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By Jeffrey W. Lin, Jonathan D. Abbott, Patrick R. Bowden, Tyson J. Plitt

Pentolite is a class of high explosives containing trinitrotoluene (TNT) and pentaerythritol tetranitrate (PETN) with PETN content typically ranging from 40 to 60 wt%. Manufacture involves melting TNT, 80 °C, followed by addition of PETN and trace ingredients to form a homogeneous mixture. Once a mix is ready to be poured, several factors can influence the behavior of the finished product including how long the mix has been at temperature and cooling rate. After the manufacturing process has been completed, storage conditions combined with manufacturing conditions may cause physical changes. Two such changes explored were exudation, liquid exuding from solid boosters, and ratchet growth, irreversible volumetric expansion. Exudation is principally caused by excess water in the process. Ratchet growth is a common phenomenon of nitroaromatic compounds such as TNT where time and temperature fluctuations can cause materials to increase volume, simultaneously decreasing density. Although neither phenomenon affects common attributes such as sensitivity, performance, and shelf-life, both can cause issues in storage and handling. In this study pentolite was cast into various forms under different manufacturing conditions and evaluated over several months of controlled storage conditions including ambient, temperature cycling and elevated isothermal. Subjective and objective measurements were made throughout the evaluation period with the aim to determine the preferred storage methodology.

Jan 21, 2025

By R. Alford

In the modern world of demolition safety is paramount and unnecessary or unquantifiable risks are not accepted (FasterCapital, 2024) and all risks must be kept As Low As Reasonably Practicable (ALARP) (BSI, 2017). This principle has led to a huge reduction in deaths in the last 50 years and the statistics continue to improve although this is starting to plateau (Beal, 2007). Under normal circumstances, this is now simply part of the normal way work is done and systems are in place to ensure both safety and economic profits are assured. What happens when the environment is less controlled and risks are unknown, such as after a natural disaster, war, an accident or a stand-up from a failed demolition attempt? A dangerous structure cannot responsibly be left alone with a fence around it so some action must be taken, but how can this be done safely and responsibly? An incident in Didcot, England in which half of a power station’s boiler house being prepared for an explosive demolition collapsed suddenly, killing four men in 2016 provides a useful case study of how technology, creativity and planning can be used to conduct complex demolition fully remotely to avoid any further risk to life.

Jan 21, 2025

By Scott G. Giltner, Alex Schwenk

This paper is an update on a paper presented at the 2022 ISEE conference. The original paper presented how the mine operator desired to open up ore reserves near several mine structures including two crushers, the conveyor belt drive and the concentrator thickeners. In order to open up additional ore for extraction (over 3 million long tons or 3 million tonnes) it was necessary to blast out two benches near the mine structures. Since the two benches have been successfully shot, the mine has now conducted nine production blasts in this area at distances as close as 116 m (380 ft) to the two primary crushers. These production blasts are full size production blasts consisting of up to 300 or more blast holes. For these blasts the two primary crushers were still the critical structures as they were the production life blood of the mine. If the crushers were shut down due to any damage from the blasting, the revenue of the mine would be adversely affected. As with the initial bench blasts, two issues provided an extra challenge to the blast design. The first was that the blast holes were still considered large diameter at 12¼ inches (311 mm) and 16 inches (406 mm). The second issue was that the bench heights were short, with the average varying from 34-40 ft (10.3-12.2 m). This combination of large diameter blast holes with a short bench provided an unfavorable geometry for the goals established by the mine management. The mine management established the following goals. 1) None of the mine structures would be damaged by fly-rock. 2) Minimize the blast vibrations at the crushers. 3) The last goal was to produce a muck pile that could be dug easily by hydraulic shovels. Electronic detonators were applied to achieve the necessary control of the blast and optimal fragmentation throughout the mine. UAV surveys of the blast area were also conducted to provide a 3-D representation of the free faces and bench surface. The 3-D point cloud produced from this was used to measure the shape of the free faces. Once the shape of the free faces was quantified, it was possible to establish proper placement of the crest holes and develop a custom explosive load for each blast hole. The results of the nine blasts have provided what the customer requested. The peak vibration level at the crushers for the nine production blasts was 1.6 in/s (40.6 mm/s) at a frequency of 18.9 Hz. There have been no fly-rock or blast vibration issues at any of the nearby mine structures. As a result, the mine has been able to maintain its production with no downtime. The muck piles have been well fragmented with reports from the shovel that they have all dug well.

Jan 21, 2025

By Hector O. Romero, Paulo C. Fernández A, Claudio C. Gajardo

Phase 06 of the Los Bronces mine, currently under extraction for development, has the particularity of being close to the installations and buildings of a neighboring copper mine. Therefore, the blasts must ensure the continuity of the operation without affecting the nearby structures of the neighboring district, which include Maintenance sheds and Warehouse. Specifically, the safeguards consider a scenario that includes: - Flyrock projections (<150m) - Edge profile studies - Vibrations according to the NCh3577 standard - Nitrous gases Additionally, Phase 06 is also within Los Bronces, so strict control over spillage into the pit is necessary to avoid blocking ramp access to this level. The challenge lies in protecting not only the operation and facilities of the neighboring mining district but also the operability of Los Bronces. Thus, addressing these considerations, blasting configurations are developed with prior simulation of vibration models, flyrock, and spillage in all blasts, with strict control of technical design and implementation to ensure the results. Currently, blasts are successfully executed with control of projections based on the proximity of the projects, vibration (<40mm/s) with decoupling of holes of 17 mm/s between holes, reactive rock tests for explosive selection (loading advancement), and spillage simulation inside the pit according to the loading design; thus, ensuring operational continuity and mine development.

Jan 21, 2025

By Paulo Couceiro, Juan Navarro

The impact of rock blasting fragmentation and heave on digging performance in open-pit mining operations is usually the first true indicator of blasting outcomes. Within the typical excavation cycle, the bucket loading time or instantaneous digging rate are the ones that present the strongest correlation with rock fragmentation size distribution, swelling, and shape of the muckpile, a part of rock mass hardness, equipment size, power, and others. As the efficiency of unit operations becomes increasingly important for long-term mining strategies, cost-effective approaches are needed to increase mine productivity. In this line, the performance of downstream operations, such as digging, hauling, and comminution, may be affected by the energy input in blasting. This requires a better understanding of the explosive’s energy role in such unit operations in order to drive consistent improvements. Therefore, this paper examines the impact of the explosive’s energy distribution on shovel diggability from production shots carried out with different explosives in an open pit gold mine, with the aim of modelling the interface between blasting and excavation.

Jan 21, 2025

By Dr. Anurag Agrawal, Steve Franklin, Clint Zimmerman, Elijah Williams

In a time when data has become a highly valued commodity within many mining and quarry operations, managing large amounts of current and historical information can be difficult. If not managed properly, trying to leverage the data to make informed operational decisions promotes another challenge. Geographic Information System (GIS) is an environment that uses computers and software to create, manage, analyze, and map all types of data. Currently, the mining industry is faced with a challenge to produce the demanded critical metals and minerals that drive our economies. GIS is leveraged in many large mining industries today to help drive decisions, save cost and plan for future operations. Specifically in the Drilling, Blasting and Quarrying industries, data is being captured at many different levels, whether it is a subsurface geological, blast performance, quarry surveys, loading and hauling, or crushing performance. Pen and paper logs and reports compiled lack the dimension that GIS can bring for extracting value from real-time or historical data. GIS connects data to maps, integrating location data with all types of descriptive information. Paired with Artificial Intelligence, additional analytical layers can be built on platforms to extract data and automate workflows. Having the ability to encompass several forms of collected data to drive operational decisions can bring huge savings to the bottom-line. This paper will dive into the areas where GIS data can drive value into operations by assisting in the management and analysis of the types of data being captured, specifically with Drill and Blast. Whether it is tracking haul road conditions, monitoring locations of equipment, environmental conditions, quantifying blast performance or developing a quarry plan based on geological models. GIS can collectively encompass all of this data to bring tremendous value to the operations, improving safety, efficiency and production.

Jan 21, 2025

By Sami Kara, Yunseok Park, Seung-Joong Lee, Namsun Hwang, Michael Laing

This study conducts a comparative analysis of construction efficiency. In the first part we compared electronic and non-electric initiation systems, focusing on tunnel contour holes. Field blasting operations were executed across a variety of delays to identify the optimal delay time. This delay for the in-situ rock mass was determined through regression analysis of blasting vibration in contour holes and for overbreak/underbreak. The blasting results with the electronic initiation system using the obtained optimal delay, applied to contour holes, were compared with the results of the non-electric initiation system. The overbreak and underbreak decreased by an average of 2.7 cm and 5.8 cm respectively, by using the electronic initiation system. Moreover, the vibration reduction rate in contour holes region was reduced by 11.9% based on the blasting vibration estimation equation proposed by the Ministry of Land, Infrastructure, and Transport (MOLIT). Underground construction projects have become increasing popular as cities grow in both size and density. This growth severely limits the amount of useable space for new project on the surface, resulting in the decision to build them underground. This new policy however brings into focus the challenge of managing and reducing blasting related vibration due to the proximity of these projects to sensitive structures, utilities and foundations often present in urban environments. For this purpose, we have been required to manage the vibration by reducing the quantity of explosives used per round. Inspired by surface blasting techniques, we applied a decking mode to address and work around this challenge. We present in this paper the first attempt to blast a tunnel face using a decking method and reduce the charging per hole from 6 kg to 3 kg per hole and keep the same advance rate for this tunnel. The results are presented in the third part of this paper. In the second part we present the results of the decking mode in shaft. The use of the electronic initiation system in tunnel construction provides the users an effective tool to improve the overbreak/underbreak and keep the vibration at a low level with a large gain on the overall project schedule and budget. This what we want to demonstrate in this paper.

Jan 21, 2025

By Dr. Zach Agioutantis, Elliott Morgan

The explosives, mining, and heavy civil industries consistently battle the uncertainty that is associated with working with a heterogenous medium like rock in blasting. This has led to studies to increase fundamental understanding of material response under dynamic loading that is associated with blasting. This study looks at the dynamic strain associated with blasting the lab Split-Hopkinson Pressure Bar (SHPB) testing while also building off of previous studies with the goal of better understanding the dynamic forces that are enacted on a geologic body during a blast loading event. This is required in order to advance geologic blast response modeling. This is achieved through analyzing the stress and strain values for each specimen that are calculated from strain data collected with a SHPB. Based on this data, the dynamic material response characteristics are able to be determined. Tests were conducted on five Berea Sandstone specimens with a rough length to diameter ratio (L/D) of 1.0. The strain data from these tests were then used to create stress strain curves as well as charts depicting failure stress to both strain rate and failure particle velocities. The tests conducted returned similar results to previous tests results on Berea Sandstone while also showing a correlation between strain rate at failure and failure particle velocities. While further research is needed, there is evidence that SHPB test data could be used in conjunction with the MBF model. The MBF model states that the peak particle velocity (PPV) of blast vibrations can be correlated with deformation (strain) at a given point. With a further understanding of dynamic material response correlated to PPV measurements, further refinement could allow for better prediction of blast performance.

Jan 21, 2025

By Dr. Tristan Worsey, Dr. Jhon Silva-Castro

Confinement is an important aspect of blasting. Reducing and increasing confinement can determine whether a blast design performs properly. Over-confined shots usually have poor fragmentation, higher vibrations, and stemming ejection, and unconfined shots usually have a lot of air blast and fly rock. When talking about confinement in blasting, static confinement conditions are typically referenced. Static confinement conditions are ruled by free faces, shot muck, burden, spacing, stemming, hole depth, toe, etc. All these conditions exist in a static state. Static confinement conditions are generally analyzed before the shot takes place, but once the shot starts, the conditions will change according to the sequence and delay of the shot. Once the shot starts, Dynamic confinement takes place. For the authors, Dynamic confinement is the confinement conditions that exist for the charge when it fires and should account not only for the variables included for the static confinement but also for the time and sequence of the shot. The paper explores the theory of dynamic confinement and its role in influencing blast performance. Time and sequence are the main influencers of dynamic confinement and will be the focus of the paper. How to generate the appropriate timing based on blast design, dynamic confinement, static confinement, and geology will also be discussed.

Jan 21, 2025

By Benoît Pinier, Jason Furtney, Gustavo Sampaio Lopes, Jorge Valencia, Johan Hawinkel

This paper describes a numerical modeling study on the effect of airdecking on vibrations, fragmentation, and movement in mining-related rock blasting. Practice has shown that air gaps reduce blast vibrations and damage while maintaining the required fragmentation and movement, yielding similar blast outcomes with less explosive mass per hole. Given that the premise of “replacing explosives with air” for better blast results is counterintuitive, this paper aims to shed light on the physical mechanisms and processes occurring in a blast with airdecks. It is hypothesized that airdecks are effective and beneficial because they load the rock at pressures lower than what is required to crush the rock. In the airdeck, the explosive gasses directly fracture rock and avoid energy loss due to crushing. In essence, the airgap allows similar outcomes in fragmentation and throw with less total explosive product, as the lower pressure gasses in the airdeck are still effective at breaking and moving the rock. This is distinct from only having less explosive and more stemming, as the stemming reduces the pressure more than an airdeck at the same position. This study uses the blastFoam software (for modeling of single and multiphase flows) to accurately calculate the pressure history throughout a blasthole and air gap. The pressure and gas loading are coupled to numerical models of vibration, fragmentation, and blast movement. Using this modeling technique, a suite of blast scenarios for typical configurations in a range of commodities is assessed with and without airdecks. Rock blasting practitioners have a responsibility to protect communities, infrastructure, and heritage — demystifying airdecks through a better understanding of the physics provides another tool in the blasting engineering toolkit to serve this goal.

Jan 21, 2025

By Julio Cesar Barbosa de Freitas, Rafael Gonçalves Araujo, Túlio Soares, Jair Koppe, Augusto Ferraz Ribeiro, Pedro Barreto Garcia

This study thesis was motivated by the fact that it is of fundamental importance for open pit mining that the slopes initially have a geometry in accordance with what is proposed in the mining planning. This occurs because an inconsistency in this design can impact the operational safety and economic solutions of the mining project. These consequences can be explained by the fact that rock blasting close to mining limits requires specific study due to the attention required. Because, when this operation is not carried out properly, the mining plan in the mine may not be respected and may create risks to the operation due to the presence of unstable blocks on the slopes (Mackenzie). In this sense, Mackenzie (2004) cites pre-split, trim blasting and buffer as commonly used explosive blasting techniques that aim to limit damage beyond the projected wall. Therefore, Enaex Brazil realized the need to better understand the pre-split method. To do this, it is necessary to understand how the energy released during detonation is perpetuated in the rock mass when this technique is used and when it is absent. Thus, this analysis is based on a seismic study that allows the creation of vibration attenuation laws and an elementary wave damage model, which allows the local characterization of the rock. With this model it is possible to relate the peak levels of vibration during blasting and the extent of damage, but a critical level of vibration (PPVc) and its relationship with the Uniaxial Comprehension Resistance (UCS) are also defined for the start of fracturing and its level (McKenzie et al, 1995). And, mainly, this work aims to address a way to measure the pre-split filter potential by comparing the attenuation law with and without pre-split, ultimately knowing whether this finishing blasting is being effective, to understand the pre-split filter capacity.

Jan 21, 2025

By Joseph A. Meyers

NYC has always been a high-profile target for both foreign and domestic terrorists. Explosives have always been the go-to tool for terrorists to bring about serious physical injury, death, and property damage in our society. Today with the anti-police movement gaining traction in the United States and anarchists groups using homemade explosives against law enforcement and municipalities, it is the responsibility of the explosives industry to ensure that every explosive product on a blasting site is secure. We must prevent the theft of these energetic materials used on projects and sold by vendors so they are not used by these terrorists. We have learned many lessons here in NYC which began with the theft of explosives used for blasting projects in NYC to supply the IRA (Irish Republican Army) 50 years ago. The liability is too significant to take short cuts in securing energetic materials. Over the years through cooperation with all agencies and the industry we in NYC have developed certain proven protocol and procedures we would like to share with the industry. An efficient and effective security plan for the logistic movement of explosives, as well as for the blast site is imperative to keeping the good name of the industry from negative repercussions and possible additional bureaucratic oversight of an industry that is highly regulated and still recovering from the pandemic. Communication, security assessments and transparency with all stakeholders and the Authority Having Jurisdiction (AHJ) will greatly improve the overall security for the blasting project. This SOP (standard operating procedure) will allow the AHJ to become a proactive partner in the security of the blasting project. If the AHJ is not a law enforcement agency, the law enforcement agency specialty unit must be notified and included in all phases of the project. The security for a blasting project with AHJ and law enforcement input starts at the inception of the project when the memorandum of understanding (MOU) is obtained, and involves the AHJ through all steps of the approval process. This includes threat assessments on new and existing structures. SME’s (Subject Matter Experts) must be present at all stages. The blasting industry and regulators must work collaboratively to improve safety, security, and create a dialogue with law enforcement and the AHJ. Relationships are built through trust, teamwork, transparency, and communication and greatly improve the safety of our great country.

Jan 21, 2025

By Travis A. Davidson, Ralph E. Burnham, Cathy Aimone-Martin, J. Kelly Ratliff

Blasters face a long list of tasks to execute daily—from vehicle inspections to blast design and layout, hole loading and tie-in, securing the site, and finally, safely executing the blast. Good practices and, in most cases, regulations and requirements necessitate documenting their work, specifically their blast report. While some blasters use paper forms, others use electronic means to streamline the process. The authors have served as attorneys and expert witnesses in representing companies and individual blasters in numerous administrative and legal matters in which documentation of the blaster’s work was both critical and detrimental to the effectiveness of defending their work. This paper discusses in a case-study manner the authors' observations concerning good blast report format, specific observations around electronic and paper report completion, record-keeping, seismograph setup and recordkeeping, video and photo documentation, internal auditing, and other topics related to documenting the blast. The paper aims to serve as a discussion guide for blasters to improve their blast record-keeping process, develop better practices that effectively document their work, and allow them to defend their work should a claim arise concerning their operations.

Jan 21, 2025

By Rachel L. Bauer, Catherine E. Johnson

Explosive demolition involves first, the use of cutting charges to sever a column and second, kicker charges to move it out of alignment. Dynamite is the traditional explosive used in kicker charges as it is inexpensive, easy to initiate, and has a consistent track record of use. Dynamite, however, has health concerns in handling, fragmentation concerns from direct contact on the beam, and availability concerns due to being manufactured at only one location in the continental United States. Recently, water-cased kicker charges have been used in industry, and research has shown that a reduced dynamite mass is possible due to the added confinement, for energetic performance, and the incompressible fluid, which aids in the transfer of explosive energy into beam movement. This research will compare two different explosives, an emulsion (DYNO AP), and binary (HELIX), to dynamite for use in kicker charges, both with and without water-casing. Emulsion is commonly used in rock blasting to create a large push or throw due to its high gas volume production which could translate to kicker charge movement. HELIX is a binary explosive commonly used by the military in breaching charges with water backing. Experimental tests placed kicker charges at the base of a hanging steel column, modifying the ballistic mortar test used to determine explosive power. The study shows that water-casing effectively reduces air overpressure and enhances explosive performance. Among the tested explosives, HELIX showed the most substantial improvements with a 1.8 dB reduction in air overpressure and a 3.2 m/s (10.5 ft/s) increase in column velocity when water-cased. Dynamite and emulsion also benefited from water casing, with decreases in air overpressure (1.1 and 0.7 dB respectively) and increases in column velocity (1.1 and 0.7 m/s (3.6 and 2.3 ft/s) respectively). This research also shows that emulsion is a viable replacement for dynamite in demolition projects, performing similarly in both traditional use and water-cased charges.

Jan 21, 2025

By Carlos Alvarado, Hernan Narea, Jhon Silva, Bryan Townsend, Katherine Gil, Brayan Caceres, Felipe Pontanilla

With the promising development of new technologies, automation in Drill and Blasting (D&B) is on the horizon. The data generated in all D&B activities, which is currently segregated, can be linked to become information and carry a logical meaning. This information can be used to identify critical activities and make decisions regarding corrective measures to accomplish the goals of D&B. Minera Caserones, supporting Alert2Gain (A2G), and Dyno Nobel, has been working on the development of a quality assurance and quality control (QAQC), system for the mine involving all D&B activities. The main variables in the model for D&B include data from the geology of the deposit, drilling, explosive products, and material loading, among others. To create the model, the mine is divided into blasting polygons. Those polygons are part of a block model. The block model is assembled following different rules, such as: • Block sizes of 4m x 4m x 15m, • Classification of the blocks to a particular blasting polygon using a geospatial intersection algorithm, • Algorithms connect all the pieces of data automatically with the minimum of human intervention and populate the block model, Because measuring data for each block is impossible, another set of rules and algorithms completes the model. Dyno Nobel generates an essential set of data for the QAQC system. Explosive truck loading rates and explosive products, among other data, are also included in the system. The system autogenerates reports every hour, and a summary of the results of each mining day (a mining shift of 12 hours) is distributed by email to all responsible persons to identify the critical tasks and then to make the proper adjustments to accomplish the goals of D&B. The information is updated every hour and available through a dashboard for easy and straightforward interpretation. This paper explains the conceptual details of the QAQC system implemented in Minera Caserones, how the data is aggregated automatically from the different sources, shows examples of the type of information in the dashboard, and presents a successful case where a deviation was detected, and the corrective measures that were implemented to keep the performance of the D&B activity. The paper finally discusses the next steps toward an autonomous D&B system based on new AI technologies, with minimum human intervention.

Jan 21, 2025

By Shadrack Nuamah, Erik Westman, Bright Afum, Jesse Addy

Rock fragmentation is the most critical aspect of hard rock production blasting due to its significant impact on drilling and blasting costs and the economics of subsequent loading, hauling, and crushing operations. This study analyzes current cost trends in the drill and blast operations of an anonymous open pit gold mine and proposes cost-effective drill and blast geometric parameters. The investigation focused on one operational pit with provided design parameters for two shots, shot 1 and shot 2. Existing blast parameters and two additional proposed sets of geometric parameters were evaluated using the Kuz-Ram and Chung and Katsabanis fragmentation models to estimate mean fragment sizes. The results indicated that the proposed blast parameters produced estimated mean fragment sizes within the mine’s desired range (not exceeding 45 cm). Additionally, the explosive energy was utilized efficiently per in-situ material blasted. The proposed parameters increased the estimated total volume of in-situ material fragmented by approximately 14% for both Shot 1 and Shot 2 compared to the current parameters. Furthermore, adopting the proposed blast parameters could lead to significant cost savings. The evaluated total drill and blast cost savings were approximately 11% for Shot 1 and 12% for Shot 2. These savings stem from the increased efficiency and effectiveness of the blast operations, highlighting the potential for substantial economic benefits. This study demonstrates that optimizing blast geometric parameters will allow open-pit mines to achieve desired fragmentation, utilize explosive energy more effectively, and realize considerable cost savings in drill and blast operations.

Jan 21, 2025

By Tacio Ferreira

A surface copper mine in the Western United States faced challenges in recovering rock and ore from final walls because of geotechnical constraints that require restrictions on methods for loading blastholes adjacent to the pit boundaries to preserve wall conditions. The operation had been using the same drill and blast designs for years. With changing geology, such as harder rock, as mining progressed, material was being left unmined in final walls because of poor breakage. The amount of unrecovered, unprocessed ore was estimated at approximately 380,000 tons a year generated from an average of 60 final wall blasts performed annually. The mine engineering team and Dyno Nobel engaged to minimize the amount of material left on the final pit walls. In this paper we present how we collected data, reviewed design standards, and found opportunities to improve ore recovery from pit final walls without increasing drilling and blasting costs. The results collected from implementing the new design on two benches showed the potential for extra revenue of approximately $3.6 million generated annually from reducing final wall unrecoverable underbreak by nearly 71% on the mine’s highwalls.

Jan 21, 2025

By D. Scott Scovira, Thomas Gustavsson

The potential of hydrogen peroxide explosives was introduced to Thomas Gustavsson and Robert Håkland by Dr Miguel Araos through his development of hydrogen peroxide gel compositions (HPG). In 2020, Thomas and Robert developed a concept project with Boliden Minerals and received Swedish government funding to evaluate HPG technology in a mine environment. The project showed HPG reacted violently with mine mineralization and concluded that HPGs did not offer a commercial solution due to safety concerns. Thomas and Robert engaged with Stefan Nilsson to develop hydrogen peroxide emulsion (HPE) compositions and the process techniques to manufacture them. In 2021, laboratory work produced a promising low carbon intensity, nitrate free, ammonia free, emulsion formulation based on industrial grade hydrogen peroxide and a fuel-emulsifier phase. Design and construction of an HPE pilot plant and underground charging unit commenced. The manufacture of hydrogen peroxide emulsion shares several similarities with the production of nitrate-based emulsions in that the plant is a facility to blend a strong oxidizer solution with a liquid fuel phase into a finished emulsion. A key differentiator between HPE and nitrate-based emulsion is that the manufacture of HPE is a cold production technology in that neither the oxidizer phase (HP) nor the fuel-emulsifier phase requires high temperature heating to prepare raw materials. A successful proof-of-concept HPE evaluation ran from April 2022 to October 2022 at Boliden’s Kankberg underground mine in Sweden. This evaluation demonstrated HPE technology's safety, performance, production, handling, and indicative environmental benefits.

Jan 21, 2025

By Johan Gjødvad, Catherine Aimone-Martin, Charles Dowding, Mathias Jern

A residential structure adjacent to a quarry in Ohio was instrumented to record structure motions, resulting wall strains and existing crack displacements in response to close-in blasting within 82 m (270 ft). The project is a cooperative effort among international experts representing the European Federation of Explosives Engineers (EFEE) and ISEE supported by more than 21 persons from eight different countries to compliment prior work performed at the Aitik Mine in northern Sweden. The focus of this study is to compare blast-induced vibration measurements relative to regulatory compliance limits as a percentage of allowable velocities among eight different countries for a one-story residential wood-frame structure with a brick-and-mortar exterior and full basement. Participating counties included Austria, France, Germany, Norway, Sweden, Switzerland, the United Kingdom (UK) and the United States (US). Geophones were placed on the foundation and in the ground in accordance with each country’s regulations to record peak velocities as a function of frequency or distance to blasting. This study extends the work performed at the Aitik Mine to include interior corner geophones to calculate global wall strains and micro-m (micro-in) displacement gauges mounted over an existing drywall crack to measure blast-induced dynamic crack responses and climatological influences on daily opening and closing of a crack. Structure responses were documented for 68 blasts conducted north of the structure from February through September 2023 of which 17 blasts were selected for detailed analyses. The highest in-ground PPVs recorded were 43 mm/s and 59 mm/s at the NE and SW corners, respectively. Measurements from these blasts plotted within each country’s limits provided a comparison of stringency among the counties. The percentage of compliance limits among counties ranged from an average of 114% for the US, UK, and Austria limits to the highest of 585% for Switzerland. Despite these high percentages of compliance for all countries, the global tensile strains induced by these blasts were at most only 12 μ-strains and occurred with the highest velocity blast that exceeded each county’s limit. This high percentage of compliance and low strain level demonstrates the restrictive nature of the regulations studied. Peak dynamic crack opening and closing during blasting averaged 20 -m (0.0008 in) while the 12-hour weather-induced crack displacement during the time period over which blasting occurred averaged 200 -m (0.008 in) and the largest 12-hr change in crack width was 356 -m. This low level of crack response validates the observation that the studied regulations have highly conservative limits for cracking potential of standard building materials.

Jan 21, 2025

By R. J. Durrheim, Y. Yabe, M. S. D. Manzi, DSeis team, N. Z. Nkosi, S. B. Mngadi, Jr. H. Ogasawara

On 5 August 2014, the Orkney M5.5 earthquake, the largest in South African gold mining districts, occurred with an unusual strike-slip mechanism at great depth of 4.78 km below the surface. In a rare case, the ML 5.5 earthquake occurred within the area covered by the legacy 2D and 3D reflection seismic data acquired in the 1990s and 2000s for gold exploration and mine development. In addition, the earthquake ML 5.5 rupture plane was recorded and accurately delineated by the underground in-mine seismic network near the source region. The integration of the legacy 2D reflection seismic data and mine seismicity data allowed us to identify a near-vertical structure, striking northnorthwest-south southeast (NNW-SSE). The ICDP-DSeis team drilled three holes (Hole A, Hole B, and Hole C), and two holes (Hole B and Hole C), intersected the upper edges of the ML 5.5 rupture. These holes recovered metasediments, metabasalts, intrusive rocks including dolerite sills and lamprophyre dykes adjacent to the fault zone, and the fault gouge. Late Prof. Tullis Onstott and geomicrobiologists installed a packer in Hole A and successfully recovered saline water and detected gas (~10 MPa). Slip weakening and rupture propagation are significantly influenced by the existence of fault gouges and the production of wear material between two sliding rock surfaces. Using the fault gouge material recovered from Hole C, we conducted friction experiments under dry and room temperature conditions at high slip velocity of ~100 mm/s and normal stress of 2 MPa. The resulting steady-state frictional strength was ~0.66 over a slip weakening distance of ~9.1 m. The steady-state frictional strength was high, which may be caused by large gouge thickness, and the rate of wear generation. As a result, it is proposed that the Moab Khotsong ML 5.5 seismogenic zone is complex and could be controlled by three main processes: a) the complex structural architecture of the seismogenic zone (e.g., intersection of fault, lamprophyre dykes, and dolerite sills); b) the mechanical process induced by tectonic and/or mining related stresses; and c) the mechanical and chemical processes caused by the water and rock interaction.

Jan 12, 2025