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By R Yang, M Lownds

This paper reports studies showing the effects of delay scatter on the peak particle velocity (PPV) of blast vibration using a multiple seed wave (MSW) vibration model developed in recent years. The case studies also show the advantage of accurate delay timing on frequency control of blast vibration. The site parameters used in one of the studies are from a case in which the MSW model has been tested and confirmed to yield accurate predictions. This study uses an open pit blast design and a tunnel design in which blast vibrations using electronic detonators are compared with those from pyrotechnic detonators. Mean peak particle velocity (PPV) and the 97.5% upper bound PPV are compared. It is found that both these values increase significantly with the increase of the coefficient of variation of the site parameter. Using an open pit blast design, the modeling shows that electronic initiation shifts vibration energy to the expected frequency for a selected point of interest. However, for the same design of nominal initiation timing pyrotechnic detonators fail to shift vibration to the expected frequency due to its large scatter of timing.

Jan 1, 2011

By Bruce B. Redpath, Doug Crice, Rob Huggins

Over the last decade, instrumentation has been developed that allows the application of seismic reflection methods to groundwater and engineering problems. At the Geological Survey of Canada, we have been developing and testing shallow reflection techniques for mapping the bedrock topography and structure within the overburden. We have attempted to develop methods which can be implemented with a minimum investment in equipment and computing capabilities. The data are recorded on a l&channel engineering seismograph, using a single high-frequency geophone per channel, and a hammer or in-hole shotgun (“Buffalo gun”) as the seismic source. Processing and display of the data can be accomplished on an Apple II+ or IIe microcomputer and an Epson wide-track dot-matrix printer.

Jan 1, 1991

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 L. Trivino

Blast-induced damage criterion based on the peak particle velocity has worked reasonably well for estimating building damage. However, the same criterion cannot be used to estimate damage to rock and mine structures such as shaft and tunnel walls. It does not take into account the nature of seismic radiation pattern in the near-field, which is very different than what is obtained at far-off distances. To investigate this phenomenon, a systematic study has been carried out involving single-hole blasts and normal production blasts, with explosive source ranging from nearly point source charges to standard borehole sizes (6-7 m long explosive column), with charge weight varying from 0.5 kg to 30 kg. In the near-field, it is shown that, both P-wave and S-wave take a dominant position compared to the mainly surface waves measured in the far-field. These are shown to depend strongly not only on the length of the explosive column but also the way it is initiated in the borehole (i.e. direct vs. reverse initiation in the borehole) with respect to the target location. The seismic radiation patterns were recorded by high-frequency triaxial accelerometer stations grouted in the rock mass. This study describes the nature of seismic radiation in the near-field from long and short charges, the role of initiation direction and their effect on frequency with respect to sensor locations or target area of interest, and their implication in prediction of blast-induced damage in the near field.

Jan 1, 2009

By Randall M. Wheeler

Using Computer software to analyze and interpret blast vibration effects has never been so practical. Fully digital seismographs and powerful desktop and portable computers have led to the development of fast and easy to use analysis software. This workshop will focus on new Microsoft Windows-based blast vibration analysis programs developed by White Industrial Seismology, Inc. The Windows point and click graphical environment is ideal for developing full-featured and yet intuitive software.

Jan 1, 1994

By Kevin Landey, Eric Gerst

Expanding blast patterns to near the limit of an explosives’ ability to do the necessary amount of work is a common practice to reduce drilling and blasting costs. Choosing less expensive explosives such as ANFO vs. emulsion, bulk product versus packaged product, etc. are also common cost savers. Both practices are only effective as long as the pattern geometries are accurately drilled. However, will pushing the limits on pattern sizes and explosive products produce consistent results at the face, minimize oversize, produce superior fragmentation, and improve crusher throughput? Sometimes, but no amount of explosives can overcome a poorly drilled pattern. Knowing the probable outcome of any changes in drilling and blasting is valuable in achieving success.

Jan 1, 2018

By J. A. Sanchidrián, P. Segarra, S. Gómez

Blasting is a common activity in mining that can cause significant damage in the remaining rock mass. The most commonly used method for predicting vibrations is the Swedish or Holmberg-Persson approach. It is a simple and fast method that uses empirical formulation to estimate the vibration levels based on the explosive charge weight, distance to the source, and other parameters. However, it has limited accuracy and does not consider the effect of free surfaces or other boundary conditions. On the other hand, recently developed methods as the full-field solution (FFS) can provide more accurate predictions of vibrations due to excitations provoked by cylindrical columns of explosive, but the inclusion of free surfaces in analytical methods is a challenging problem. This paper presents a new approach that includes free surfaces in the FFS to predict vibrations analytically in the near-field. The main obstacle to including free surfaces in the FFS was the belief that the solution was non-decoupleable in P- and SV-waves separately. The Heelan's approach was previously used to decouple them, but it only provides valid radiation patterns in the far-field and does not account for intrinsic attenuation. In this paper, we address this problem successfully, allowing for the inclusion of free surfaces in the FFS.

Jan 1, 2024

By O. Rielo, P. Katsabanis

Traditionally fine aluminum is not used in dry commercial explosives due to the hazard associated with aluminum dust explosions during mixing. An industrial process has been developed which enables the safe use of paint grade Aluminum with ANFO. The addition of fine aluminum particles resulted in increased velocity of detonation of ANFO compositions. Velocities of detonation, in 52mm (2 1/16 in.) diameter confined charges were 20% higher than velocities of detonation of straight ANFO. The detonation performance of fine grained ANFO was not benefited by Al at the diameter tested. Furthermore use of larger Al flakes resulted in decreased velocities of detonation. The results are compatible with the experience of Al addition to high explosives. Tests were also conducted using bio-diesel, finding no substantial difference in the performance of AN fuel explosive compositions which used bio-diesel.

Jan 1, 2009

By Brian W. Stump, David P. Anderson, John Wiegand

Mining explosions are designed for a variety of purposes including the fragmentation and movement of materials. The blast design is dependent on the particular application intended and the material properties of the rock. The range of mining applications from hard rock quarrying to coal exposure to mineral recovery leads to a great variety of blasting practices.

Jan 1, 1997

By Randall M. Wheeler

It is important to be able to quantify the effects of blast delay designs on vibration characteristics. White was the first company to develop commercially available software, called Alpha-Blast, for this purpose. The program can indicate relative amplitude and frequency results to be expected from the use of particular delay intervals. If enhanced vibration effects from delays are a problem, a technique to evaluate this situation will be invaluable.

Jan 1, 1994

By R Castedo, L. M. Lopez, J. A. Sanchidrian

In 2014 the authors presented results from 13 tests made with two blasting seismographs on a vibration exciter. They measured coupling transmissibility as function of frequency (i.e. ratio of the velocity of the sensor mount to the velocity of the ground motion) from 16 to 200 Hz at one or two vibrations levels (5 mm/s or 0.2 in/s, and 20 mm/s or 0.79 in/s) with mounts freely placed, sandbagged, and anchored to a granite slab firmly attached to the plate of a vibration exciter. As the memory capacity of one of the seismographs prevented to cover low frequencies, e.g. 4-16 Hz, a new measuring campaign has been recently made to extend the study down to 2 Hz. In this campaign, two more techniques, in which the sensor mounts were fixed with thermal adhesive or a combination of duct tape and gypsum plaster, have been also investigated from 2 to 200 Hz at 5 and 20 mm/s. Free and sandbagged mounts lead to a weak coupling of the mounts to rock, so that transmissibility depends on the characteristics of the imposed rock motion (peak velocity and frequency). Measurements are accurate only at low frequencies (below 17 Hz for free mounts and 10 Hz for sandbagged) in the tested conditions (velocities up to 20 mm/s). Above these frequencies, ground motion in the measurement can be modified by a factor of 0.16 to 1.22. Anchored, glued and plastered mounts achieve a stiff rock-to-ground coupling, ensuring consistent measurements for the frequencies commonly found in blasting independently of the vibration level and the mount characteristics

Jan 1, 2015

By Bruce Vandenberg

Two tests were set up as part of the course given by Blasting Analysis International. Both tests were performed using the prototype Velocity of Detonation Recorder (VODR). The prototype has several limitations, which have been rectified for the production units.

Jan 1, 1990

By Frank Sames

The control of the environmental effects, especially blast vibration and airblast, has become a dominating planning criterion for most surface blasting operations. Compliance with existing regulations is generally achieved through constraints in the blast design, or monitoring programs. Commonly, blast vibration and airblast signals are rated and compared only by their maximum amplitude and the principal frequency associated with the peak.

Jan 1, 1997

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

By Adrian J. Moore, Alan B. Richards

Responsible blasting requires that rock throw be controlled to ensure that no danger will result to people and property. This paper describes the development and testing of empirical field calibrated formulae that can be used to evaluate rock throw, provide an early warning of when reduced burden will endanger people and property, and prevent flyrock incidents. Inputs to the formulae are charge mass, burden or stemming height, and a site constant that lies within a general range that can be tightened by site calibration. The output is the distance that rock will be thrown, and this ‘design your own flyrock’ quantification can be used to establish both safe clearance distances, and the critical range of burdens and stemming heights where the situation changes rapidly from safe to hazardous. Examples are given of the use of the model to control flyrock in open-pit mining and quarry operations, in situations which are controlled by both burden and stemming height.

Jan 1, 2004

By Kwang-Yeom Kim, Dong-Gyou Kim, Hyo-Kwan Yoon

This study was intended to simulate the blasting model using notched-hole with numerical approach. Numerical analysis approach was applied to compare and evaluate the blasting model using notched-hole and circular hole. To implement non-linear dynamic blasting model, blasting analysis was carried out with AUTODYN code. Behavior of two models was compared and evaluated using AUTODYN and visual analysis and quantitative evaluation based on pressure and stress to verify the effect to induce the destruction territory to the specific direction when blasting with notched hole was attempted.

Jan 1, 2010

By M. Hagfors

On the underwater testing of explosives, the measuring system consists of water filled test pond, tourmaline based pressure sensor, measuring cable and measuring unit, which supplies the DC current to the pressure sensor. Depending on the length of the measuring cable, it is always possible that some signal damping may occur in case the measurements are carried out without the signal amplifier to keep the measuring system as simple as possible. Therefore the length of the measuring cable should always be as short as possible.

Jan 1, 2006

By Ronald W. Roberts

For years, blasters have experienced near-misses, injuries, and yes, even fatalities as a result of the dangerous nature of our business. Yet, some blasters continue to portray the immortal attitude: nothing-would-or-could-ever-happened-to me syndrome. As we all know, that attitude can become disastrous to yourself or colleague(s).

Jan 1, 1996

By Adrian Moore, Alan Richards

"It has been common practice to set blast vibration limits for structures using an “observational”approach whereby limits are set at a level based on observations of damage, or the lack ofdamage, combined with a tendency to further reduce the permitted level due to uncertainty. Suchan observational approach was used in the USBM RI 8507 to produce the frequency dependent‘Safe Levels of Blasting Vibration for Houses’ which has become a universal Standard for overthirty years."

Jan 1, 2013

By Derek T. Novotny

Blasting cap precision is of major importance to advanced blast design. New technologies have introduced the use of microchips within detonator casings in the hope that the electronic control of the timing element will increase the accuracy of the cap and therefore improve the results of perimeter control blasting applications. The electronic detonators have proven to be accurate in timing tests done to date. They boast cap scatter results to microsecond accuracy, but the question is, does this degree of accuracy actually prove to be beneficial during practical use in the industry, or are conventional technologies applicable.

Jan 1, 1998