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By Alejandro Rosario, Ricardo González

The restrictions imposed by the Brazilian environmental legislation regarding natural caves lead to a block of substantial amount of mineral reserves. Mining activities can released caves, as long as the company ensures that the activities will not cause any damage to them, requiring profound and time-consuming studies. Since the use of explosives in the mine are potential sources of some damage to any structures, it leads to a deep need for controlling the rock blasting activities. In this context, the maximum charge per delay used in operations close to cave regions must follow some internal blasting assumptions that have been developed during specific tests and mining activities. By the seed wave technique, it is possible to determine the behavior of a seismic wave, which travels through a rock mass and it is generated by blasting a known explosive charge. This technique has proved to be an effective tool because it is able to accurately include the physical characteristics of the rock and different lithologies. This paper discusses about modelling blasting induced vibrations in order to improve caves protection, which surround the mining operations.

Jan 1, 2019

By Catherine Johnson, Kelly Williams

The ability to measure the overpressure of a shock wave is necessary for explosives research such as shockwave focusing and field testing of blast-resistant designs for buildings and vehicles. To record the peak overpressure of the nearly instantaneous pressure rise at the shock front, pressure transducers with a fast response rate and streamline pencil design are needed. Time spent setting up sensors coupled with the expense of high-frequency data acquisition systems, and the inconvenience of low impedance cables can make the process challenging. Additionally, only small inaccuracies in sensor position can drastically change the measurement recorded. Advances in high-speed video imaging make it possible to see the refraction of light due to the high-density gradient at the shock front without the need for parabolic mirrors or additional light sources necessary for Schlieren or shadowgraph imaging. The average shock front velocity between two points can be calculated by dividing the change in position by the elapsed time between the images. Using the Rankine-Hugoniot relationship demonstrated by Swisdak the peak overpressure of the shock wave can be calculated from its velocity eliminating the interference of the gage and mount. This paper investigates the accuracy of this method by setting dual transducer pencil probesat0and180 degrees perpendicular to the central axis of a285-gram(0.63-pound)cylindrical charge to record pressure versus time for comparison to the high-speed video. The axis of the camera lens is aligned with the central axis of the charge with both pencil probes in view. The pencil probes have two pressuretransducersset100millimeters (3.9 inches)apart to measure the time of arrival and are used to validate the velocities calculated from the high-speed images. This method can be used to evaluate the shock wave propagation from more complex prismatic charges with different cross-sectional shapes where precise placement of cumbersome pencil transducers in the near field is almost impossible.

By AJ Rorke

Blasting trials using Daveytronic Electronic Delay Detonator systems (EDD’s) were conducted at the Alpha Ferro Quany (Pretoria) and the Eikeboom Colliery near Witbank in November 1999. The objectives of the trials were to determine the influence of accurate hole firing on rock fragmentation, blast-induced vibration and blast throw. This paper provides an outline of the trials and an analysis of the results. The results were compared with a normal shock tube initiation system. Fragmentation was measured using video-imaging techniques at the hard rock Ferro Quarry for one conventional shock tube blast and two EDD blasts. No significant difference was measured in the fragmentation between the shock tube blast and the two electronic detonator blasts. Joint planes mostly defme the fragments at Ferro Quarry. The fragment sizing was therefore controlled mainly by the rock structure and the blast timing appeared to have no influence. Vibration measurements made at Ferro Quarry indicate that electronic detonators have a marked effect on vibration frequencies compared to shock tube systems. The more accurate detonators resulted in a narrower f+equency band at lower amplitude with similar timing. By modifying the blast timing, the dominant frequencies were changed. The electronic detonators had a significant positive influence, therefore on blast vibration and its control. The timing scatter measured from the shock tube blast was considerable, with measured inhole detonator scatter at 48 ms over a sample of 19 units. Surface delay periods less than 42 ms would therefore not be able to provide effective sequential firing. The scatter of the Daveytronic units was below the 2 ms resolution of the high-speed camera used to film the blasts. Reliable sequential firing, even at very short delay intervals was considered the main reason for notable improved throw in an overburden blast at Eikeboom Colliery. Blast throw was improved by 25% for the test blast.

Jan 1, 2000

By Jason Rock, Rob Thompson, Lee Julian

Reactive ground is ground that undergoes a spontaneous exothermic reaction after it comes into contact with nitrates. This is commonly caused by inert rock hosting sulphide minerals, such as pyrites that act as the reagent. The presence and subsequent rate of reaction with nitrate based bulk explosives can be difficult to predict. Once identified, only explosives that are tested and proven to be compatible with the reactive ground may only be used. These typically take the form of inhibited ammonium nitrate emulsion blended with a limited volume of ANFO or porous prilled ammonium nitrate (PPAN) to ensure that all AN prills in the blend are wholly encapsulated and thus protected from the reactive ground. The requirement for high emulsion content bulk products limits the suite of products available for use to high energy, and high expense products. Further, if chemically sensitised products are used, charged holes must be left unstemmed to allow for gassing to occur, adding delay and exposing the blast crew to an unconfined charge in reactive ground. A range of inhibited products has been developed that are solid sensitised and can be bulked to as low as 0.9 g/cc (56.2 lb/ft3). The use of a solid sensitiser enables stemming to occur immediately after each hole is charged, confining any unplanned detonation more safely within the rock mass. The effective and precise manufacture of bulked inhibited products required a new and innovative Mobile Processing Unit (MPU) design. This MPU required the ability to blend two solid raw materials (AN prill & sensitiser) along with two liquid ingredients (AN emulsion and process fuel). This MPU has been designed, manufactured and has used successfully to manufacture low density inhibited explosives. This paper presents an innovative shift in inhibited bulk products with specific reference to their manufacture and application.

By P D. Katsabanis, S Kim

A number of small scale fragmentation tests have been conducted to analyze the effects of blasting effort on the grindability of granite, granodiorite, limestone and iron ore. Powder factors were modified, post-blast fragments were screened and drop weight tests were conducted on fragments of different sizes to deliver a variety of specific impact energies. The fragmentation from the drop weight tests has been analyzed to examine the effect of impact energy and powder factor on size reduction. A consistent effect of blasting on the various fractions of the fragmentation distribution has been obtained for all rocks used. The effect of powder factor on the impact fracturing of the rocks has been expressed in a convenient relationship between progeny size, impact energy and powder factor used in obtaining the primary fragmentation. It is clear that explosives consumption affects downstream size reduction; depending on the rock, the effect can be substantial at coarser final sizes but very small in the case of grinding to small final sizes. Differences from the expected trend can be attributed to changes in blast design. As an example, the effect of in-hole collision of detonation waves is analyzed.

Jan 1, 2011

By Nan H. Lee, Christopher J. Hunter, Stephen H. Chung

Several factors affect the productivity of mining operations. The geological structure of a mineral deposit and the fragment size of blasted material are considered to be most influential. It is well known that productivity varies with mucking cycles and that this is related to the explosive energy produced by a blast.

Jan 1, 1991

By A. W. (Sandy) Neilson

Whether you are a general contractor who hires subcontractors to perform blasting work or you have your own blasting crew, it is extremely important to understand how Business Liability Insurance works, regardless of who is ultimately providing the coverage. If close attention is not paid to the limitations and preblast survey requirements under most policies that provide blasting coverage, you could find yourself facing an uninsured loss.

Jan 1, 2002

By Frank Hirthammer

Since the introduction of the Explosives Track & Trace in Europe in 2014 for manufacturers and 2015 for end-users, a lot has changed in all areas of the supply chain and the use of explosives. The regional associations, manufacturers' organizations, and trade associations have proven that it is possible to overcome a hurdle, that looks almost impossible in the beginning, through consistent cooperation. The paper gives an insight into the problems involved in introducing such a requirement, identifies ways and solutions, and concludes them. When looking at the current situation, the paper describes the process by which a prescribed change in business processes are transforming into a solution that increases productivity, security, and handling.

Feb 1, 2020

By Remi Proulx, Ruilin Yang

The effectiveness of presplit in soft or fractured ground is hard to visualize or quantify. There have been many attempts by the blasting community to measure and quantify the effectiveness of presplit blasts. Various methods have been adapted by different researchers, and the results are debatable.

Jan 1, 2019

By Frank Hirthammer

Since the introduction of the Explosives Track & Trace in Europe in 2014 for manufacturers and 2015 for end-users, a lot has changed in all areas of the supply chain and the use of explosives. The regional associations, manufacturers' organizations, and trade associations have proven that it is possible to overcome a hurdle, that looks almost impossible in the beginning, through consistent cooperation. The paper gives an insight into the problems involved in introducing such a requirement, identifies ways and solutions, and concludes them. When looking at the current situation, the paper describes the process by which a prescribed change in business processes are transforming into a solution that increases productivity, security, and handling. It shows examples from daily work, in which possibilities for optimization, improved quality assurance, and work facilitation are explained. It presents the resulting potential by comparing process flows, before and after the introduction of Track & Trace solutions. What challenges will we face in the future concerning the use of T&T solutions? Will the tracking of explosives become the norm worldwide? What are future hardware and software developments to be expected? What impact will this have on the global supply chain?

By S. Klerkx, R Battulwar, J Valencia, J Sattarvand, E Emami, M. Soleymani Shishvan

A new technology for energy distribution optimization, supported by NIOSH.

Feb 1, 2020

By Juan Carlos Vasquez, Romel Villanueva

We present the results of our field research on the variation of the density of the gassed explosives and their influence on the blasting results in the Peruvian mines: Yanacocha, Toquepala and Antamina. Currently, 90% of Peruvian mines uses gassed explosives, for their economic and technical benefits. But new practices and design criteria have had to be adopted, and the most important a careful control of the in-hole density, whose variation in the depth of the hole strongly affects the detonation process.

Feb 1, 2020

By Randall M. Wheeler

Pre-blast surveys are used to document the condition of a structure prior to the commencement of blasting activities. They provide the best means of determining the pre-existence of visible cracking and deterioration in a structure before blasting is initiated. A small investment in a good pre-blast survey, coupled with good public relations, could mean a large cost savings for a company in the future.

Jan 1, 1992

By Jim Peterson, Ricardo Freire, Mason Biernat

Variable nature of rock and face conditions, varying execution and changing nature of blasting are making ongoing optimization challenging. Intelligent planning and on-going analytics are required to mitigate variability and convert blasting into a predictable outcome by use of technology. Blasting operations generate a huge amount of data which can be used intelligently for optimization. In this paper, details are provided of a system which is used for blasting data collection in the field – Key details around blast parameters, explosives, initiating system details, video, photographs, vibration and fragmentation are collected in a cloud-based platform. Data can also be collected through a mobility device in the field (even without internet connectivity) and synchronized with cloud-based system. Also, data from various sources can be imported in excel formats in the software including from upstream and downstream processes from blasting. App also gives indication about exceeding of vibration, air blast overpressure, fragment size etc. Thus, making it possible to perform QA-QC before charging and deciding initiation timing and sequence at the blasting site. The data can be processed and analyzed to spot trends, help predict events, and formulate strategies at the design and execution stage. Data gathering of blast parameters, explosive used processing and analysis can be used to optimize operational efficiency, improve safety and environmental controls.

Jan 1, 2019

By M. K. Ameen, R. El-Hacha

This paper presents the analytical results obtained from numerical simulation of reinforced concrete slabs strengthened with various FRP systems and subjected to blast loading. A three-dimensional finite element model using AUTODYN software was used to predict the overall behavior of the slabs. The numerical results were validated by comparing with experimental results from a program carried out to investigate the efficiency of different strengthening systems on the blast resistance improvement of small-scale reinforced concrete (RC) slabs. The experimental program consisted of testing nine RC slabs strengthened with three different externally bonded (EB) FRP systems attached at the bottom side of the slabs and one RC slab tested without strengthening for comparison purposes. The EB FRP strengthening systems investigated included two layers of Carbon Fiber Reinforced Polymer (CFRP) sheets, two layers of Glass Fiber Reinforced Polymer (GFRP) sheets, and one layer of Glass-Fiber Resin Polymer (GRP) sheet. Different epoxy resin, patching mortars and impregnating epoxy adhesives were used for the slab surface preparation and FRP system application of the strengthening layers. The aim was to evaluate the residual strength of the test specimens after exposure to blast loads. The blast loading parameters were evaluated for each test using AUTODYN simulation and compared with the computer program CONWEP. All specimens were subjected to same spherical TNT charge weight and stand-off distance with the respect to the slab top surface. Extensive comparison is made between the experimental results and the AUTODYN simulations for the control unstrengthened slab and the strengthened slabs including time history records of the bottom steel strain and mid-span acceleration and the peak dynamic deflection of the slabs.

Jan 1, 2010

By D G. Dressler, Paul Yeager

A previously little-known facet of seismic frequency spectrum analysis is gaining significance. The frequency spectrum of seismic waves promulgated from blasting is a significant factor in causing blasting complaints and threshold (architectural type) damages.

Jan 1, 1987

By H J. MacDonald

An Exploding Bridgewire Detonator (EBW) is an explosive initiator which contains only secondary explosives such as PETN and RDX. It is safer than the normal blasting cap because it requires both high electrical energy and a very fast application of that energy to function

Jan 1, 1981

By R J. Roach, D Roy

After months of discussion on ways and means to improve productivity in the shaft sinking process, it was decided to look at those areas where, historically, methods have been stagnant for many years. These categories included drilling, hole diameter, drill patterns, explosive types, explosive loads, initiation techniques, cut design, wall control, fragmentation and heated magazines.

Jan 1, 1997

By D T. Froedge

A new system for acquiring blast vibration data and a method for presenting that data in such a way that there can be an extraordinarily enhanced insight into the understanding of vibrations produced by blasting is described in this paper.

Jan 1, 1989

By Sean Cahill

The Blasting In the summer of 1999, a Southern California drilling and blasting company conducted blasting as part of the grading operations at the Highlands Ranch development in San Diego, California. Highlands Ranch was a new single family residential project located near older residential properties in the area. Blasting was necessary to remove indigenous meta-volcanic rock associated with the local geology.

Jan 1, 2003