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By Pharis E. Williams

The ability of voids, microballoons, and even solids to sensitize explosives has been known and used for many years. This phenomenon has generally been studied and reported under the terminology of "hot spots" because of the increase in local pressure and temperature when a shock wave encounters such sensitizers. A method for treating this phenomenon in detonation theory or in a detonation model has been studied for almost the same length of time. Perhaps because of the complexity and non-linearity of the void, or microballoon collapse, several of these studies have used the expediency of including additional terms in the burn rate law to account for the influence of hot spots. The detonation model proposed here considers the sensitization due to discontinuities in the shock impedance to be a mechanical phenomenon to be accounted for in the mechanical equations governing the detonation and not in the burn rate law. While this is not a new contention, the method for handling this non-linear phenomenon within the proposed model is new. The model also includes a method which accounts for the manufacturing variables of emulsion matrix cell size, microballoon size and type, as well as energetic additives.

Jan 1, 1992

By Gour Sen, Peter Bellairs

Blasting conducted in rock temperatures greater than or equal to 55°C (13 1 “F) and / or in rock containing sulphide minerals and their oxidation products can result in unplanned detonations. Blasting practices involving the identification of the affected areas together with the use of speciality explosive products and rigorous attention to quality control are required to safely blast in these types of environments. Sulphide dust explosions occur in some underground mines where the primary blast results in a secondary explosion of the sulphide rock dust which propagates some distance from the primary blast area. This phenomena results in considerable damage and the generation of significant volumes of toxic gasses delaying re-entry to the affected area of the mine thereby increasing both costs and safety concerns. The exothermic reaction between ammonium nitrate based explosives and rock types containing partially oxidised sulphides have resulted in numerous high risk blasting incidents. These reactions can occur at ambient temperatures and often result in premature detonations / deflagrations causing a great deal of consternation at the affected minesite resulting in lost production and considerable expenditure to solve the problem. Rock masses at elevated temperatures can also result in unplanned detonations unless appropriate precautions are taken. This paper discusses each of these hazards, cites some case studies and details appropriate generic safe and efficient blasting techniques for each of the above applications using appropriately formulated explosive products.

Jan 1, 2000

By Sergio Segovia Parra, Victor Hernan Sheen Uriol

This contribution of the concept of mass blasting both closing and production allows breaking paradigms, to limit the number of tons to thunder. The areas of geotechnical different mining large mining companies worldwide and especially from the National Copper Corporation (CODELCO, Chile) has been declining volumes closing blasting and production, with the misconception to protect the end walls of the pit, before any geotechnical risks caused by various types of faults; especially the circular faults. A blasting of small tonnage can do more damage to a wall when it is not properly sequenced, leading to the coupling of the wave train and therefore the exponential damage in/s (peak particle velocity, PPV) on the wall of the Tagus. Blasting closing mass production and contribute technically and operationally in the dynamics of the following operations: loading, hauling, crushing, processing and preparation of the final product; eliminating delays to return to thunder small volumes where one must stop all mine equipment, incurring high costs and especially losing valuable time in the continuity of the following unit activities.

Jan 1, 2015

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 Anders Lagerkvist, Agne Rustan, Tommy Edeskar

Landfills containing house hold waste produces methane gas during its decomposition. This gas can be recovered and used for heating purposes or as fuel for vehicles. Gas drainage pipes are installed in the landfill and connected to a central suction point. Methane gas is produced over several years until the slots in the drainage pipes are clogged by black mud. And the bottom of the vertical drainage pipe are filled with mud and water. The hypothesis tested in this paper is if blasting in the drainage pipes could activate the production and flow of methane. In the first part of the paper we have studied what maximum linear charge concentration could be used in different size of PE-pipes place vertical on surface and surrounded by air. The results show that the maximum linear charge concentration for single blasts varied between 5-10 g/m, depending on the diameter of the pipe (90, 100 and 160 mm). Maximum charge concentration for the repeated blast varied between 2-5 g/m. In the second part of the paper we study what maximum linear charge concentration could be used in situ for full scale blasting tests in a special prepared test area which later on was dug out after the blastings. Up to 40 g/m could be used without damaging the top of the 160 mm diameter pipes. The increase in methane flow was so low so it could not be measured c4.5 m3/h. The conclusion therefore is that the stimulation of methane flow by explosives is not enough.

Jan 1, 2000

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

By Lina Lopez, Jose Sanchidrian, Jean Du Mouza, Essaieb Hamdi

This paper evaluates the actual energy delivered by the explosives used in the fragmentation of rock during blasting vs. the available theoretical explosive energy. The evaluation of the fragmentation energy of the blast is first done. Fragmentation by blasting can be seen as a process in which creation of new surfaces within the rock mass is made by generation of new cracks or extension of pre-existing ones. From this idea, the fragmentation blast efficiency can be assessed as the fraction of the available explosive energy used for creation of new surfaces. The evaluation of new cracks area created by the blast is based on the SIMBLOC methodology and the corresponding fragmentation energy is then obtained by the Griffith theory. Secondly, the amount of energy delivered down to a certain pressure or volume along the detonation product expansion process, given by the useful work, is calculated. This is done by first determining the CJ state of the reacted explosive and subsequently performing an adiabatic expansion calculation of the detonation products from that state. W-Detcom code has been used for the calculations using the BKW equation of state with the Sandia parameter set. The fragmentation energy and the useful work are calculated for blasts performed in two mines in Spain. Multiple regression is applied to the results in order to give an assessment of the better description of the explosive energy .

Jan 1, 2002

By James H. Redyke

In August, 1980, while finishing construction of the new stack, one of the flues mysteriously collapsed, killing three people and injuring several others. Several months later a British international steeple-jack company was hired to demolish the remaining portion and make a detailed inspection of the balance of the chimney. During this contract almost one hundred core samples were taken from all parts of the structure including the 32-inch thick base. As the result of these tests and the investigation, the Power Company decided to demolish the complete structure. Because of the critical time element, the decision was made to use explosives in the removal of the structure. To give you some perspective as to the size and dimension of the stack, it was 900 feet tall, 80 feet in diameter at the base, and 70 feet in diameter at the top. The two remaining flues were 25 feet in diameter and extended 30 feet beyond the top slab of the chimney. The outside of the structure was referred to as a wind shield. The lower 120 feet were 32 inches thick and the remaining 780 feet were 12 inches thick. The decision was made to prepare and shoot the chimney at the 120-foot elevation because the debris from the collapsed flue was confined in the base section and could not be easily removed. After extensive and costly engineering, we determined it was necessary to construct steel columns to bear on the lower 120-foot section, which would act as a hinge and guide during the dropping of the structure.

Jan 1, 1982

By Dale Preece

In the late 1970’s and early 1980’s substantial resources were devoted to research focused on producing oil from the vast oil shale reserves in the western United States. Since the oil is solidified in the pore space of the shale, extracting it in production level quantities presented monumental technical challenges. Major advances were made in the methods used to extract oil from the shale in large quantities. Extraction methods evolved to culminate in the underground in-situ retorting process. In-situ retorting relied on explosive blasting of the shale to fragment the rock and induce sufficient porosity and permeability for a burn front to propagate through the oil shale. That burn front consumes some of the oil and liberates a substantial portion of it (~30%) for collection and further processing. Oil shale retorting is a blasting intensive process where the entire retort is rubblized in one very large, delay timed blast. Retort 7 in Western Colorado consumed 540,857 lb of slurry explosive to rubblized 348,940 tons of oil shale. Current rock blasting fragmentation predictive capabilities have evolved substantially since these retorts were designed and tested. It is the purpose of this study to simulate the explosively induced fragmentation of oil shale using state-of-the-art computer codes and material models and to infer retort design implications for future development.

Jan 1, 2007

By L D. Lawrence, R S. Day, Gordon Coleman

Commercial emulsion explosives are typically characterized by their relatively high detonation velocities due to the intimacy of oxidizer and fuel and to their sensitization with glass microballoons. However, numerous blasting operations in softer, more porous rock formations are better fragmented with slower shooting explosives. Although mixtures of emulsions with large amounts of ANFO (60-80%) can considerably reduce the high velocities, little water resistance is achieved with low levels of emulsion blended with ANFO. "Water proof" blends containing typically 50 percent of emulsion become quite costly due to escalating powder factors in ANFO patterns. Blends of sensitized emulsions with 20-30 percent ANFO retain the high velocity characteristics of the emulsions as well as increased densities which can also adversely affect blasting results in softer rock formations. The introduction of a reliable and predictable on-site gassing process for sensitization and density control of repumpable emulsions, with or without added ANFO, offers the end user the option of supplying a final product more suited to his blasting needs. The capability to widely vary final product loading densities and consequently product detonation rates better tailors the final explosive to different rock characteristics. The beneficial advantages of this system in softer rock formations have been well documented. Overall comparison between these variable density products with typical repump emulsions containing solid density control will be reviewed. Besides the obvious cost advantages and safety advantages of these systems the end user is provided more definitive control of his blasting operation.

Jan 1, 1990

By John Kemeny

There are many methods used to predict blast fragmentation, including empirical and numerical models, field trials, and experience from ongoing blasting. All of these methods require an accurate measurement or prediction of the rock mass properties. These properties include the characteristics of the rock fractures, including fracture density, friction angle, orientation, length, roughness, fill, etc. They also include the hardness of the intact rock, water content, and other parameters. This paper describes three new technologies that can be used to automatically or semi-automatically obtain rock mass properties: digital image processing, 3D laserscanners, and drill monitoring systems. Each of these technologies is described, including the current state of the art, current limitations, and their future potential. Each of these three technologies has advantages and disadvantages. These new technologies, however, have the potential for providing accurate rock mass information in an automated and real time fashion. This information can then form the basis for a new generation of real-time, database driven blast fragmentation models.

Jan 1, 2004

By Mark S. Stagg, David E. Siskind

The Bureau of Mines arranged to have a wood-frame test house built in the pat of an advancing surface coal nine so it could investigate the effects of repeated blasting on a residential house. Structural fatigue and damage were assessed over a 2-yr period. The house was subjected to vibrations from 587 production blasts with particle velocities that varied from 0.10 to 6.94 in/s. Later, the entire house was mechanically shaken to produce fatigue cracking. Failure strain characteristics of construction materials were evaluated as a basis for comparing strains induced by blasting and shaker loading to those induced by weather and household activities. Cosmetic or hairline cracks 0.01 to 0.10 mm wide occurred during construction of the house and also during periods when no blasts were detonated. The formation of cosmetic cracks increased from 0.3 to 1.0 cracks per week when ground motions exceeded 1.0 in/s. Human activity and changes in temperature and humidity caused strains in walls that were equivalent to those produced by ground motions up to 1.2 in/s. When the entire structure was mechanically shaken, the first wallboard tape joint crack appeared after 56,000 cycles, the equivalent of 28 yr of shaking by blast-generated ground motions of 0.5 in/s twice a day.

Jan 1, 1985

By Josephine Bones, Robb Larson, Daniel Miler

Avalanches are commonly mitigated through the use of explosives at ski resorts and above transportation corridors. Surprisingly, very little research has been conducted on snowpack response to explosive inputs, and efforts to model this response have been limited. The purpose of this ongoing research project is to ascertain an understanding of the dynamic snowpack response in relation to explosive size and height above the snowpack, coupled with snow conditions, to enhance avalanche control. A system of sensors and computer-controlled data acquisition components has been created to record the movement of snow resulting from the charge detonation. The system records acceleration vertically and radially within the snowpack at two distances from the point of detonation as well as blast air pressure at one location during explosive events. The data at two locations allows inferences to be made about the transmittance and attenuation of shock waves through the snowpack radially as well as vertically. The data shows that raising charges above the surface results in increased snowpack dynamic response when compared to surface detonations. Applying power function regression to accelerations for individual charge elevations, it was determined that both radial and vertical rates of attenuation were not dependant on charge elevation. Additionally, raising the charge also resulted in increased dynamic response at depth within the snowpack

Jan 1, 2012

By Mario Karfakis, G. Langlois

Well stimulation is the process by which any production well, whether for production (extraction), storage (injection) or deep interaction (remediation, monitoring, etc) can be made or stimulated to flow at higher levels. This stimulation is driven by active methods to increase the permeability in the near-well environment and create a larger zone of communication between a well and the reservoir it services. Well stimulation is a crucial aspect of well completion and reservoir engineering and is a subject of careful pre-drilling planning. In many modern industrial endeavors the effectiveness of well stimulation is often critical to economic viability. Because of the broad impact of well engineering on several large industries (petroleum and natural gas extraction and storage, geothermal power, groundwater monitoring, extraction and management, environmental remediation, mining and minerals extraction, etc.) changes in the state of the art in well engineering and well stimulation can affect the capabilities of very diverse and disparate industries. This paper is an effort to communicate the status and effectiveness of current practice and technology in well stimulation. The intention being that effective communication of progress can spur innovation in industries that require well stimulation but are removed from immediate communication of technological or practical improvement.

Jan 1, 2009

By Scott G. Giltner, Paul N. Worsey

During the short duration of an explosive blast, many events occur which are too quick to be detected or observed in detail with the naked eye or by normal photographic techniques. Through the use of "hightech", high speed video, many of these events can be observed, instantly played back and recorded for later use. The use of a Spin Physics SP 2000 Motion Analysis System at a blast casting operation is presented. The variable range of recording speeds offered by the SP 2000 allowed it to be used for examination of different areas of blasts. At its maximum full frame rate of 2000 frames per second the SP 2000 can easily pick up the flame front as it travels down a nonel tube and the flash from the surface delays as they fire. The system was used for a variety of tasks including, but not limited to,the determination of delay accuracy to within 0.5 ms, the velocity and trajectory of the faces during blasts, and pinpointing geological problem areas. The effectiveness of the system as used on site is discussed along with detailed method of set up, recording, playback and data processing. Other details including site specific environmental and lighting problems are also covered.

Jan 1, 1986

By Greg Mclellan, Mark Johnson, John Pepper

Several large quarrying projects recently occurred in Miramar, Florida. These were closely monitored by the Seismologist of Record and Broward County in accordance with County and City regulations. In addition to this monitoring, the City of Miramar employed The Pepper Engineering Group, Inc., to provide additional spot check monitoring and to review the records of the other two parties on a routine basis. Broward County ordinances require that the location of each shot and the nearest protected structure be recorded along with seismograph measurement of each shot at the nearest protected structure. The positions of the blasts and nearest protected structures were determined using GPS. The blast vibrations were measured by seismograph. Over 600 shots, which are the subject of this study, were measured both by the County, the Seismologist and, on many occasions, The Pepper Engineering Group. As such, the vibration data was constantly cross-checked for consistency. The blasting contractor also provided blast designs for each shot. In this paper, the measured vibrations are plotted in terms of Resultant Peak Particle Velocity (RPPV) versus Scaled Distance (SD) on logarithmic scales. The data curves are fitted with least squares and upper 95% and 99% prediction limits are provided. Equations are presented to predict the RPPV based on scaled distance and prediction level using power fits. Statistical information concerning the derivation of the various limits is presented. The raw data used to develop this paper, along with other information concerning the shots, will be posted on the Internet for use by other researchers.

Jan 1, 2000

By Raimo Vuolio

"Over the past 30 years, the Nordic countries have developed similar practices for estimating damage caused by rock blasting vibrations. However, over the last few years the risk of damage has sometimes been estimated by using international values, which have created unnecessary costs, since they are too conservative. This paper gives a proposal for Finnish blast vibration standards and a calculation model for the extent of the zones for building inspection, risk analysis, and vibration measurements. The international conclusion is that particle velocity is the best descriptor for limiting damage potential for structures. Over 900 000 vibration data recordings from 52971 blasts were collected for this paper during 1970-1989. They show that the most practical description is the vertical component of the peak particle velocity. As rock is a nonhomogeneous medium, it is hard to predict the need and scope of risk analyses, building inspection, and vibration measurements. As a large number of blasts were monitored for the recording of the peak particle velocity in several locations in Finland, and the data combined, it is possible to establish safe scaled distances for the calculation of the need and scope of risk analyses, building inspections, and vibration measurements."

Jan 1, 1991

By Changa-Ha Ryu, Hae-Moon Choi, Sang-Don Lee

The rock mass to be excavated is classified using data obtained from the initial site investigation, and the design of excavation and support is then made based on the rock class. Rock classification provides an empirical design with guidelines for tunnel support compatible with rock mass quality and the method of excavation. Although most clients provide standard patterns corresponding to each rock class, the patterns of drilling and blasting have only been used in estimating the excavation cost and not used in the construction stage. The purpose of the study presented in this paper is to establish a standard blast pattern to yield optimum blasting performance along with an attempt to reduce a difference between design and construction. A series of test blasts were carried out at two tunneling sites of Central Inland Highway crossing the country. Long hole blasting was tested in rock mass whose RMR value is over 60. The blasting results were evaluated by measuring degree of fragmentation, advance rate, muckpile distribution, overbreak, etc. Based on the results of test blast, several patterns were proposed for a twolane highway tunnel.

Jan 1, 2005

By R L. Calhoun

A paper on High Pressure Air must start with the industry accepted definition of High Pressure Air and, for the reader who is unfamiliar with High Pressure Air systems, include basic information on which type of Drilling Rigs can benefit from the use of High Pressure Air. The operation of a modern Downhole Drill must also be reviewed.

Jan 1, 1976