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By E. Contestabile, B. von Rosen

On August 5th, 1998, a tractor-trailer carrying approximately 18,000 kg of blasting explosives, struck a rock face on the side of the road near the town of Walden, Ontario. Eye-witness accounts of the incident state that there was an intense fire for approximately 30 minutes before the detonation. The detonation caused severe damage to the tractor-trailer, shifted the pavement and caused blast damage to the rock face. A rock fragment was recovered almost 2.5 km from ground zero and a 70 kg piece of an axle assembly was recovered over 1 km from the site. Windows were cracked at distances of almost 3 km.

Jan 1, 2001

By Lewis L. Oriard

Some two million cubic yards of sandstone and orthoquartzite were blasted and excavated at Upper Stillwater Dam, located high in the Uinta Mountains in northern Utah. The material was processed to produce concrete aggregate for the construction of the largest roller compacted concrete (RCC) dam ever constructed, and one of just a few in existence. The dam cross-section is shown in Figure 1. The aggregate was sound rock produced from required dam foundation excavation and from a quarry located about 1/2 mile from the dam site. Representative compressive strengths of the sandstones and quartzites were in the range of 20,000 to 30,000 psi.

Jan 1, 1993

By Kenneth Medearis

There is considerable evidence that more rational damage criteria need to be generated with regard to low-rise structures subjected to blasting vibrations. There is not sufficient basis for specifying a maximum ground particle velocity damage criterion such as 2 inches/second. A peak ground velocity guideline does not currently take into account a number of significant parameters, including the predominant frequencies of the ground motion excitation and the structure being excited. Although a number of states have adopted, or are adopting, maximum particle velocity criteria, such criteria have been ruled inadequate in certain legal decisions affecting blasting operations. The development of more rational damage criteria is thus of significant importance.

Jan 1, 1978

By Benjamin Cebrián, María Gil, David Flores

In many occasions during the Mining operation life, blasting engineers find different and controversial results of fragmentation, dilution or wall control for the same geotechnical domain and blast design (pattern and explosive charge). Most of the times, the difference between same blast designs is not measured, not controlled. Once a blast designed is defined, the most important part of the process after that is the implementation of every step of the blast on site. Almost nobody is measuring it, controlling it, but just controlling implementation is possible to relate blast design with results in a consistent way, to optimize the full process of D&B. Controlling implementation not only per event but also to check and change trends and decision-making is paramount for optimization and saving millions of extra costs every year. The lack of resources and the hardness to manage all the info created every day in a blast make this process very tough and difficult to maintain in long term. The use of new technologies on site and software that allows a best, more consistent and continuous control of blast implementation have been proved to be the key for optimizations and cost saving. This document shows the evolution of drilling and blast digitization process, savings and trends in a mine, using new technologies that creates business opportunities and general improvement of D&B process.

By S. M. Geerts, M. T. Wild

In this paper the performance effects of various shaped charge liner designs will be discussed. Several different charges will be tested and the liner design will be reviewed based on the performance in testing. The first type of shaped charge to be tested is a conical charge with dual confinement. For the purpose of this paper, dual confinement is a shaped charge with two liners but containing one explosive charge. Several charges with different dual confinement designs will be tested. Variations in configuration include charges with similar angle and similar diameter. The second type is a double conical shaped charge configuration. A double shaped charge will be considered to be two complete charges formed into a single cone. The goal of the project is to determine if any of the designs increase the efficiency and/or effectiveness of the shaped charge in comparison to the standard conical shaped charge. A standard conical charge will be detonated against a witness plate to get a standard depth of penetration or a baseline. All charges will have a seven cone diameter standoff, allowing the data to be compared to the control charge. Computer modeling will be used to predict the results of the testing that will be conducted. The actual results will be compared to the computer simulation for validation.

Jan 1, 2010

By Angel Rafael Fernandez, Yahya Khader Al-Harbi, Benjamin Cebrian Romo, Antonio Morato Medina

The kingdom of Saudi Arabia has set the goal to diversify their economy from oil into different fields including mining. As the vast Arabian Peninsula is explored, orebodies of Aluminium, Copper, Gold and Phosphates are found in high grades and tonnages. Hard rock is present in most of the projects and require high quality blasting in regard to ore dilution, wall control and fragmentation. Maaden Gold has currently 4 open pit mining operations 1 new opening and 2 underground. More projects are coming online in the next few months and years. A new generation of mining engineers need to apply drilling and blasting techniques that compete with modern and efficient open pit and underground mines.

Feb 6, 2023

By J. Silva, T. Worsey

The Worsey-Silva equation determines the optimal row timing for the smallest fragmentation and allows fragmentation models to be adjusted due to row timing. The equation utilizes the concept of dynamic confinement to determine when the best time to fire the next row or sequence series would be if the smallest fragmentation is desired. Full-scale testing was conducted at an aggregate quarry in Ontario to support the theory and equation. The full-scale testing comprised six (6) blasts, two (2) different contractors, and three (3) different sequences. The test parameters were kept consistent, besides changing the timing between sequential charges to explore the timing sequence’s influences on fragmentation. From this research, the theory of dynamic confinement relating to row timing was discovered, and the equation to determine the optimal timing for the smallest fragmentation was derived. An equation to adjust fragmentation based on row timing was derived from the full-scale testing and literature review. The Worsey-Silva equation can be used with other fragmentation models as it takes the fragmentation results from the other models and adjusts them based on the row timing used. The paper explains the theory behind the equation, the research supporting the findings, and the developed Worsey-Silva equation for row timing

Jan 1, 2024

By Ankit Jha, Sudarshan Rajagopal, Purushotham Tukkaraja

Geologic structures are one of the crucial parameters in blast design. Structural geology and rock properties influence drilling patterns, blast layout, and initiation systems. A comprehensive understanding of structural characteristics is essential to achieve the desired blasting objectives. This paper aims to identify geologic features in a bench using images obtained from the drone. Images obtained from mine site are annotated for geological features such as faults and joints. Semantic segmentation of images is achieved using an encoder and decoder structure available in the machine-learning pipeline. The encoder consists of initial convolution and pooling layers to capture essential features of the geology and rock patterns from two-dimensional RGB images. Batch normalization is used to put all the features on the same scale. These images are then inputted as training data for the machine-learning algorithm. Machine learning model is trained on sub-section of interest to achieve reasonable accuracy. Initially, 1000 best annotations were used to train the model and additional samples were added later to achieve more accuracy and avoid iteration of machine learning model in wrong convergence. After the model achieves reasonable accuracy, it is used to recognize geological features on new data. Geological features identified on the new data can be used by the blasting crew in blast design and keeps the geological maps updated that can help the geotechnical team.

By Jan Mehren, Arild Neby

Underwater Tunnel Piercing or Lake Tap, often also called the Norwegian Method, will in many projects be an important part of the hydro electric development scheme. The very last blasting round in the Lake Dorothy Lake Tap Tunnel, which penetrated into the lake at a depth of 120 ft (36 m), was such a key step in constructing the Lake Dorothy Hydroelectric Project. A lake tap project is multidisciplinary. Besides the pure blasting and construction technique aspect, engineering geological and geometric considerations that aim to optimize the tunnel alignment making a lake tap possible at minimized risk are of significant importance. Output data from numerical model analysis of the hydrodynamics resulting from the blasting is vital for the final adjustments to the geometrical layout. The planning of monitoring systems for the surveillance of hydrodynamic impact on valves and pipes as well as control with water levels and air pressures prior to and during the blasting, are all additional crucial elements in the design. More than 600 lake taps have been successfully performed in Norway since the 1890`s. The technique, which deserves to be called well proven, has been applied mostly in the hydropower sector but over the last 20 years also for shore approaches in the oil and gas industry. The demand for this technique seems to be ever more growing.

Jan 1, 2009

By W. Birch

The traditional concept of scaled-distance modelling for predicting blast induced ground vibration holds many drawbacks, not least of which is the major effect data scatter imparts on confidence determination. An investigation by the Department of Mining and Mineral Engineering, The University of Leeds, England has resulted in the development of simple but effective method of improving prediction capacity through the reduction of effective error by incorporating individual location response into a scaled-distance model. The work is the product of an l&month blast-monitoring campaign at a limestone quarry situated in North Yorkshire, England. The data, when presented in the form of a scaled-distance model, indicates a typical scenario where a good overall correlation becomes marred by the extent of data scatter. Examination of the individual monitoring locations however indicates that the response of the individual location is an important factor in the explanation of the large residuals. The novel approach thathas been developed incorporates a series of locational site factors which when incorporated into a scaled distance model reduces the effective error and therefore improves prediction capacity. The approach is based on using a standard computer package “spread sheet” on the understanding that these are commonly available on all quarry or home computers. This approach has been validated by comparison with a more rigorous statistics method.

Jan 1, 2001

By Paulo Couciero

Since explosives are the source of all energy used for rock blast fragmentation and heave, multidimensional effects in the detonation driving zone become essential to better describe the detonation process. In order to use the explosive as an energy source-information for more realist blasting performance simulations, a simple and effective modelling strategy is desirable. Facing this challenge, an engineering approach to two-dimensional unconfined non-ideal detonation is proposed. Based on the elliptical construction of the shock locus, the model combines the axial cylindrical stick Q1D solution with some additional limiting conditions to determine the sonic edge of the charge. For a given set of rate law parameters and velocity of detonation, a complete axial solution is firstly computed through the Q1D model. From this solution, a vital relationship between the axial shock curvature with the shock shape parameters can be stablished. Once this relationship is found, the problem simply reduces in finding the shock shape parameters subject to the sonic edge condition. As a result of this calculation, the corresponding charge diameter can be found. Consequently, the proposed model can map the diametereffect curve by relating the unconfined velocity of detonation with its corresponding diameter. Finally, because of its low computation cost, the proposed engineering approach can be also used for characterizing the rate law parameters by fitting to data from unconfined detonation experiments

Jan 1, 2019

According to the Directive 93/15/EEC, given on 5th of April 1993, all the commercial explosives placed on the market and transfered in European Union and EFTA countries have to be certified and contain the CE-marking. Before the products can be awarded by the CE-marking they have to fulfil the Essential Safety Requirements (ESR) of Appendix 1 of the Directive. From the beginning of last year the commercial explosives could not have been be sold in Europian Union countries without the CE-marking. The legitimacy of the Directive 93/15/EEC encompasses High Explosives, Detonating Cords, Safety Fuses, Gun Propellants and Detonators. At the moment in Europe, there are seven Notified Bodies (NB) working in the field of commercial explosives. They are in Spain (LOM), Germany (BAM), France (INERES), England (HSL), Netherlands (TNO-PML), Sweden (SP) and in Finland (PvTT). The Swedish SP has qualifications only for the detonators and the Finnish PvTT for High explosives, Detonating cords, Safety Fuses and Gun Propellants, but not for the detonators. The role of the NB is to work as a third independent body between the client and the manufacturer testing, studying and certifying explosives by the commission of the manufacturer. The Notified Bodies are operating independently competing the clients, the explosives manufactures.

Jan 1, 2004

By A K. Raina, P B. Chourdhury

Flyrock is the unwanted throw of rock fragments to excessive distances in opencast blasting. The incidence is relative in nature incorporating the distance of objects of concern like structures within and outside the mine, equipment within the mine & near the blast and persons within and off the mine. Several attempts to predict and defi ne fl yrock made worldwide could not address the problem since the phenomenon is not a regular feature in blasting. This probabilistic nature of fl yrock allows for risk calculation. CIMFR, India developed a Factor of Safety based risk criterion (10, 14) for evaluation of throw/ fl yrock in opencast mines that incorporates all the above in terms of distance and allowable limit of throw – which in turn determines the risk. The criterion provides the blaster a tool for mathematical evaluation of fl yrock risk in terms of a Factor of Safety and threat ratio (defi ned for the 1st time), thereby enhancing confidence when blasting. The method is easy to use and has been applied to several mines in India and the results are signifi cant. This paper details the evolution of the concept and its application in three limestone mines of India and the results obtained. The application of the method for defi ning a fl exible danger zone is also discussed.

Jan 1, 2008

By Matthew Graham, Tapan Goswami, Geoff Brent

In dragline coal mining operations, throw blasting is used for the controlled placement of overburden to maximise coal exposure rates or to minimise overburden removal costs. This may necessitate sacrificing thin coal seams, generally less than one metre in thickness, which are often present in proximity to the main coal seam. This represents not only a significant loss of potential revenue and profit but also a waste of a valuable energy resource.

Jan 1, 2010

By Lon Santis

Although unproven, it is suspected that there have been eleven locations since 1988 where explosive generated carbon monoxide (CO) gas moved through the earth and accumulated in nearby underground enclosed spaces. This paper summarizes the incidents, which involved about 30 suspected or medically verified CO poisonings and 1 fatality. Ten incidents occurred in residences and one occurred in a manhole. Although practically nothing is known about the mechanism behind the suspected gas migration, review of the incidents and available information indicates there are certain warning signs and a successful remediation technique available. In each case, overburden heavily confined the explosive in the blasts, preventing release of explosive-generated gases to the atmosphere. All the blasts were in residential areas, and none were excavated immediately. Where the distance from the blast was recorded, 5 of the blasts were within 20 to 50 feet (ft) (6 to 15 meters [m]) of the underground enclosed spaces, 3 were 100 to 150 ft (30 to 46 m) away, and 1 was 400 to 500 ft (120 to 150 m) away. Investigators often identified suspected pathways from the blast site into the underground enclosed spaces. One technique appeared successful at quickly correcting an existing condition. This technique involved applying negative pressure to the earth and removing the CO from the ground surrounding the underground enclosed space.

Jan 1, 2001

By W. L. Saunders

RBH Note: In the early days of drill & blast tunneling the jobs utilized large crews of drillers and muckers. Advance per round was limited (typically around four feet) but two rounds per 8-hour shift were expected, around the clock. The scene after a shot must have been chaos, with the muckers expected to quickly make space for the drill setup. Makes one wonder how much time was allowed for the smoke and fumes to clear. Note the headgear of the tunnelers.

Jan 1, 2011

By Neal Lee

Reduced relief horizontally means an increase in energy expended vertically into the rock surrounding the stemming column, and potentially through the stemming column. The vast majority of holes in any surface blasting operation are afforded two horizontal relief faces at the moment of firing, whether by existing relief faces in front of and to one side, or previously blasted hole(s) in front of and to one side of the holes in question. When the energy expended in any hole on the blast pattern has less than two Horizontal Relief Planes or faces (referred to moving forward here as “HRPs”) available to it at the moment of firing, a higher percentage of the available energy is directed vertically. In the analysis of recorded videos by the author, one will note the fact that stemming ejection/flyrock is observed to a much greater degree from the center of almost all patterns when they are timed to “pull out of the middle” (“box cut" timed patterns). This is because the first hole to fire in each row has only one Horizontal Relief Plane, which significantly decreases horizontal avenue for energy release for these holes. This of course results in an increase in the amount of energy expended vertically. This paper proposes a novel methodology to modify the stemming to better use the explosives energy of each hole, while controlling side effects such as flyrock and airblast.

Feb 6, 2023

By M. K. Ameen, R. El-Hacha

This paper presents the analytical results obtained from numerical simulation of reinforced concrete slabs strengthened with various FRP systems and subjected to blast loading. A three-dimensional finite element model using AUTODYN software was used to predict the overall behavior of the slabs. The numerical results were validated by comparing with experimental results from a program carried out to investigate the efficiency of different strengthening systems on the blast resistance improvement of small-scale reinforced concrete (RC) slabs. The experimental program consisted of testing nine RC slabs strengthened with three different externally bonded (EB) FRP systems attached at the bottom side of the slabs and one RC slab tested without strengthening for comparison purposes. The EB FRP strengthening systems investigated included two layers of Carbon Fiber Reinforced Polymer (CFRP) sheets, two layers of Glass Fiber Reinforced Polymer (GFRP) sheets, and one layer of Glass-Fiber Resin Polymer (GRP) sheet. Different epoxy resin, patching mortars and impregnating epoxy adhesives were used for the slab surface preparation and FRP system application of the strengthening layers. The aim was to evaluate the residual strength of the test specimens after exposure to blast loads. The blast loading parameters were evaluated for each test using AUTODYN simulation and compared with the computer program CONWEP. All specimens were subjected to same spherical TNT charge weight and stand-off distance with the respect to the slab top surface. Extensive comparison is made between the experimental results and the AUTODYN simulations for the control unstrengthened slab and the strengthened slabs including time history records of the bottom steel strain and mid-span acceleration and the peak dynamic deflection of the slabs.

Jan 1, 2010

By Jerome H. Stofleth

In June of 1998, the DeBruce Grain Elevator was devastated by an accidental explosion caused by the unintentional ignition of grain dust. The DeBruce grain elevator was the largest ‘single head-house’ grain elevator in the nation. It was comprised of 450 cylindrical grain silos, 30 feet in diameter by 120 feet tall, with a centrally located headhouse. Immediately after the explosion, rescue operations were started for seven missing workers. The Federal Emergency Management Agency (FEMA) had taken over operations of the site by day two. On day three FEMA contacted the Washington DC office of the Department of Energy for explosive expertise, who in turn contacted explosives experts at Sandia National Laboratories (SNL) and Los Alamos National Laboratories (LANL). FEMA was looking for guidance in making the decision to downgrade their operation from a rescue to a recovery operation. Based on some chemical equilibrium calculations, and basic explosive engineering techniques, the SNL/LANL team was able to provide the necessary input to allow the decision to be made for the operational downgrade. At this point, only one worker remained un-recovered.

Jan 1, 2004

By C. K. McKenzie

Presents outline of flyrock model and a field procedure to validate predictions of maximum projection distance. Field results are presented from 13 field tests with two different hole diameters.

Feb 1, 2020