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By Andrew P. Ritter, James W. Reil, Douglas A. Anderson, Stephen R. Winzer

We have developed a method for predicting and controlling ground vibration from blasting using a rigorous scientific approach. The method is based upon the superposition of seismic waveforms generated by a single-hole free-face shot, recorded at seismographs deployed in an array that includes environmentally sensitlve locations. Waveforms generated by single-hole shots are shown to be reproducible. The waveforms for each of the sites are used to construct synthetic seismograms for delayed shots based upon linear superposition. A computer code systematically constructs the seismograms for the delayed shots, with incremental delays between holes of 1, 2, or 3 milliseconds (ms). A Fourier amplitude specs-rum is calculated for each synthetic seismogram and the spectra are plotted on a map in delay-frequency space, i.e., each row of the map represents the Fourier spectrum for a blast with a particular delay interval. For single-row shots, the delay between holes in a row is used; for multiple-row shots, the delay between holes In a row is kept constant and the delay between rows is incremented. Predicted vibration varies strongly as a function of delay and h

Jan 1, 1985

By Robert Martin, Brian W. Stump

As part of a series of seismic experiments designed to improve the understanding of the impact of mining blasts on verifying a Comprehensive Test Ban Treaty, a sixteen station network of three-component seismic sensors were deployed around a large cast shot in the Black Thunder Mine. The seismic stations were placed, where possible, at a range of 2.5 kilometers with a constant inter-station spacing of 22.5 degrees. All of the data were recorded with the seismometers oriented such that the radial component pointed to the middle point of the approximately 2 kilometer long shot. High quality data were recorded at each station. Data were scaled to a range of 2.5 kilometers and the sum of the absolute value of the vertical, radial, and transverse channels computed. These observations were used to construct radiation patterns of the seismic energy propagating from the cast shot. It is obvious that cast shots do not radiate seismic energy isotropically. Most of the vertical motion occurs behind the highwall while radial and transverse components of motion are enhanced in directions parallel to the highwall.

Jan 1, 1997

By Jennifer P. Harrell, D. Joseph Hagerty

In many areas of the eastern United States, especially in the Midwest, past mining activities have left large and extensive underground openings. Now, renewed mining is occurring in such areas in surface pits. Also, construction blasting often occurs in rock over such old openings. Within the last fifteen years, some attention has been given to the interaction between surface blasting and underground cavities; concern has been expressed about the possible changes in vibrations transmitted through areas underlain by old mine workings (Siskind, Stachura and Nutting 1987). Previous studies also had indicated that underground openings could influence transmission of surface mine blast vibrations (see, for example, Woodward-Clyde Consultants 1977). The principal concern is that underground openings under surface blasting may intensify low-frequency vibrations. If such intensification occurs, use of available equations to predict peak particle velocities and to design blasting patterns and select blasting parameters could lead to possibly damaging ground shaking.

Jan 1, 2002

By Goran Cirkovic, Zvonimir Ester, Josip Krsnik

During the reconstruction of the motorway Zagreb-Krapina three reinforced concrete bridges were demolished, for their width was not adequate for the new motorway. Demolition of the three bridges was carried out by blasting as duration of the traffic cut on the motorway and the railway was limited to maximally 4 hours. During that period of time the demolished bridges had to be removed. Therefore, very tiny granulation was requested suitable for loading and not endangering the surrounding structures. Before each of three main blasting, trial blasting were carried out including the seismic measurements registering the seismic effects. The nearest residential building was at the distance of less than 30 m from the place of blasting. Additional difficulty was the fact that by each of the three bridges there is a new bridge, with minimal distance between the old and the new bridge being 30 cm. As each of the bridges is of different construction and of various thickness, particular blasting technique has been prepared for each one of the bridges.

Jan 1, 1997

By Lon Santis, David Leidel, John Tatom, Meredith Hardwick

This paper describes the development and methodology of the Institute of Makers of Explosives’ Safety Analysis for Risk (IMESAFR), a risk analysis software program for commercial explosives operations. IME is a nonprofit safety and security association devoted to the safe and secure manufacture, transportation, storage, and use or disposal of commercial explosives in the US and Canada since 1913. The software methodology’s basis is the U.S. Department of Defense Risk Based Explosives Safety Criteria Team’s Safety Assessment for Explosives Risk (SAFER) software. A diverse group of industry and government experts contributed to modifications to SAFER that reflect commercial operations. IMESAFR is intended to supplement the American Table of Distances (ATD) and offer standardized methods of managing risk from a wide variety of commercial explosives operations where the ATD does not apply. The modifications made to SAFER primarily involved the addition of commercial activities and potential explosives sites (PES). A review of commercial explosives accidents and operations over the last 20 years served as the basis for establishing probability of event values. An industry survey of commercial PES types in the U.S. and Canada was conducted to identify and address critical differences in commercial structures as compared to the military structures in SAFER. The paper concludes with discussion of the potential uses for quantitative risk analysis (QRA) and a description of other explosion effects software

Jan 1, 2007

By Daniel Roy, Chris J. Preston, Ron J. Elliott

This paper discusses the use of pressure transducers in water filled boreholes in conjunction with surface mounted geophones to gather field data for in-situ dynamic rock properties determinations. A high speed collector is used to capture the data in the field. The calculated P and S wave velocities and rock density measurements are used as input into the Blastcalc program where the values of Young`s Modulus and Poissons Ratio are calculated. The rock properties information is used along with geological structural data and explosives properties in a 3-D blast modelling program to calculate predicted fragmentation distribution and other blast performance criteria based on the proposed blast design.

Jan 1, 1996

By Corry Goumans

The job location is at Bear Lake Hydro Project located north of the town of Sechelt, British Columbia, Canada

Jan 1, 2013

By Tom Hale

Developers and blasters are faced with increasing public demand and regulatory restrictions to maintain the lowest possible levels of noise and vibration from blasting operations in populated urban areas. Pyrotechnic products have proven to be a low noise, low vibration alternative to conventional blasting for close-in rock excavation and concrete demolition applications. Pyrotechnic breaking charges often yield 1/10th the vibration and noise compared to traditional explosives, and have been demonstrated to increase public confidence and decreased damage potential where they have replaced explosives, thus allowing new opportunities for work and greater job profitability. This paper presents a practical approach to utilizing pyrotechnic products in various applications including trenching, mass excavation, demolition, and dimension stone production, providing methodology for pattern design, vibration probability and loading calculations. Field research data is reviewed and compared to conventional explosives.

Jan 1, 2008

By Virgil J. Stachura, Calvin L. Cumerlato

The Bureau of Mines conducted a series of tests to develop a blasting method that would reduce overbreak and rockfall hazards at a limestone quarry in northeastern Wisconsin. Reductions in overbreak were achieved by shortening the main explosive column and reducing the explosive load in shortened stemming zones in shotholes which were to form the highwalls. Two blasthole diameters, 3 and 4 inches, were used with 7 by 7 foot and 9 by 12 foot burdens and spacings respectively. ANFO, Comsol 300, or PowerAN were used in the body of the shots and Gelmax or 40 pct extra dynamite cartridges were used in the reduced load zones. Smoother highwalls were visually apparent, however further analysis by seismic refraction techniques were performed as an aid to studying overbreak within the rock mass.

Jan 1, 1989

By A. S. Tawadrous

The stress field around a detonating charge in a borehole was calculated using AUTODYN for a variety of in-situ stress conditions. Calculations were conducted for zero in-situ stress, hydrostatic conditions at 100MPa, uniaxial stress conditions of 100MPa, and bi-axial state of stress with amplitudes of 200MPa and 100MPa along the axes. Two different explosives, ANFO and emulsion, were used for the calculations. It was shown that in-situ stress fields had an effect on the tensile and compressional damage zones around the blasthole, calculated on the basis of the maximum amplitude of the stress pulses in the rock after the detonation of the explosive in the blasthole. The extent of compressional damage increased around the borehole, whereas, the extent of the tensile damage decreased. The damage zones are of elliptical nature with their axes parallel to the direction of the principal stresses. The difference between the major and minor axis of the elliptical damage was not very significant in the case of the compressional damage; however it was significant in the case of the tensile damage.

Jan 1, 2007

By O E. Jr Crenwelge

Recently promulgated regulations governing blast induced ground vibrations in the mining industry contain a frequency criterion as one option for verifying compliance. This criterion is based upon an oversimplified method which assigns the entire peak particle velocity amplitude to one frequency. Depending upon the nature of the vibration time history, it is possible that this frequency may not even be one of the predominant frequencies of the signal. In addition, the criterion does not specifically define the data analysis approach to be used by the industry for obtaining either the amplitudes or the frequencies of the vibration components. And because personnel in this industry generally have little understanding of vibration phenomena, a number of different approaches are currently being used for satisfying the criterion. This paper presents a method for obtaining both the Fourier amplitude-frequency spectrum and the integrated predominant amplitude-frequency components for the vibration record. The method is both physically and mathematically correct and is in common use in a number of other industries. Therefore, it should be of help to regulators, blasters, and consultants charged with developing, enforcing, or implementing ground vibration criteria.

Jan 1, 1988

By Daniel B. Conn, John L. Floyd

PhotoSeis™ is a blast analysis method that combines the advanced technologies of high speed motion picture photography and digital seismology. When fracturing rock with the use of explosive energy, the human eye cannot detect the details of the process due to its short duration. An extended time base is required to accurately quantify the response of the rock mass to the detonation process. This time base is provided by the use of high speed motion picture cameras. The control of ground vibrations and airblast is an important consideration when developing efficient blast designs. High vibration and airblast levels can be an indication of improper design, inaccurate detonators, or adverse geology. Since many factors can elevate airblast and ground vibration, a greater understanding of the site specific response to the blast design is needed that is beyond the scope of simple seismographic recordings. By synchronizing the photographic record provided by the high speed motion picture cameras with the airblast and vibration information from digital seismological monitoring, the Photoseis™ technique can be of great assistance in controlling airblast and vibration and optimizing the use of explosive energy for rock fragmentation.

Jan 1, 1990

By Lina Lopez, Jose Sanchidrian, Manuel Lopez, Pablo Segarra

Previous work in which rock properties and blasting parameters (geometry, charging and timing) were reported together with truck filling times, is taken as a starting point for a thorough analysis of the influence of the former on the mucking velocity. The experimental set was composed by 11 blasts made in an open pit mine. Non-parametric, distribution-free statistics is applied. The mucking rates (in bank cubic meters per unit of bucket volume and per hour) appear to be clearly dependent on the explosive energy and powder factor, both magnitudes combined as energetic powder factor (energy per unit of rock volume). The mucking rate is a non-monotonic function of such factor in the range of the blasts analyzed. The determination of the function is optimum when the fraction of the explosive below grade is not considered and when the explosive energy is qualified as that delivered at a partial detonation regime. Different types of loaders seem appropriate for different energy levels. At low levels both front loaders and rope shovels obtain small productivities without a statistically significant difference in their performance. At high energy levels, front loaders qualify higher than rope shovels. Mucking velocities can be equally small at low energy powder factors and at high ones if rope shovels are involved.

Jan 1, 2008

By Elias Poulakidas, Marco Arellano

The impact of a higher copper price on the open pit metal mining sector has derived in a faster and safer way in which the mining operation of broken and mineralised material is carried out. In this regard, a good control of bench stability allows a lesser extra removal of material and so more safety to get the planned ore. The stability is ensured through an efficient drilling and blasting, applying the current technology and available know-how. An efficient use of energy through low-density explosives which are the most adequate for the existing solid rock releasing energy in a smoother way through a deterministic detonation sequence which is the application experience presented here. This application experience has two main technological factors; the adequate type of explosive for the kind of rock, in terms of velocity of propagation (Vp) together with the use of a determined detonation sequence and the appropriate designs, which allow to reduce the level of damage to the walls and to maintain a minor backbreaking through quantification with vibration modelling carried out at the near field. The reductions achieved were 30% lower in peak particle velocity.

Jan 1, 2008

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 Chuck Kliche, Bill Clements

This paper relates some of the experiences, good and bad, of blasting adjacent to residences of the primary author during his 15+ years of field blasting in the Northern Great Plains region. During this highly-rewarding blasting career, the author has become aware of two major issues in residential blasting: 1) What we call “Risk/Reward Ratio.”Some questions that must be asked by the blaster prior to taking on any blasting job include: - Can we eliminate or minimize the risk? - Is the reward worth the risk? - Do I have a measure of “nervous confidence” about the shot? 2) Public Relations. Two key elements to public relations are: - Notification - Education All the education in the world to the adjacent populous of what’s happening, of blasting in general, or of what to expect from the blasting does little good without notification. Good public relations is a key to controlling the cost of liability in a litigious society.

Jan 1, 2009

By Thomas A. Gelormino, Ulrich La Fosse

"Deep blasting was used to densify foundation soils for a large manufacturing facility inChicopee,Massachusetts. A 360,000 square foot building, whose construction began inthe summer of 1990, is founded on alluvial deposits up to 90 feet in depth. These deposits are comprised of saturated very loose to loose fine to medium grained sands with traces of silt and gravel. During the building foundation design it was found that to withstand earthquake forces without soil liquefaction, it would be necessary to improve portions of the alluvial deposits by densification. The zone in need of densification extended from approximate depths of 20 to 50 feet. Several conventional densification methods, including vibrocompaction and deep dynamic compaction, were evaluated along with deep blasting. Detonation of 1-3/4 inch diameter charges of 65 percent gelatin dynamite (Atlas Power Primer) installed inside 2-inch diameter PVC casings to a depth of up to 40 feet, was used to achieve the desired densification. This method was selected over others due to its lower cost and decreased construction time. Although used in New England once in1940 for a dam and once in 1960 for a transmission line tower to improve foundation soils, there is no precedent found in the literature for densification by blasting to improve liquefiable soils below a proposed building. Details of a test program and the production blasting, including vibration data are presented. Pre-and post-blasting data conclusely shows an increase in the density of the sand deposit after blasting."

Jan 1, 1991

By Quian Liu

Since the establishment of the CANMET Experimental Mine in Val d'Or, Quebec in 1991, research activities in rock fragmentation have been carried out not only in the underground laboratory but also in production mines in the north-west Quebec region. Among the instruments available for rock fragmentation, the Kodak EktaPro 1000 Motion Analyzer (also called the high speed video system) has been one of the most useful tools for monitoring blasts in both underground and open pit. This system is capable of recording events at rates from 50 to 12,000 frames per second (fps). The buffer memory has a capacity of storing 2050 images. To use this system in the underground, a steel box was made with a bullet-proof glass in the front to protect the camera. The processing and recording equipment are placed in an aluminum case which can be located about 30 m away from the camera via an extension cable. For each blast monitored, high frequency geophones and accelerometers were used to monitor ground vibrations and give a timing reference of the explosive detonations to correlate with the observation of the captured images.

Jan 1, 1994

By Jason Baird, Seokbin Lim

Run up is a factor in Linear Shaped Charge (LSC) cutting for which an account must be made. It occurs on the initiation segment of the charge, and the cutting performance during this period is significantly lower. Previous investigations by the UMR Explosives Group observed that similar effects occur not only with LSCs but a wide range of other explosives applications, including explosive-driven flux-compression generators. Prior to this investigation, it was believed that the main contributing factors to run up were from the combined effects of explosive run up (detonation pressure), lack of confinement at the free, initiation end of the charge, and penetrator transition from segmented pieces to a long-rod penetrator blade. As an initial step to understanding the mechanics of LSC run up, a series of investigations was performed in which the testing series was divided into several sub-categories (explosive detonation pressure run up, lack of confinement and long-rod penetrator concept) in order to reveal the effect of each on the run up. Predominantly, commercially manufactured LSCs were used for the investigation, and the entire testing was completed by the UMR Explosives Group.

Jan 1, 2006

By W. J. Birch, R. Farnfield

All shock-tube based initiation systems have a time lag relating to the propagation velocity of the shock-tube itself. This paper examines the exploitation of this inherent time lag to achieve delay blasting with accuracies approaching that achievable with electronic systems albeit over a much shorter delay range. The system employed consists of a combination of standard shock-tube, plain detonators and various shock-tube branching components. The accuracy of the complete system depends on the scatter in delay time induced by each component. In order to quantify this scatter a series of trials were undertaken to determine the variability for each component. These trials are described along with a detail statistical summary of the data recorded.

Jan 1, 2009