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By Wilfred G. Comeao

Close-in blasting occurs every time the use o f explosives for excavation or demolition requires the surpassing of the commonly accepted cosmetic damage criteriain order to arrive at reasonable and practical explosive weights per delay. One of the many effective blast design procedures consists in establishing a reasonable charge weight per delay with respect to scale, geometry, costs, requirements and constraints of the project. Once this reasonable charge weight per delay is determined, it’s environmental effects have to be estimated with respect to the surroundings.

Jan 1, 1991

By Paulo José Costa Couceiro Junior, Manuel Lopez Cano

In 2011, two historic outcrop rocks known as Teffé and Itapema located in the navigation channel of the Port of Santos, Brazil (Latin America’s largest port) – were excavated by drilling and blasting techniques. Sensitive structures - a passenger terminal and an 80-year old warehouse were exposed to ground vibrations generated by underwater blasting. The warehouse had existing structural problems due to a combination of factors such as the presence of an unstable soil, previous repair work, and intense seismic events generated by the daily traffic of cargo trains nearby during eight decades. Since the worsening state of the structure was attributed to ground vibration from underwater blasting, particle velocity time histories generated by underwater blasting and by passing trains were monitored. By analyzing the energy spectral density of these events using spectrograms, it was possible to observe the seismic energy levels in time and spectral domains. Since the hysteretic energy dissipation by structures is related to the duration of the seismic event and the limited dissipation capacity of the structure, one could expect damages to appear in the structure once energy levels exceeded this dissipation capacity. As the quantity of energy transmitted to the structure is proportional to the duration of the seismic event, the transmission of seismic energy to the warehouse structure over time was more significant in the case of the train-induced ground vibrations (several minutes) than those generated by the underwater blasting (few seconds). Thus, for the warehouse, train-induced ground vibrations have a larger impact on the structure rather than ground vibration generated by controlled underwater blasting techniques.

Jan 1, 2016

By M. Hokkanen, M. Hagfors

The Finnish Defence Forces has destroyed old and spoilt munitions in open surface mass detonations at Hukkakero fell in municipality of Kittilä, Lapland, since 1988. The technique was learned from Sweden. The destruction camp is organized every year at autumn and it lasts 4-5 weeks. During the disposal period one or two charges are exploded per day. The gross weight of a typical charge varies from 150-250 tons including 15-25 tons of explosives. They mainly consist of TNT, but may also contain smaller amounts of amatol and hexotol. As a booster there have been used 2-3 tons of emulsion explosives.

Jan 1, 2015

By C. Rutledge

The new mining method of multiple strata blasting, called StratablastTM, is described in a separate paper presented at this conference. The current paper presents three case studies where the technique was implemented in three different configurations in large-scale blasts in Australia. The first two blasts were in the Hunter Valley of NSW while the third was at Ensham Mine in Central Queensland. All blasts comprised multiple layers that were blasted in a single drill and blast cycle, with unique designs applied to each layer to achieve different blast outcomes from the various layers.

Jan 1, 2006

By Randall M. Wheeler

Many of us have used a seismograph to measure peak particle velocity and frequency. But do we really understand why? Also, why do we measure particle velocity instead of displacement and/or acceleration? What is the vector sum? How do these items relate? Where does frequency fit in? This workshop will attempt to answer these and other questions. Some of the answers may surprise you, others may not.

Jan 1, 1997

By Randall M. Wheeler

"Fourier analysis is a very powerful frequency analysis tool. However, it is frequently misunderstood and sometimes used inappropriately. Part of this workshop will involve the basics of Fourier series, the Fourier integral and finally the Fourier transform. Included will be a brief discussion of analysiswindows, including the box and Hamring windows."

Jan 1, 1998

By Rob Farnfield

In the UK all new developments, including mines, quarries, tunnels, etc., are subject to a system of planning control. If the use of explosives is anticipated then such developments will attract a number of so-called ‘planning conditions’ relating to the blasting operation. This paper will outline a ‘typical’ set of conditions and how operators ‘plan to comply’. British Standards relating to both human and structural response are also reviewed and contrasted to the typical planning conditions previously outlined.

Jan 1, 2005

By W Barry Gregg

The rock blasting and mining industries use a system of detonators and explosives for mining operations. Many detonators use small metal bridgewires, which are heated by passing a current through the wire, heating and igniting the pyrotechnic powder in contact with the wire, Typical bridgewires require a current of at least 3 amps, applied for a few milliseconds, for an explosive output. The semiconductor bridge (SCB), in comparison, initiates an explosive in 0.01 to 0.1 of a millisecond.

Jan 1, 1992

By Mark A. Williams, James D. Humphrey

Without question, draglines are one if not the most effective tools available to the surface mining industry for overburden handling. With few moving parts and a two- or threeman crew, this machine silently sits and chews into millions of yards of overburden annually. A 100 cubic yard machine operating for 30 years will excavate three-quarters of a billion yards of material during that time. That is 750,000,OOO yards of material!

Jan 1, 1990

By Don McCarthy

Modern mining has been dominated by the drill-and-blast method for more than a century. There have been steady improvements in drilling technology, explosive products, methods of initiation and integration of the two techniques but the essential cyclical nature of drill-and-blast rock excavation naturally limits continuous improvements in cost and productivity. Dynamite and safety fuses, compressed-airdriven tools, and most of the crushing and grinding machinery in use today were all developed before 1900. Moreover, virtually every mechanized mining system used today was in use by the late 1950’s.

Jan 1, 1998

By S J. Brace

About 180 000 tons of explosives are used annually underground in South Africa. Most is loaded into holes less than 50mm in diameter. 75% is consumed in the gold and platinum mines where holes are between 25 and 4omm in diameter and no more than 3.0m in length. The small amount of explosives per hole with extreme conditions of heat, humidity and seismic activity, make the choice of explosive on safety and technical grounds very important to the success of a blasting operation. Taken together with the fact that many underground precious metal operations are now marginal then the choice of an explosive, when its price is also considered, becomes critical to the very viability of some mines.

Jan 1, 1994

By Enrique Albarrán, Julian Hernández

"In 1942 The “Presa Mixcoac” dam was built, along with 15 other dams, to control the rain fall waterin the mountains west of Mexico City. Mexico City’s population at that time was around 1.5 millionpeople, and the dam was way out of the city."

Jan 1, 2016

By M Thierry Bernart

The software QUALITIR is a software developed by CNSIDCI, framework on five research and experimentation years. This conceived tool by specialists for professionals is a decision aided design tool concerning mining. It makes party the rare software regrouping the different themes approached by the profession namely, the general idea of blast design, blasting sequences, the fragmentation as well as the study of vibrations. Henceforth it is by the intermediary of such tools that performances in term of profitability, security or impact on the environment will be able to be realized.

Jan 1, 1997

By Rufus Flinchum

Two of the most critical concerns a blaster faces today are airblast and flyrock. Airblast, sometimes called noise or overpressure, can cause damage to neighboring structures, especially windows. It also is the cause for many vibration complaints. The human sense of hearing is often more acute to identifying source than the sense of touch. When a blast occurs, the airblast is what identifies the event. The vibration that may be felt is then associated with the airblast. Vibrations of greater magnitude, such as passing trucks or construction work on the house, go unnoticed because their sounds are familiar or expected. Flyrock is the number one killer and cause of damage. Elasting laws provide limits for these two concerns. Failure to comply may result in fines, closing of the operation, and even prison. Airblast and flyrock originate from two distinct areas, the open face and the bench surface. Each of these areas is addressed in the detailed proven procedures that follow, and if used by the blaster in conjunction with his own blasting knowledge, a sound blasting plan can be developed to minimize the occurrence of airblast and flyrock.

Jan 1, 1992

By Peter Moser, A. Gaich, E. Grasedieck Zechmann

In The SMX Blast Controller is a novel tool for precisely controlling the geometry of a blast based on the technology of 3D imaging. It enables to derive precise information about the geometry of the face of a bench in a quarry from a pair of stereoscopic images taken from the bottom level of a bench with a calibrated standard digital camera. Apart from staking out the blast position with delimiters that mark the area to blast and taking then two images (freely), no further actions are required which allows performing the data acquisition without requiring any surveying skills. The 3D image generation and blast planning does not require special computer. It is estimated, that every blast foremen is able to work with the system after a one-day training as the system includes a high grade on automatism. The software package allows the blast foreman to design and stake out a blast, based on provided geometric values, such as burden, side spacing, hole inclination, sub-drilling, row number & distance and drilling pattern. The software connects these values with the 3D information acquired by the digital images. All the drill & blast information can be used also for blast documentation. The SMX Blast Controller overcomes also the problem of doing the back transfer from maps derived by surveying into nature as the resulting 3D image and all the information associated to it (hole position, etc.) can be correlated with the nature by visual comparison and the help of a single reference line, defined by two points. The system is designed to be used also in small to medium quarries. It can help, that the control of the geometry of the bench face and the precise design of the charge of the blast on a borehole per borehole basis will become an accepted daily routine.

Jan 1, 2006

By Carl Lubbe, Ron Frye

Numerous articles have been written regarding the effects of blast control plugs in an attempt to quantify stemming ejection rates, air overpressures, fragmentation’and other parameters measured using these devices. In an effort to further attempt to understand the function of these devices, field and laboratory research conducted with various stemming devices was performed to enhance existing data sets and analyze otherphenomena that occur when these products are used.

Jan 1, 1998

By A Tawadrous, P D. Katsabanis, S Kim

A series of small scale tests, have been performed to establish the effect of powder factor and initiation timing on the grindability of rocks. The blasts were performed in high quality granite blocks, which were cut from stone prepared by dimensional stone quarry operations. Three different types of granite, Barre, Stanstead and Laurentian, were tested. The charge consisted of detonating cord placed in five holes with water as a coupling medium, or concentrated charges of equal mass of high exolosive, fully stemmed or air decked. Powder factor was varied from 0.39 to 1.17 kg/m3. Charges were detonated simultaneously or with a small delay and in some experiments, detonation waves collided in the middle of each borehole. All fragments were collected and screened, and drop weight impact tests were performed on selected size fractions, using different levels of impact energy, to calculate the resistance of the rock to impact breakage. The work index of some of the blasted samples was measured using standard Bond mill grindability tests. The experiments generally showed increased softening of the rock with powder factor, manifested by the increasing initial slope of the relationship between t10 and impact energy. The rate of change of the initial slope decreased with increasing powder factor. Changes in the work index were small and consistent in trend with the results of the single fragment impact characterization tests. Charge configuration, timing as well as in-hole collisions of detonation waves affected the initial fragmentation but had little effect on the impact breakage of the samples.

Jan 1, 2009

By Gerald W. Longenecker

For decades, traditional hydraulic engineering approaches have been used for sizing stream channels when stream relocation efforts have been necessary to allow for the advancement of quarry and other surface mining operations. These approaches have been based on various ydraulic models to design channel cross sections and slopes that could pass the required regulatory design storm such as the 2-, 5, lo-, 25-, 50-, or even loo-year events. Designing the stream channel to handle these more extreme ,storm events would often lead to large channel designs which required extensive bank and channel bottom stabilization techniques including concrete, rip rap, gabions, or other expensive approaches. The constructed channels often required ongoing maintenance to remove accumulated sediment and other debris which would settle out and reduce the hydraulic capacity of the channel.

Jan 1, 1998

By Alejandro Ferrada Vergara, Héctor Espinoza Muñoz

Drilling and blasting stages are considered factors that impact downstream processes significantly and over all the mining business value chain. Adequate control of these processes may represent energy savings in comminution processes. There has historically been a resistance to design change as this implies more drilling and implementation costs due to new technologies in explosives, which added value is difficult to quantify.

Jan 1, 2016

By Tjaar A. Louw, Albert P. Van Niekerk, Johannes J. Louw, Attie J. Goosen

Unlike molecular high explosives, commercial explosives based on ammonium nitrate do not detonate ideally according to the theoretical model for steady state, one-dimensional detonation. One of the reasons for this deviation from ideal detonation is the slower chemical reaction, due to less intimate contact between the oxidiser and fuel components. It is well known that the inclusion of gas pockets, such as microballoons, in the formulation of ammonium nitrate based emulsions and watergels enhances the performance of these explosives. Various different interpretations of the “hot spot” theory have been proposed to explain this phenomenon.

Jan 1, 1997