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By Stephen Mansfield

In metalliferous mining operations, subdrill is that portion of the blast hole that is drilled below the target grade elevation, and in most cases loaded with explosives. Its primary aim is to enable efficient excavation down to the target floor level. Subdrill is often described as being expensive and that excessive subdrill should be avoided, as it can result in damage to the subsequent floor, lead to difficult drilling conditions and higher vibration levels. As a result, many operations aim to apply the bare minimum amount of subdrill in order to excavate to the target floor. At a large open cut copper operation, challenging geological structure resulted in slabby and blocky fragmentation in the stemming region, resulting in poor crusher throughput due to bridging. To overcome the poor fragmentation in the top of the bench, longer than conventional subdrill was used to precondition the top third of the bench. The technique significantly improved the run of mine fragmentation and resulted in feed to the in-pit crushers that is more consistent, which produced less crusher downtime due to bridging. A new method of quantifying the energy in a blast has been created. Termed the linear powder factor, or energy factor, the calculation considers the energy contributed by the subdrill of the upper bench and its impact on the energy in the lower bench. The technique enables blast designs to be optimised to deliver finer fragmentation and more consistent blast outcomes. To support the layer of preconditioned rock at the top of the bench, an innovative new device was developed. The device is inserted into the drill collar immediately after drilling and remains in position throughout the subsequent steps of hole depth measurement, priming, loading and removed prior to stemming. The device not only supports the broken rock at the top of the bench, but also minimises the amount of drill cuttings that fall back into the hole. Furthermore, the device helps protect the hole from damage by external factors such as weather events, drill tracks, vehicle tyres and movement around the collar during measurement and loading of the blast hole.

By Joshua Micah Hoffman, Jhon Silva-Castro, Kylie Larson-Robl

A coal mine impoundment failure has the potential to be environmentally devastating and life-threatening. It is well documented that after seismic events slope failures in impoundments can occur. It has been concluded that often the main driven factor of the failure is the increase in excess pore pressure due to ground vibration. A small amount of research has been done regarding the stability of coal mine impoundments under natural seismic events; however no research has been done considering vibrations from mine blasts. If it is taken into account that current environmental restrictions oblige to increase the capacity of coal mine impoundments, thus increasing the hazard of such structures, it is necessary to evaluate the effects of near-by mine blasting on the stability of the coal mine impoundments in order to mitigate and control the potential of slope failures. To study the behavior of excess pore pressure under blasting conditions, scaled simulations of production blasting events were set up inside of a controlled sand tank. The research was divided in two stages. The first one was done, using dry conditions, while in the second part, the same set of tests were performed under saturated conditions. This document shows the partial results for stage one (dry conditions). For the tests, explosive charges were set off within the sand tank at various distances to simulate different blasting distances. Information was collected from geophones, accelerometers, microphones and high speed video camera for dry and saturated scenarios and additionally from piezometers under saturated conditions to assess the behavior of the material under blasting conditions.

Jan 1, 2015

By Alan: Moore Richards

Effective control of airblast requires that significant factors be identified and satisfied by blast design and careful implementation. Significant factors include charge mass, distance, face height and orientation, burden, spacing, and initiation sequence, stemming height and type, topographical shielding, and meteorological conditions. This paper utilizes case histories of blasting in Australian open pit mines to demonstrate techniques that have been used to control airblast to applicable limits.

Jan 1, 2006

By Enver Alan, MerkeziYapı

People are migrating because of economic, social, natural and political reasons. These natural and humane factors effects the distribution of populations. The need for tunnels has grown in order to provide a comfortable life and reduce losses such as waste of time, labor, energy, efficiency and so on. It is inevitable to carry out excavations in rock tunnels (shears, platforms, lines, connections, wastewater, distribution, energy, transportation etc.), that will be built by excavating with conventional method, by controlled blasting regarding with constrains. In this study of applied explosives engineering the blasting applications are evaluated, which were carried out for research and development purposes at Yenisahra Station tunnels in Kartal Formation which was built with the aim of solving İstanbul's transportation problem within the framework of the Kadıköy-Kartal Metro Project. Twenty-four shots were made by using explosives in 60 blastholes that were drilled in the tunnel faces, which were located between and outside of two different faults. Six microphones were used to measure the air shock and eight geophones were used to measure the parameter values of the vibrations (particle velocity, frequency, displacement, acceleration, amplitude, wavelength etc.), which were placed at predetermined points of the surface, occurred during the blasting applications. Data from the geophone and microphones were recorded on six seismographs. The coordinates and the distances between the shot points and the measurement stations are determined by an electronic theodolite. The total number of seismic records, recorded in seismographs, is 118. The number of records of vibrations that crossed the faults is 42 and the number of records of vibrations that did not cross the fault is 76. The particle velocity, frequency, amplitude, acceleration, displacement and wavelength were measured in transverse, longitudinal and vertical directions. The total number of measurements is 354. By evaluating all seismic records, the effect of delay intervals, faults and scaled distances on the particle velocity, frequency, amplitude, displacement, acceleration, wavelength and air shock were investigated. When the vibrations formed during the Research & Development (R&D) blasts were examined, it was determined that the parameter values of vibrations that crossed the faults are lower than the ones that did not cross the faults. In addition, when the particle velocity values of all vibrations are examined according to the present circumstances, it is determined that the waves did not cross the fault in all delay intervals are superposed in all directions, and that the least superposing occurred in the 50 ms delay range.

By Anthony J. Konya, Calvin J. Konya

Mine sites and construction projects have faced problems with blasting a smooth back wall. This lead to safety concerns with slope stability and rock falls from the walls. Decades ago Dr. Calvin Konya began a special type of blasting called “Precision Presplitting”. This form of presplitting used relatively light loads based on the rock type being blasted. The explosive loads were estimated for each rock type and adjusted as blasting progressed. This current research project also determined a new equation for prediction of the ground vibration from one type of presplitting and compared it to vibration from production blasting.

Jan 1, 2016

By Conny Postupack

The first principle one usually learns about blasting is that competence in this field is best gained by experience in making blasts rather than by reading a book or by listening to a lecture. The reason for this is that there are a large number of variables affecting blasting results and not all of these can be accounted for by a few rules or a few sets of equations. Even an experienced in a new area, may have co make one or two himself to the new conditions with which he blaster when operating shots just to acclimate is faced.

Jan 1, 1991

By J A. Singer, S R. Iverson, C A. Link

High resolution seismic refraction tomography has proved to be a useful tool to effectively estimate depth of blast induced damage in a mine face. Excavation blast damage can be as shallow as 1 to 2m and requires resolution at a fraction of a meter for effective imaging. We used an accelerometer with flat frequency response to 1000Hz to record data at spacings of approximately 0.25 to 0.5m along mine walls. First arrival times from the seismic data were used to produce P-wave velocity tomograms. The tomograms show transition from low velocity zones to velocity associated with competent rock. We interpret the low velocity zones to indicate residual fracturing from blasting. Experiments on a concrete test block and at two underground mine locations give results that are consistent with fractured rock transitioning to competent rock. Our method can be applied efficiently in an underground environment to provide continuous velocity information with depth into a mine wall over a span of approximately 10m.

Jan 1, 2009

By Roger S. Jackson

"This study interprets vibrations produced by single underground shots, recorded on surface by 135 digital seismographs laid out in four linear arrays. Several vibration anomalies were observed and are investigated. A novel method of displaying the blast-induced vibration iso-contour data relative to the three-dimensional representations of the geological rock units and structures leads to the following interpretations:• The identified faults commonly dampen or amplify vibrations, on the evidence of the peak particle velocity,• Strong anisotropy of geologic formations produces different vibration attenuation in the various directions of interest,• Low-vibration “depressions” can be related to the presence of faults, and• Higher vibration levels than expected based on ‘scaled-distance’ principles are observed close to intersecting faults.The interpretations from this study document a better understanding of the geotechnical influences on blast induced stress wave propagation in a geologically complex area. The practical benefit of this understanding is better control of surface vibrations, experienced from underground mining activities."

Jan 1, 2010

By Stewart A. Silling, Dale S. Preece

The two key results of rock blasting are fragmentation and movement of geomaterials. Movement/flow of the blasted rock is often referred to as heave. Modeling the movement of full scale blasting is now possible with 3D distinct element models and parallel processing.

Jan 1, 2016

By U. Gorkhan Akkaya, N. Enver

Geographic information system (GIS) is one of the most accurate and useful tools to help decision – making for decision-makers. As to expert systems, it provides solutions to the problems faced by mimicking reasoning of the human experts. Blasting operations in mining include high risks for the vicinity of the operations. GIS having required mechanisms to take right decisions for the people who have to make right and precise decisions, while it is utilized as a integrated system with expert reasoning, is thought to be considered important tool that provides to take decisions with ease, and also to reduce the risks in the blasting operations. It is possible to find out both of the economic and optimum solutions to solve the various encountered problems in the mining activities such as blasting operations, only when GIS integrated expert systems is used. Managing the spatial data unified with expert reasoning is the one of the greatest advantages of the system. In the scope of the study, various scientific studies were investigated. The benefits of the system were figured out and the phases of a unified system were proposed in the blasting operations.

Jan 1, 2013

By Unknown

More than 60 years ago Lakota (Sioux) Chief Henry Standing Bear asked Korczak Ziolkowski to create a monument of Crazy Horse in the sacred Black Hills. Today, you can see Standing Bear’s dream has grown into enormous reality. Crazy Horse Memorial, mankind’s largest mountain carving in progress, is being carved in the round and when completed will be 641 feet long and 563 feet high. Crazy Horse is only 17 miles from Mount Rushmore National Memorial, giving South Dakota unique boasting rights for having two extraordinary mountain carvings in such close proximity

Jan 1, 2009

By Dale S. Preece, J Paul Tidman, Stephen H. Chung

A discrete element computer program named DMC-BLAST (Distinct Motion code) has been under development since. 1987 for modeling rock blasting (Preece & Taylor, 1989). This program employs explicit time integration and uses spherical or cylindrical elements that are represented as circles in two dimensions (2-D). DMC-BLAST calculations compare favorably with data from actual bench blasts (Preece et al, 1993).

Jan 1, 1998

By Brian T. Burch, Paul N. Worsey

When fired, submerged Linear Shaped Charges (LSCs) lose all effectiveness in the cutting of steel. Users in underwater applications have reported having to substantially increase the charge size to the point where brute explosive force shears rather than cuts the target.

Jan 1, 2015

By M Scoble

This paper will report on the application of data collected through the performance monitoring of large diameter surface rotary blasthole drii and electric mining shovels, in an integrated approach to blast optimizatiion.

Jan 1, 1992

By Mark A. Williams

Topography and geology greatly impact the decision of how to plan and operate a surface mine. To extract coal, five primary surface mrning methods are practiced in the United States. These include contour strip. mountamtop removal, area, modified area, and open pit mining methods. The first four approaches are commonly associated with coal mining while open pit techniques, although used in the mining of coal, are more commonly applied to the mining of hard rock, metals, and aggregates. Various sub-routines of the primary surface mining methods are likewrse applied rn the industry.

Jan 1, 1991

By Lon Santis, Dale Ramsey

The use of aircraft to support blasting operations in mines, quarries and construction sites goes back to the early days of aviation. Invaluable at times, aircraft use has been limited by cost, the unpredictability of weather impacts and other factors. Recently several technologies have matured to open up a new way to acquire aerial data with unmanned aircraft systems (UAS), commonly called drones. Equally important, the U.S. Federal Aviation Administration has recently implemented an exemption process and rulemaking to implement the commercial use of UAS into the United States’ National Airspace. The skies are opening for many applications of UAS. The most notable may be photogrammetry, which is the science of making measurements from photographs, especially for determining the exact positions of surface points.

Jan 1, 2016

By Vic Sterner

As cities and towns continue to grow, the need to install sewer, water, gas and other utilities becomes a necessity and the blasting of trenches for these service lines probably constitutes one of the most important forms of blasting in built-up areas. There f o re, understanding how explosives can be safely used in the most efficient manner is of prime importance. The need for protection against flyrock must be emphasized. The first consideration is that all explosive c h a rges should be located well down in the blastholes. The golden rule is to ensure that the depth of top stemming is never less than the burden on the hole. In the case of shallow holes, the minimum depth of stemming should not be less than 18 times the charge diameter, if airblast and flyrock are to be controlled. If there is a doubt, then additional cover and/or blasting mats should be used. Putting too much burden on blastholes is another possible cause of flyrock and raising ground vibration levels. Overburdening of explosive charges will also result in the blastholes not breaking to grade. This in t u rn re q u i res additional drilling of shallow holes down in the trench to achieve grade, thus further increasing the h a z a rd of flyrock .

Jan 1, 2004

By Grigor Mishev, Georgi Petrov, Benjamin Cebrian

Before designing a single blast or all the blasts on a pit level, it is critical to assess the main goal on each. To do this, a series of constraints must be taken into account: wall protection, vibration control, flyrock hazards, fragmentation required, desired displacement as well as economy, equipment efficiency. The tool to do this is the Blast Master Plan. Many mines fail to integrate on its elaboration key stakeholders such as planning, operations, geology/geotechnical and milling departments. Designs not only have to provide consistent behavior of the blasts, but have to make sense all in one with the geological and geotechnical conditions as a starting point. Once blasts are designed under an organized set of priorities, and complemented with quality controls, optimization is possible on a large scale.

Jan 1, 2016

By William C. B. Gates

Demolition blasting next to an active railroad can be very challenging because of track safety, blasting vibrations, potential track fouling by blast debris, and short work windows on a live track. Recently, in eastern Washington, one of the major railroad companies has been aggressively constructing a second main track to accommodate the expected increase in rail traffic of natural resource products. To accommodate construction of the second line, the railroad company used blasting demolition techniques to remove an old railroad trestle pier on the Milwaukee Road that was in the footprint of the new track bed. The trestle bridged the present rail line and flanked the track with two massive 550-ton (499 tonne) twin-columned steel reinforced concrete piers. The railroad contracted with a specialized contractor to remove the south pier using blasting demolition techniques. The blasting design presented the following challenges: blasting during live track conditions and short work windows; designing a V-notch blast pattern to ensure the pier fell away from the live track; drilling, loading, and timing of the shot; maintaining blasting vibrations at the track below 4 in./sec (102 mm/sec); maintaining ambient overpressure noise below 133 dB; control of fly rock and debris; and track protection and emergency debris removal plan.

Jan 1, 2016

By Joseph Nawrocki, Margaret Hettinger, Dr. Catherine Johnson

"Optimized rock fragmentation is essential for minimizing downstream costs to mining operations.Photographic fragmentation analysis, vibration monitoring, and high-speed video all providemeasurements of blast effectiveness and supply data that allows operations to modify blasts to achieve downstream goals."

Jan 1, 2016