El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / Presplitting is a controlled-blasting technique with applications in open-pit mines. The main purpose of this technique is to prevent and control overbreaks caused by excessive vibrations due to blasting. This technique is especially effective in controlling overbreaks because it provides a separation surface between the main blasting pattern and the walls of the final slopes. The drilling mesh and loading conditions in the drill are designed in this study by considering the uncontrollable variables of the rock mass as important factors. The proposed model for the presplitting optimization process helps to optimize controlled-blasting designs. The main idea of the proposal is to develop a model that includes the most relevant processes, as well as the most suitable parameters for an efficient design. Copyright 2019.

This paper presents a blasting method called controlled trim blasting, in which the rock mass of an unstable gallery where high levels of vibration have been detected is analyzed. This methodology comprises a drilling mesh with two-contour gallery assessment, producing its drilling machines and determining the type of explosive used and burden and spacing, which will be detonated after the internal blasting. Further, the internal blasting will possess its drilling machines, burden, spacing, and a second type of explosive. The separation of the gallery into smaller parts will improve the blasting, as verified in the recorded simulation. In addition, the rock-mass stability improves because the explosives used in the perimeter of the gallery are low-power with mild detonation pressure, which does not generate high levels of vibration. This is a practical and efficient method in areas where the rock mass is not good or there is a mixture of rock types.

A project report submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master ofil science in Engineering. / Given the high capital intensity of the dragline operation, the mine can not afford to" tolerate fragmentation problems with its concomitant low dragline productivities. At Syferfontein colliery very large boulders and completely unfraqmented sections resulting in Low digging efficiency of the dragline were encountered in the interburden blast, This project, investigates the causes of the blasting related problems with an intent of improving dragline productivity at the minimum possible cost. This is achieved through blast monitoring, evaluation of the existing practice (blast design) using empirical relations, fragmentation assessment using a model, analysis of operators performance and dragline availabilities. Dragline productivity is evaluated in the light of the various productivity indices , viz, fill factor, fill time and BCM/H. The results indicated explosive incompatibility with the blasting environment and. questionable practices regarding blast design and Delay performance. Engineering field controls such as reduction in drill pattern, reduction of VODof explosive and improvement in draqline utilisation are found necessary. Contributing 61% to the total cost I concentrating on reducing draqline cost must receive preference over drilling and blasting cost as it would produce the most tangible advantage in any cost reduction effort. Regression equations relating cbst and productivity are established. / Andrew Chakane 2018

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / This article analyzes the applicability of an appropriate design of blasting engineering for an underground mine to be used in a Peruvian grain context through the data collection and observation method using the Bieniawski rock mass geomechanical classification system, average vein power weighting, and operational dilution of the pits. The generation of solutions is under both the McCarthy approach formula and final results analysis of the dilution behavior obtained in relation to the initial ones. Moreover, the database provided by a mining company is analyzed with respect to the geological conditions for the rock mass classification of the roof box and floor box to determine the quality of the rock, ore grades, power of the vein, and the percentage of dilution. Then we proceed to determine the continuity and thickness of the vein in a given block and analyze the dilution based on the fundamental criteria of blasting engineering.

No description available.

Abrasive blasting is a common process for cleaning or roughening the surface of a material prior to the application of a coating. Although the process has been in practice for over 100 years, the lack of a comprehensive understanding of the complex interactions that exist with the process can still yield an inferior surface quality. Subsequently, parts can be rejected at one of many stages of the manufacturing process and/or fail unexpectedly upon deployment. The objective of this work is to evaluate the effect of selected input parameters on the characteristics of the blasted surface characteristics so that a more useful control strategy can be implemented. To characterize surface roughness, mechanical profilometry was used to collect average roughness parameter, Ra. Decreasing blast distance from 6” to 4” gave ΔRa = +0.22 µm and from 8” to 6” gave ΔRa = +0.22 µm. Increasing blast pressure from 42 psi to 60 psi decreased the Ra by 0.33 µm. Media pulsation reduced Ra by 0.56 µm and the use of new media reduced Ra by 0.47 µm. Although blasting under the same conditions and operator on different days led to ΔRa due to shorter blast times, there was no statistically significant variance in Ra attributed to blasting on different days. Conversely, a ΔRa = +0.46 µm was observed upon blasting samples with different cabinets. No significant ΔRa was found when switching between straight and Venturi nozzles or when using different operators. Furthermore, the feasibility of fiber optic sensing technologies was investigated as potential tools to provide real time feedback to the blast machine operator in terms of substrate temperature. Decreasing the blast distance from 6” to 4” led to ΔT = +9.2 °C, while decreasing the blast angle to 45° gave ΔT= -11.6 °C for 304 stainless steel substrates. Furthermore, increasing the blast pressure from 40 psi to 50 psi gave ΔT= +15.3 °C and changing from 50 psi to 60 psi gave ΔT= +9.9 °C. The blast distance change from 8” to 6” resulted in ΔT = +9.8 °C in thin stainless steel substrate temperature. The effects of substrate thickness or shape were evaluated, giving ΔT= +7.4 °C at 8” distance, ΔT= +20.2 °C at 60 psi pressure, and ΔT= -15.2 °C at 45° blasting when comparing thin stainless steel against 304 stainless steel (thick) temperatures. No significant ΔT in means was found when going from 6” to 8” distance on 304 stainless steel, 40 psi and 60 psi blasting of thin SS, as well as angled and perpendicular blasting of thin SS. Comparing thick 304 and thin stainless steel substrates at a 6” blast distance gave no significant ΔT. / Master of Science

Blasting is a critical part of most mining operations. The primary function of blasting is to fragment and move rock. For decades, attempts have been made at increasing the efficiency of blasting to reduce costs and increase production. Most of these attempts involve trial and error techniques that focus on changing a single output. These techniques are costly and time consuming and it has been shown that as one output is optimized other outputs move away from their optimum level. To truly optimize a blasting program, the transfer of explosive energy into individual components must be quantified. Explosive energy is broken down into five primary components: rock fragmentation, heave, ground vibration, air blast, and heat. Fragmentation and heave are considered beneficial components while the remaining are considered waste. Past energy partitioning research has been able to account for less than 30% of a blast’s total explosive energy. The purpose of this dissertation was to account for a greater percentage of the explosive energy available during a blast. These values were determined using measurement techniques not previously applied to energy partitioning research. Four small-scale test series were completed, each designed to isolate individual energy components. Specific energy components measured include borehole chambering, elastic deformation (ground vibration), translational and rotational kinetic energy (heave), and air overpressure (air blast). This research was able to account for 73% of the total explosive energy. Borehole chambering (13%), rotational kinetic energy (25%), translational kinetic energy (5%), and air overpressure (28%) were determined to be the largest components. Prior research efforts have largely ignored rotational kinetic energy and have only been able to offer predictions for the values of borehole chambering and air overpressure energies. This dissertation accounted for a significantly higher percentage of total available explosive energy than previous research efforts using novel measurement techniques. It was shown that borehole chambering, heave, and air blast are the largest energy components in a blast. In addition to quantifying specific energy partitions, a basic goal programming objective function was proposed, incorporating explosive energy partitioning and blasting parameters into a framework that can be used for future energy optimization.

Coal mine impoundment failures have been well documented to occur due to an increase in excess pore pressure from sustained monotonic loads. Very few failures have ever occurred from dynamic loading events, such as earthquakes, and research has been done regarding the stability of these impoundment structures under such natural seismic loading events. To date no failures or damage have been reported from dynamic loading events caused by near-by production blasting, however little research has been done considering these conditions. Taking into account that current environmental restrictions oblige to increase the capacity of coal impoundments, thus increasing the hazard of such structures, it is necessary to evaluate the effects of near-by blasting on the stability of the impoundment structures. To study the behavior of excess pore pressure under blasting conditions, scaled simulations of blasting events were set inside a controlled sand tank. Simulated blasts were duplicated in both saturated and unsaturated conditions. Explosive charges were detonated within the sand tank at various distances to simulate different scaled distances. Information was collected from geophones for dry and saturated scenarios and additionally from pressure sensors under saturated conditions to assess the behavior of the material under blasting conditions.

Emerging health concern for gaseous nitrogen oxides (NOx) emitted during surface mine blasting has prompted mining authorities in the United States to pursue new regulations. NOx is comprised of various binary compounds of nitrogen and oxygen. Nitric oxide (NO) and nitrogen dioxide (NO2) are the most prominent. Modern explosive formulations are not designed to produce NOx during properly-sustained detonations, and researchers have identified several causes through laboratory experiments; however, direct sampling of NOx following full-scale surface mine blasting has not been accomplished. The purpose of this thesis was to demonstrate a safe, innovative method of directly quantifying NOx concentrations in a full-scale surface mining environment. A small unmanned aircraft system was used with a continuous gas monitor to sample concentrated fumes. Three flights were completed – two in the Powder River Basin. Results from a moderate NOx emission showed peak NO and NO2 concentrations of 257 ppm and 67.2 ppm, respectively. The estimated NO2 presence following a severe NOx emission was 137.3 ppm. Dispersion of the gases occurred over short distances, and novel geometric models were developed to describe emission characteristics. Overall, the direct sampling method was successful, and the data collected are new to the body of scientific knowledge.

The research presented in this dissertation consists of four topics. The first of these topics is an experimental study of rock fracturing due to rapid thermal cooling, and the other three topics are related to mine-to-optimization. This includes the development and testing of a site-specific model for blast fragmentation, the development of a technique for utilizing digital image processing and ground-based LIDAR for rock mass characterization, and an experimental study of the effects of ore blending on mineral recovery. All four topics are related through the subject of rock fracturing and rock fragmentation. The results from this research are important and can be used to improve engineering design associated with rock excavation and rock fragmentation. First of all, a successful set of laboratory experiments and 3D numerical modeling was conducted, looking at the effects of rapid thermal cooling on rock mechanical properties. The results gave the unexpected finding that depending on the rock type and the thermal conditions, rapid cooling can result in either overall crack growth or crack closing. Secondly, a site-specific model for predicting blast fragmentation was developed and tested at an open-pit copper mine in Arizona. The results provide a practical technique for developing a calibrated blasting model using digital images and digital image processing software to estimate in-situ block size, and a calibrated Schmidt hammer to estimate intact tensile strength. Thirdly, a new technique was developed to conduct cell mapping in open-pit mines using the new technologies of digital image processing and ground-based LIDAR. The results show that the use of these new technologies provide an increased accuracy and the ability for more sophisticated slope stability analyses with no increase in field time only a moderate increase in data processing time. Finally, a successful set of laboratory experiments was conducted looking at the effects of ore blending and grinding times on mineral recovery from a set of six ore from a copper mine in Arizona. The results gave the unexpected finding that for a fixed grinding time, the mineral recovery of the blended ores exceeded the average of the individual recoveries of the same ores unblended.