotile and a variety of amphibole minerals, including glaucophane, winchite, actinolite, tremolite, and other asbestos-related amphiboles. This article explores the unique characteristics of the blueschist that required extensive protective measures to be undertaken by the contractor to protect workers and surrounding sensitive receptors. This article will provide an overall summary of the dimensional characteristics of the airborne blueschist elongate mineral particles encountered during construction activities to compare and contrast current understanding of cleavage fragments versus asbestiform mineral fibers.

Effective Assessment of Blast-Induced Ground Vibration Using an Optimized Random Forest Model Based on a Harris Hawks Optimization Algorithm

Most mines choose the drilling and blasting method which has the characteristics of being a cheap and efficient method to fragment rock mass, but blast-induced ground vibration damages the surrounding rock mass and structure and is a drawback. To predict, analyze and control the blast-induced ground vibration, the random forest (RF) model, Harris hawks optimization (HHO) algorithm and Monte Carlo simulation approach were utilized. A database consisting of 137 datasets was collected at different locations around the Tonglvshan open-cast mine, China. Seven variables were selected and collected as the input variables, and peak particle velocity was chosen as the output variable. At first, an RF model and a hybrid model, namely a HHO-RF model, were developed, and the prediction results checked by 3 performance indices to show that the proposed HHO-RF model can provide higher prediction performance. Then blast-induced ground vibration was simulated by using the Monte Carlo simulation approach and the developed HHO-RF model. After analyzing, the mean peak particle velocity value was 0.98 cm/s, and the peak particle velocity value did not exceed 1.95 cm/s with a probability of 90%. The research results of this study provided a simple, accurate method and basis for predicting, evaluating blast-induced ground vibration and optimizing the blast design before blast operation.

Erosive Wear Testing of Laser Clad and HVOF Coatings for Drilling in Mining

Drilling is a major cost factor to mining operations (exploration, drill and blast operations), and wear of components is a significant driver of drilling costs. For drilling, the so-called Down-the-Hole (DTH) hammers or Reverse Circulation (RC) hammers are used. These drills break the rock through repetitive impact. Cuttings are removed via a high-velocity air stream. The main wear mechanism for these hammers was found to be erosion. To combat erosive wear, laser clad coatings with a Nimatrix and different-sized fused tungsten carbides FTC (WC/W2C) (angular and spherical) and monocrystalline WC were developed. In addition, hard Fe-based HVOF coatings were investigated. Wear-resistant steel, WCCoCr HVOF, electroplated chrome and a high-chrome cast iron as bulk served as references. An erosion-testing apparatus which follows ASTM G76 was developed. Testing was carried out at incident angles from 15-90°. Coating performance was assessed via volume loss, obtained using 3D profilometry. At low angles, the WCCoCr coating lost the least volume, and at high angles a Ni/WC laser clad coating with spherical FTC provided the best erosion resistance. Imperfections like cracks, pores and voids serve as weak points where material loss out of the surface commences.

Monitoring Study on CO and Dust Diffusion in High Altitude Tunnel under Blasting Operation

In the high altitude area, the air density and the air pressure are low. CO and dust diffusion in tunnel construction have special rules. In this paper, combined with a high altitude tunnel engineering in Tibet, CO and dust diffusion during blasting operation was monitored, and diffusion situation before adopting treatment measures was compared with that after adopting treatment measures. The result shows concentration of CO and dust produced by blasting operations is high, which is more likely to cause damage to operators in areas with thin oxygen at high altitudes. Therefore, necessary treatment measures should be taken. In the longitudinal direction, the change rule of the CO and dust are totally the same. With the increase of distance from tunnel face, dust concentration declines gradually. In the range of 100m∼500m from tunnel face, the disadvantage effect of blasting is little. In this project, CO and dust concentration are reduced to a certain extent after the measures of strengthening ventilation and dust removal by water curtain are adopted.

Numerical Investigation on Influential Factors for Quality of Smooth Blasting in Rock Tunnels

The quality of smooth blasting including the volume of over‐/underbreak and blasting‐induced damage of surrounding rocks has been extensively considered to be highly correlated to both the cost and advancement rate of rock tunnelling excavated by the drill‐blast method. A general control strategy for smooth blasting is too difficult to be available due to the uncertainties and complexity of rock masses, as well as the varying blasting operations. As prerequisite for the evaluation of the blasting quality, effective identification of the influential factors affecting smooth blasting usually plays a significant role in the improvement of smooth blasting design. Compared to the expensive and time‐consuming experiments including physical modelling and field tests, numerical modelling, as a cost‐efficient approach, offers an attractive alternative to investigate the influential factors in terms of weight, which might be more applicable and reliable for the optimization of smooth blasting parameters. In this case, the dominant factors and secondary factors can be quantitatively identified. Considering the dominant factors often orient the development of things; in this work, a numerical‐based approach was proposed to quantitatively identify the dominant factors influencing the quality of smooth blasting. Proposed 3‐dimensional blasting modelling was based on LS‐DYNA to simulate the occurrence of smooth blasting in rock masses, and the erosion algorithm was also employed to determine the fracturing of jointed rocks. The orthogonal experimental design method was utilized to optimize the experimental arrangement. Seven factors with 4 levels including the perimeter hole spacing, line of least resistance, charge concentration, charging explosive, type of rock mass, detonation velocity, and drilling deviation were taken into account. The geological setting and project background of a real rock tunnel served for the Chengdu‐Chongqing high‐speed railway were selected as the site conditions to perform the numerical investigation. Calculated area and distance of overbreak as the observed parameters indicating the quality of smooth blasting were utilized to determine sensitivities of factors based on the range analysis of orthogonal experiments. The results suggested that the type of rock mass has the greatest influence on the blasting quality, whereas the charge concentration and detonation velocity can be considered as the secondary factors under the specific site conditions. The proposed numerical approach for assessing influential factors of quality of smooth blasting under specified geological conditions is expected to improve the parameter design and operation of smooth blasting in practical applications.

Prediction accuracy of underground blast variables: decision tree and artificial neural network

Accurate prediction of blast induced ground vibration variables such as particle velocity and frequency are of interest for safe design of controlled blasting operations for mining, tunnelling or excavation projects. There are certain limitations in the widely used empirical and numerical approaches especially when number of variables is large. Various data driven approaches have been employed for producing correct estimates for such cases. Decision tree (DT), earlier successfully employed for solving variety of civil engineering problems, is employed for prediction of blast variables for the first time in this article. The performance of DT models was found to be equally good (for particle velocity variable) or better than (for frequency variables) ANN models developed in this study, and unequivocally superior to the SVM or RF models reported in literature. Additionally, the clarity in decision rule-based estimation foster easy comprehension and future implementation.

Applying Rock Engineering Systems Approach for Prediction of Overbreak Produced in Tunnels Driven in Hard Rock

Drilling and blasting is the predominant excavation method of the tunnels driven in hard rock. Overbreak is an undesirable outcome of blasting operation that has a profound effect on the safety and cost of tunnels. Determination of overbreak and the corresponding risk is of vital importance. The main aim of this research has therefore been to assess the risk associated with overbreak as well as its prediction. To do this, a rock engineering system (RES) based model has been proposed. The research data in this study was drawn from four tunnels located in Bakhtiari dam project, Iran. For 54 blasting operations carried out in the investigated tunnels, the values of 14 causative factors in overbreak were carefully measured. The result of this study shows that the developed RES based model with a high value of coefficient of determination (R2 = 0.91) is a reliable technique to predict overbreak. Furthermore, the evidence from this study suggests that the Tunneling Rock Quality Index, perimeter specific charge and burden to spacing ratio play a large part in the values of overbreak. From the risk assessment conducted for the investigated tunnels, no blast operation was found to be highly problematic. Also, the overall risk level posed by overbreak was in medium range where the overbreak might be slightly problematic, and need to be monitored. The newly suggested RES model is also evaluated using 8 blasting operations, showing high level of performance.

Evaluation and Optimization of Prediction of Toe that Arises from Mine Blasting Operation Using Various Soft Computing Techniques

Drilling and blasting operations are one of the most effective techniques for rock removal in mines. However, these operations are associated with some environmental issues such as the problem of toe. This issue has a deep impact on blasting cost where there is a need to conduct secondary blasting due to this problem. Therefore, it is beneficial to predict and subsequently optimize this issue. This study attempts to predict toe resulting from blasting by developing artificial neural network (ANN) and decision tree (DT) techniques. To do this, 100 blasting were considered and collected in the Hawzak limestone mine, Iran. Then, the most effective parameters were considered as model inputs and many models of ANN and DT were developed to predict toe induced by blasting. For comparison purposes, multiple regression (REG) was also applied. Three performance indices were used to evaluate the developed models. Coefficients of determination (R2) of 0.76, 0.83 and 0.91 were obtained for testing datasets using the REG, DT and ANN models, respectively, which indicate that ANN can provide higher performance capacity for prediction of toe induced by blasting. In the optimization phase, imperialism competitive algorithm (ICA), which is a new optimization technique in this field, was applied to determine optimal blasting pattern parameters in order to minimize toe induced by blasting. By developing ICA technique, the amount of toe was reduced from 431 to 288 m3 (49.35%), which shows the excellent ability of ICA in optimizing the minimization of toe that arises from blasting operations.

Monitorowanie oddziaływania robót strzałowych na otoczenie – nowe rozwiązania

Blasting operations carried out in open-cast mines generate seismic vibrations, which can adversely influence nearby structures. As a result, open-cast mines undertake measures to define the conditions for the execution of blasting operations, which are safe for the surroundings as well as documenting the level of this impact. Documenting the seismic interference through cyclic control measurements and the assessment of this interference carries one disadvantage, which is its periodic implementation. This drawback is eliminated by applying seismic monitoring. In Poland, the influence of blasting on the surroundings is monitored by a system called Mine Vibration Monitoring Station (MVMS). The system was designed and built at the AGH University of Science and Technology in Krakow and has been modernized and updated over the last few years. Presently, it is a remotely controlled system which maintains communication via the internet, with data collected at the central server of the University. Evolution of the system and its technical capabilities are presented in the article.

Support algorithm for blast furnace operation with optimal fuel consumption

Fuel consumption in blast furnaces depends on many factors that are mainly conditioned by the technological level of a given blast furnace, the steel mill in which it operates, and the type and quality of ferrous feed, coke, and additional reducing agents. These are global factors which a furnace crew cannot control during operation. On the other hand, using their own experience and decision-making software, a crew can run a blast furnace with minimal fuel consumption under current batch and process conditions. The paper presents a model-based algorithm for optimizing the operation of blast furnaces to achieve the lowest fuel consumption. The algorithm allows the heat demands to be continuously calculated and highlights any wastage that could be reduced without affecting the stable operation of the blast furnace.

Molecular Dynamics Simulation on the Effect of MgO/Al2O3 Ratio on Structure and Properties of Blast Furnace Slag Under Different Basicity Conditions

The SiO2-Al2O3-CaO-MgO is the basic structural system of blast furnace slag and the composition directly affects the performance of the slag. Molecular dynamics simulations were carried out to analyze the local structure, structural unit, bond angle, transport properties, and enthalpy of the slag with the increase of MgO/Al2O3 mass ratio under different basicity conditions. It was found that the change of MgO/Al2O3 ratio does not affect the short-range order structure, but it will reduce the overall stability of the network structure. Through the analysis of the structural unit of the slag, it was found that the polymerization degree of the system decreases with the increase of MgO/Al2O3 ratio, indicating that the complex network structure of the system is partially depolymerized. Besides, the self-diffusion coefficients of each ion were concluded and the magnitudes were observed to be in the following order: Mg2+>Ca2+>Al3+>O2->Si4+. The diffusivity of the slag increases with the increase of MgO/Al2O3 ratio and the corresponding viscosity decreases. And the enthalpy of the slag is increased with the increase of MgO/Al2O3 ratio or basicity, therefore the fuel consumption should also be properly adjusted during the operation of blast furnace to ensure the target temperature.

Effect of MgO/Al2O3 ratio on the structure and properties of blast furnace slags: A molecular dynamics simulation

SiO2-Al2O3-CaO-MgO is the most significant slag system in the blast furnace ironmaking process and it is very important to investigate the microstructure and viscosity of the system. In this paper, molecular dynamics simulations were carried out to explore the effects of MgO/Al2O3 ratio on structure and properties of the system. Based on the self-diffusion coefficients, the viscosities were calculated by Einstein-Stokes equation and compared with the experimental value and the Factsage value. The results showed that with the increase of MgO/Al2O3 ratio, the stability of [SiO4]4− and [AlO4]5− tetrahedron became weaken and the relative proportions of bridge and non-bridge oxygen showed a decrease. And due to the increase of MgO, more Mg2+ ions are used as network modifiers to reduce the degree of polymerization of the system, resulting in a decrease in the viscosity, which is consistent with experimental results. Finally, based on the present study, in the case of increasing Al2O3 content of blast furnace slag, the fluidity of slag could be adjusted by controlling MgO/Al2O3 ratio, thereby providing a basis for stable operation of blast furnace ironmaking.

Experimental Study on the Seismic Efficiency of Rock Blasting and Its Influencing Factors

The seismic efficiency of a blast is the percentage of seismic energy in the total energy delivered by the explosives. It is a key indicator of the blast effects in civil engineering and seismic exploration. A method to determine seismic efficiency has been proposed based on the assumption of spherical wave radiation in an indefinite elastic medium and has been used in a series of blast tests performed at the construction site of a nuclear power plant. Analysis of the influencing factors of seismic efficiency shows that seismic efficiency increases with an increasing explosive charge and stemming length of the blastholes, while it decreases with an increasing decoupling coefficient. Generally, seismic efficiency is markedly lower in bench blasts than in paddock blasts due to free surface effects. Under any circumstances, the seismic energy only accounts for a few percent of the explosive energy. A comparison with theoretical solutions proves that the errors in the present method are low and acceptable in engineering. Therefore, some practical measures have been proposed to improve or lower the seismic efficiency according to the specific requirements of the blast operations.

Critically Stressed Areas of Earth’s Crust as Medium for Man-caused Hazards

Despite advances in rockburst studies, suddenness of major geodynamic events is reported in a number of cases. Phenomenological tectonophysical model is suggested to explain some geodynamics phenomena. Prof. Petukhov I.M. suggested a concept: the Earth crust's critical stress condition is developed due to horizontal compressive forces and entrains rock strata from the sub-surface to a certain depth. The conditions that induced earthquake in 2013 at Bachat coal field in south west Kuzbass are considered in terms of critical stress developed in the top layer of the Earth crust. Estimates show that the size of the critical stress zone, produced presumably by interaction of huge (over 100 km) crustal blocks is at least 10km. Whereas critical stress zone is located in the top part of Earth's crust, mining operations in the pit including blast operations was making a direct impact on this area. Shallow occurrence of critical stress area and its size can provide insight into why mining works brought about induced earthquake with hypocenter at the depth of several kilometers. The conclusion has been made that regional areas of critical stress within rock massif developed as a result of crustal blocks interaction create hazard medium for mining.