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By S K. Mandal, S Dasgupta

"Damage is classifi ed as loss in the integrity or deterioration in the quality of rock massand is infl uenced by methodology of excavation on the geo-technical properties of rockmass. Overbreak, on the other hand, is the result of damage and is quantifi ed in either of the terms viz., extra mucking, shot-creting, application of extra support system and extension of scheduled completion time. Damage or overbreak in rock mass by the impact of blasting, is generally unavoidable but, the magnitude can be minimized so that it does not deteriorate the quality or integrity of structure. The paper, here, analyses magnitude of overbreak of a powerhouse cavern with respect to different blast patterns implemented at the site. The magnitude of overbreak was analyzed in terms of profi le measurement with the help of laser profi ler and percentage of halfcast markings observed on the periphery rock wall. The paper revealed the impact of decoupling ratio, blast pattern and geometry of blasting patch on the magnitude of overbreak. The authors observed that presence of un-favourable joint pattern or foliation plane along the periphery rock wall couldn’t contain magnitude of overbreak within allowable limit. The analyses revealed that percentage of half-cast markings on periphery rock wall was infl uenced by response of rock towards detonation of explosive and cannot be a single parameter to assess the effectiveness of a blast. The analyses also revealed that magnitude of overbreak for down-stream wall was more than that observed in up-stream wall."

Jan 1, 2008

By Timothy D. Stark

Blasters are usually strictly liable for injury or damage caused by flyrock (trespassory invasion) and blast-induced vibrations (non-trespassory invasion). The application of strict liability to non-trespassory invasions has resulted in significant litigation that has hampered the use of blasting and the blasting industry. Stark (2002) proposes that blasters should not be held strictly liable for non-trespassory invasions but should be liable only if their conduct is proven to be negligent. This change in legal standard was proposed because improvements in blasting technology over the last thirty years allow blasting to be conducted without substantial risk of harm to property and thus the amount of harm imposed by a blast can be related to the level of care exercised by the blaster. It is anticipated that negligence standard will reduce the amount of litigation because a plaintiff will have a greater burden to overcome. To facilitate the acceptance of negligence standard by a court of law, this paper illustrates the application of the negligence and strict tort liability frameworks using actual cases in which a decision was rendered. It is evident from these cases that some of the successful claims under the strict liability framework would not have been successful, and probably not litigated, under a negligence framework, which could result in substantial cost savings to the blasting industry and consumers.

Jan 1, 2004

By Robert Hopler

In use, blasting powder is exploded by a spark from fuse, electric squib or miner’s squib, or by a primer of some high explosive, the last being employed only in heavy charges on open work. In mining, and sometimes in light charges on open work, blasting powder is made into cartridges by means of a paper tube or cylinder sealed at one end, which is known as the Du Pont tamping bag. Sometimes the paper cylinder is made by the miner by coiling a section of heavy paper, known as blasting paper, around a wooden pin, called a cartridge pin, and securing it with what is called blasting soap. The removal of the pin leaves a cylindrical cartridge open at one end, into which the powder is poured and the top folded and sealed with blasting soap.

Jan 1, 2014

By Dale Preece

In the late 1970’s and early 1980’s substantial resources were devoted to research focused on producing oil from the vast oil shale reserves in the western United States. Since the oil is solidified in the pore space of the shale, extracting it in production level quantities presented monumental technical challenges. Major advances were made in the methods used to extract oil from the shale in large quantities. Extraction methods evolved to culminate in the underground in-situ retorting process. In-situ retorting relied on explosive blasting of the shale to fragment the rock and induce sufficient porosity and permeability for a burn front to propagate through the oil shale. That burn front consumes some of the oil and liberates a substantial portion of it (~30%) for collection and further processing. Oil shale retorting is a blasting intensive process where the entire retort is rubblized in one very large, delay timed blast. Retort 7 in Western Colorado consumed 540,857 lb of slurry explosive to rubblized 348,940 tons of oil shale. Current rock blasting fragmentation predictive capabilities have evolved substantially since these retorts were designed and tested. It is the purpose of this study to simulate the explosively induced fragmentation of oil shale using state-of-the-art computer codes and material models and to infer retort design implications for future development.

Jan 1, 2007

By Clayton Thompson

Linear detonation wave generators (DWGs) shape a detonation wave so that every portion of the wavefront reaches the target “line” simultaneously. A projection-type linear DWG uses Gurney plate velocity predictions and Taylor deflection angle predictions to estimate the angle at which a thin projected flyer (typically metal) will impact a target. A mousetrap-style planar DWG consists of two projection-type linear DWGs working in succession to create a planar wave-front through shock initiation of each successive target explosive. The angle of deflection is critical to yielding a planar or linear wave profile. Gurney predictions, nominally accurate to within 10% of empirical results, may not yield ideal linear or planar detonation behavior when used with a grazing projection-type DWG, which typically requires accuracy within 2%. Simulations were conducted using AUTODYN hydro code to compare deflection angle prediction methods. Ranges of minimal error between Gurney and Taylor predictions and the results from the hydro code were determined, using PBX-9404-driven polyethylene flyers.

Jan 1, 2011

By Alain Blanchier, Pascal Bernasconi

Blasting operations took place on Channel coast NW of France to extend Flamanville Nuclear Power Plant (EPR new generation). The closest operating reactor building was monitored by a 24 remote vibrations transducers network to fulfil, on one hand, the severe environment constraints and satisfy high degree of productivity required by the project, on the other hand. Although these requirements usually are incompatible, this challenge compelled to introduce a seismic modelling technique to optimize blast designs using electronic initiating system. The “Hybrid Seismic Modelling” (MSH) uses blastholes signatures (seismic vibrations records) which are greatly dependent on geology and alteration of rock mass, explosives, charge geometry, blast configuration, and the final excavation shape. In order to respect severe vibrations limits, excavation layout was divided into areas with specific blasting modules - type and number of charges, single charge, initiating sequence. Thanks to this technique, it has been possible to reach lowest blasts vibrations levels and a better productivity compared to classical blasting operation at the same location in the past. After the modelling method presentation - principle and use precautions, technical improvements are reported.

Jan 1, 2008

By S. Behera, K. Dey

This paper presents a methodology for finite element (FE) modelling to analyse the total deformation of rockmass under blast-load, with a focus on predicting backbreak that may occur during surface blasting operations. Backbreak can result from improper use of explosive energy, leading to damage beyond the excavation zone and jeopardizing operational safety and productivity. The paper highlights the impacts of backbreak on bench stability, excavator operation, drilling operation, flyrock generation, and improper fragmentation and boulder formation in surface blasting. However, prior estimation of extent of rock breakage zone can provide an idea to formulate the blast design to control the backbreak. While vibration-based prediction models are commonly used to estimate backbreak, they require physical blasting experimentation. To overcome this limitation, the paper describes the development of a FE model using ANSYS Explicit dynamics, which simulates rock blasting and calculates the total deformation of the rockmass. The rockmass deformation is modelled using Drucker-Prager (D-P) strength model with the Jones-Wilkins-Lee (JWL) equation of state for the explosives. The accuracy of the FE model is evaluated through physical experiments, and the results are compared with the vibration models. The FE model demonstrates close proximity to physical observations as well as vibration model result in predicting backbreak, thereby offering a promising alternative to vibration-based prediction models. The primary objective of the study is to predict the response of the insitu rockmass to explosive blast loading and determine the effective rock breakage zone.

Jan 1, 2024

By Rafael Tadeu Pinto e Moura, Giorgio De Tomi, Jacopo Seccatore

This paper describes a research and development project in an open-cast mine with the goal to achieve an average P80 of 300 mm (11,8”) in the run-of-mine (ROM) product without altering the existing budget. The project included several variables in the blast design that were not previously taken into account, such as the orientation of natural joint sets in the rock mass, specific energy of the explosive and firing sequence. The new blast design method considered the directions of natural joint sets and determined the drilling pattern and the firing sequence accordingly to favor the movement of the blasted rock along its preferential direction, to reduce its confinement. At the end of the project, it was achieved an average P80 of 304 mm (12”) in the ROM, 50% lower than the one at the beginning of the project. The final blast of the project showed a reduction of 3% of the drill and blast cost, employing the same powder factor and the same drill pattern size used at the beginning of the project. The results achieved show how rock fragmentation is related to variables that are not contemplated in the most common fragmentation models: the firing sequence and the direction of movement in the blast.

Jan 1, 2015

By Takeo Ueda, Masashi Nakano

We have developed a new blasting system remotely controlled by an electromagnetic firing method, which has proved advantageously applicable to sites where rapid tidal current or deep water may cause serious troubles in underwater blasting operation by a conventional method.

Jan 1, 1983

By Jack Eloranta

Proper selection of stemming has a profound effect on blast performance. This paper describes several methods of evaluating stemming performance in 16-inch blastholes. Tests are done on stemming ranging in size from nominal 1/4" crushed rock up to railroad ballast size rock (2 1/2" > diameter < 3/4"). Concrete plugs (both pre-cast and poured) are evaluated as well as air decking.

Jan 1, 1994

By Calvin Konya, Anthony Konya

Presplitting is a form of blasting that when executed properly will create a smooth wall that will minimize secondary conditioning. In recent years, presplitting has become a popular technique to be used in both the mining and construction industries, however, presplitting fails on many occasions because of ‘geologic conditions’. This is typically because of improper explosive loads consisting of overloading and underloading blastholes. In this paper the authors introduce new factors such as a presplit factor which varies for different rock types, selection criteria for the spacing of presplits, and the optimization of explosive load for the technique of Precision Presplitting.

Jan 1, 2017

By David Jones, Jeff Bregar, Damien Bell

We have analyzed overpressure and ground vibration measurements for construction blasting for a large pipeline project. These field-measured levels have been compared to existing prediction curves in the literature and new curves have been proposed for overpressure and ground vibration for pipeline construction blasting activities.

Feb 1, 2020

By Ruilin Yang

Kinematic approach of blast modeling refers to using the velocity, strain, or displacement as controlling parameters to model blasting, rather than the stress and the material constitutive relations. The rock stiffness or constitutive relations is very hard or impossible to obtain due to the complexity of the rock mass property.

Feb 1, 2020

By Ian A. Niell, Alastair C. Torrance

A joint research programme conducted by BHP Central Research Laboratories and Du Pont Wesfarmers Pty Ltd examined the effect of the size of cast primers on the run up and steady state detonation velocities of ammonium nitrate based explosives as a function of blasthole diameter. Both continuous and point to point velocity of detonation measurement techniques were used. The field trials examined a number of the Du Pont HDP series of primers in conjunction with ANFO, emulsion and watergel explosives. Results indicate that the run up velocity of 187mm diameter ANFO charges is negligible using cast primers as small as 1509. However, emulsion and watergel explosives did exhibit run up in both 187 and 311mm diameter blastholes, independent of the size of primer. This could last from 7 to 10 blasthole diameters.

Jan 1, 1990

By Armin Iravani, Changping Yi, Matthias Wimmer, Daniel Johansson, Santiago Gómez, Håkan Schunnesson

Sublevel caving (SLC) is a mass mining method based upon the utilization of gravity flow of blasted ore and caved waste rock. Drilling and blasting are the initial and the major impact on primary fragmentation and later material flow characteristics. The heterogeneity of rock mass has a great impact on materials’ mechanical properties and plays a significant role in rock fragmentation by blasting. In this work, a numerical model for sublevel caving based on 3D Voronoi tessellations was developed to section rock mass into arbitrarily shaped regions for modelling the heterogeneous rock mass. A coupled finite element and discrete element method was employed to investigate both the fragmentation due to blasting and the gravity flow of ore in a heterogeneous orebody. In the coupled model, the caved waste rock was modelled with loose discrete particles while the orebody to be blasted was simulated with bonded particles. The detonation of explosives was described with a particle blast method and a finite element model was used to model the remaining orebody. The results indicated that the fragmentation at the upper part of the ring is coarse while it is fine at the lower part of the ring. The heterogeneity of rock mass induced some boulders after blasting.

Feb 6, 2023

By Hike Humphreys, Geoff Baldwin

A project aimed at blast optimisation for large open pit coal mines is utilising blast monitoring and analysis techniques, advanced dragline monitoring equipment, and blast simulation software, to assess the major controlling factors affecting both blast performance and subsequent dragline productivity. This has involved collaborative work between the explosives supplier, mine operator, monitoring equipment manufacturer, and a mining research organisation.

Jan 1, 1994

By J. D. Aubertin

Rock blasting is a complex engineering process that requires in-depth knowledge of operations and geomechanical conditions. Acknowledged design precepts are based on cratering behavior associated with stiff hard rock masses. Other cratering mechanisms may however arise under certain geomechanical conditions such as extremely fractured rock masses, or with soft rocks such as rock salt and potash. The burden dimension also plays an important role in the prevalent cratering mechanisms of a given blasting condition. The present article investigates the variability of cratering profiles and geometrical trends based on characteristic geomechanical differentiation and considering the influence of burden. The differences in observable mechanisms are examined through small and large-scale single hole blast (SHB) tests. SHB tests involve a series of individual shots blasted parallel or sub-parallel to an open face. The burden dimension is varied to obtain burden dependent characteristic trends. The breakout shape is represented by a crater model in the form of a power law equation capable of describing prismatic, concave and convex cratering. The formulation comprises two reference index parameters that can describe the geometrical and geomechanical conditions. SHB test campaigns conducted in rock salt, limestone, massive amphibolite, pinolite, and grout blocks are compiled in quantitative manner to demonstrate the influence of geomechanics on cratering profiles. The observed trends are corroborated through numerical modelling carried on Finite Element Model (FEM) LS Dyna to investigate the prevalence of specific cratering mechanisms. A series of SHB tests at large and small burden values are also used to showcase the influence of geometry on the prevalent cratering mechanism and the resulting crater

Jan 1, 2024

By Michael Wieland

Three laboratory tests were developed for rating the wave-impact ruggedness of cap-sensitive explosives that are used for blasting in underground coal mines. Destructible pipe fixtures, called simulators, reproduce the shock wave or rift compression registered during the cross-hole wave interactions. The rift-compression fixture was modified to render quasi-static desensitization, when utilized with a remote air supply. Waves that were recorded near charge explosions show narrow pulses resembling underwater shock waves, followed by wide, weak humps, called rift compressions.

Jan 1, 1996

By Bob de Raadt

The main problem in blasting a fly-over spanning a main road is the brief time available for blasting and the removal of the debris, in order to minimize the ensuing traffic disruption in the public highway below. The blasting plan is consequently based on an extreme "time is money" concept, in which speed and public safety are predominant factors. This paper discusses reliable blasting parameters for this type of demolition.

Jan 1, 1984

By J T. Patterson

The mining, quarrying and construction industries are often blamed for causing damage to residential-type structures when explosives are used. The claim experience for blasting vibration damage has been poor. This coverage is excluded from the Comprehensive General Liability (CGL) policy. To obtain this coverage, the policyholder must meet additional criteria and an additional premium must be paid. The risk management process offers the explosives user a technique for minimizing the risk of complaints and vibration damage claims on his insurance program and his cash flow. Case histories indicate that the vibration damage claims expense may be a lower risk than the risk of interference with production and cash flow. An annotated bibliography on risk management and defense of vibration damage claims is provided.

Jan 1, 1978