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By Roger G. Sprague

With the passing of time, changing marketplaces and years of hard service, coupled with new machines, increased productivity, rapidly improving technology, equipment which used to be the latest in modern mining have now slipped into obsolence. Mining companies need reliable, productive equipment in order to compete in today's market. In Western coal mining, as coal seams become deeper, older equipment must be replaced with that which can do the job more efficiently.

Jan 1, 1998

By Rolf Koenig

After the Dynatronic firing system was demonstrated for the first time at the SEE conference in Miami in 1987, it was officially approved in Germany at the beginning of 1993. Dynatronic has now been on the market for 5 years. At present, it is used in several European countries and successful test series have been running in Australia.

Jan 1, 1998

By Minoru Kawamura, Yukio Kato, Yoshikazu Hirosaki, Satoru Suzuki

A wireless blasting system for tunnel construction which consists of a loop antenna, oscillator and blaster, has been developed. The basic technology of this method had been studied in the 1970s to develop a wireless initiation system for undersea blasting and has been successfully used as a Remote Controlled (RCB) system in the Honshu/ Shikoku Bridge construction project in Japan.

Jan 1, 1998

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

Choosing the correct delay time for many blasting applications is an important and critical blast design parameter for controlling fragmentation, muckpile shape, swell, digability, throw, ground vibration and airblast. BAl and its affiliates have monitored thousands of full scale blasts in a variety of field conditions, spanning over 15 countries, with sophisticated blast monitoring instrumentation. In some blast environments, a small change in the choice of delay times used had a dramatic and pronounced effect on the overall blast results. In other blast environments, large changes in the choice of delays used had absolutely no effect on the final results in terms of specific outputs. In environments which were sensitive to the delay selection, the type of explosive, dynamic response time of the rock mass (TMIN), integrity of the material, burden and rock mass geometry, all played a very important ,role.

Jan 1, 1998

By John L. Floyd

One of the key factors that controls the overall profitability of surface operations is the required volume of excavated material. If the overall angle of final walls can be maximized the amount of material excavated will be reduced. However, as the slope angle becomes steeper the wall's factor of safety decreases. As a result, the development and implementation of efficient wall control blast designs becomes critical to achieving stable walls. Many site specific conditions should be taken into account when defining the methods that will be used to lessen blast induced wall damage. This paper will discuss the steps needed to properly evaluate the site and develop efficient designs. Four variations of wall control blast designs will be evaluated in terms of cost and performance. In addition, the paper will include the quality controls needed to successfully implement and refine the blast design.

Jan 1, 1998

By Qi Jinduo, Gong Min

On the basis of actual parameter of wall control blast in Nanfeng mine, China, the process of dynamic stress changing between two column charges was studied recently for a presplit-cushion blast by holographic photoelasticity. In the experimental model, two holes were simultaneously detonated from both ends (four ignition points). The bottom of the holes were loaded more than other parts (heavy charge). Under these conditions, four consecutive isochromatic fringe patterns at different times were acquired in one loading run, and the characteristics of the stress distributions were compared at different places and times in the holes. It was found that interaction types of stress waves vary along the holes. The theory is posed that the stress wave which is formed by the interaction of earlier producing P wave and later S wave along a distributed line charge is the most important part in all stress waves. Research indicates that a heavy charge in the bottom of the holes is crucial to producing a presplit-cushion effect at the bottom. "End Effect" doesn't affect the magnitude of stress along linking lines between the bottoms. The chief fields of the "End Effect" are also explained in the paper.

Jan 1, 1998

By Tianrui Xu, Chaohong Liu, Bangqing Ding

The authors were responsible for a series of large scale multiple chamber charge blasts conducted in the granite mountain area for making construction space on the southeast sea coast in China during 1993-1996. This paper describes the blast design and damage control of one mountain blast 320m in length and 280m in width in the vicinity of two wharfs and a dam. In order to obtain better rock fragmentation and muckpile, the explosive charge should be well-distributed in the mountain. The charge pattern, therefore, was designed with mainly 5 rows of tunnel charge in regular terrain in combination with a chamber charge in irregular topography area and the maximum burden was limited to be less than 38m. In order to protect the dam and wharfs the firing sequence was carefully arranged in 29 intervals and the distance between different charges of the same delay to the dam or wharf was taken into account as an additional delay interval based on the difference of p-wave propagating times. The maximum charge fired in an interval was also limited to less than 34t explosives through dividing the larger charge by a stemming deck.

Jan 1, 1998

By Zhang Shixun, Wang Xuguang, Wang Guoli

A massive millisecond blast at an open-pit mine of large scale can be realized by using the blasting technology of pre-loaded explosives, which can enlarge production scale, reduce the frequency of blasting and of large production equipment movement, and raise the production efficiency. The reason why application of this technology is restricted at high sulfide ore deposits of variable and complex geological conditions is that an exothermic reaction will take place when explosives contact sulfide ores, which could lead to accidents such as spontaneous burning and detonation of explosives pre-loaded in boreholes, influencing blasting and production safety. The thermal decomposition reactions of emulsion explosives of different prescriptions in contact with pyrite have been studied by differential thermal analysis (DTA), kinetics parameters calculation and accelerating rate calorimetry (ARC), and on the basis of the above studies, the safety of emulsion explosives used in sulfide mines has been evaluated with the safe contact time of different emulsion explosives with pyrite determined.

Jan 1, 1998

By Kwang-Tae Kim, Yong-Kun Choi, Jeong-Soo Chong, Yun-Jae Lee

An annex building at the former Agency for National Security Planning(NSP) complex located in downtown Seoul was demolished by progressive collapse method. This work was done as a part of efforts to restore the landscape of Namsan Mountain which lies in the Center of Seoul. The five-story reinforced concrete structure was razed in 5.5 seconds by the 29kg of high powered explosives which were placed in some 320 holes in the building with floor area of 2,577 m². The asbetos and all the other finishing materials in the building were removed before the demolition and the specially coated wrap minimized the spread of blasting dust. Seismic and air overpressure waves were monitored at 8 points, which were below safety limits and the continuous communication with neighborhood prevented any complaint.

Jan 1, 1998

By Robert Martin, Brian W. Stump, David P. Anderson

2We use field measurements to quantify physical processes that accompany different types of mining explosions. The data sets collected include three-component ground motion, acoustic, video and high speed film, three dimensional topography, geological and geophysical properties, design blast pattern and timing, and velocity of detonation in the explosive for individual borehole detonation times. The explosions include simple single-fired contained explosions, ones designed to bulk and fracture material and those that cast material. Our goal is a physical understanding of these sources for the purposes of optimizing blasting practices.

Jan 1, 1998

By Harry L. Siebert

Pre-splitting was substituted for line drilling to achieve stable rock slopes and reduce excavation beyond the pay line on a Connecticut highway project in 1962-63. Changes have occurred in developing rock slopes that were not foreseen by Alan Bauer and Jim Scott who in the early days understood the relationship of explosive energy to stable slopes. Cushion blasting as currently used produces slopes designed to blend or complement the natural landscape with slope holes detonated after the main body of holes. Pre-splitting is the opposite. The best results have been achieved by detonating the pre-split line of the holes first to allow readjustment of the slope plane fracture and a separate blast for the main body of loaded holes.

Jan 1, 1998

By Harry L. Siebert

A major Arizona highway project is jeopardizing site safety and security because of the lane rental policy. One million cubic yards of rock must be fragmented to provide two additional lanes parallel to the existing roadway. Traffic is stopped during blasting operations.

Jan 1, 1997

By David R. Ziegler

The concept and facts concerning "threshold blast damage" are not considered "general knowledge". Perhaps because of a lack of knowledge, understanding, and experience of blasting effects, property owners and lay-persons may attribute a wide range of common cosmetic conditions to "blasting damage".

Jan 1, 1997

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 Paul Worsey, Gerald Rupert, Mark Kirkbride

The realignment of Highway H in the proximity of Crystal Cave (Springfield MO.) required the development of a blasting program that was both economical and efficient for construction, yet ecologically safe for the cave. Three component seismographs were strategically placed underground near prominent and sensitive cave features and the vibration levels from the construction blasting continuously monitored. Peak particle velocity (PPV) values were found to obey the square root scaling law and a peak particle velocity value of 0.3 in/sec was chosen as the safe maximum limit. This value proved adequate in preserving the integrity of the cave and its features. Scaled distances for the maximum and lower values enabled blasting personnel to select explosive charge weights per delay for given distance to the cave. Delays were determined from the dominant frequencies recorded underground.

Jan 1, 1997

By Carl Lubbe, Ron Frye, Wayne Curtis, Julie Pecori, Dan Leach

Blasting conducted in the USA using the new Electronic Initiation System developed by Altech has shown that an accurate delay system will benefit the customer. Results from test work clearly showed that improved fragmentation was effected and blast vibration was at least similar to that currently found at the test venue with improvements possible.

Jan 1, 1997

By Ed O'Connor, Per-Anders Persson, Manhong Zhou

This chapter deals with the concepts of shock waves and detonation waves together, because a detonation wave is really a shock wave, supported by the explosive reaction that the shock wave ignites and propagates as it travels through the explosive material. In the context of rock blasting, furthermore, there is justification for treating shock waves and detonation waves together, because the mechanical effect of the detonation in an explosive in a drillhole in rock is propagated and its effects are spread throughout the surrounding rock by means of a shock wave. The overall performance of an explosive in rock blasting or any other application is of course dependent on how much thermal energy is released in the chemical reaction that occurs when the material detonates, and on how much useful mechanical work the reaction products can do as they expand. A major portion of this chapter deals with the prediction and measurement of explosive performance, a subject which is now still in a process of rapid development.

Jan 1, 1997

By Dennis G. Wright

The Minister of Fisheries and Oceans for Canada is responsible, under the Fisheries Act, for the protection of all marine organisms and their habitats. The detonation of explosives in or adjacent to fish habitat has been demonstrated to cause disturbance, injury and/or death to aquatic organisms, and/or disturbance, destruction or alteration of their habitats. The Department of Fisheries and Oceans recognizes that the use of explosives may be the most practical or cost effective method by which to complete a project and has undertaken the development of a set of guidelines that will prevent or minimize the destruction of or disturbance to aquatic organisms and their habitats while at the same time allowing scientific and industrial users of explosives to proceed with their projects.

Jan 1, 1997

By J Deen, P Sterk, W Forsyth

Homestake Mining Company has made a firm commitment to develop a functional and cost effective perimeter blasting program. The goal of the program is to develop smooth, sound walls in all development ends. A good perimeter blasting method will improve safety, reduce waste rock handling, allow easier support installation and reduce scaling time. All the benefits will contribute to an overall reduction in total development costs.

Jan 1, 1997