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By Joshua Micah Hoffman, Lifeng Li, Jhon Silva-Castro

Since millisecond detonators were first introduced, at least two variables among others have been more closely considered when timing a mining blast; the accuracy and the precision of the initiation system. Unfortunately, those variables are often ignored when designing timing for mining blast. Despite the lack of consideration of the characteristics of the initiation system, in some situations, e.g., firing a blast hole with one deck and two detonators, changes in the blasting sequence can be the results of the overlapping between blasting charges. The consequences of such overlapping involve flyrock events, fragmentation and diggability problems, and other difficulties affecting the operation of the mine.

Jan 1, 2015

By John Eloranta

This paper is a case study showing the assembly of available rock property parameters for the purpose of blast design. Blast optimization now includes subsequent milling and requires a full knowledge of the rock mass. Individual blast holes should be designed using all available data. The parameters include: geologic layer from diamond drilling, shovel performance, crushing plant experience from that area, drill monitoring, magnetic susceptibility from a downhole probe, size analysis history from digital image analysis, compressive strength tests of problem areas and cross hole sonic testing. Bedding thickness observed from drill core appear to have a strong influence on fragmentation.

Jan 1, 1996

By A N: Zditovetsky Shishov, M G. Menzhulin

At present in a building industry demand for products from granite, gabbro and other rocks, steady to erosion, natural and chemical weathering, was essentially increased. It has caused the enlargement of exploitation of stone block deposits and necessity of creation of new technologies of hard stone cut.

Jan 1, 1996

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 R Mancini, G Borla

This paper analyses the first results of a part of an EEC research project ("Blasting control for underground mining"). This research that involves three universities (Paris, Torino and Leoben) has been carried out at the Eisenerz test mine in Austria. In the experimental campaign here reviewed, parallel holes rounds have been fired "decomposed", which means with enough delay between the explosions of the successive blastholes groups to allow for a separate evaluation of their effects on the rock. The seismic effects have been recorded by geophones placed at small distance from the blast, the aim being to find out correlations between the features of the seismogram and the good or poor performance of the single blastholes, or of the groups pertaining to the same delay. Indeed, the seismogram is the only safe and cheaply obtainable description of what happens during the blast. The seismogram should be transformed in a diagnostic tool in the round 'calibration' stage, and in a routine control device during excavation.

Jan 1, 1995

By Thomas L. Barkley

This paper describes an unusual design for a 12 foot diameter, 30 foot deep circular shaft shot in a close in urban environment less than 100 feet from occupied structures. It uses diagrams, video footage, and vibration results to describe a 3 deck, 17 hole burn round used to pull 17 feet in one lift.

Jan 1, 1994

By Malcolm Scoble

The estimation of digging, ripping and blasting requirements in advance of mine production is a difficult task. The characteristics of the superficials and rock mass govern the type and intensity of ground preparation required as a prelude to loading. The incentives for optimum planning of preparation are primarily economic but also relate to mining method and equipment selection, productivity and environmental impact.

Jan 1, 1985

By Erik C. Nygaard

ANFO is the most used industrial blasting agent in the world, and is often used as a reference for comparison of other explosives. It is known to work very well under dry conditions in large borehole diameters, whilst in small bore hole diameters the formation of high amounts of toxic fumes (CO, NO and NOz) can result. In underground blasting, problems can also occur with reduced visibility caused by uncombusted ammonium nitrate.

Jan 1, 1999

By Thomas L. Barkley, Michael A. Indihar

The new Cyprus Northshore Mining Co. has taken the previous blasting methods of Reserve Mining Co.'s mine in northern Minnesota and adapted them to a new competative Iron Ore Industry. Cyprus was challenged to develop new blasting methods to reduce costs and improve results over the previous mining operation. Many of the older procedures have been kept, but others have been changed in ways that bring the mine operation up to state of the art technology. In addition, unique ideas not previously tried in the North American Iron Ore Industry have been instituted. So far, this has reduced Cyprus's blasting costs by 70 percent.

Jan 1, 1991

Drilling through unconsolidated material I need to drill blastholes through a mix of consolidated and unconsolidated material. This material is hung up in an underground ore pass. The total length of the holes would be approximately 200 feet. We have attempted to drill through the material with conventional ITH drilling, but were unsuccessful. Does anyone have a suggestion? I am more than willing to bring in a contractor to do the job, if they have solid experience with this type of problem.

Jan 1, 2011

By Tristan Worsey, Nathan Rouse, Daykin Schnell

The authors were retained by a proposed underground metals mine operation to evaluate the potential blast vibration amplitudes that could be generated at surface structures above the proposed mine. Literature reviews of published blasting documentation gave little information, data, or models on surface blast vibrations produced by underground mines. At the client’s request, the authors contacted a number of underground mining operations to evaluate interest in sharing blast vibration data with the authors so that the authors could develop an underground-to-surface blast vibration regression equation. The authors worked with three underground metals mining operations to collect surface blast vibration data produced by heading blasts and stope blasts. The data included blast vibration amplitude values, seismograph records, blast design geometry, charge weights, and detonator delay and sequence designs. The total amount of information was used to produce a regression equation and summary dataset that could be used by the proposed underground mining operation to evaluate blast vibration amplitudes that will be generated on the surface. This work is published and presented so that operations with proposed underground mines or proposed underground mine extensions can use these equations to predict vibration amplitudes on the surface above the mine workings before any blasting occurs.

By D J. P Jordan, C V. B Cuningham, A J. Rorke, C G. Ladds, O L. Davey

"During the early stages of the boxcut mining at the Arthur Taylor Colliery, Open Cast Mine(ATCOM), problems were experienced with blasting results. Very large boulders andportions of completely unfragmented rock were commonly encountered. A full blastmonitoring programme was instigated by the mine and the explosive supplier to solve theproblems and to optimise future blasting operations at the mine."

Jan 1, 1993

By Dale Nies, David P. Childs

The open pit gold and silver mining operations in the State of Nevada have historically used simple row by row, echelon, or chevron delay patterns. Common practice has been to use detonating cord trunklines and either detonating cord downlines or nonelectric common in-hole delays in conjunction with surface delays. Several operations use a series of downhole nonelectric delays with an entire row loaded with the same delay to develop similar patterns.

Jan 1, 1991

By Pat McLaughlin, J R. (Dick) Daniels

Current practice in establishing quarries in remote areas with hilly or mountainous terrain tends to the use of airtracs (or similar pioneering units) drilling horizontal holes to establish a face, followed by bench development with light excavating equipment. The authors propose the use of a hybrid coyote blast design that incorporates long-round tunneling techniques. This method would, in effect, use down-the-hole (DTH) drills to advance the drift cut to the final depth, allowing longer and more rapid drift advances, and replace the cross-cut drifts with clusters of DTH holes to achieve the same explosives distribution.

Jan 1, 1995

By Michael Wieland

Delay blasting in underground coal generates shock waves and rifting forces that damage charges remaining in the blast pattern. Damaged charges detonate poorly, raise fume toxicity and reduce coal breakage. Such circumstances could be prevented by using explosives resistant to cross-hole interaction damage. The design of rugged explosives is fraught with contradictory requirements, but tradeoffs related to hard-particle size characteristics prove useful. Hard particles, related voids or trapped bubbles represent reaction nucleation centers which strongly influence the performance of coal mine explosives.

Jan 1, 1992

By B J. Kennedy, G W. Sengstock

During the last two decades, many advances have been made in open cut coal mining technology as new mines have come on stream and old mines have faced increasingly difficult mining and operational conditions. The need for close control of operating costs has necessitated consideration of modified excavation methods.

Jan 1, 1995

By D. Lee Petersen, Travis Davidsavor

The 2003-2004 expansion of a Duluth medical center required rock blasting adjacent to the existing structures, a Mn/DOT retaining wall and other urban structures. This case history describes the methods of a blast damage assessment, based on blast parameters, excavation locations, and critical vibration receptors (including surgical suites, a linear accelerator and a major retaining wall). The assessment concluded that blast vibrations could be controlled, by limiting charge weight, to eliminate impact at the critical receptors. Prior to construction, we conducted preconstruction surveys on structures susceptible to vibration damage. During construction, we reviewed submittals, observed test blasts, reviewed blasting logs and monitored blasting vibrations. Up to 13 seismographs were used simultaneously. Close coordination with medical center operations personnel was necessary to prevent impacts to critical medical procedures. Measured vibrations were clustered around the predicted values, and attenuated at the predicted rate. High-frequency blast induced ground vibrations induced low-frequency vibration of an adjacent MnDOT retaining wall. Medical center structures were observed to significantly attenuate the ground-borne vibrations. This paper was first published in the Proceedings of the 56th Annual Geotechnical Engineering Conference, 2008, at the University of Minnesota.

Jan 1, 2010

By John Brulia, Grant ODell

The AIRDEK blasting method has recently been introduced as an overbreak control blasting technique. This paper discusses the use of a modified AIRDEK blasting method for use in open-face blasting to make cap stone riprap (6-20 ton size) at the Clinton Point quarry of New York Trap Rock Corporation, Lone Star Industries.

Jan 1, 1990

By P. Ross, O. Rielo, P. Katsabanis

Selection of delay times to optimize fragmentation has been a controversial topic among researchers and blasting practitioners. The paper reviews all available experimental information, ranging from small and medium scale tests in geologic materials to small scale tests at the laboratory and synthetic materials, simulating rock. Tests have been re-analyzed and discussed in terms of the information they present and the limitation of the testing environment in representing actual conditions. New results obtained from blasting experiments in specimens made of a grout have provided a clear picture of the effect of delay on fragmentation. The grout used has a strength of 60 MPa (8700 psi), density of 2.5 g/cm3 and P-wave velocity of 4000 m/s (13100 ft/s). Each block was placed in a yoke to eliminate unwanted reflections and the desired delay was obtained using the appropriate length of detonating cord between holes or sub-millisecond electronic detonators. Delays ranged from 0.1 ms/m (0.03 ms/ft) of burden to 16 ms/m (4.9 ms/ft) of burden. Fragmentation was obtained using screen analysis of the collected fragments. Delay time has been shown to be a significant parameter affecting fragmentation and back break. Generally larger fragments and less back break was observed at short values, while fragmentation somewhat deteriorated at significant delay times, compared to what was observed at intermediate delay times. The work is now extended to include the effect of energy partition on fragmentation as well as the effect of initiation point and coupling ratio.

Jan 1, 2014

Blastserve, ISEE’s Listserve is being replaced by our new Blasters Forum-online, an exclusive member benefit. Our goal is to provide an ISEE forum for you to network with your peers and exchange technical information and get answers to your technical questions. This forum is unique in the fact that only ISEE members are permitted to review or post on the site. Over time you will be able review the discussion history and use the archived discussion as a valuable resource for trends in the industry. The following are a sample of the discussions that too place recently on Blastserve

Jan 1, 2013