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By D. Goodings, W. L. Fourney, Bonenberger, R., Uli Leiste

The problem of the maximum depth at which a mine buried in the surf zone or beach zone is a threat to landing vehicles is being studied by Naval Surface Warfare Center (NSWC), Indian Head Division, Naval Research Laboratory (NRL), and The University of Maryland Dynamic Effects Laboratory. The problem was divided into two parts: The first part involves determining how deep a pressure plate mine can be and still detect a vehicle passing over it. This requires determining the distribution of stress within dry and saturated sand when a vehicle passes over a buried mine. The results obtained from that study are presented in a related paper (1). This paper will cover the second part, which entails determining the impulse delivered to the vehicle. This is equivalent to determining the impulse delivered to a plate suspended above the detonating explosive charge and includes an investigation of the distribution of the impulse over the plate. The purpose of the research is to develop a scaling law and/or computational capability which will permit predicting impulse to be expected in the field from tests conducted in the lab. The computational effort is aimed at the development of and confidence in computer codes that can be used to predict stresses and strains in plates due to the detonation of buried mines.

Jan 1, 2004

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 K. G. Holley

Blasting is usually required to produce easily-excavated broken rock, while leaving surrounding rock masses as undamaged and stable as possible. In mining applications, it is common to utilise production blasting in the centre of an open pit, and specially developed limits blast designs when blasting adjacent to the excavation perimeter. In open pit blasting, limits blast designs generally include pre-splitting, trim blasts, or buffer blasts, all of which are designed to limit, or eliminate, damage beyond the designed pit wall. This paper reports on the findings of a study of the profile of damage in rock masses surrounding blasts, determined by a combination of vibration monitoring, displacement monitoring using extensometers, and video inspection of open holes drilled at various distances behind blasts. The results obtained suggest that the profile of damage may extend for the full depth of the bench, for distances of up to 12 to 15 metres behind blasts. This suggests that entire berms may be affected by blasting, displaying loss of friction and cohesion along joint and fracture planes. The study has considered production blasts and trim blasts with small diameter blastholes and pre-splits.

Jan 1, 2004

By Richard H. Granhom

Detonation pressure, or Chapman-Jouguet pressure, is an intrinsic property of an explosive, and like detonation velocity, is an indicator of explosive performance. Pressure and velocity are also important for calibrating computer codes and for other calculations such as the stress imparted to rock or metal by an explosive. The detonation pressures, P~cj, of many "ideal" explosives have been measured indirectly by recording some hydrodynamic flow variable other than pressure, with P~cj being inferred from hydrodynamics and the assumed Chapman-Jouguet equations. One such method is the difficult and expensive "aquarium technique''.] Commercial explosive manufacturers generally rely on estimates of P~cj generated by computer codes not explicitly designed for non-ideal explosives typically used in commercial applications. Over the last decade, U.S. national and government laboratories have developed in-situ gauge techniques such as the manganin gauge, for direct measurement of detonation pressure. Manganin is an alloy of copper, manganese and nickel, and is ideally suited for use as a pressure transducer because its electrical resistance changes with pressure, but is nearly constant with changes in temperature. A simplified manganin gauge technique adapted for use at a commercial test site is described and some initial results from measurements on commercial emulsion explosives are presented.

Jan 1, 1991

By Diane F. Baker, Cathy Aimone-Martin

A series of small-scale explosive experiments were conducted in a perlite mine near Socorro, New Mexico. These experiments were a joint effort between Los Alamos National Laboratory, New Mexico Institute Of Mining and Technology, Southern Methodist University, and Defense Nuclear Agency. The purpose of these tests was to measure the changes in the shock wave and seismic coupling as a function of depth of burial and structural setting. The size of the explosive charges ranged from 1 to 68 kg. Over 1150 measurements of velocity and acceleration were made on thirteen experiments using three component sensors. The sensors were placed to maximize the azimuthal coverage as well as to provide data at a variety of ranges from ~1 to 130 m A few far field measurements were made at ranges of ~2Êkm. While the bulk of the measurements were made on the surface, high g accelerometers were placed in one instrumentation borehole to provide some free-field measurements. Preliminary results indicate that significant differences in the amplitudes of signals can occur when the location of the explosive charges are changed by only meters. Part of the observed difference is attributed to variations in the rock immediately adjacent to the charge affecting the shock coupling; and part to the effects of the site characteristics.

Jan 1, 1994

By W. Jiao, Y. Yongqi, R. Shan

Soft rock mines are distributed through out P.R.C. And drilling and blasting is still the main method of driving a tunnel in these mines. Traditional smooth blasting has been widely and deeply studied and put into practice in P.C.R since 1970s. But the cartridge and blast hole are both columns, the stress field in the rock around blast hole at the beginning is symmetry around hole axis, and the original cracks in the rock can be activated randomly. So serious overbreak and underbreak at the boundary of an excavation occur often, especially when the excavation is in soft rockmass, and the rates of half-hole marks are generally about 50% in medium rock, and 20-30% in soft rock in Chinese coal mines. For the sake of overcoming the situation, we have been studying directed crack blasting since ten years, and have got some obvious achievements in this respect. Slotted cartridge control blasting in soft rock is studied in this paper. Through model experiments, reasonable decouple coefficient range and slot width are gotten, and unsymmetrical dynamic strain field is analyzed. Through underground test in soft rock with a strength lower than 1OMpa in Dayan Mining Bureau, The results of which the rates of half-hole marks and the nonsmooth grades of the cut contours are 83.3% and 1OOmm respectively have been achieved.

Jan 1, 2000

By R R. Singh, U K. Dey, S K. Roy

"Commercial explosives being a heterogeneous mixture of many chemical compounds in prefixed proportion, their velocity of detonation (VOD) may vary from batch to batch, due to variations in the proportion of the chemical composition and process parameters even within their tolerance limits. Inherent limitations of measuring methods and human variations during measurement also add to the variation in VOD values determined practically. Therefore, it is customary to define a range of VOD values rather than a fixed value of VOD for a particular explosive.Variations in VOD values of four commercial permitted explosives in India were evaluated under open unconfined condition using Dautriche method and a resistance wire method based continuous VOD meter. Comparative evaluation of VOD values of selected explosives were aimed to check the relative effectiveness of continuous VOD measurement of small diameter cartridged permitted explosives using cheaper co-axial wire instead of recommended costly VOD rods along with the continuous VOD meter. Results of evaluation revealed that continuous VOD of commercial small diameter cartridged explosives could be determined using cheaper co-axial resistance cable with comparatively better accuracy than the most commonly used Dautriche method."

Jan 1, 2007

By Sehoon Lee, Duhwoe Jung, Eunsu Cha, Kyeonghwan Jeong

This case study presents the effectiveness of underground rock blasting to facilitate the trench cut in the hard rock layer using a conventional trench cutter for the construction of a diaphragm wall. Rock blastings are pre-performed up to the scheduled depth and then the fragmented rocks can be easily cut using a conventional trench cutter. Two trial underground rock blastings have been performed and the effectiveness of pre-blasting is presented in terms of a cutting rate, a loss of cutter heads and an amount of overbreak. Based on the results obtained from the trial underground rock blastings, the following conclusions can be appropriate: 1) A pre-blasting of hard rock layer located in depth can help to overcome the limitation of the trench cut using a conventional trench cutter. If the hard rock layer is fragmented after blasting, the fragmented rocks can be easily cut using a conventional trench cutter, 2) The speed of cutting works was accelerated and the loss of cutter heads was significantly reduced in the sections where the blastings were applied prior to cutting. 3) The amount of overbreak, expressed in terms of the amount of poured concrete, can be reduced to some extent. However, the location of blast holes in the trench can also contribute to the amount of overbreak. The closer the location of blast holes to the edge of the trench, the more extensive fractured and cracked zone can be formed on the face of the trench. This can increase the amount of overbreak if the trench is left empty for a while.

Jan 1, 2000

By L. O. Souza, J. F. Gewher, M. P. Scussiatto, C. S. Mendonca, R. A. McClure, B. T. Kuckartz, J. Kloeckner

Blasting is the most effective and economical tool available to fragment and move rock for most applications. If properly executed, it can improve down-stream operations such as loading, hauling and crushing. It is not possible, however, to have full control over the energy released by the explosives when a poorly designed blast pattern is used. A poorly designed blast can produce serious damage to equipment and create a potentially hazardous condition to people. Advanced mining technology has been developed to address these potential hazards and optimize the blast pattern. This profiling technology can assist with blast planning and provide quick, precise data about the condition of the rock structure to be blasted. The 3G BlastMetrix system presented here uses three-dimensional (3D) stereo photogrammetry to model the rock mass in a fast, practical and safe manner. Through the image overlapping method, a 3D model is created with thousands of points that provide a significant amount of data regarding geology, geometry and topography conditions. The blasting plan can then be made in a way to optimize the rock fragmentation and avoid areas that could create flyrock. This paper is a case study concerning usage of stereo photogrammic surveying and borehole survey systems in a blasting operation at the Brazilian Quarry, Incopel. One 3D image of a drilled bench was generated using photogrammetry survey technology and the borehole survey data collected using the rodded Boretrak borehole survey system. Utilizing the minimum burden profile reports, explosive loading could be done accurately, resulting in an optimized blast with good heave and fragmentation as well as increased safety.

Jan 1, 2013

By Miie Shields, Ed Billington

Trail blasters for the National Park Service (NPS) live and work in remote mountain terrain throughout the western states, where any support or resupply may be sporadic and ditlicult and mountain weather affects every activity. Mechanical “aids” are the pick, shovel, rock-bar, wheelbarrow, and a Pionjar or Cobra dritl. The blaster is usually faced with an extraordinary range of work, t?om delay blasts in weathered rock using driiole depths of 18” (46cm) to as little as 4” (1 Ocm), through reducing boulders and talus fields to useable tread, blasting stumps, snags and log-jams, to the explosive disintegration and casting of animal czcasses. One day he/she might provide a 500cf (14 cu meter) anchor excavation for a suspension bridge, the next day directionally fall 60” (1.5m) diameter snags in a camp area, and the following day blast a 3-foot-wide (1 meter) tread bench across a steep bedrock slope. To be effective, the blaster must design each and every blast around desired end result, crew and public safety, maximizing effective use of limited quantities of explosive, and the minimnation of environmental effects. Since almost all drillhole blasting occurs in the weathered zone of the rock, blasting is more the art than the science of judging rock density, hardness, cohesion and prefracturing, and selecting explosives, drill and delay patterns, and loading techniques responsive to those conditions. For these reasons the NPS issues its own Blaster’s License, with a basic requirement of at least 40 hours of NPS blaster training and 3 years of supervised Blaster in-Training experience. The focus of this pre-license requirement is on safety and using explosives as a precision tool, versus just “blowing things up”.

Jan 1, 2002

By Paul Worsey, Braden Lusk

Differences exist between public perception of construction blasting and quarry blasting. In general, people are able to tolerate short term inconveniences much better than long term ones. The paper focuses on the public perception of quarry blasting in St. Charles County, MO. This expanding urban environment has seen new legislation targeting preexisting quarry operations that have been in place for many years. A survey was made comprising interviews conducted to gauge perceptions of persons with varying demographics. Interviews covered topics involved with quarry blasting and its reporting methods. The purpose of the interviews was to determine public perception of blasting and how best to report results of vibration measurements. The use of different, less technically complicated measurement scales for vibration and airblast was considered as an alternative reporting system. The question for the industry is, “Has our past haste in adopting complex scientific scales and units been detrimental to us?” In other words, are we reporting the correct things? For airblast, the decibel scale was evaluated against millibar in the public eye. Peak Particle Velocity was also compared to that for displacement. Current legislation in the county is based on complaint levels rather than damage criteria. The complaints most likely not only come from ignorance to the affects of blasting on structures, but also sparse understanding of the units used to report these affects. The past practice of treading softly as an industry has been proven to be a poor choice, and education of the public as well as lawmakers on all levels is necessary. The Mississippi Valley Chapter of ISEE has begun to conduct seminars to this end. One educational seminar has taken place for officials and lawmakers in the St. Louis area, and others are in the planning stages. The focus of this paper is to gauge perception of the damage criteria reported today, and locate focal points for future education of the public in rapidly expanding suburban environments.

Jan 1, 2005

By Frank Hirthammer

Since the introduction of the Explosives Track & Trace in Europe in 2014 for manufacturers and 2015 for end-users, a lot has changed in all areas of the supply chain and the use of explosives. The regional associations, manufacturers' organizations, and trade associations have proven that it is possible to overcome a hurdle, that looks almost impossible in the beginning, through consistent cooperation. The paper gives an insight into the problems involved in introducing such a requirement, identifies ways and solutions, and concludes them. When looking at the current situation, the paper describes the process by which a prescribed change in business processes are transforming into a solution that increases productivity, security, and handling. It shows examples from daily work, in which possibilities for optimization, improved quality assurance, and work facilitation are explained. It presents the resulting potential by comparing process flows, before and after the introduction of Track & Trace solutions. What challenges will we face in the future concerning the use of T&T solutions? Will the tracking of explosives become the norm worldwide? What are future hardware and software developments to be expected? What impact will this have on the global supply chain?

By Fumihiko Sumiya, Yukio Kato, Yoshikazu Hirosaki

Secluential blasting is one of the most popular methods in blasting. tiowever, it is well known that an emulsion explosive can be dead-pressed by dynamic pressure generated by the previous detonation. It is difficult to gain the expected blasting performance due to tb.e malfunction of explosive caused by deadpressing and shock desensitization. Such malfunction of an explosive is undesirable for safety blasting operation. Voids in the emulsion explosives will considerably affect the performance of explosives such as sensitivity, detonation velocity (DV), pressure-resistance and so on. To clarify the detonability and the performance of precompressed emulsion explosives, the DV was measured. Three types of microballoon or micro bubble ; two types of glass microballoon(GMB), resin microballoon@MB) and chemical gas bubble ; were used as sensitizers for the sample emulsion expiosives. The underwater explosion test was carried out to load dynamic pressure into the sample explosives. The dynamic pressure was generated by the detonation of a donor explosive, and the DV of the sample explosives as acceptor was measured by ionized gap terminals. The dynamic pressure level and initiation interval for the donor and the acceptor were chosen as experimental factors. The detonability was carefully investigated at short initiation intervals taking into consideration the interaction between same delays caused by the deviation of the ignition time of the electric detonators. From these experiments, the following results were obtained ; A) The DV of precompressed emulsion explosives was low compared with that of uncompressed emulsion explosives in all pressure conditions. B) The decrease of DV in the sample explosives sensitized by GMB s was larger than that of DV in the sample explosives sensitized by RMBs or chemical gas bubbles. C) The recovery of the detonability occurred rapidly in the sample explosives sensitized by RMBs and chemical gas bubbles. However, a long period was needed for the recovery of detonability in the sample explosives sensitized by GME! s. It was concluded that the type of microballoon and micro bubble significantly influenced the detonability of precompressed emulsion explosives.

Jan 1, 2002

The underwater explosions have been used for several decades for the determination of energy content of explosives. This test method is the only one by which shock, fly rock and total energy can be measured separately. It enables to develop the energy content of explosives for different purposes; the military high explosives should contain more shock energy whereas the fly rock energy is very important feature for the blasting explosives. The purpose of this study was to establish a test place for the underwater experiments in an old water filled open pit, to estimate the repeatability of the energy measurements, to calculate the standard deviations and to compare the total energy content of commercial explosives to the theoretical values calculated by the thermo dynamical program. The test method seems to work quite well especially for the homogeneous explosives. The difference between the energy content of theoretically calculated and measured values for the homogeneous emulsion explosives was about -3% and for the dynamite about -5%. The energy difference for the unhomogeneous ANFO was detected to be -19%. The diameter of the charge was 15 cm and it was obviously too small for ANFO to detonate ideally. On the basis of the test results this test method seems to fit best for the cap sensitive, completely homogeneous, spherical charges whose masses are big enough and which are initiated from the centre of the charge. The underwater explosions as a test method is the only one which can separate shock, bubble and total energies from each other and therefore makes it possible to develop the properties of explosives for different purposes which is very important feature of this method.

Jan 1, 2005

By Peter Duniam, Vivian Patz

History of the ExEx 1000 CAB system. l What we’ve learned using electronic timing. l Requirements for a second generation. EDD system. l The ExEx 2000 system - simple, versatile and cost effective

Jan 1, 1997

By Martin L. Smith, Robert L. Hautala

The objective of blast optimization can be approached either in a qualitative sense of designing a blast which will be "trouble free", or quantitatively in the sense of minimizing overall mining costs. Blast design simulators and fragmentation models have become an accepted tool in blasting over the last decade. Numeric simulators are very useful for solving quantitative problems, but are limited in their ability to address more qualitative problems such as post-blast bench condition. Also, current blasting models are limited by the complexity of site-specific blasting and are not functionally suited to mathematical optimization. As a result a great deal of expertise is still needed in optimizing a blast. The following describes the application of an expert system approach to integrating both a symbolic model of the expertise of the blasting engineer for attaining a trouble free blast, and a numeric optimization model relating fragmentation to unit operations from drilling to grinding. Research into this application of a coupled modeling approach to blast design is being carried out to develop a modeling methodology which will provide a suboptimal design for qualitative design goals as well as minimizing blast related costs.

Jan 1, 1991

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 W. Birch

The traditional concept of scaled-distance modelling for predicting blast induced ground vibration holds many drawbacks, not least of which is the major effect data scatter imparts on confidence determination. An investigation by the Department of Mining and Mineral Engineering, The University of Leeds, England has resulted in the development of simple but effective method of improving prediction capacity through the reduction of effective error by incorporating individual location response into a scaled-distance model. The work is the product of an l&month blast-monitoring campaign at a limestone quarry situated in North Yorkshire, England. The data, when presented in the form of a scaled-distance model, indicates a typical scenario where a good overall correlation becomes marred by the extent of data scatter. Examination of the individual monitoring locations however indicates that the response of the individual location is an important factor in the explanation of the large residuals. The novel approach thathas been developed incorporates a series of locational site factors which when incorporated into a scaled distance model reduces the effective error and therefore improves prediction capacity. The approach is based on using a standard computer package “spread sheet” on the understanding that these are commonly available on all quarry or home computers. This approach has been validated by comparison with a more rigorous statistics method.

Jan 1, 2001

By Lina Lopez, Jose Sanchidrian, Jean Du Mouza, Essaieb Hamdi

This paper evaluates the actual energy delivered by the explosives used in the fragmentation of rock during blasting vs. the available theoretical explosive energy. The evaluation of the fragmentation energy of the blast is first done. Fragmentation by blasting can be seen as a process in which creation of new surfaces within the rock mass is made by generation of new cracks or extension of pre-existing ones. From this idea, the fragmentation blast efficiency can be assessed as the fraction of the available explosive energy used for creation of new surfaces. The evaluation of new cracks area created by the blast is based on the SIMBLOC methodology and the corresponding fragmentation energy is then obtained by the Griffith theory. Secondly, the amount of energy delivered down to a certain pressure or volume along the detonation product expansion process, given by the useful work, is calculated. This is done by first determining the CJ state of the reacted explosive and subsequently performing an adiabatic expansion calculation of the detonation products from that state. W-Detcom code has been used for the calculations using the BKW equation of state with the Sandia parameter set. The fragmentation energy and the useful work are calculated for blasts performed in two mines in Spain. Multiple regression is applied to the results in order to give an assessment of the better description of the explosive energy .

Jan 1, 2002

By Greg Mclellan, Mark Johnson, John Pepper

Several large quarrying projects recently occurred in Miramar, Florida. These were closely monitored by the Seismologist of Record and Broward County in accordance with County and City regulations. In addition to this monitoring, the City of Miramar employed The Pepper Engineering Group, Inc., to provide additional spot check monitoring and to review the records of the other two parties on a routine basis. Broward County ordinances require that the location of each shot and the nearest protected structure be recorded along with seismograph measurement of each shot at the nearest protected structure. The positions of the blasts and nearest protected structures were determined using GPS. The blast vibrations were measured by seismograph. Over 600 shots, which are the subject of this study, were measured both by the County, the Seismologist and, on many occasions, The Pepper Engineering Group. As such, the vibration data was constantly cross-checked for consistency. The blasting contractor also provided blast designs for each shot. In this paper, the measured vibrations are plotted in terms of Resultant Peak Particle Velocity (RPPV) versus Scaled Distance (SD) on logarithmic scales. The data curves are fitted with least squares and upper 95% and 99% prediction limits are provided. Equations are presented to predict the RPPV based on scaled distance and prediction level using power fits. Statistical information concerning the derivation of the various limits is presented. The raw data used to develop this paper, along with other information concerning the shots, will be posted on the Internet for use by other researchers.

Jan 1, 2000