Search Documents

By Dale S. Preece

"Detonation delay timing has been an important aspect of quality rock blasting for decades. Detonators that enable delay timing have improved over the years especially with the recent advent of precision electronic detonators. The positive effects of precision delay timing have been observed repeatedly in the field with improved fragmentation, heave and overall blast control. Three-dimensional computational capabilities in terms of software, material models and computer speed have recently made possible the computer simulation of multiple blast holes in a bench configuration with precise delay timing between holes. Some of the key physical phenomena enabled by precise delay timing include: 1) collision and interaction of stress waves produced by adjacent blast holes, 2) reinforcement of stress waves from multiple holes as they reflect from the bench face and ground surface, 3) reflection of stress waves from “dynamic free surfaces” created by previously detonating holes, and 4) deformation induced fracturing, cracking and fragmentation. Simulating rock blasting in 3D has shed light on the physics involved and is resulting in an evolution of our understanding of fragmentation mechanisms. Routine use of these 3D computational tools will result in a much better understanding of the complex physics set in motion by the rock blasting process and allow predictionof improved blasting."

Jan 1, 2009

By Robert Hopler

As a part of the depression and rectification work on the Port Morris branch of the Harlem Division of the New York Central & Hudson River Railroad, a short tunnel is being driven under St. Mary’s Park. The park is near 149th St. and St. Ann’s Ave., in the Borough of the Bronx, New York City.

Jan 1, 2006

By Dale S. Preece, Stephen H. Chung

Electronic detonators and the attendant precise detonation timing that they facilitate are having a measurable effect on rock blasting in terms of improved fragmentation and vibration control. These improvements are increasingly well documented which is driving the expanding use of electronic detonators. In spite of the growing body of positive evidence concerning the benefits of precise delay timing, very little work has been done to document the impact of electronic detonators on the movement of rock. In this study 3-D computer programs, used to predict blasting induced rock heave, including the effects of detonation timing, are used to simulate the effect of precise timing on rock movement. Implementation includes quick, precise timing between blastholes going down a row and then much longer delays between rows of blastholes. For example an effective blast design might call for precise 3 ms delays between blastholes along a row and then 60 or 72 ms between rows. Several options are studied in this paper using computer simulations to draw some conclusions about the underlying physics affecting the process and how precise timing might have a positive impact on blasting induced rock motion.

Jan 1, 2005

By Sam Bang Jr, Rodney Burke

As mining progresses in the West, the depth of material has increased, making highwall stability a major factor in safety and production. The Jim Bridger Coal Mine’has made highwall stability a priority, concentrating on safety as well as increasing and improving production. Overburden depths are increasing dramatically; the geological environment consists of medium to sot? material, faulting, water, and current pit alignment not favorable to joint planes. Angle drilling the presplit at 20 degrees became necessaryas vertical presplit drilling produced wall failures.

Jan 1, 1998

By Paul Worsey, Larry Frost, Braden Lusk, Seok Bin Lim

For certification of blast resistant windows, current tests consist of arena tests or large air gun tests. Arena tests involve the detonation of more than 1000 pounds of explosives with windows placed in the range of hundreds of feet. The result of an arena test is a loading on a window consistent with an expected industrial or terrorist blast. Due to the nature of this type of test, only a limited number of facilities are available and operational costs can be extremely high. Air gun tests involve the use of compressed air and a failing diaphragm fired through a large tube. Although this test is more cost effective and easier to administer with lower environmental impacts, it is not an explosive loading and does not create a negative phase on the tail of the pressure pulse. Simply using a small charge in close proximity to the window is not a viable option either. The pressure peak can be reached using this method, but the duration of the pressure pulse is such that the positive phase impulse is on the order of ten times less than that for an arena test.

Jan 1, 2006

By Leon del Valle, Joe Phillips

First, I want to thank my co-author, Leon del Valle for his help and collaboration in the preparation of this paper, and also ORICA S.S. our explosive supplier and contractor at the Refugio mine site for their collaboration. The Southern Andes Mountains present a number of challenges for mining operations, and associated blasting operations. This region of the world, in Peru, Bolivis, Chile and Argentina is an area of rapid growth in precious and base metal mining, and will continue to be a large growth area for explosives products and services. This paper will attemp to discuss some of the special considerations encountered in operating a safe and effective blasting program at high elevation and under extreme weather conditions, as well as outlining a recent improvement in blasting techniques at the Refugio gold mine in northern Chile. This paper is presented from a mine operator's perspective, which may be a bit of a disappointment for some of you interested in a detailed technical review of our program. It willl, however, provide an insight in how in-pit blasting techniques tie into the metallurgical processes at a modern precious metal mine and thereby become a key elemnet in its success.

Jan 1, 2000

By Robert B. Hopler

Explosives, originally used only in fireworks and warfare, became legitimate contributors to human progress when miners in Eastern Europe began using them to break rock in the early 1600%. Since that time these powerful materials have had a dual role in the world: as agents of destruction in war, and as irreplaceable tools necessary to advance civilization. In the latter role, they serve as agents to enable mankind to produce metals, build roads, and drive tunnels. In other words, to provide those materials, services, and infrastructure without which the modern world could not exist.

Jan 1, 1997

By Charlie Brumbaugh

Antarctica with its diverse conditions such as severe cold, high winds, rock and ice structure and limited explosives available posed many obstacles. This paper will give an overall view of the methods used to overcome these obstacles on a daily basis on the highest, driest, coldest continent on earth.

Jan 1, 2000

By Kurt Oakes, Paul Worsey, Braden Lusk, Tony Brasier, Scott Crabtree, Randy Wheeler

Theoretical description of destructive wave interference and the use of sacrifi cial holes is included and is supported by data collected at Springfi eld Underground. Finally, the process by which the reduction in vibration was achieved in practice is described. Results are discussed for several production blasts taking place over a one year period.

Jan 1, 2008

By David S. Bowling

The ER-300 Series White Recorders were developed to provide on economical, yet invaluable instrument for those who desire permanent recordings of such data OS displacement, vibration, concussion (air borne effect) and velocity information. The precise monitoring of earth displacements and air blast magnitudes aids quarrymen and construction contractors in estimating safe blasting limits when operating in populated areas. A refraction model is available for recording velocities which permit the determination of weathered zone depths as well as the .depths to other subsurface formations. The dual purpose (Refroction- Displacement) systems ore utilized for velocity studies and displacement - oir blast measurements.

Jan 1, 1990

By Richard R. Brochu

At the International Society ofExplosives Engineers Annual Conference held in Nashville, Tennessee in February 1995, a Seismograph Standards Committee was established. The purpose of this wmmittee was to develop objective performance specifications for vibration measurement instrumentation and field use practices. It was also understood that due to geology, temperature, and moisture in the soils, it is not possible to design and build an instrument to give ‘results which are absolutely comparable for ground vibration. It was, however, considered essential to standardize instrumentation by which vibration can be measured under closely defined conditions so that results obtained by users of seismographs are always the same ,&thin stated tolerances.

Jan 1, 1998

By Bruce Vandenberg

A 3D, PC based computer program is currently under development by Blasting Analysis International, Inc., to analyze the kinetics of full scale blasts with two or more high-speed motion picture cameras.

Jan 1, 1990

By Dale Preece

A carefully designed and controlled in-place destruction experiment was performed on a concrete bunker buried in 4.27 m (14 ft.) of soil. The objective was to determine if the explosive charges would collapse the structure in-place without requiring mechanical excavation. Collapse of the buried structure was first attempted by drilling holes in the soil and placing four 13.38 Kg (29.5 lb) Comp B explosive charges at a depth of 2.13 m (6.7 ft.). The configuration of the charges when detonated was 2.13 m (6.7 ft.) off the top of the concrete roof and 3.66 m (12 ft.) apart in a square pattern. Detonation of these charges created a crater ~4.88 m (16 ft.) in diameter and 2.13 m (6.7 ft.) deep, leaving ~2.13 m (6.7 ft.) of soil covering. Very limited spalling occurred on the ceiling of the concrete structure as a result of detonating these four charges. The second attempt to collapse the structure consisted of placing another single 13.38 Kg (29.5 lb) charge, identical to the first four, near the geometrical center of the bunker roof. This charge was detonated in the soil cover 100 to 200 mm (4 to 8 in.) above the reinforced concrete roof, collapsing it. Due to the collapsed roof and remaining soil cover, the structure had been collapsed in place, requiring no further demolition.

Jan 1, 2006

By Douglas Anderson

Even though there is always a feeling of anticipation before a blast is detonated, most blasts are part of a day’s work. Once in a while there is an event that impresses even the most jaded blaster. Few blasts have had the impact of the Kingdome implosion in March of this year. Fortunately for both the Seattle area and the explosives community, the “impact” of the implosion was far less than many local residents had feared. This outcome, of course, was not by chance, but the result of careful planning and design. An urban implosion requires a mix of engineering, logistics, and public relations. Unique challenges on this project tested the resourcefulness of the entire team.

Jan 1, 2001

By Dennis R. Jr Bell

Before beginning any site development or mineral extraction activity, it has been well documented that it is first prudent to gain an understanding of the prevailing geologic conditions.Whether it’s identifying the depth to type of bedrock, or determining the quality and quantity of the in place mineral deposit, these factors should always be considered in a project’s fatal flaw analysis. In situations where there is limited subsurface information, geologic models have been proven to be one of the most valuable and cost-effective tools used by the developer and/or his consultant.

Jan 1, 1997

By Daniel P. Lathrop, Leslie C. Taylor, William L. Fourney

Except when the target is on the surface, e.g. a tank track, the most important loading mechanism from a buried charge on a target above it is the impact of soil propelled at the target by the expanding gas from the explosion. Detonation of a shallow buried explosive generally yields an unstable interface between the rising soil and the air which appears to be the result of Richtmyer-Meshkov instability. Irregular “fingers” of saturated sand extend into the air above a more generalized dome of soil. These fingers move at a much higher velocity than the material between them at smaller stand off distances. As a result, the local load on the target at positions on the target at the same distance from the charge may vary by 50% or more from shot to shot or even within a single shot. This variation requires a large design safety factor to assure the integrity of design of mine-resistant vehicles.

Jan 1, 2009

By Gordon Revey

The challenge of managing blasting risk, types of risk, public perception, and a system for managing risk were covered in the first part of this article in the May/June 2000 issue of the Journal of Explosives Engineering. This final part of this two-part series provides a method for identifying specific blasting risks and reviews the importance of community relations.

Jan 1, 2001

By Brian Carr

This workshop will display all of the existing products that are available as stemplug devices and discuss the general concept of the use of them. Actual results will be discussed along with several case histories. There will be adequate time for questions and answers.

Jan 1, 2000

By Dan L'Heureux, Joe Haid, Stephen H. Chung

Most coal deposits in Western Canada involve steeply dipping multiple seams. An efficient way to recover coal seams would be to drill through the seams and blast both the overlying and underlying waste material in one shot without disrupting the coal seams while fragmenting the waste rock for easy removal. This requires special blasting techniques as reported by Chung and Jorgenson in 1985.

Jan 1, 1998

By Pat McLaughlin

Blast design in the construction industry has often been based on past practice or powder factors. This is to some extent understandable, since construction projects do not have the longevity of mining or quarrying operations and therefore have less opportunity to pursue potential improvements. The main concern of the operator is whether or not the technique will work, and at what cost to the downstream processes. Time, not long term savings, is of the essence.

Jan 1, 1994