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By Denis Rickman, Jon Windham, Stephen Akers, Byron Armstrong

The soil crater formed by detonation of an explosive charge is of considerable military interest because of the common use of explosives to create soil obstacles. The soil crater is also an important piece of forensic evidence for the investigation of terrorist bombings. With recent advances in numerical codes, modeling and simulation of explosively-formed soil craters is becoming an attractive means of analyzing this phenomenon. Consequently, the need exists to better understand the relationship between soil properties and the resultant soil crater. An extensive database has been developed for the case of explosives detonated in or above in-situ soils of various types. However, in most cases, the soil properties were either not adequately quantified or the soil materials themselves varied such that the gross properties were poorly understood. A research program is underway to improve methods of relating soil crater dimensions to soil identification properties such as USCS classification, particle-size distributions, and Atterberg limits, as well as to soil composition properties such as density, moisture content, and volumes of solids, water, and air. As part of this effort, both explosive detonations conducted over well-controlled and well-documented soil backfills and companion numerical simulations were studied. This paper presents an overview of the effort.

Jan 1, 2010

By Douglas Bartley, Kevin Hachmeister, Rich Barry

The use of explosive energy as a tool in mining and construction is the most effective way to move large amounts of rock that is otherwise unable to be efficiently excavated. Since the early days of explosive engineering utilizing black powder initiated by cap and fuse to the present day diversity of specialty products and technologies the goal has always been to "Break and Move" as much rock for the least expense possible. It has primarily been the competitive nature of our economy that has driven the advancement of technological innovations and practice. However, the concept of removing rock is not specific to the mining and construction industry. Since the dawn of creation, man has used rock as a medium to express his creativity in the form of sculpture. Even though the process of sculpture requires the removal of rock, the final work is defined by the rock that remains intact. This typically necessitates the extreme care of the sculptor to painstakingly chip away the rock allowing the image to emerge from the original mass of stone. The famous sculptor Michelangelo once said, "I saw an angel in the marble and carved until I set him free."

Jan 1, 2004

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 Norman Paley, Zachary Pickett

The Red Dog Mine is a high-grade zinc-lead mine located in northwest Alaska which began operations in November 1989. In June 2014 the upper half of a charge in a trim shot in the Aqqaluk pit deflagrated. No other holes in the area were observed to react and the remainder of the pattern was shot without incident. This was the only known case of a deflagration in the 25 years of operations. As part of the investigation into the cause of this incident rock samples were obtained from the area of this hole and from other areas in this pit. The samples were assayed and tested for reactivity using the Reactive Ground Catalyzed Adiabatic test. Approximately half of the samples were found to be reactive with standard blasting agents. Unexpectedly, some of these were found to be reactive with blasting agents doped with urea to act as an inhibiter. Relationships between element grades and reactivity and between Specific Heating Capacity and reactivity were developed; however, the small sample size led to these models having an unrealistically large number of geological model blocks tagged as reactive. A program to better understand the behavior by testing more samples was initiated. Drill core was selected based on the predicted level of reactivity using the aforementioned relationships. The samples covered a greater range of grades and lithologies and included rock from the soon to be developed Qanaiyaq pit. The samples were dry pulverized then split for elemental assay, Reactive Ground Catalyzed Adiabatic testing, Specific Heating Capacity (SHC) determination, and X-ray Diffraction (XRD) mineralogical analysis. From this data, a Red Dog Mine specific assay based classification for separating reactive from non-reactive ground was developed. Furthermore, it was possible to divide the reactive ground into two subgroups: i) rock which reacts with ANFO-emulsion blends even when manufactured specifically with a reactivity suppression agent like urea and ii) rock which reacts with ordinary ANFO-emulsion blends only when a reactivity suppression agent like urea is absent.

By Sarah Guzzelli, Enrigue Munaretti, Anneliese Botelho, Jair Koppe

Drill and Blast (D & B) is one of the main operations in the mining production cycle, which aims to fragment rock according to a pre-defined plan for proper loading, haulage and processing specifications. In this sense, data from a Brazilian iron ore mine was analyzed, given emphasis on blasthole length, subdrilling and stemming. The D & B report, including mining data such as number of blastholes, length, and diameter and stemming aspects, was analyzed in order to be able to compare these results with the blast design. The study showed significant differences between the designed blasting pattern and that one obtained by the operation. As a consequence, problems such as inadequate fragmentation, incorrect size distribution and loss of energy, were identified. For example, when stemming has a different length than it should have, noise and flyrock can occur, including inadequate fragmentation and vibration in both situations. Therefore, a comparison between the usual D & B procedures and recommended D & B design based on literature reveals the most important deviations and their consequences. The study intends to identify solutions for simple problems, improving D & B operations and safety practices.

Jan 1, 2014

By David Kennedy, Noel Hsu, Miguel Araos

The use of bulk explosive for mining applications started in the 50’s. Since then millions of tons of that material have been transported by road. However during that time, there have been several road incidents involving them. This type of incident has forced the explosives manufacturers as well as regulatory organizations to look for a better classification of explosives in order to regulate the industry as well as to mitigate community concerns over the classification of mixtures of substances that are regarded as precursors to explosives.

Jan 1, 2006

By Adrian Moore, Alan Richards

A real-time system for prediction of the effect of meteorological conditions on airblast overpressure levels has been established in the Hunter Valley Coalfield in Australia. Real-time meteorological data from continuously operating sounding equipment and a predictive meteorological model is input to an atmospheric refraction model that enables the effect of meteorology on airblast overpressure levels in the area surrounding the blast site to be evaluated. Graphical outputs from the model, which are superimposed over a scaled airphoto of the mine and surrounding area, show the extent that airblast levels will be increased. When combined with inputs that quantify the effect of blasting specifications, the airblast levels that will result in the surrounding area from the combined effect of blasting specifications is determined. The model permits those responsible for blasting to make more accurate decisions on suitable times that blasting may take place to conform with applicable airblast limits.

Jan 1, 2009

By Sandor Nagy

The Explosive and Blasting Department of the Hungarian Mining Research Institute is responsible for the research and development of industrial applications of explosives. Appropriate explosives technology is developed for each application, including the explosive demolition of structures, which belongs within our charge.

Jan 1, 1977

By D Anonby

The Fox Pit at EKATI Diamond Mine is designed with 11 m wide benches excavated using a double benching technique leaving 30 m high faces. Blasting tests were conducted to increase the percentage of benches that meet an 11 m catch width. The subdrill depth for the lower bench trim blasts and the blasthole diameter for the upper bench trim blasts were reduced to maintain the bench crests. Raising the lower trim blastholes by 0.5 m decreases the depth of broken rock below the final bench elevation, and consequently reduces damage to rock that forms the bench crest below. The use of smaller diameter (165 mm vs. 270 mm) blastholes in the A and B rows for the upper trim blast reduces the charge per delay during detonation, reduces the powder factor slightly, and reduces the energy affecting the final pit wall and crest.

Jan 1, 2007

By Ruilin Yang

This paper presents a fragmentation model for large production blasts. The model uses peak particle velocity (PPV) induced from the blast as a controlling parameter to predict the fragmentation size distribution. The PPV can be related to shock pressure or strain under a given rock condition. The fragmentation size is calculated at three-dimensional grid points within the blast volume. The grid size defines the calculation resolution of the model. The fragment size distribution is assumed to be in the same form as the crack distribution within a cube (of the size equals to the grid size) surrounding a grid point. The crack distribution in rock from impact is based on the finding from previous researchers (Seaman et al., 1976). The fines and oversized blocks are calculated explicitly. The summation of the size distribution at all calculation grid points over a specified volume of the blast yields an overall size distribution for the volume.

Jan 1, 2015

By Ruilin Lang

This paper presents an application of 3-D plots and non-linear regressions to define a sitespecific form of the charge weight scaled distance. The PPV (PPA) of single hole blasts is normally considered as a function of two independent variables - the charge weight and the distance. It is of great importance to obtain the relationship of the function accurately for a concerned site in terms of blast vibration analysis and modeling. However, in pre-computer time it was difficult to plot 3-D graphs. Consequently, a charge weight scaled distance was used to plot the PPV (or PPA) against the scaled distance as 2-D graphs. Blast vibration investigators use several forms of the charge weight scaled distances to plot data. We can exemplify them with the cube root of charge weight scaled distance, the square root of charge weight scaled distance, and other forms (Hossaini and Sen, 2004). Each of these scaled distances assumes relative contributions of the charge weight and the distance to the vibration attenuation. For example, the charge weight is assumed to have a less contribution to vibration in the cube root scaled distance than it is assumed in the square-root scaled distance. In reality, for different sites the relative contribution of the charge weight and the distance may be different and site-specific. This may explain that in some cases, the blast vibration data plots using these charge weight scaled distances are scattered. This could be largely due to the fact that the definition of the form of the charge weight scaled distance is not adequate for the particular site condition.

Jan 1, 2006

By Joshua Hoffman, Rhys Baker, Tim O’Brien

Numerous agencies in the Executive Branch of the United States Federal Government have regulatory jurisdiction over the explosives industry. These agencies develop the rules by which the explosives industry must operate, and many have the authority to enforce those rules. Likewise, there are entities in the Legislature that have oversight of those agencies and develop the laws that agencies must operate under. These entities in the Legislative Branch are Congressional Committees. Each committee has their respective jurisdictional authority over various agencies and issues. There are several Congressional Committees with jurisdiction over the agencies that govern the explosives industry and they differ slightly between the House of Representatives and the Senate. This paper discusses this division of power as it relates to the explosives industry. Each branch is responsive to the public and the processes through which each promulgates regulation and legislation require public input in different forms. Options for civic involvement for engaging each of these bodies of power in their respective processes are presented. The differences between legislation and regulation are highlighted along with the processes by which each are promulgated. A proper understanding of the governmental mechanics that affect the explosives industry are critical for the industry to be able to be proactive in playing a role in these processes in a democratic way.

By Roger E. Scholl

Data on off-site low-rise building damage from underground nuclear testing at the Nevada Test Site (NTS) of the United States Atomic Energy Commission (AEC) [The AEC has been called the United States Energy Research ant Development Administration (ERDA) since 1975, but because the data presented here were gathered between 1966 and 1970, the AEC rather than ERDA is referred to in this paper.] are available for seven large tests in the period from 1966 to 1970. The data, while sparse, provide an adequate sample for the investigation of motion-damage relationships. Damage in the study is statistically described in terms of the incidence of damage complaints, the incidence of buildings damaged, and damage cost. Using 5%damped response spectrum acceleration amplitude to characterize ground motion, the plotted data fit reasonably well with previous motion-damage relationships established from extensive data available from the 1969 RULISON underground nuclear explosion (UNE) experiment conducted in western Colorado.

Jan 1, 1976

By Michael Wieland

Sharp transient stress waves generated during the delay blasting of underground coal can damage unfired borehole charges remaining in the delay pattern. These tremendous stress pulses in coal bear a strong resemblance to underwater shock waves, despite differences in rise times, damping rates, and scaling relations. "Shock wave" terminology is adopted to distinguish the sharp transient waveforms propagating through the coal from the gas-driven stresses that rift the coal. Reported waveform characteristics of shock waves through underground coal were utilized to design a simulator test for rating the impact resistance of cap-sensitive explosives. Theoretical minimum borehole separations were determined for each cap-sensitive explosive from the requirement that worst-case waves hitting an unfired charge would not exceed its impact resistance rating. Rugged explosives have higher impact resistance and will function properly at smaller borehole separations. Additional work is required to verify the findings from the simulator technique and modeling relations reported here.

Jan 1, 1990

By Jeff Gore, Jack Dermody, David Gribble, Brett Macaulay, Bart Sharpe, Paul Klaric, Paul Thornley, Ben DeVries

Optimal Fragmentation in Block Caving is difficult to achieve as it is generally defined by the rock mass itself and the way in which the cave is initiated. The lower portion of the cave has even less chance as the material has little time for self comminution. Blast Preconditioning of the Block Cave is designed to engineer the lower section of the rock mass to produce material of a suitable size to assist in the initial cave propagation and improve initial drawbell productivity. At Cadia East a plan was developed to drill 150-metre long, vertical up-holes from the undercut level and blast them fully confined to produce fractures in the rock mass. The blast itself was a simple undertaking. However, in the year preceding the first production blast, all aspects of the process were designed, tested and refined across multiple trials. As this type of challenging application had not previously been encountered in Australia there were many unique situations to address. Products and systems had to be developed and adapted to overcome these challenges. These included: Formulating and manufacturing an explosive that is robust and of a high VoD; designing and manufacturing easy to use electronic initiation systems; and, designing pumping systems to combat high head pressures to allow for successful and safe loading of the holes. Close collaboration with the customer ensured that the trials culminated in successfully blasting a hole containing almost 3.3t of explosive. These trials have since led to the blasting of four holes instantaneously, which contain almost 13t of explosive. This paper describes the various components of the system, the challenges and the final result.

Jan 1, 2013

By James G. Stuart, Tassilo N. Baur

We will discuss the kind of procedure that we use to predict the no-fire (for safety) and all-fire (for reliability) current levels for any given type electric detonator. The basic idea is to expose several detonators to different levels of electric current, so we can estimate the probability of firing as a function of current. We call this a statistical firing test. But what about the uncertainty in measuring the current? Suppose we are not quite sure what stimulus level we apply? This is the question that we will consider here. This relates to both safety and reliability. Surprisingly enough, we will find that some uncertainty in measuring the levels during our statistical firing test improves our long-term safety and reliability

Jan 1, 2019

By Jesus Pascual, Jose Sanchidrian, Pablo Segarra

The surface vibration field in the area above an underground mine prior to its development has been investigated, in order to assess the vibration levels expected in existing buildings and in the planned mine facilities from future underground blasts. Shots of 50 and 100 kg of explosive placed in drillholes at depths of 100 to 150 m were fired, and the vibration events were recorded using an array of 40 seismographs in a 400 m square grid, covering a 2×2 km area. Contours of isovelocity were obtained for each shot, showing some directional transmission patterns. Propagation laws were obtained from the results of each shot and also from the bulk of data, both for the whole area and dividing it into four quadrants. The shift of dominant frequency with distance was also analyzed.

Jan 1, 2002

By Wayne Rogers, Sarma Kanchibotla, Alan Tordoir, Bryon Bisiauz, Seth Ako, Eric Engmann

Blast induced rock mass displacement can have a significant impact on ore loss & dilution. The mischaracterization of the grade boundaries both prior to, as well as a result of blasting can lead to significant financial losses on account of ore loss and dilution. Ore dilution occurs when waste material is miscategorised as ore and sent for processing diluting the run of mine head grade and recovery. Ore loss takes place when valuable mineral is miscategorised as waste and sent to the waste dumps, thus never being processed and recovered.

Jan 1, 2012

By Catherine T. Aimone-Martin, Elena Oana Jacobs, Brent Meins

Accurate pressure measurements during underwater detonations are critical for the protection of structures and mitigating impacts to fish and marine mammals. Current guidelines that limit underwater pressures are based on past studies, many of which used sample rates of 48 and 65 kS/s (48,000 and 65,000 samples per second). These sample rates may be insufficient to accurately record high frequency, sharp rise time blast pressures. As such, pressure thresholds associated with fish and marine mammal injury or mortality may be underestimated, calling into question the pressure and sound pressure level guidelines that govern underwater blasting today.

Jan 1, 2019

By P A. Gibson, J R. Brinkmann

The South African gold mining industry fires approximately 800 000 sloping blastholes daily. A programme aimed at characterizing the stope blasting process is underway in order to identify areas for improvement and to provide blasting related information for the design of mechanized sloping systems.

Jan 1, 1985