Search Documents

By Paul Worsey, Matthew K. Coy

New blasting mat designs are currently tested in the field on actual blasting jobs and only undergo qualitative rather than quantitative assessment. The majority of matted blasting occurs in trenching in which the blast designs and field conditions vary considerably. In order to assess a new blasting mat material and design, a new standard test was devised.

Jan 1, 2015

By Catherine T. Aimone-Martin, Elena Oana Jacobs, Brent Meins

Accurate pressure measurements during underwater detonations are critical for the protection of structures and mitigating impacts to fish and marine mammals. Current guidelines that limit underwater pressures are based on past studies, many of which used sample rates of 48 and 65 kS/s (48,000 and 65,000 samples per second). These sample rates may be insufficient to accurately record high frequency, sharp rise time blast pressures. As such, pressure thresholds associated with fish and marine mammal injury or mortality may be underestimated, calling into question the pressure and sound pressure level guidelines that govern underwater blasting today.

Jan 1, 2019

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

By Larry R. Fletcher

The Bureau of Mines obtained blasting accident data from the Mine Safety ant Health Administration (MSHA), U. S. Department of Labor. These data were analyzed to determine the most frequent causes of accidents in mine blasting. Accident totals for 1971 through 1981 are tabulated for metal-nonmetal and coal mines both surface and underground. In the past 11 years (1971-1981, inclusive) there has been an annual average of 9 fatal and 121 nonfatal blasting accident victims. Underground mining averaged 6 fatal and 93 nonfatal injuries each year.

Jan 1, 1983

By Brian Wingfield, Rick Givens, Greg Williams

Many technological advancements have been made in explosive products and applications over the last 15 years resulting in productivity and cost gains. However, the applications of total energy (engine horsepower) in the majority of rotary drilling technology, has remained virtually unchanged over that period. While advancements have been made in components, efficiency, and types of hydraulic systems used on drills, the application of current hydraulic technology to improve drilling productivity has not been interactive with end users. This paper will investigate how traditional design assumptions, regarding typical application of horsepower in current rotary drill systems, can actually limit productivity.

Jan 1, 1996

By B Mohanty

Full-face blasting rounds have been used to excavate a 4.6-mdiameter shaft at Atomic Energy of Canada Limited's Underground Research Laboratory near Pinawa, Manitoba. Both standard pyrotechnic delay detonators and the newly developed electronic delay detonators (EDD) were used on the project. The full-face blasting technique, employing 89-mm-diameter relief holes and 38-mm diameter blast holes, NG-based explosives, and the regular long period delay detonators, has been standard practice at the site, giving excellent wall control and fragmentation results. The comparison blasts using pyrotechnic detonators and EDDs were carried out to test the operational logistics, timing accuracy and blast results obtained with the latter. The long period pyrotechnic delays ranged from O to 18, with the nominal delay varying between 350 ms and 800 ms. The EDD blasts used the same number of periods, with the respective delay interval between successive periods set precisely at 190 ms and 210 ms for the two blasts. Based on a broad range of critically assessed parameters, the EDD blast results proved to be signficantly superior to those obtained with regular pyrotechnic detonators. The results have been analyzed in detail and the relative merits of the two delay systems have been determined. Alternative designs to derive maximum benefits from EDDs in shaft and tunnel blasts have also been suggested.

Jan 1, 1990

By A Lance McAnuff, Robert T. Booren

Construction of a dock facility for the Lake Erie Development Project of Stelco Steel involved underwater blasting in commercial fishing waters near Port Dover, Ontario. The most stringent environmental constraints were imposed and a monitoring program involving water overpressure recordings, using equipment developed specifically for this assignment, correlated with observation of caged fish specimens at various distances from the blast source, was undertaken to determine the effects on fish life and to establish whether a protective air-bubble curtain system should be installed around each blast area.

Jan 1, 1989

By G. F. Revey

When rock blasting occurs near new concrete of varying age, engineers representing project owners often express concern that vibration from the blasting will crack nearby concrete. Regulations and/or specifications for civil construction projects usually include particle velocity vibration limits intended to protect concrete. In some cases specified limits are unreasonably low and needlessly restrict and increase the cost of excavation work. This paper discusses how methods of predicting resulting flexural strains caused by blast-motion can be used to develop safe and reasonable PPV limits to protect new concrete. Three case histories demonstrating how these evaluation techniques were used to establish higher PPV limits designed to protect concrete of various structural condition are also presented.

Jan 1, 2006

By Jesus Pascual, Jose Sanchidrian, Pablo Segarra

The surface vibration field in the area above an underground mine prior to its development has been investigated, in order to assess the vibration levels expected in existing buildings and in the planned mine facilities from future underground blasts. Shots of 50 and 100 kg of explosive placed in drillholes at depths of 100 to 150 m were fired, and the vibration events were recorded using an array of 40 seismographs in a 400 m square grid, covering a 2×2 km area. Contours of isovelocity were obtained for each shot, showing some directional transmission patterns. Propagation laws were obtained from the results of each shot and also from the bulk of data, both for the whole area and dividing it into four quadrants. The shift of dominant frequency with distance was also analyzed.

Jan 1, 2002

By Doug Wathen, Philip M. E Thomas

The City of Fort Myers needed to replace a 40-year old 42-inch storm sewer line in downtown Fort Myers with a new 54-inch line to accommodate population growth. The old line had to be kept operational while a new line was installed. the contractor spent two months using a drop ball, a hoe ram, and large rippers trying to break the three to four feet of rock that needed to be removed to accommodate the new pipe. Mechanical trenching was considered but was proven to be overly expensive. On very short notice, Ireco of Florida was asked to design and execute a blasting procedure that would allow this project to proceed. Nearby buildings were over 80 years old, three of them containing antique shops specializing in glass antiquities with attorney offices above them. High water table compounded problems with a 20-year old steel water main and clay drainage pipe 15 feet from the new sewer line. Holes had to be drilled within six inches of the edge of the existing pipe to four feet below the pipe on either side of the pipe and blasted. No interruption in the sewer line flow was to be tolerated.

Jan 1, 1996

By Earl C. Hutchison, John Loviza

At the Metropolitan Nashville International Airport, with its more than 600 scheduled daily flights from American Airlines hub operations, other scheduled airline flights, Tennessee Air National Guard operations, as well as numerous industry air flights, the excavation of 300,000 cubic yards of rock was required without disrupting airport operations for a cut and cover underground tunnel with a 4 lane US Highway and new airplane runway to extend across it's top. In addition to the excavation, the removed rock was to be broken to specification type that was clean and of small size for fill in another area of the airport property. The blasting was limited to two 1/2 hour windows per day and stiff monetary penalties were in place for schedule slippage of each phase of the project.

Jan 1, 1992

By David R. Holberg

In the Kansas City metropolitan area, mineable Bethany Falls Limestone occurs 80 ft below river level under the 700 acre Park College Campus on the north bank of the Missouri River at Parkville. For 20 years prior to this project various firms passed over this opportunity to mine this property for construction aggregate because of uncertain costs, financial risk, and the difficulty of constructing an entry tunnel. This paper describes the drill and blast construction, rock bolting, and shotcrete lining of a 750 ft. long, 15% declining grade, truck tunnel through several Pennsylvanian limestones and shales.

Jan 1, 1997

By Michael S. Wieland

This report discusses the U.S. Bureau of Mines research regarding the desensitization and malfunction of cap-sensitive explosives deployed in underground coal mines. Delay blasting in underground coal generates severe shock waves and rifting forces that fracture and heave coal. These dynamic interactions can damage other charges still remaining in the delay pattern. The debilitating impacts precipitate degrees of reduced charge performance ranging from misfires to weak detonations or out-of-sequence firings. Damaged charges react poorly, perform less useful work, and/or generate atypical fumes with higher toxicity.

Jan 1, 1993

By R J. Hill

Blasters are well aware of the problems and expense faced when trying to load in wet bore holes; problems of poor coupling and poor density, as well as the expense of higher priced cartridge product. In answer to these problems, I developed a system for dewatering using nozzles with lay -flat plastic liners which I have used successfully over the last few years. I found the system not only gave me better shots than I could have expected in the circumstances, but also dramatically decreased costs. The system has been adopted by two large roading contractors and a quarry operation in Eastern Canada.

Jan 1, 1986

Introduce self – thanks for having me.Indiana program – spent first 15 years of program telling folks how smart we are and to trust us. “We are from the government and we are here to help you.” How well would that go over with you if the IRS invited you in for an audit and that was their openning? Our audience was the same way – not thrilled or inspired. We decided we were the problem – being nice guys just was not enough. We had to learn to communicate with people who did not know us. I am here to share a few things we have learned – and are still learning.

Jan 1, 2007

By Paul Worsey, Barbara Robertson

In June 2007, Missouri Science & Technology (formally UMR) successfully held its 5th and 6th Explosives Summer Camps. The camps, which include substantial industry participation, have been an outstanding success with both the students and their parents. They have also spawned a large amount of local, state and national media attention, including NPR and an article in the New York Times on the 3rd of July 2007.

Jan 1, 2008

By Raymond M. Dixon, Dale L. Ramsey

Upon being introduced to the MAGNETIC COUPLING concept,Balsinger,Inc. wanted to conduct field trials to explore the potential of Magnetic Coupling in the U.S.. Although the Magnetic Coupling Concept has been widely used, the U.S. proposed blasting criterion not previously addressed by the system. Modification to the system assembly and blasting accessories had to be made to make the system adaptable to our specific requirements. The field trials and system modifications are the basis of this paper.

Jan 1, 1990

By E. Contestabile, B. von Rosen

On August 5th, 1998, a tractor-trailer carrying approximately 18,000 kg of blasting explosives, struck a rock face on the side of the road near the town of Walden, Ontario. Eye-witness accounts of the incident state that there was an intense fire for approximately 30 minutes before the detonation. The detonation caused severe damage to the tractor-trailer, shifted the pavement and caused blast damage to the rock face. A rock fragment was recovered almost 2.5 km from ground zero and a 70 kg piece of an axle assembly was recovered over 1 km from the site. Windows were cracked at distances of almost 3 km.

Jan 1, 2001

By I. Petropouleas, J. Croll, R. Bassett

A programme of tests on controlled internal explosions to a class of circular reinforced concrete columns, has allowed the relationships between the blast energy and the extent of local damage to be understood. These tests have also demonstrated the important additional effects on the damage levels of preexisting axial loads.

Jan 1, 2006

By G Dean Barrett, Ed Jr Smith, Calvin J. Konya

The purpose of the project was two fold: 1. To determine whether Pyrodex, a propellant, manufactured by the Hodgdon Powder Company, could be used as a substitute for high explosives for presplitting in granite and other materials. 2. To determine if Pyrodex, a slow reacting propellant which produces no stress waves in rock because it reacts subsonically, could cause the rock to crack similar to the results achieved with high explosives.

Jan 1, 1986