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By Andrea Francioso, Roberto Folchi

In order to comply with the latest European Highway Standards, the highway Salerno - Reggio Calabria, in southern Italy, had do be widened and upgraded to reduce its vulnerability to earthquakes. Reinforced concrete viaducts, no longer needed for the new road, had to be demolished. Many bridges still to be used for the highway required refurbishment due to 50 years of wind, frost and salt corrosion. This re-furbishment and new construction had to be carried out simultaneously. To keep the highway open dur-ing the renewal process, all traffic was directed to one side of the road. Demolition was conducted ex-tremely close to operational roadways and viaducts, as close as only 2 cm (0.8 in). Care had to be taken to ensure that the stresses (vibration levels), resulting from the demolished pylons and decks hitting the ground, were below the no-damage thresholds for the nearby acceptors (structures receiving the vibra-tion stresses). These structures included bridges, houses and buried pipelines (water, oil and gas). In some cases, care also had to be taken to preserve the existing pylons supporting decks that were being demolished; since the same pylons were going to be used for the new viaducts (bridges). New continu-ous decks in weathering steel replaced the old reinforced concrete decks.

Jan 1, 2013

By Tom Goforth, Rongmao Zhou

The interest of seismologists in mining explosions has increased substantially with the construction of the International Monitoring System (IMS). The IMS supports the Comprehensive Nuclear Test-Ban Treaty by providing global data coverage from seismic, hydro acoustic, infrasonic, and radionuclide sensors that will detect a host of natural and man-made events at regional (<2000 km) distances. Ideally, the recorded data can be used to identify those events that have explosive characteristics and therefore might be clandestine nuclear tests. The regional observations assure the detection of mining explosions, and these must be properly identified to avoid false alarms of the monitoring system. Cooperation with the mining industry, including documentation of the firing programs, provides critical information necessary to characterize the seismograms.

Jan 1, 2006

By Derek Morris, Vito Saccheri

In the monitoring of seismic exploration (whether by explosive or vibratory energy sources), the intensity of shaking at neighboring structures can now be measured quite accurately and comprehensively with portable equipment. However, the interpretation of the results is open to considerable debate and mis-interpretation. One conventional approach is simply to compare the maximum measured peak particle velocity (PPV) with a permissible standard – usually 0.5 inches/sec (1.3 cm/sec) because this is the value generally referred to in the U.S. Bureau of Mines standard. This can be very conservative, both for surface structures, and especially for buried structures like pipes, for which absolute reliance on PPV obscures the true complexity of field problems. Quite apart from the fact that the full Bureau of Mines standard is actually a reasonably complex function of frequency (for the simple reason that in differing parts of the frequency spectrum, damage may be displacement or acceleration controlled), the effects of spatial direction and orientation are often ignored.

Jan 1, 2009

By Daniel Johansson, Markus Danielsson, Håkan Schunnesson

In sublevel caving, blasted material flows gravitationally into the drawpoint from above in a periodical manner. This type of flow behavior entails muck pile conditions that are variable along the course of extraction. The effect of this variability on the LHD (Load-Haul-Dump) operation in terms of loading efficiency and ability to undermine the blasted ring is not fully understood as of today. This paper presents results from a field test in LKABs Malmberget mine in Sweden, where the influence of fragmentation on the loading operation has been studied in detail. Drawpoint filming was conducted for extraction of two rings equivalent of roughly 10000 metric tons (~9842 long tons) of material each. The analysis includes fragmentation measurements, muck pile classification, and general estimations in terms of loadability. Further, an evaluation of LHD machines from two different manufacturers was conducted to identify and highlight differences. The results show that fragmentation, muck pile compactness, and flow characteristics are all interdependent. Flow disturbances and the subsequent loading of compacted fine material in the back of the ring have been identified as the main reason for occurring problems and prolonged digging times. However, the ability to sufficiently undermine the blasted ring has been identified to primarily depend on digging depth which is only observed to be high during flow disturbances. An absence of flow disturbances seem to promote high loading efficiency but simultaneously limit the maximum digging depth. A mid-range particle size distribution with a low amount of fines has proven beneficial for overall loading efficiency. The various LHDs employed showed significant variations in terms of ability to handle difficult loading situations (e.g. compactness, boulders, etc.).

Jan 1, 2018

By Braden T. Lusk, Brett C. Jackson

The Kentucky Commissioner of the Department for Natural Resources, accompanied by a motion for accident prevention from Kentucky’s Explosive Industry and other associated fields, have requested for an Industry Flyrock Prevention Task Force to be formed by an Explosive Industry panel. This task force is led by Dr. Braden Lusk at the University of Kentucky. The mission of this task force is not only to identify the base causes of flyrock incidents based on analyzing historical data from events in the past, but also to track the advancement of flyrock elimination into the future.

Jan 1, 2014

By Hae-Moon Choi, Sang-Don Lee, Hee Soon Shin, Choon Sunwo, Chang-Ha Ryu, Hyun-Koo Lee

Building tunnels means dealing with what rock is encountered. Relocation of the site of the underground structure is rarely possible. Tunneling engineers and miners have to cope with the quality of the rock mass as it is. Different tunneling philosophies and different rock classification methods have been developed in various countries. Most of the rock classification methods are based on the response of the rock mass to the excavation. Tunnel support requirements could be assessed analytically, supplemented by rock mass classification predictions, and verified by measurements during construction. Rock mass classifications on their own should only be used for preliminary, planning purposes and not for final tunnel support. Design of blast pattern in tunneling projects in Korea is also for the most part prepared according to the general rock classification methods such as RMR or Q. It, however, does not take into account the blast performance, and as a consequence, produce poor blasting results. In this paper, the methods of general rock classification and blast design for tunnel excavation in Korea are reviewed, and efforts to develop a new classification method, reflecting the blasting performance, are presented. Copyright ©

Jan 1, 2004

By Tapan Goswami

A column of stemming material keeps explosion gases at high pressure for longer times in a blasthole. In general, use of appropriate stemming enables the achievement of the desired level of fragmentation and looseness of muckpiles, as well as the reduction of airblast and fly rock. The ejection resistance of a stemming column varies with the type of stemming material employed. In an effort to optimise stemming at Mt Owen Mine in the Hunter Valley, Australia, a trial was conducted to assess the efficiency of two types of stemming materials. Mt Owen mine relies on through seam blasting and stemming quality is important in this challenging blasting environment. Each type of stemming was trialed in different section of a blast. The blast was designed using Orica’s SurveyPlus@, LoadPlus@ and ShotPlus@ software. Measurement was done using high speed filming of the blast and then post blast information was obtained from analysis of the film. Data analysis included determination of the ejection velocities and percentage swell. Digging rates were measured from excavator production rates. Despite the presence of rounded surfaces and finer particle sizes, River Pebble stemming material showed superior ejection resistance. It also appeared to perform as well as more angular and expensive Crushed Stone, a finished quarry product, based on excavator productivity and heave. It was recommended that future blasts at the mine be stemmed with the River Pebble stemming material.

Jan 1, 2000

By C. T. Aimone-Martin, V. L. Rosenhaim

Blasting near residential areas has become frequent in many locations throughout Brazil. It was deemed necessary by the authors to have a better understanding of how typical Brazilian structures respond to blast vibrations and compare this response to environmental forces that naturally act on these structures. Typical Brazilian structures are built with clay bricks and cement-mortar. Foundations comprise concrete beam perimeter walls and thin concrete slabs. Roofs are very heavy as they are construction with clay tiles over a wood frame. Typically, walls are cover with cement grout, spackling (or plastered) and then painted. Interior walls are made of clay bricks and mortar to divide in rooms inside the structures.

Jan 1, 2014

By Steven Richardson, E A. Cameron, Reza "Ray" Jambakhsh

This paper outlines the design and implementation of a method to use Long hole Carbide drilling to blast an "Upper Blind Slot Raise" in the range of 12m (40 ft).

Jan 1, 1992

By Scott Scovira, Ruilin Yang

This paper presents a non-waveform blast vibration model for the near-fi eld. The model uses the concept of a dominant charge augmented by other contributing charges estimated using a scaled time window. The model accounts for the effect of broken ground created by earlier fi ring holes, amplitude attenuation, effects of signal broadening with travel distance from frequency attenuation, as well as asynchronous propagation of different wave types due to the wave velocity difference, the delay time effect, and non-linear superposition of near-fi eld vibration. The model uses an effective distance defi ned from the broken ground screening, and determines a dominant charge contributing to the PPV at a monitoring station. Then the model uses a time window for each individual charge to determine if it contributes to the PPV. The time window has a variable width to model the effects of the signal broadening with travel distance. For modeling the signal broadening, a generalized rock quality factor Qd is proposed. The time window includes a weighting function that diminishes the contribution for charges fi ring further from the dominant charge and this accounts for contribution arising from the timing difference between a contributing charge and the dominant charge. The model uses a non-linear charge weight superposition technique that scales the charge weights within the time window to the same distance of the dominant charge and superimposes the scaled charge weight. The case study demonstrates that the model provides useful predictions for near-fi eld blast vibrations.

Jan 1, 2008

By Billy Rosseau, Mike Cammack, Richard O’Meara, Gustavo Azpilcueta

During the summer of 2014, the U.S. Army Corps of Engineers (USACE) sought proposals to vastly improve and expand the small boat harbor in Valdez, Alaska. It would be a multi-year project, and construction was scheduled to begin in the spring of 2015. One aspect of the project was the construction of a 3,100 feet (1000 m) rubble-mound breakwater to protect a mooring basin. An estimated 208,500 tons (190,000 t) of rock, ranging in size from 160 to 3500 lbs (73 – 1600 kg), were needed to build the breakwater. The Glacier Point Quarry was selected as the rock source due to its proximity to the project and the quality of the rock meeting all of the USACE rock standards.

Jan 1, 2017

By Kurt B. Oakes, Brian M. Fortelka

Unimin Corporation operates an underground Silica Sand mine at Guion, AR located in North Central Arkansas. The Silica Sand deposit at Guion is part of the St. Peter Sandstone Formation, which is overlain by a competent dolomitic limestone from the Joachim formation, acting as the roof directly above. Both the St. Peter and the Joachirn Formations are of Middle Ordovician age.

Jan 1, 1999

By Calvin Konya, Steven S. Spagna, Ed Smith

During Summer 2001, the U.S Army Corps of Engineers awarded a contract to the construction firm of Bush and Burchett of Allen, Kentucky, for the purpose of developing a 13 acre redevelopment site by removing approximately 2.5 million cubic yards of rock (fig. 1). The Redevelopment Site will be the future home for a large portion of the City of Grundy, Virginia. Additional work items include the construction and relocation of 3,000 feet of the Norfolk Southern railroad bed, the placement of 95,000 cubic yards of fill and the placement of 16,000 cubic yards of stone slope protection along the Levisa Fork River. Bush and Burchett received a notice to proceed with construction in July 2001. Currently, the contract is near completion. Current activities include: hauling of material from the Redevelopment Site to the disposal area; placing fill material on the Redevelopment Site, and placing Stone Slope Protection (SSP) along the Levisa Fork river. Approximately one year into the construction highly weathered rock, degraded to near soil- like condition, was encountered in the upstream portion of the excavation. Over one-third of the original cut slope was adjusted and the blasting specifications had to be amended to accommodate for the material that was encountered in this area.

Jan 1, 2005

By David E. Siskind

Increased mineral consumption and environmental concern have caused much interest in potential damage and annoyance from ground vibration and airblast produced by production blasting in surface mines and quarries. Ground vibrations are traditionally blamed for "shaking the house to its foundations," but often the airblast is responsible, particularly when the distances from mine to structure are large. Simultaneous measurements of ground vibrations, structure vibrations, and indoor and outdoor noise from blasting are being used by the Bureau of Mines to determine the relative importance of the ground and airborne blast energy in shaking the structure and making windows, dishes, etc., rattle.

Jan 1, 1977

By Thomas Kovalchuk, Kenneth Eltschlager, William Shuss

In April of 2000, two adults and their newborn infant, were poisoned by carbon monoxide in their home and received medical treatment at a Pennsylvania hospital. Carboxyhemoglobin levels were; child - 3 1%, father - 28Oh, and mother - 17%. Initially the furnace was blamed but after further review, blasting at a nearby coal mine was determined to be the source. All other sources of carbon monoxide were ruled out. The blasting was about 400 feet from the house. The conditions that led to the migration of gas include: the blasts were highly confined, the geologic structure contained fractures that served as conduits for the carbon monoxide to reach a hand-dug well outside the house, and the well was atmospherically connected to the basement floor drains.

Jan 1, 2001

By Seung-Kyu Baek, Chang-Ha Ryu, Yang-Kyun Kim

Safety concern is one of the most important parameters in the design of building demolition by explosive blasting. Accidents were sometimes reported due to the flying chips of fragmented materials in building demolition work in urban area. Laboratory experiments were performed to investigate the failure behavior of reinforced concrete pillars under blast loading and to develop an effective protection technique. Sixteen reinforced concrete pillars were constructed with two sizes: 450×450×1800 mm and 600×300×1800 mm. The failure behavior and the flying chip velocities were observed by means of a high-speed camera. Protection scheme was designed and the effects of several protection materials were investigated. Two kinds of non-woven fabrics and wire net were tested as protection materials. The results showed that reinforcing bar was one of the important factors to determine specific charges, and that mesh size of wire net and tied-up method affected the protection of flying chips. Control of gas effects is also a key to the control of flying chips. It was recommended to use both wire net and nonwoven fabrics as primary and secondary protection materials. Such protection scheme was successfully applied to the explosive demolition of 16 and 17-story apartment buildings.

Jan 1, 2002

By Ruilin Yang

Based on large amounts of field data, this paper evaluates the validity of the above equations. During the evaluation, the different selections of the frequency in the equations were examined with field data. It is found that when they are used to estimate the vector sum values the above equations could result in large deviations from the values obtained directly from the field measurements or the waveform integration. The simple equations may be used to make rough estimations for single components of blast vibration provided that appropriate safety factors are taken into account. For single component vibration, the principal frequency (from ‘zero-crossing’) seems more effective to describe the blast vibration than the dominant frequency (fron FFT) for vibration peak value estimation using the simple equations.

Jan 1, 2012

By Florian Bauer

The Fording River mine in British Columbia produces hard coking coal in an open pit operation. Coal seams are exposed by blasting overburden and digging blasted muck with rope shovels. The drilling and blasting process presents a considerable cost factor to the operation. Reducing the amount of explosives needed therefore contributes considerably to costs saving initiatives. However, reducing the powder factor only makes sense if the subsequent loading processes by the shovels are not compromised in terms of productivity.

Jan 1, 2014

By John Cowin, Dan McCutchen

Cowin & Company has specialized in underground construction since 1924. This paper reviews the sinking of two shafts in the Alabama coal fields using bulk-loaded explosives. Each shaft is eighteen hundred feet deep, and their diameters were twenty feet and twenty-three feet. The first consideration in changing to a new explosives system was safety. Safety began with the explosive supplier training the miners in the use of the new system, from explanation of the pumping unit on the surface to hands-on training in the shaft. The considerations covered include establishing a thunderstorm exit plan, and reducing exposure time of the crew to explosives while loading. The system consisted of a specialized pumping unit and an advance emulsion product. Eliminating the need for nitroglycerin based explosives, and reducing sensitivity to mechanical shock were goals that were met. Performance in the shaft and ease of use meant morale of the miners using the system remained high and positive. Performance benefits discussed include reducing the number of holes in the round, and cutting explosives loading time in half. Damage to the ribs of the shaft was greatly reduced, making it safer to work near the ribs on succeeding rounds. Cleaning the bottom before drilling the next round also showed marked improvement. The economics of the system became very apparent when cycle time saved was allocated against fixed cost of sinking these shafts.

Jan 1, 2000

By Juan Pablo Guevara, Victor Munoz, Rob Bush, Gonzalo Marias

Cerro Negro Mine, property of Goldcorp Inc., is in the process of developing four separate underground access ramps for the exploitation of high grade, narrow vein gold deposits with vertical to sub-vertical dips. The Mariana Central, Mariana Norte, and San Marcos accesses are primarily in the development stages, while the Eureka access began production stope blasting in April of 2013. Mariana Central will also begin production in May or June of 2014.

Jan 1, 2015