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By Travis Davidsavor, Stanley: Dong Vitton

Concrete is a common construction material used throughout the world, and with increasing demand of fast-track construction, blasting and concrete casting are occurring simultaneously at many sites where rock is being excavated for concrete placement. However, there has been significant disagreement in the construction industry as to what intensity of shock vibrations green, or fresh concrete can tolerate. Peak particle velocities are often arbitrarily chosen, or are simply based on materials such as plaster and drywall that have been more thoroughly studied in relation to damage. Previous research on green concrete has used the concrete’s static strength subjected to shockwaves at different ages as the primary damage criteria. In addition, the static strength tests have been based on curing time. However, changes in temperature or humidity can dramatically alter the hydration rate, which affects strength development of different cements. To account for temperature changes and humidity the concept of concrete maturity is commonly used and allows the researcher to see where the concrete was in terms of hydration progress. In general, static testing determines the failure stress that the concrete’s macrostructure can handle, and often failure occurs in the natural materials first or along large defects in casting techniques. Dynamic testing or high strain rate testing, on the other hand, loads materials at such a high rate that larger defects do not have time to react and instead the microstructure is more highly stressed leading to higher strength and stiffness values. This is known as the material’s strain rate sensitivity. Since dynamic testing better tests the microstructural strength, it is believed that it may provide a better way to assess damage to green concrete. Testing includes both static and dynamic compression as well as static and dynamic splitting tensile strength to assess whether damaged has occurred to the concrete. No significant statistical evidence was discovered that damage to the concrete occurred at five different “green” maturities from peak resultant velocities ranging from 10.66 in/s (271mm/s) to 4.40 in/s (112 mm/s) with average intensity of 6.7 in/s (170mm/s).

Jan 1, 2003

By J T. Schamaun

Recent applications of explosives and blasting agents to rubble rock have led to requirements for more elaborate design and analysis methods. In most blasting uses, it is necessary not only to fracture the rock, but also to move the broken rubble in a predictable manner. Many in situ extraction techniques require; rubblization to take place in a confined region where rock motion is a predominate factor in creating a permeable broken bed. In this paper, an engineering model is presented which describes the large rubble motion during blasting. This model is intended to provide the blast designer with a tool for evaluation and further refinement of blasting patterns and timing sequences.

Jan 1, 1983

By A Gene Riggs

The Cerrejon Coal Project in Colombia, South America is one of the largest coal mines in the world. The mine is located in northeastern Colombia on the La Guajira penninsula. The area is in a remote valley 132 miles east of the city of Barranquilla.

Jan 1, 1984

By A. S. Tawadrous

The stress field around a detonating charge in a borehole was calculated using AUTODYN for a variety of in-situ stress conditions. Calculations were conducted for zero in-situ stress, hydrostatic conditions at 100MPa, uniaxial stress conditions of 100MPa, and bi-axial state of stress with amplitudes of 200MPa and 100MPa along the axes. Two different explosives, ANFO and emulsion, were used for the calculations. It was shown that in-situ stress fields had an effect on the tensile and compressional damage zones around the blasthole, calculated on the basis of the maximum amplitude of the stress pulses in the rock after the detonation of the explosive in the blasthole. The extent of compressional damage increased around the borehole, whereas, the extent of the tensile damage decreased. The damage zones are of elliptical nature with their axes parallel to the direction of the principal stresses. The difference between the major and minor axis of the elliptical damage was not very significant in the case of the compressional damage; however it was significant in the case of the tensile damage.

Jan 1, 2007

By Les Willan, Chris Batten, Matt Sparkes

In late 2008 Xstrata Newlands Coal Mine in Central Queensland and Orica Mining Services engaged in discussion to investigate methodologies to change their current mining practices and overcome the issues in the mining of steeply dipping coal seams, the associated coal loss risk and to assist in improving mining productivity. A strategy was developed and it was determined that through-seam blasting was essential to the success of winning the coal from the Wollombi Pit at Newlands.

Jan 1, 2010

We had a cold, gray winter here in Kansas City and I spent a lot of time watching out my den window at the squirrels and birds trying to get by in the lousy weather. I remember too well working in the cold, loading shots. I was frostbitten several times since I couldn’t tie in MS connectors with gloves on. Those old connectors had a piece of detonating cord on either end of a metal tube that held the delay and you tied them to the trunk lines with square knots. Doing this on a “warm” day in Alaska or Montana shooting ditch for a pipeline could be a frosty experience. Also remember how hard it was to connect up electric caps (detonators to you new guys) in the cold. Now I don’t want you to feel sorry for me ‘cause I suspect most of you younger fellows have also paid your dues in the cold and for that matter in the heat too. Wowee, the heat at the bottom of a Chicago dolomite quarry in August was enough to fry the brains of all that were there. Maybe that’s why the third deck of my brains doesn’t exist.

Jan 1, 2004

By R C. Berglund

Since the Republic Mine began production in the mid 1950's, drilling and blasting practices have continually changed. In recent years, progress has been achieved through the development of more precise blast engineering methods, in greatly increasing the use of non-water resistant ammonium nitrate explosives, and in changing to a non-electric in-hole delay initiation system. Also, recent experience indicates that ammonium nitrate fueled with nitropropane and methanol is a viable substitute for aluminized AN-FO.

Jan 1, 1980

By R Malo, A Yetter

The use of large diameter blastholes for underground mining began approximately twelve years ago and are now routinely employed in a variety of ore types and stope designs. These large boreholes, ranging in size from 4 1/2 inch to 8 inch diameter, were first utilized in the same fashion as in open pit bench drilling. However, a variety of changes quickly followed in order to accommodate the unique conditions encountered while using a blasthole sloping method.

Jan 1, 1984

By Neal Lee

Reduced relief horizontally means an increase in energy expended vertically into the rock surrounding the stemming column, and potentially through the stemming column. The vast majority of holes in any surface blasting operation are afforded two horizontal relief faces at the moment of firing, whether by existing relief faces in front of and to one side, or previously blasted hole(s) in front of and to one side of the holes in question. When the energy expended in any hole on the blast pattern has less than two Horizontal Relief Planes or faces (referred to moving forward here as “HRPs”) available to it at the moment of firing, a higher percentage of the available energy is directed vertically. In the analysis of recorded videos by the author, one will note the fact that stemming ejection/flyrock is observed to a much greater degree from the center of almost all patterns when they are timed to “pull out of the middle” (“box cut" timed patterns). This is because the first hole to fire in each row has only one Horizontal Relief Plane, which significantly decreases horizontal avenue for energy release for these holes. This of course results in an increase in the amount of energy expended vertically. This paper proposes a novel methodology to modify the stemming to better use the explosives energy of each hole, while controlling side effects such as flyrock and airblast.

Feb 6, 2023

By Evan Jannoulakis, Wilfrid Comeau

Using the Scaled Distance (SD) and the vector sum Peak Particle Velocity (PPVvs) from a single delay, preferably single blasthole, in a shot, a number is derived which has shown itself to be consistently related to blasting efficiency, as experienced by one of the authors of this paper over the last thirty years. The numbers derived by this process range in value over one order of magnitude more or less. This variation, a function of distance, weight of explosive in the delay, blasthole diameter, blast design, powder factor and the geological environment, can be consistently related to two of these factors, powder factor and distance. In actual use the measured "BED" representing good blasting results should not vary by more than + 33 to + 50 percent of the estimated "BED" in non calibrated cases, and + 10 to 20 percent where previous experience is available. Relatively high "BED" values are indicative of poor blasting results while relatively low "BED" values may be precursors of poor blasting results in a shot. There are many variables in the geological environment which can affect the "BED". A case study is presented from a surface coal mining operation in eastern Canada. This case study tries to evaluate the reasons for the variability in "BED" values derived from multi-hole shots. A problem in using "Signature Vibrations" from a single-hole shot to predict blasting vibrations from multiple-hole production shots is identified.

Jan 1, 1998

By C. Lownds, U. Steiner

In 2008 a paper from the same source describing four actual cases of exposure of electronic detonators to lightning strikes was presented. It was shown that electronic detonators, like other initiation systems, are vulnerable to very close or direct lightning strikes. At the time of submitting this abstract no further incidents with lightning have been experienced. As a result of those original incidents, and in order to understand how the safety devices inside electronic detonators break down, two series of tests have been done, each with 2 detonator designs. In the first series detonators were subjected to capacitor discharges up to 6kV and 1kJ in energy. In the second series the intensity was increased to 800kV and 24kJ in energy. In the second series, more electrical energy was delivered to the detonator assembly than the explosive energy of the detonator. In both series both detonators showed a spectacular ability to resist very high discharge energies. The tests are described in detail with supporting photographs. The data for both pin-to-pin and pin-to-case (more relevant to lightning) are presented and discussed. The mechanism of breakdown of safety devices is now understood better and the learning is being used to design more robust products. This high-voltage testing is relevant in understanding how electronic detonators might initiate as a result of a very close or direct lightning strike 1. Orica

Jan 1, 2009

By Florian B. Janoski

The annual consumption of electric blasting caps in the United States approaches 100,000,000, so, over the last eleven to twelve years about one billion have been used. The author has made hazard assessment measurements in connection with proposed electric blasting operations in many places: under a giant, operating electrical generating station, under some of the highest voltage power lines in the country, and around many large electrical distribution substations. Electric blasting was safely conducted in all instances. Measurements of stray current, and of pickup under high voltage power lines are easily made, but it was always a more complex chore to make a good radio frequency hazard assessment "close in" to a high power RF transmitting source.

Jan 1, 1977

By Donald C. Clark

The Blasting Contractor as an Insurance Risk involves a discussion of changing times in the insurance market and changing methods of operation in the construction industry. Since the advent of Internal Revenue Service~1 and Occupational Safety and Health Act~2 regulations by the Federal Government in the early 1970's, operations have changed. Many small users of explosives have discontinued any use in favor of subcontracting the drilling and blasting to specialists. This change in operations along with the change in the insurance market has created coverage problems which is the subject of discussion of this paper. Although no definite conclusions are reached, it is an attempt to promote understanding and further the efforts toward equitable solutions.

Jan 1, 1977

By Farshad Rashidi Nejad, Ali Asgari, Sanaz Norouzi

Blasting is known as the first step of rock breakage in mines. An indication of the importance of blasting is that more than 1 billion kg (2.2 billion lb) of explosives are used annually in Australia and 3 billion kg (6.6 billion lb) in the United States for rock breakage, more than 85% of which is used in the mining industry. The notion that blasting, as the first step of comminution, plays a significant role in crushing and grinding energy consumption is not an unfounded thinking. It can be noted that the comminution electrical energy consumption decreases in these ways: First, if the feed size to the primary crusher is decreased, less energy will be required to crush the ore to the same product size. Second, a decrease in work index (Wi) related to additional macro fracturing and micro fracturing within individual fragments.

Jan 1, 2015

By Sami Kara, Yunseok Park, Seung-Joong Lee, Namsun Hwang, Michael Laing

This study conducts a comparative analysis of construction efficiency. In the first part we compared electronic and non-electric initiation systems, focusing on tunnel contour holes. Field blasting operations were executed across a variety of delays to identify the optimal delay time. This delay for the in-situ rock mass was determined through regression analysis of blasting vibration in contour holes and for overbreak/underbreak. The blasting results with the electronic initiation system using the obtained optimal delay, applied to contour holes, were compared with the results of the non-electric initiation system. The overbreak and underbreak decreased by an average of 2.7 cm and 5.8 cm respectively, by using the electronic initiation system. Moreover, the vibration reduction rate in contour holes region was reduced by 11.9% based on the blasting vibration estimation equation proposed by the Ministry of Land, Infrastructure, and Transport (MOLIT). Underground construction projects have become increasing popular as cities grow in both size and density. This growth severely limits the amount of useable space for new project on the surface, resulting in the decision to build them underground. This new policy however brings into focus the challenge of managing and reducing blasting related vibration due to the proximity of these projects to sensitive structures, utilities and foundations often present in urban environments. For this purpose, we have been required to manage the vibration by reducing the quantity of explosives used per round. Inspired by surface blasting techniques, we applied a decking mode to address and work around this challenge. We present in this paper the first attempt to blast a tunnel face using a decking method and reduce the charging per hole from 6 kg to 3 kg per hole and keep the same advance rate for this tunnel. The results are presented in the third part of this paper. In the second part we present the results of the decking mode in shaft. The use of the electronic initiation system in tunnel construction provides the users an effective tool to improve the overbreak/underbreak and keep the vibration at a low level with a large gain on the overall project schedule and budget. This what we want to demonstrate in this paper.

Jan 21, 2025

By Hung Tran, Denis Fleury, (Ken) Qian Liu

Pastefill technology has gained an increasing popularity over the past decade. The main advantages are: environmental performance (mainly in tailings disposal), low operation costs and ease of operation, as well as homogeneous properties. However, its weaker nature compared to other types of fill makes it more vulnerable to blast damage. In the last few years, Louvicourt Mine has experienced some cases of pastefill sloughage during the mining of secondary stopes. In order to reduce pastefill sloughage, some studies have been undertaken to investigate the causes and to find possible solutions by looking at stope design, extraction sequence, ground support and blast design. This paper presents the results of a blast damage study carried out at Louvicourt on the 860m level. The instrumentation included vibration monitors (using 6 sets of triaxial geophones grouted in the pastefill), a borehole camera to observe the damage in the pastefill, and a cavity monitoring system for three-dimensional surveys of the blasted stope. The test stope was mined out by four slot blasts and three mass blasts. Most of the damage was created by the mass blasts. It was found that the accumulation of ground vibration was mainly due to the low seismic velocities in the pastefill and the relatively tight delay between blastholes. In addition, there was a substantial difference between the critical PPV in the confined and unconfined pastefill. In practice, these findings have led to modifications of blast design to minimise the exposure time of pastefill walls to air. Such modifications included changes of blast sequence in secondary stopes and delay layout between heavily loaded blastholes. Over the paste two years, the implementation of new blast sequence has shown encouraging results in terms of reduced pastefill sloughage and dilution.

Jan 1, 2000

By Francisco Sena Leite, Vincius Miranda, PhD Machado Leite, PhD Pinto, Raquel Carvalhinha, Alexandre Julio, Dorival de Carvalho

Rock blasting, in particularly the drilling process, is one of the first processes in the stage of rock fragmentation and plays a fundamental role by influencing all the following stages. Given its importance, some proposals to optimize this process have been presented over the last few years. These proposals, while having different approaches, aim (in a large part) to minimize the costs of drilling and blasting respecting the limits of fragmentation required by primary crushing. Reviewing some recent articles leads us to an enriching experience, since the authors of these articles clearly model the problem, but do not address the mathematical solution of these models, which in turn, given their non-linear nature, have no directly and easy solution. Simple and even robust optimizers present in the market show different results and often do not converge to a single solution. To address this problem, an adapted gradient heuristicbased model was developed to try to find optimum values. Heuristics search for values of stemming, subdrilling, burden and spacing that minimize the costs of blasting and drilling. This search, which by the nature of the heuristic moves the solution in the direction of the gradient with maximum decrease to find optimal solution, found values that in turn, when compared with values presented by market solutions not only equaled them as, in some situations, even improved the proposed solution. The algorithm was tested and validated on the field, and although the results have already been presented in papers published in the last year by the authors of this paper, it is now presented with its mathematical formulation and comparison with the other solutions. This approach is expected to be able to improve (and even demystify) the process of pattern expansion and be the basis for future work in the continuation of the optimization process.

Jan 1, 2019

By Gordon M. Matheson, David K. Miller

Sinkhole development in karst terrains is a serious problem and risk to facilities built in these areas. The potential for sinkholes are a function of many things including the chemistry of the underlying rock, the location of water conductive fractures and fissures in the rock, the natural fluctuation of the ground water table, vibrations from various sources and surface regrading activities. When sinkhole open near quarry operations the occurrence of these features is occasionally attributed to vibrations from quarry blasting. The purpose of this paper is to review the evidence regarding the development of sinkholes as a result of quarry blasting. In general, it has been found that sinkholes result from collapse or piping of overburden soils into cavities or caverns developed within underlying carbonate rocks that have been in existence for many thousands of years. The overburden soils in karst areas are typically clayey and as a result are not subject to densification or liquefaction as a result of vibrations. The primary cause of an increased rate of sinkhole development can be attributed to changes in the ground water table or local surface water drainage. These changes may be caused by seasonal fluctuations, ground water level lowering in drought periods, dewatering of excavations or quarries, or local changes in surface drainage resulting from grading activities.

Jan 1, 1998

By T Davids, O J. Jordaan, M D. J Bonneau

As in most other parts of the world, the surface coal mining industry in South Africa is introducing emulsion explosives as the primary bulk blasting agent for use in wet borehole conditions where AN/FO cannot be used. Most of the emulsion products presently in use are gassed to provide sensitivity. The intimate mix between the fuel and oxidizer in the emulsion has been shown to produce a highly efficient explosive. However, a major difference between emulsion and the previous slurry products is its relatively low physical strength. This prompted Rand Mines' Duvha Opencast Mine, a major South African Escom power colliery, to conduct test work to illustrate the effect of emulsion physical consistency on blasthole loading. This paper presents the results of test work conducted at Duvha to investigate the problems associated with loading both AN/FO and emulsion in water filled holes, stemming emulsion holes, and in particular, to illustrate the difficulty in correctly introducing a stemming deck into the emulsion column. Time dependent behavior of the loaded emulsion holes is investigated. Velocity of detonation measurements for freshly manufactured emulsion, and for emulsion after loading through water with sleep times of up to 10 days, are presented.

Jan 1, 1987

By Gregory S. Parker

The explosives community has seen tremendous technological advances during the past several decades. When this industry was in it's infancy and even past, Powder Monkey's defied the odds by relying on daring and cunning to unleash the power contained in nitroglycerin and black powder. Unlike the manufactured improvements, there has been little in professional evolution amongst the blasting fraternity unless provoked (for the most part) by the government. It is the intent of this author to advance the cause of an industry wide training and certification program, uniform in nature and broad-based enough to be voluntary, giving states whose outstanding programs are already in place, the opportunity to provide input. In creating this type of atmosphere, grandfathering, reciprocity and accessibility would be paramount. With ISEE taking a firm leadership role during the inception and NICET's involvement in the administration, the idea postulated here is intended to spark interest and debate, bringing the inception of such a program to the forefront.

Jan 1, 1995