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By Peter Moser, Michael Messner, Florian Bauer

The existence of ammonia in underground blasting fumes was frequently measured in various field tests (6, 7). Ammonia in fumes with a TLV (threshold limit value) of around 30 ppm (slightly different in various countries) is a toxic gas but not considered to be a high risk for the underground work force as ammonia smells very itching and is extremely annoying. This might be the reason why ammonia is hardly measured in routine underground blasting fumes control. Another reason for the lacking measurement might be the circumstance that ammonia is a very reactive gas and the ammonia sensors available on the market are very cross sensitive to other gases like carbon monoxide. Nevertheless, especially since the introduction of bulk emulsion explosives in underground blasting, complaints from miners about ammonia in the blasting fumes increased. Research work by various institutions [8] around the world relates the ammonia in the fumes back to various mechanisms. Amongst others these comprise: a) non ideal (low temperature) detonation of explosives, with NH3 in the reaction products; b) reaction between rock and non detonated bulk explosives (especially when the rock is of a basic nature (high pH value); c) reaction between shotcrete and non detonated bulk explosives. Numerous blasting tests in an experimental underground set up have been made in order to check these hypotheses for ammonia origin in blasting fumes. None of them has been found to be responsible for sometimes high concentrations of ammonia in the fumes. The major reason for ammonia concentration in blasting fumes has been found in mine water of a high pH value (either natural or from using shotcrete). The mechanism identified is as follows: the moment a non detonated ammonium nitrate bearing explosive comes in contact with mine water of a high pH value, ammonia is formed immediately. The source for the undetonated explosive is twofold: firstly there is a certain spillage of explosives when the holes are charged (especially when using bulk products) and secondly not the entire explosives detonate completely. These undetonated remaining of the explosives end up in the muck pile after blasting. In case there is water of a high pH value the reaction between the explosives and the water starts immediately. This explains also the observation why ammonia can be measured in the blasting fumes quite a long time after the blast. The majority of the ammonia is not formed during the detonation; it is formed inside the muck pile even a considerable long time after the blast.

Jan 1, 2010

By Chris Breeds, Larry Leone, Jerry Wallace

One of the Authors was recently retained to provide a professional engineering analysis of the potential impacts from underwater blasts used to enlarge intake tunnels at the Cheesman Dam near Denver in Colorado and to design Blast Protection Bags that could be installed in each tunnel to protect the 100- year old downstream valve structures.

Jan 1, 2012

By David Leidel, Beth Shimer, James Stuart

Periodically, the Institute of Makers of Explosives Safety Library Publications are reviewed, edited and updated to reflect recent technical developments, new commercial explosive products and new regulatory requirements. The rapid proliferation of electronic devices, particularly portable communication systems, inventory management devices, navigational aids, etc., required the revision of the IME Safety Library Publication 20, “Safety Guide for the Prevention of Radio Frequency Radiation Hazards in the Use of Commercial Electric Detonators”. The new edition of SLP-20 has been updated to correct alterations to U.S. frequency allocations and maximum transmitted power permitted and a discussion of communications and tracking systems required in underground mining by the Miner Act. Also, an entire section was added dedicated to safe distances from RF sources to the special type of resistorized electric detonators used in the upstream oil and gas industry on wellsites and an enlarged section describing the particular types of RF sources that the blaster may encounter, perhaps in construction blasting operations.

Jan 1, 2012

By Jonathan Heiner

Rio Tinto Bingham Canyon Mine started its South Wall Push Back (SPB) in 2011. This push back will mine through the only road to the pit bottom (the 10%). The pit bottom is the main ore sector for the mine and supplies about 80 to 90% of the ore. In late 2017 the mine set off a blast in SPB that created a small wedge failure on the high wall between SPB and the 10%. This wedge failure released a rock approximately 20 minutes after that blast that rolled down the wall landing on the 10% near and then contacting a light vehicle

Jan 1, 2019

"Large scale open pit mining and quarrying operations dictate safe and reliable pit wall stability. The current approach of employing the particle velocity-scaled charge distance approach to estimate and minimize damage to residential structures is considered inadequate to protect rock slopes. This study utilizes close-in blasting vibration data as input to an advanced 2D numerical code to study its applicability to serve as a predictive tool in terms of blast-induced rock slope failure. Two tri-axial accelerometer stations, consisting of high-frequency and high-amplitude (20 kHz, 100g) sensors, located within ~100m of the blast, but at two different bench levels, were used to monitor a production blasting in a quarry. The production blast consisted of double-decked explosive loads in 155 mm (6 in) diameter holes, with an inter-deck delay of 42 ms, and each deck consisting of 130 kg (285 lb) of emulsionexplosive. The blasting vibration data obtained at the two bench levels were critically analyzed, and thevibration results served as input to the numerical model consisting of a single rock block with a 45 degree persistent joint plane but with specified strength properties, significantly different from that of the intact rock. The model was able to characterise progressive accumulation of damage in the form of micro-cracks along the joint surface as a function of the vibration load from successive explosive decks. The results showed that such a numerical model can serve as a very good diagnostic and predictive tool, when backed up by careful vibration monitoring and further supported by detailed slope monitoring."

Jan 1, 2017

By Jacob Miller, Phillip Mulligan

"Measuring the blast pressure associated with an explosion suspended above the ground (Free Air Burst)is a common research objective in Explosive Engineering. Theoretically, the shockwave from a Free Air Burst (FAB) configuration expands radially and the shockwave is assumed to have a smooth (uniform) shock front. The way in which the FAB explosive charge is suspended, packed, and the charge geometry can affect the shockwave expansion. These factors can generate a non-uniform shock front. As the scaled distance between the pressure sensor and the FAB increases, the shockwave expansion averagesnon-uniformities into a uniform shock front, at which point the FAB suspension system becomes less critical than when the scaled distance is “close-in” (Z <3)."

Jan 1, 2017

By Ricardo González Dumuihual, Carlos Scherpenisse

A monitoring campaign to record dynamic pressures generated by detonation of a single blasthole was implemented at Barrick Gold´s Pueblo Viejo Open Pit mine (PVDC), located in the Dominican Republic . Pressure amplitudes beyond the dynamic compressive strength of the electronic detonator´s capsules have the potential to damage these electronic devices, generating misfires along with all the associated risks and entailed safety implications. In most instances, misfires generated from high dynamic pressures are a direct consequence of drilling deviations resulting in blasthole distances smaller than originally designed.

Feb 1, 2020

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 David Siskind, Mark Stagg

Vibrations from Dade County (Miami area) quarry blasting and structure responses were measured at 11 locations between February and April, 2000, and 10 homes were inspected to analyze the characteristics of their cracking and other damages. These results were combined with information collected by the County and other studies done in south Florida for a blasting impact assessment specific to this area. In addition over 40 quarry blasts in the nine-week monitoring period, about 800 measurements were available from previous monitoring in Dade and neighboring Broward counties. An overall worst-case analyses based on the highest individual amplitudes suggested that vibrations in some areas could have been as high as 0.35 in/s. While amplitudes in the study period were below this value, they were found to be relatively high for the distances and charge sizes. Attenuation with distance is less in Dade County than found elsewhere with quarries having to use scaled distances several times higher than similar sites in the north. Consequently, the vibrations are perceptible at very large distances.

Jan 1, 2001

By Hung Tran, Qian Liu, Patrick Andrieux, Dave Counter

Blast damage in open stope mining has been an important concern in controlling ore dilution. Severe damage to the surrounding rock mass can result in the caving of waste rock and/or backfill materials, as well as general instability of the ground. The blast damage study conducted at Kidd Mining Division in 1995 was aimed at measuring the damage zone around blastholes and at identifying other factors which influence the damage. An approach and methodology developed mainly by Blastronics, together with Noranda under a project with the Mining Research Directorate, was adopted for this project. The principle was to combine vibration measurement results with borehole camera observations to derive the blast damage criteria at the specific site. The Holmberg-Persson Equation was used for the regression of near-field vibration data. The damage criteria was examined with both borehole camera observation results and rock elastic and mechanical properties. Details of this methodology, including instrumentation, are reviewed in this paper and an implementation case study of the blast damage evaluation is presented.

Jan 1, 1998

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 John L. Floyd

The use of explosive energy to displace overburden or waste material can provide substantial savings to operations which normally rely on mechanical means for material removal. To optimize the available explosive energy, it is important to quantify the rock's response to the type of explosive and explosive accessories used. During a blast, rock breakage and movement occur so rapidly that the naked eye cannot detect the details of the fragmentation process. A relatively high speed motion picture camera (500 frames per second) can provide the extended time base needed to analyze in detail the site-specific rock response to the explosive detonation. The data of importance to blast casting that can be quantified from these films includes initial face movement, trajectory of rock, and differential face velocities of the material shot. In addition, the ground swell velocities, stemming confinement, and stemming ejection velocity can be determined. The performance of explosive products and delay element accuracy can also be ascertained. The use of high speed motion picture photography and analysis can reduce the number of field trials necessary to maximize explosive performance and increase the benefit provided by blast casting, and in turn, lower production costs. This paper will discuss the methods used for data accumulation and analysis. In addition, three field studies conducted at three separate mining operations will be presented.

Jan 1, 1988

By David Leidel, James Stuart

The 50 ohm resistorized electric detonator is commonly used in the oilfield for initiation of wireline conveyed perforating guns and other downhole explosive tools. This type of electric detonator provides some degree of safety above that of the conventional one ohm electric detonator, since a higher current level is required to initiate the device. In order to obtain the necessary data to develop safe distance tables from RF sources for the 50 ohm electric detonator, laboratory tests were conducted to determine the detonator’s “no-fire” current, AC impedance, and its susceptibility to ESD. The results were surprising as two types of failure modes were observed. The “no-fire’ current levels determined from Langlie “One-Shot” Test Methods were determined for the devices tested providing values for the 0.999 probability “no-fire” power level at a 95% confidence level. This data will serve as the basis for sets of safe distance tables from RF sources that will appear in the forthcoming edition of the Institute of Makers of Explosives Safety Library Publication 20, “Safety Guide for the Prevention of Radio Frequency Radiation Hazards in the Use of Commercial Electric Detonators, (Blasting Caps)”.

Jan 1, 2010

By Adrian Moore, Alan Richards, Andrew Brodbeck

Structural blast vibration limits should be based on the strength of the structure, the stress induced by blasting, and a responsible factor of safety. In this paper a methodology that uses direct strain measurements to determine the stress induced by blasting is described

Feb 1, 2020

By Raúl Mondaca Aracena

Mantoverde mine requires increasing its production level to double. EMTS - Projects performs far and near field vibration studies to make changes to the D&B design and sequences, in order to equalize the current vibration levels, applying massive blasting in its process.

Feb 1, 2020

By Dave Weymer

Falling timber in BC has always been a hazardous job. Huge, often rotting trees and steep, rugged terrain combine to create difficult and dangerous conditions. Death and injury rates are among the highest of any occupation in North America. In BC, the men that head out, saw in hand, are called fallers.

Jan 1, 2013

By Jorge Alvarez

In a large-scale open-pit mining operation, continuous efforts are made to control damage to the slope walls. An essential tool in this effort is determining the PPVc (critical peak particle velocity) in areas of interest. By knowing this value and generating criteria, drilling and blasting designs can be established to reduce vibrations that affect wall construction. It is crucial to understand that the PPVc changes as different mining phases develop, especially due to exploitation on the benches, which leads to vertical inherited damage. Therefore, it is imperative to regularly update the PPVc based on field tests that provide accurate data. With this information, vibration damage criteria can be established, and drilling and blasting techniques can be designed to minimize the impact on the remaining rock mass. This document presents a methodology for generating scaled criteria that best represent the reality of the rock mass.

Jan 21, 2025

By Rakesh Raghavaraju, Bibhu Mohanty

The paper analyzes the decay of shock pressure as a function of distance from the borehole, and its implication on shock-induced fracture properties of the target rock as the first step in predicting fracture and fragmentation behaviour in a well-characterized rock.

Feb 1, 2020

By Rakesh Raghavaraju, Bibhu Mohanty

Prediction of fracture and fragmentation characteristics of a rock mass subjected to dynamic loads, such as in blasting remains a major technical challenge. The present study is aimed at characterizing the shock transmission properties in controlled experiments in small scale in a well-characterized granitic rock, under varying borehole coupling conditions. Single blast-hole tests were conducted in a granitic rock sample of 145 mm (5.7 inches) diameter and height. The boreholes (in two diameters: 6.4 mm (1/4 inch) or 9.5 mm (3/8 inch)) were loaded with detonating cord of varying charge weight (5.3 g/m or 25 grains/ft to 31.8 g/m or 150 grains/ft of PETN). The effect of explosion gas penetration into the target rock was eliminated by inserting a thin-walled copper liner along the borehole wall. Embedded carbon composite resisters were employed at varying distances from the borehole to measure transmitted shock pressure for two coupling conditions (i.e. air and water) at distances of 1x to 9x the borehole diameter. The paper analyzes the decay of shock pressure as a function of distance from the borehole, and its implication on shock-induced fracture properties of the target rock as the first step in predicting fracture and fragmentation behaviour in a well-characterized rock.

By Jonathan D. Aubertin

The unique nature of rock salt blasting is compared to traditional hard rock practices. Rock salt geomechanical nature is discussed in the context of rock blasting events. A cratering mechanism prevalent in soft rocks is presented and exemplified through a series of single hole blast tests performed in salt deposits.

Feb 1, 2020