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By Jianping Li, Ernesto Villaescusa, Kelly Fleetwood

During blasting, stress waves propagate through a rock mass, inducing stress and strain changes. This applied deformation affects intact rock, existing discontinuities, mine excavations, and engineered structures in the proximity of the blast. Traditionally in blasting, stress waves are quantified in terms of peak particle velocity (PPV) or peak particle acceleration (PPA), based on the method of measurement and the specified allowable tolerances. During analysis, the peak particle motion is coupled with an explosive source through various scaling laws to develop rock-specific attenuation relationships. Some studies have expanded this practice to the development of damage threshold values based on measured or predicted peak particle velocities. PPV-related thresholds are generally based on empirical models, where observation of overbreak, cracking, or fall-off are used to quantify damage. This method is often paired with the application of elastic plane wave equations to calculate the blast induced strain or the PPV threshold for tensile rock failure. Other factors that must be viewed critically in such models are the methods used to collect and analyse blast vibration data and the application of inappropriate vibration attenuation relationships.

Jan 1, 2009

By Enrique Munaretti, Vitor Rosenhaim, Jair Carlos Koppe, Joao Francisco Feijo

The B3 mine is a multiple coal seam strip mining in operation in Rio Grande do Sul, the southernmost state in Brazil. A traditional truck & excavator operation is used to remove the overburden and selectively mine coal seams, ranging in thickness from 30 cm (1 ft) to 2.5 m (8.2 ft). Blasting is required in order to excavate part of the sedimentary rock overburden where the rock is too hard for mechanical excavation, and to mine the coal seams, selectively.

Jan 1, 2012

By C. Heiss, A. Hofmann

Due to an explosion in an Austrian steel works during the basic oxygen process, the Chair of Mining Engineering and Mineral Economics at the Montanuniversitaet Leoben was assigned with the set-up of a test arrangement to study the effects of large-scale particle emissions on the plant´s installations and the testing of various structures and structure-combinations to be applied as explosive-proof enclosure.

Jan 1, 2012

By Dennis Wilzbacher, John Wiegand

In an effort to reduce the cost of bulk explosives, Vigo Coal Company found that the addition of coal mined at their Friendsville Mine, not only reduced explosive costs, but also appeared to actually enhance blasting performance. The Friendsville Coal lies at the base of the Mattoon geologic formation within the Mcleansboro Group of the Missourian Series of the Pennsylvanian Geologic System in Southern Illinois. Vigo Coal Company commissioned VIBRONICS, INC., an independent blasting consulting company to quantify actual blasting performance. Insitu sonic velocity testing of overburden was conducted to determine the P-wave velocity of the sandstone present at Vigo’s Cypress Creek Mine, where the initial testing was conducted. Numerous VOD (velocity of detonation) recordings were obtained for varying blends of ANFO/Coal (now named Carbo*Prill). Cast blast percentages were determined for both Carbo*Prill and non coal blended bulk explosive blasts. The VOD of the coal blended product was intentionally reduced so as to more closely match the P-wave velocity of the sandstone overburden. Explosive blends containing as much as 40-50 percent coal were tested. Explosive blends containing greater than 30 percent coal, have been used in Cypress Creek Mine overburden production blasts. The coal blends appear to produce better fragmentation and yield excellent cast blast performance. Safer mining conditions were also observed. Flyrock potential was reduced. The blasts produced less back break, producing a safer highwall. Stripping dozer and shovel production rose during the testing period and equipment repair costs were lowered due to an increase in overburden fragmentation. Blasting vibrations were reduced, in part due to the lowered detonation velocity of the ANFO/Coal mixture. The Friendsville Coal Seam appears to contain inherent chemical and physical properties that enhance blasting performance. The use of Carbo*Prill has been approved by MSHA, BATF, the State of Illinois, and the State of Indiana. This paper will provide details concerning testing procedures, blast performance analysis, recommendations and conclusions for using this alternative blasting mixture.

Jan 1, 2007

By Thierry Bernard

Considering rock fragmentation by explosive as the ultimate goal in mines and quarries, vibrations are definitely one of the main drawbacks faced by the Industry. If we can accurately predict vibrations level and frequencies, taking into account the whole set of the involved parameters, this will bring a major benefit to each of us, in our daily production process optimization effort. The model presented in this paper answers to this need thanks to a "holistic" approach of the vibration mechanism. By holistic, we mean that we approach the vibration effect (wave propagation) as a whole, by understanding all of the mechanisms that contributes to the process and comprehending how they are connected.

Jan 1, 2009

By Luiz Felipe Mendonça de Amorim, Adimir Fernando Rezende, Gustavo Sampaio Lopes, Claudio Cesar Gajardo Arraño, Eltton de Sousa Veras, Manuel Villalobos Calderon

Many technical challenges were encountered while conducting near-field construction blasting between the critical intersection of Interstate 10 and multiple active railroad tracks in El Paso, Texas, for the Loop 375 Border West Expressway Project. Blasting was utilized for the removal of an andesite bedrock ridge in preparation for the construction of a new elevated super structure to be suspended over the existing railroad tracks. There was concern that the excessive vibrations and/or permanent rock deformation produced from the blasting within near proximity (20 feet, or 6.09 meters) of the railroad tracks would induce excessive stress and foul the tracks by shifting the alignment. This could result in a major loss of scheduling control between the two major railroad companies that operate in this area. There was also concern that the blasting may cause rock fragments to land on and interfere with critical interstate transportation. Blasts

Jan 1, 2019

By Lewis L. Oriard

Both theory and experience tell us that spatially distributed energy sources generate a more complex family of seismic waves than do point sources. The resulting effects in the near field (for close-in blasting) are significantly different than those from point sources although, at great distances from the source, the seismic waves take on many of the characteristics of point sources and can often be treated as such.

Jan 1, 1992

By Joshua Hoffman, William Chad Wedding, Braden Lusk

The University of Kentucky employs an explosively driven shock tube in the course of experimentation. A good deal of the work completed relates to the verification of blast mitigation products and strategies. The work is dependent upon reliably reproducing specific pressure time histories called out by the test in question. The facilities are located in the workings of an underground limestone quarry in Georgetown Kentucky. As such, the temperature maintains fairly consistent 60°F (15.6°C), making it a comfortable work environment year round. Unfortunately, the relative humidity follows the prevailing weather conditions allowing a wide variation, especially between the winter and summer seasons. A study was undertaken to gauge the influence of relative humidity on shock wave generation, including the positive and negative phases of the wave.

Jan 1, 2011

By Doug Hoy

The scope of the Cliff Avenue Reconstruction Project in Sioux Falls, South Dakota was to widen a two lane highway to five lanes, along with removing and reconstructing both above and below ground utilities located along the project limits. The objective of this paper is to present the blasting techniques used in the rock excavation phase of the Cliff Avenue Reconstruction Project.

Jan 1, 1992

By Ingvar Hansson, Bjorn A. Jonsson, Bernt Larsson

In the Kiruna Research Mine, Sweden, four large open stopes have been mined, leaving intermediate piIlars and crown pillars. At the final stage of mining mass blasting of the crown pillars above two of the stopes was carried out. The crown pillars contained some 290,000 tons of iron ore. In the mass blast a new initiation technique was used, utilizing the new non-electric system NONEL ? UNIDET. The blasting technique including vibration control is described. The mass blast resulted in high recovery, good fragmentation and low vibration levels.

Jan 1, 1986

By Jhon Silva-Castro, Russell Lamont

Understanding the behavior of materials subjected to high strain rate conditions is of fundamental importance to the mining industry. Several stages of the mining process involve high speed loading rates including blasting, scraping, comminution, etc. Technical comprehension of how rocks deform, fracture, and fail under these loads is a fundamental first step required prior to any serious attempts at optimization of the energy utilized for pertinent activities in the mining process. A Split-Hopkinson Pressure Bar (SHPB) was designed and constructed at the University of Kentucky to study the dynamic properties of various types of rocks.

Jan 1, 2017

By Matthew Clay, Colin Chambers, Susan Hookham

Opencast (quarries) and underground mines around the world use blasting methods to mine valuable ore. Traditional blasting systems use technologies such as electric delay detonator systems (developed in the 1950s) and non-electric detonator systems (developed in the 1970s) to initiate a detonation train to blast rock more effectively, and so retrieve valuable product more efficiently. However, the lack of precise control over blast timings with these approaches can result in undesirable outcomes such as significant flyrock, excessive ground vibration, uneven grade of rock and misfires (in which sections of the blast can remain unfired). The development of Electronic Initiation Systems (EIS), first used in the 1990s, introduced a higher level of control over the blast. These systems greatly reduce the negative issues associated with blasting. However, this precision introduces complexity, and with this complexity comes difficulty in demonstrating the predictability, safety and reliability of such systems.

Jan 1, 2017

By Leslie C. Taylor, Scott A. Yamada, William L. Fourney

Previous studies have shown that the pressure load on a target by a buried explosive charge is not smoothly distributed. The effort reported here was undertaken to explore the mechanisms believed to cause this uneven pressure distribution: jets from the surface originating in instabilities caused by the explosive shockwave interacting with surface irregularities. Small-scale tests using conical, hemispherical, and cylindrical indentations in the sand surface above a buried charge were conducted to identify trends in the velocity and form of the resulting jets. In these tests, the most important factor affecting the resulting jets was the distance between the bottom of the indentation and the top of the charge. Cylindrical indentations resulted in higher jet velocities than those from comparable hemispherical and conical indentations.

Jan 1, 2012

By Jean M. Bouvet, Pierre M. Vuillaume

There is not just one ANFO: ANFO explosive behaviour depends significantly on the blasting conditions and on its physico-chemical characteristics. For instance, ANFO effficiency increases whereas AN porosity is higher and consequently loading density of the explosive is less. This can be argued against generally admitted ideas. Therefore, the efficiency of industrial explosives related to ANFO (for example "relative weight strength" or "relative bulk strength") is a tool that must be used with caution.

Jan 1, 1993

By Tristan Worsey, Nathan Rouse, Daykin Schnell

The authors were retained by a proposed underground metals mine operation to evaluate the potential blast vibration amplitudes that could be generated at surface structures above the proposed mine. Literature reviews of published blasting documentation gave little information, data, or models on surface blast vibrations produced by underground mines. At the client’s request, the authors contacted a number of underground mining operations to evaluate interest in sharing blast vibration data with the authors so that the authors could develop an underground-to-surface blast vibration regression equation.

Feb 1, 2020

By Richard J. Mainiero, Eric S. Weiss

This project investigates the behavior of blast waves from the detonation of high explosives in an underground mine. A series of explosive tests was conducted in the underground and surface facilities at the Bureau of Mines' Lake Lynn Laboratory to evaluate the potentially dangerous effects of blast waves produced by open shooting, blown out holes, or accidental detonations of explosives. Shots of C4 and TNT were fired at the dead end of a 6 ft high by 20ft wide entry, at the intersection of two entries, and on the surface. C4 and TNT were chosen for this research because they exhibit very consistent performance. Behavior of the blast wave was evaluated through recording of the pressure as a function of distance from the explosive detonation.

Jan 1, 1995

By Ron J. Elliott, David G. Otto

This project involved deep blast densification of recent volcanic avalanche debris deposits consisting of a 43 meter thickness of loose clean to slightly silty sand, gravel, cobbles and boulders deposited as a result of the 1980 eruption of Mt. St. Helens, Washington, U.S.A. This project was carried out to enhance the resistance to liquefaction or dynamic settlement of soil deposits under the bridge abutments for construction of the 59.4 meter long South Coldwater Creek Bridge. As this bridge is located close to the Mt. St. Helens fault, it will in all likelihood be subject to earthquakes in the order of 6.5 with expected accelerations of 0.55g. Without soil densification, the bridge would suffer severe structural damage in the event of a significant earthquake.

Jan 1, 1994

By Sven-Erik Johansson, Gosta Rundqvist, Donald Jonson

In Stockholm a new road traffic system called Södra Länken (Southern Link) will be in operation in late 2004. The total length of the road system is 6 kilometres of which 4,5 kilometres run through tunnels under suburbs immediately south of Stockholm inner City. The new traffic tunnels together with existing Metro tunnels, which mostly are in rock, will be the determining factor for blast design for many projects in the future. To set reasonable and safe permitted vibration levels the Swedish National Road Administration, Stockholm Region and Stockholm Transport Rail System have together financed a project to determine guide levels for blast-induced vibrations in traffic tunnels in rock. The purpose of the project has been to establish guide levels that are appropriate for different types of rock tunnels.

Jan 1, 2004

By Greg Rappard, Francois Holowenczak, James Rickard

The King George V (KGV) Shaft forms part of MTR Corporation Limited (MTRCL) Works Contract 703 extension of the underground West Island Line on Hong Kong Island. The Shaft and the associated adit was the sole access to excavate the running tunnels. Originally during the Detailed Design stage, it was concluded that blasting was not feasible at the KGV Shaft due to the close proximity of sensitive receivers in the form of residential buildings, electrical cables and hospitals. As a result, the Contractor planned to excavate the Shaft using mechanical means with a programme time of seven months. The Contractor appointed a Sub-contractor to analyse the feasibility of excavating the Shaft by blasting. The Sub-contractor reviewed the proposal and recommended the use of an innovative blasting technique that had never been previously employed in Hong Kong. The Sub-contractor recommended the Shaft be blasted using DetNet electronic delay detonator technology, manufactured by AEL Mining Services in South Africa, with an initial 1.5m depth of water ballast covering the blast face. The electronic delay detonators provided initiation accuracy to ensure there would be no overlap between sequentially detonating blastholes. The water ballast makes use of the effect of energy lost through the shock front causing the water to break up into droplets creating a spray dome resulting in the attenuation of the energy imparted into the surrounding rock mass. Various tests have demonstrated that both the maximum overpressure and impulse density are significantly reduced when water of a minimum depth is in direct contact with detonating explosives. This innovative blasting technique reduced the excavation programme by three months, saved HK$5 million in direct costs and totally mitigated the impacts on the public and other stakeholders nearby the KGV Shaft. Peak Particle Velocities (vibrations) rarely exceeded 2-3mm/sec (0.08-0.12in/sec) at a distance of 30-40m (98-131ft) from the blast location and air overpressure levels were reduced below the Hong Kong target level of 120dBL. In total, 24 blasts were fired with an average advance of 1.6m (5.25ft) with an average powder factor of 2.03kg/m3 (0.127lb/ft3) to 1.84 kg/m3 (0.114lb/ft3). The initiation pattern had 5ms between sequentially detonating blastholes and 20ms between adjoining rings.

Jan 1, 2013

By M-C. Lee, Shomaker, R. Turcotte, B. Short

This research program was undertaken to better understand the factors causing abnormal NOx fumes generation from blasting operations in surface coal mining. More specifically, unusual quantities of nitrogen dioxide and nitric oxide have been observed at several surface coal mines in the Powder River Basin, Wyoming. All these mining operations have several points in common: (i) Blasting is performed using gravity loaded emulsions or emulsion/ANFO blends (ii) Unusual NOx (Oxides of Nitrogen) emissions are observed mostly when blasting is conducted in the overburden as opposed to the coal seam itself (iii) The overburden consists of very weakly consolidated ground strata, providing relatively weak confinement conditions for the explosives, and (iv) Significant ground water is observed.

Jan 1, 2002