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By N Gkikizas-Lampropoulis

Selection of delay times to optimize fragmentation has been a controversial topic among researchers and blasting practitioners. This paper interprets previous experimental information on the effect of delay on fragmentation with the aid of some new experimental observations of the time of detachment of the free face of the blast as well as results of numerical modelling. It was shown that detachment of the burden occurs at delays shorter than the one which produced optimum fragmentation in the experiments, suggesting some fragmentation improvement due to gas action. In addition, at the spacing to burden ratio of the experiments, the damage zone from an earlier detonating charge extends the distance to the neighboring charge, essentially affecting the burden of some of the holes of the blast, at detonation time. Computer modelling demonstrated that increased spacing results is less overlap of stress induced damage zones meaning that there is less influence of delay on stress wave induced fragmentation. It was also shown that simultaneous initiation results in less back break, while increased back break may result even with short delay times.

Jan 1, 2016

By Agus Sasmito, Akash Adhikari, Srivatsan Jayaraman Sridharan, Purushotham Tukkaraja

Previous studies on blast fumes(CO + NO2) clearance and workplace re-entry time have overlooked the effects of toxic gases entrapped in the muckpile. The currently available models forcalculatingthe mine re-entry times assume that all post-blast fumes are emitted upon detonation. However,recentstudies reportedthat as much as 60% to 70% of the fumes or gases produced during an underground development blasting couldremain entrapped in the adjacent rock mass or in the muckpile. Entrapped fumes are slowly released,and when disturbed, high concentrations are released, representing a possible risk during the digging and transportation of the muckpile. This study uses CFD, SC-Flow software to understandthe behaviorof the entrapped fumes and theireffect on mine re-entry time.

Feb 1, 2020

By Sharon K. Reamer, Klaus G. Hinzen

A series of controlled seismic experiments was performed in a limestone quarry in southern Germany to study seismic effects of cylindrical charges fired in both a half space (HS) (burden 63 m) and quarter space (QS) (burdens of 3 and 3.5 m) geometry. Charge columns contained from 20-32 kg of explosives and initiated from the bottom. The explosives formed a cylinder 4 m (20 kg) and 5 m (32 kg) high and 90 mm in diameter at depths from 3-8 m below ground level. Prior to each of the larger explosions, small charges of 0.12 kg seismogelit were fired at 4 m and 8 m depths in the same boreholes. Seismograms were obtained from 23 three component surface stations and up to 10 three component borehole stations (6 m depth). For each experiment, stations were located on three linear profiles of length 72 m at different azimuths from the source and one semicircular profile at a constant range of 30 m.

Jan 1, 1991

By Amos Bryant, Jesse Davis

This paper compares the predictions of the latest Institute of Makers of Explosives Safety Analysis for Risk (IMESAFR) model versus physical test data recovered from ISO-1 and ISO-2 tests in Woomera, SA. ISO-1 testing included placing 1054 kg (2324 lbs) of ANFO (ammonium nitrate-fuel oil) inside an ISO container on a flat bed truck. ISO-2 testing was identical except the NEW was 4000 kg (8818 lbs). The IMESAFR predictions are based on model runs using the best match available to the actual donor type involved in the test. This type of debris analysis is not the standard output of IMESAFR, as the program is designed to assess the probability of human fatality. However, all of the IMESAFR predictions presented were obtained from the use of the actual model equations and algorithms without adjustment. Test results from ISO-1 and ISO-2 will be presented as well as findings from the comparison between model results and actual explosive results from the ISO testing efforts.

Jan 1, 2010

By John Norman

This paper will cover blasting techniques that are applicable to underground and other rescue that involves removing obstacles and breaking rock in close proximity to rescuers and subjects.

Feb 1, 2020

By Robert Hopler

After the disbanding of the Gunpowder Trust Association in 1904, the Association of Independent Powder and Dynamite Manufacturers was formed, followed in May of 1906 by the formation of the Association of Manufacturers of Powder and High Explosives. Due to a lack of success in attracting all manufacturers to membership, these organizations did not survive.

Jan 1, 2014

By Ayman Tawadrous

Cave mining offers a flexible technique to exploit large, low grade, deep ore bodies with low operating costs. It is typically done in either a top down approach; i.e. sublevel caving, or in a bottom up approach; i.e. block or panel caving, to extract ore bodies that may have been previously considered unfeasible to mine. Sublevel Cave (SLC) mining, in particular, is a cave mining method based upon the utilization of gravity of blasted ore while the overlying host rock fractures and caves under induced stresses and gravity. Thereby the caved waste originating from the overlying rock mass fills the temporary void created by ore extraction to achieve a controlled collapse of the roof.

Jan 1, 2015

By Travis A. Davidsavor, David A. Provost

A segment of high-pressure steel petroleum pipeline needed to be replaced on a hillside and beneath a waterway within an existing right-of-way containing multiple petroleum pipelines. The pipeline replacement required excavation of sedimentary rock to allow placement of the new pipe. As a result of an existing right-of-way limitation, steep slopes, and hard rock, blasting would be required as close as 7.8 meters (25 feet) from two operating pipelines.

Feb 1, 2020

By Travis Davidsavor, David Provost

A segment of high-pressure steel petroleum pipeline needed to be replaced on a hillside and beneath a waterway within an existing right-of-way containing multiple petroleum pipelines. The pipeline replacement required excavation of sedimentary rock to allow placement of the new pipe. As a result of an existing right-of-way limitation, steep slopes, and hard rock, blasting would be required as close as 7.8 meters (25 feet) from two operating pipelines. Existing pipeline company standards would have effectively precluded the construction of the replacement pipe by blasting rock. To facilitate the required construction and evaluate actual pipe stress during blasting to ensure pipeline integrity, a comprehensive evaluation methodology was developed by a team of pipeline, mechanical, geotechnical, instrumentation, and blasting engineers. A total of 60 strain gages were affixed to the steel pipe and seismographs were buried at the surface near the blasting area. Test blasting allowed pipe stresses with corresponding ground motion to be monitored. A conservative analysis approach evaluated individual peak strains and revealed that only small pipeline strains, and therefore stresses, were induced in the pipeline as a result of blasting. This evaluation allowed specific procedures to be developed to inform the blasting operation of maximum explosive loading and minimum charge distances. Additionally, this effort provided the pipeline operator with appropriate pipeline operating pressures during blasting activities to limit total stresses in the pipeline to be below allowable stresses imposed by code, regulators, and company operational limitations. Recommendations were developed to measure the blast generated ground vibrations with seismographs buried at the depth of the pipe, near the pipe, and limit the ground vibrations from blasting to 150 mm/s (6 in/s). If ground vibration intensities of 120 mm/s (4 in/s) or more were observed, additional engineering review is recommended. Finally, all blasting would be suspended and all activities reviewed at peak ground vibration intensities of 230 mm/s (9 in/s). The evaluation effort resulted in effective and efficient construction of the pipeline replacement and allowed the pipeline operator to better understand blasting induced stresses on their assets.

By Robert Hopler

A detonator is a copper tube about a quarter of an inch in diameter and an inch and a half long, closed at one end and containing in the closed end a small charge of fulminate of mercury, which has been found to be the best explosive for detonating dynamite. The fulminate charge is a very powerful explosive very sensitive to friction, lows or heat and very poisonous. When exploded it has an intense local action, shattering things in its immediate vicinity, but not extending very far away from the explosion. This kind of detonator is intended to be exploded by a spark from burning fuse.

Jan 1, 2014

By R. Hazael, R. Alford, R. Critchley

The ability to compare explosives is fundamental. Numerous methods are used and while simple conversion factors are often used, the use of TNT Equivalency (TNTe) is not a simple subject as explosives exhibit very different equivalencies depending on whether the pressure or impulse are being considered as well as other conditions. The scaled distance has been found to have a significant effect on the TNTe but due to the difficulty of taking measurements at very close ranges, no TNTe have been quoted for charges in direct contact (Z=0). This paper describes the use of a ballistic pendulum to measure the impulse from contact charges and presents some surprising results that require a two-stage propulsion, as originally described by Backofen, to be explained.

Jan 1, 2024

By Martin Langenderfer, Catherine Johnson, Phillip Mulligan, Kelly Williams

The physical geometry of a charge has a direct correlation to the geometry of the shock wave. This relationship appears strongest within the boundaries of the visible fireball. As the shock wave propagates outward past the limits of the fireball, the theory states that the geometry of the shock wave should even out and become more spherical. This paper investigates pressure vs. time at two distances, one ‘Near Field’ at the extent of the fireball and one ‘Far Field.' The two Fields were instrumented with three free-Field pressure probes from PCB oriented at 0, 45, and 90 degrees to the front face of the charge, in the same horizontal plane as the charge. This orientation allows for the comparison of the shock wave from the face and vertices of the charge. All the pressure sensors were connected to a Data Acquisition System (DAS) recording at 2 million samples per second (2MS/s). Two high-speed cameras, a Phantom and an MREL Ranger II, recorded the detonations for qualitative examination of the fireball, and the shock wave. Three charge geometries were used and compared to the shock propagation of a sphere. The other geometries tested are cylinders, cubes, and tetrahedrons. Charges were made from a PETN based sheet explosive. In the Near Field, a lower pressure is observed along charge vertices with highest pressures from each face. In the Far Field, vertices record a higher pressure, possibly due to the shock waves from the adjacent faces intersecting, indicating that shock pressures do not always even out in the Far Field. This paper will describe the methodology and findings of this experiment and attempt to determine causality for trends in the data gathered.

Jan 1, 2018

By Alyse Munro Hindley

The increasing negative public opinion toward blasting has led to stricter regulations and increased costs. This paper outlines alternative methods of rock excavation and the safety regulations and certification required by blasting professionals. Most importantly, however, it showcases the benefits and accomplishments that controlled blasting bring to society, giving the public a better understanding of the necessity of blasting in modern society.

Jan 1, 2015

By DuPont Magazine

RBH Note: as stated many times in these articles, frozen dynamite was one of the greatest hazards facing the blaster. It wasn’t until the late 1920s that it was solved for good, with the introduction of nitrated ethylene glycol as a partial replacement for nitroglycerin in dynamites. The du Pont low freezing dynamites contained TNT, DNT, or nitro-substitution compounds of various sorts.

Jan 1, 2015

By T. G. Sitharam, P. B. Choudhury

Prediction of ground vibration (peak particle velocity, PPV) and frequency is an important task in geoscience. Till date, many empirical equations are derived from conducting trial blasts in the mines, to arrive at attenuation predictors. These predictors are usually site dependant and hold good for one particular type of rock/strata. These predictors cannot be used for geologically different rocks/strata. This paper presents the application of support vector machine (SVM) model, for predicting blast induced ground vibration and frequency, using a one comprehensive model for three different types of rock. Inputs to the SVM model formulation involve twenty one parameters consisting of geotechnical properties of the rock mass, blast design geometry and explosive properties, and the output of the formulated model is peak particle velocity and its associated frequency. The data has been acquired from eight limestone mine, five coal mine and two manganese mines. The comprehensive SVM model is formulated using 400 datasets and tested with 143 datasets. The performance indicators to the model not only justify its formulation but also the advantages it has over site specific predictor models. The SVM model not only predicts PPV, with higher correlation coefficients as compared to predictor equations, but also the associated frequency.

Jan 1, 2010

By Kain Petterson, P D. Katsabanis

Blast fragmentation, determined using image analysis was correlated to drill monitoring parameters in an open pit operation. Average fragment size and 80% passing size showed strong correlation with specific energy of drilling as well as with torque, while the same passing sizes did not correlate well with the rate of penetration. It was also determined that the uniformity of fragmentation decreases with the specific energy of drilling. Thus drilling monitoring parameters appear to be valuable in determining the blastability of the rock mass, enabling adjustment of blast loading to respond to changing conditions in the rock mass.

Jan 1, 2013

By Duncan Chalmers, Rob Nowell, Miguel Araos

Australian underground mines produce in excess of 60 mtpa of coal. Most of these use the longwall method, and they require the use permitted explosives (which are called “permissible” in other countries) for challenges that appear during the day-to-day activities. To obtain the approval for these explosives, they should pass Testing Memorandum #2 (TM-2), which sets out the test required for each category of permitted explosive. These categories are P1, P3, and P5. With P5 being unrestricted use and P3 and P1 have conditional use in underground mines. The TM-2 test was originally set up for NG-based permitted products around 1900. With the closing of NG plants around the world, ammonium nitrate explosives were the natural replacement, and therefore these explosives need to pass the TM2. Australia does have a P1-emulsion based explosive available. For high-risk scenarios (like blasting coal), no P5 explosives are available. The lack of P5 explosives has been prolonged for more than 25 years, since the phasing out of nitroglycerine-based permitted explosive products around the world. The main problem has been that when emulsion based permitted products are tested in the deflagration cannon, the results obtained were not considered in the TM2 criteria and therefore the tests were invalid. A research work on permitted explosives began in 2005 funded by the Australian Coal Association Research Program (ACARP). The aim of the project was to address the lack of P5-type permitted explosive (and, potentially develop them further, i.e., develop safer explosives) and understand the behaviour of emulsion explosive and the results they presented in the tests. Both bureaucratic and technical barriers appeared along the way. On the bureaucracy side, the facility was shut down, reopened, and shut down again. In view of these difficulties, assistance was sought overseas. On the technical side, from the very start the results of the tests when using emulsion-based permitted explosives were not established in the criteria, ignitions occurred for trial samples that were expected to be P5-type, etc. The aim of this document is to present the painful journey in the Australian industry to have a P5-type emulsion-based permitted explosive, for use in UG coal. Also, the technical learning acquired about emulsion explosives and the ignition path of mixtures methane / air will be shown.

Jan 21, 2025

By Jose Luis Pineda Villarreal

New technologies emerge every day with practical applications for open pit mining. For every operation, managers need to understand the best way to increase efficiency in drilling, blasting, fragmentation and hauling routes.

Jan 1, 2018

By William Gates, Gabe McClain, Thomas Pallua, Joe Schrank

The Tennessee Capitol Corridor connects the Cordell Hull Building (CHB) to the State Capitol, which isa 232-foot-by-124-foot (71 x 38 m) structure in Nashville that includes porticoes built from local massive limestone. This connection was affected by the Capitol Connector Pedestrian Tunnel (CCPT) project, which is part of the overall Cordell Hull State Office Building and Central Services Demolition, New Construction and Renovation Project (Cordell Hull Renovation Project). To construct this connection, the two existing elevator shafts and a new emergency stairwell in the State Capitol were extended down to anew lobby area—the elevators by about 50 feet (15.2 m) and the stairwell by about 60 feet (18.3 m). This lobby was connected to the CHB by a 435-foot-long (133 m) pedestrian tunnel. It was predicted that most of the tunnel would be excavated in a relatively strong limestone; therefore, considering the project features and constraints, drill-and-blast techniques were selected as the primary excavation method. Because of restrictions on blasting in urban areas and, more importantly, the proximity of this construction to national historic landmarks, blasting operations were extensively monitored to measure and correlate ground vibrations as peak particle velocity (PPV), frequency, and strain—these being the major factors that would impact the surrounding buildings. As a result, copious amounts of data were gathered and interpreted within a short time to estimate blasting parameters and optimize the subsequent blast rounds. To calculate the ground response factor, the scaled distance of each shot was compared to the ground vibration as PPV, generating a subsequent regression curve with an R2value of about 0.7. Using the best fit curve equation, the estimated ground response factor was about 150 for the best fit line. Other than some cases with relatively high (> 2 in./sec [51 mm/sec]) recorded PPV values, the blasting operation was successfully conducted as planned and the observed strain on the monitored buildings was very low, mainly within ±2 με (0.0002% elongation). (In general, the recorded PPV was lower than 2 in./sec at frequencies of more than 50 Hz.). The strain gauges at key locations (cold joints and old fractures) in the Capitol and on other critical structures demonstrated strain was insignificant in relationship to ground vibrations from the blasting operations. The apparently small vibration-induced strains were related to the massive limestone construction of the Capitol and ancillary buildings, as the induced strain plus the existing strain did not exceed the critical strain of the massive structures.

By C. Adcock, R. Farnfield, G. Adderley

The use of explosives to create special effects in the film industry is a well-known past time. A recent production required simulation of a large scale water splash from the effect of a statue falling from a cliff edge and impacting on an open body of water. This was to be achieved through the use of precisely delayed explosions detonated near the surface of the water. A survey of the area revealed a breeding farm for sea bass approximately 250 metres (273 yards) from the intended blast area. It was initially thought that the water pressures produced for the detonation of the explosives may cause harm to the fish. Much work has been carried out over the past few decades on the effect of open water blasting and its effects on aquatic wildlife; this includes water pressure modelling techniques which can be used as predictive tools.

Jan 1, 2010