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By Qi Jingyue, Wang Zhongquian, Yang Nianhua

Qinling Tunnel is the longest tunnel in China. The rock stratum is very hard rock - intact mixed gneiss. At the beginning of the construction, drift-pilot excavation is very costly due to the use of regular drill and blasting methods. After tests on the acoustic impedance match between rock and explosive, watergel explosive, which has a high velocity of detonation and high brisance, has been used for hard rock blasting. In addition, different cut plans have been compared. It was found that four-large-hole cut is the most effective. And the number of drillholes and specific charge cut down and the average advance reaches more than 94% of the blastholes depth. Thus, the difficult problem of hard rock blasting in drift pilot is successfully solved, while safe and quick construction is guaranteed.

Jan 1, 1998

By Jeff Wachendorf

As the title "Cast Blasting Around Town" implies, this paper details the starting of a cast blasting program in and around the town of Colstrip, Montana. As strip ratios have increased, the need to adapt and find solutions to provide coal at a reasonable cost to the captive power plants has risen. Colstrip, Montana has a long history of coal mining which dates back to the early 1920's when Foley Brothers began supplying coal strictly for powering locomotive engines. Early mining days starting in the 1920's and the progression up through the 1970's when mine mouth power plants were built will be discussed. To accomplish the desired results, early mining techniques included steam and electric powered equipment as well as a lot of actual horse power.

Jan 1, 2009

By Justus Deen, Paul V. Sterk

Through the 119 year history of the Homestake Mine various methods of raise mining have been used, these include conventional, bored, and drop raises. These raises provide passage for men and supplies, provide ventilation, transfer broken rock from level to level, and serve as emergency escapeways. As the 1980s came to a close, many of the larger ore bodies in the mine had been mined out. This has resulted in many crown pillar situations that required a method to mine them. In addition, the Homestake ore body also contains numerous ore reserves that have short vertical height. The ore itself can be from vertical to 50 degrees in dip. Due to the high cost of drift and ramp development many of these ore bodies are sub-economic using conventional mechanized cut and fill mining.

Jan 1, 1996

By Rolf R. Schillinger

It is established to an increased extent that the basic questions about raw material extractions deal with water, dust, noise and vibrations. If it has not been definitely proven that these points won?t lead to excessive environmental strains, attempts at any explanations will meet with disapproval in advance. In order to answer the basic questions about dust, noise and vibrations quality management becomes most important, particularly with respect partly unavoidable emissions of production processes. The specific questions have to be answered within the context of good blasting practices, latest discoveries of the explosives industry, and by use of a Blasting Works Quality- Management, which includes both production quality and Risk-Management. The paper shows a practical way to work out a Quality-Management Program for companies involved in blasting activities.

Jan 1, 2002

By Edward J. Walter

A vibration record is a complex of motions resulting from a combination of direct, reflected and refracted seismic energy that originated at a blast source. Multiple hole blasting using delays further complicates the motion in that overlapping of seismic wave trains may occur when delays do not fire in the programed sequence. This can result in variations in amplitude, frequency and wave-1ength of the vibration. Amplitude may be doubled, frequency may oscillate between the highest and lowest frequencies present and wave-length may approach doubling of the longest wave-length present. These effects can present serious problems to conducting a safe blasting program since increased amplitudes and lower frequencies present higher damage potentials for structures. The development of these effects is described and illustrated graphically to show how these effects can occur.

Jan 1, 1989

By Wendell W. Harris, Stanley J. Vitton

In the United States each year it has been estimated that expansive soils cause approximately $9.0 billion in damage to buildings, roads, airports, and other facilities. This figure alone exceeds the damage estimate for earthquakes, floods, tornadoes, and hurricanes combined. Unfortunately, some cases of expansive soil damage (swelling) are blamed on rock blasting operations if the blasting operations are located within the immediate area. While simple tests, such as the Atterberg limits test, can characterize a soil as expansive, it does not necessarily answer the question whether the foundation soils are causing distresses to a structure. In particular, it appears that once a soil has been labeled as nonexpansive it is no longer considered as a problem soil, in which case blast vibrations become the prime suspect.

Jan 1, 1996

By Mo Jadbabaei, Scott Harrison

There is very limited information available regarding the air pressures, flow rate, and velocity profiles in blast hole air drilling applications. Currently, many people are using incompressible flow correlation to calculate the bailing velocity. In this article, air pressure, flow rate, and velocity profiles are calculated using compressible flow theory. The airflow at the bottom of the hole is simulated using the jet flow theory. The concept of choking condition is introduced, and it is concluded that the velocity at the nozzle exit cross section cannot exceed sonic velocity. The minimum pressure required for achieving choked condition at the nozzle cross section is calculated. Choked and overchoked flow conditions at the nozzles are examined, and the maximum achievable cleaning power is correlated to the nozzle size and pressure.

Jan 1, 1999

By N Vijay Mohan, K V. Balamukund, G Ananth Ramulu

Jointing of steel rods in reinforced concrete structures needs careful consideration as it renders the structure weak at the joint. The jointing is usually done at sections of structural members, where the bending moment and shear force are least. Jointing is done either by overlapping the rods or welding or by mechanical splicing. A novel method of jointing them is by inserting the two rods in a steel sleeve and cladding it on to the rods by subjecting the sleeve to explosive energy. A rod jointed in this fashion is tested for direct tension and bending when used in a reinforced concrete beam. The test results show that it is an effective method. The advantage is that a number of joints can be made in a single operation.

Jan 1, 1993

By Justus Deen, Paul V. Sterk

Through the 119 year history of the Homestake Mine various methods of raise mining have been used, these include conventional, bored, and drop raises. These raises provide passage for men and supplies, provide ventilation, transfer broken rock from level to level, and serve as emergency escapeways. As the 1980’s came to a close, many of the larger ore bodies in the mine had been mined out. This has resulted in many crown pillar situations that required a method to mine them. In addition, the Homestake ore body also contains numerous ore reserves that have short vertical height. The ore itself can be from vertical to 50 degrees in dip. Due to the high cost of drift and ramp development many of these ore bodies are subeconomic using conventional mechanized cut and fill mining.

Jan 1, 1996

By John T. Aler

The U.S. Bureau of Mines has been studying the problem of why explosives detonate weakly or misfire during blasting in underground coal mines. Cross-borehole shock wave interaction has been identified as a predominant mechanism causing explosives to function improperly (1)(Underline numbers in parenthesis refer to items in the list of references at the end of this report.). Cross-borehole shock wave interaction can be simulated in a laboratory setting, making possible the replication of tests in sufficient numbers to understand and quantify some of its effects on permissible explosives (2). The work presented here investigates the capacity of explosives to partially recover from the desensitizing influence of the shock wave. The recovery trend of different explosives can indicate optimum blasting patterns useful for minimizing borehole charge malfunctions.

Jan 1, 1991

By P Wapner, C Lo Edwards, S CO Schmidt, J N. Johnson, R Oliver

Shale oil recovery rates that can be achieved in underground in situ retorts can be strongly influenced by the shale breakage and fragment-size distribution achieved during rubblization. Since the fragmentation pattern in the retort is a direct result of the blast design used for rubblization, the characterizing blast parameters should be carefully selected. Explosives should be matched to the host material and blast geometries properly chosen so that the required fragmentation results are achieved at optimum costs. Special attention must be directed to selecting blast parameters that produce uniform bed permeability, suppression of fines, proper fragment size distribution, and minimal damage to the retort walls and ceiling. The influence of joints and natural fractures should also be known. In instances where the requisite blasting parameters are unknown, they should be determined from test blasts.

Jan 1, 1979

By Terry Nichols, Karl E: Warkwick Burgher, Charles J. Wideman

The application of Fourier spectral analysis to records of ground vibration generated by over 100 explosions from an open pit mine is used to develop empirical predictor equations that relate the response spectra to the blasting parameters used to generate the excitation motion. Time series representations of ground particle velocity are transformed into the frequency domain where the appropriate modifications are made such that the inverse Fourier transform yields the time series representation of particle displacement and acceleration. Compensations are made for the transform function of the recording system in the frequency domain. Spectral analysis of the three types of ground motion is correlated with the blasting parameters. The results show that the frequency content of ground vibrations generated from a mine blast can be quantified in terms of the predictor equations.

Jan 1, 1990

By Richard J. Mainiero, Eric S. Weiss

This project investigates the behavior of blast waves from the detonation of high explosives in an underground mine. A series of explosive tests was conducted in the underground and surface facilities at the Bureau of Mines' Lake Lynn Laboratory to evaluate the potentially dangerous effects of blast waves produced by open shooting, blown out holes, or accidental detonations of explosives. Shots of C4 and TNT were fired at the dead end of a 6 ft high by 20ft wide entry, at the intersection of two entries, and on the surface. C4 and TNT were chosen for this research because they exhibit very consistent performance. Behavior of the blast wave was evaluated through recording of the pressure as a function of distance from the explosive detonation.

Jan 1, 1995

By M. Khaled, K. Abdel Rahman, M. Khattab

Helwan limestone quarry is located at a distance of 35 km (21.7 miles) to the south of Cairo downtown. Drilling and blasting operations are used to extract the limestone for the Helwan Cement Company (HCC). In 1980’s a new urban community was constructed adjacent to the quarry. This situation led to shifting of the old quarry 5.0 km (3.1 miles) to its current location, to avoid causing blasting problems to the new community. Unfortunately, the new quarry is opened in a highly faulted area, with weak zones of brittle materials. The drilling and blasting crew is facing many difficulties due to the geological complexity along these zones. Moreover, the extension of this community towards the new quarry makes the control of ground vibrations is very important.

Jan 1, 2008

By D. Swanson

Cold Detonation Physics (CDP) is a patented new field of explosives and the name for the explosive that is produced when non-toxic dry ice (frozen carbon dioxide) is combined with powdered metals such as magnesium and aluminum, which are non-toxic and nitrogen-free. The explosive is detonator-sensitive and detonates according to the rapid reduction of carbon dioxide back to carbon, which produces solids comprised mainly of metal oxides and about 5% carbon. CDP was determined to produce a maximum of 300 liters of carbon dioxide per kilogram (4.81 ft3 /lb) and about 1.5 liters of carbon monoxide per kilogram (0.024 ft3 /lb). Both these figures shift according to metal content where higher metal produces less gases. According to theoretical modelling, the relationship between static pressure and metal content was determined to be an inverse parabolic curve with optimum pressure at 25% to 31% metal, depending on the type/s of metal/s used. Velocity of Detonation (VOD) was determined by measuring light at the wavefront with fiber-optic cable inserted into a series of holes drilled into the side of a 3-inch diameter (76 mm) schedule 40 steel pipe containing the mixture. The highest VOD was observed at 25% magnesium and measured between 2,500 to 4,500 m/s (8202 to 14,764 ft/s) when initiated by a 454-gram (1-pound) booster and an electric detonator. A 25% 50:50 alloy of magnesium and aluminum sample shot at a higher velocity than magnesium, according to how the alloy generated smaller pieces of shrapnel when compared with shrapnel from a magnesium test. CDP, using 25% alloy, was tested for blasting limestone by drilling 3.5-inch holes (89 mm) and inserting a 3-inch x 4-foot cardboard tube (76 mm x 1.22 m) with the mixture, packed to a density of 0.62 g/cm3 . The blast was initiated with an electric detonator, behaved like ANFO with more energy and fractured rock sufficiently across the entire length of the borehole. Seismic analysis determined that CDP produces lower ground vibrations than traditional explosives.

Jan 1, 2024

By Travis Davidsavor, Stanley: Dong Vitton

Concrete is a common construction material used throughout the world, and with increasing demand of fast-track construction, blasting and concrete casting are occurring simultaneously at many sites where rock is being excavated for concrete placement. However, there has been significant disagreement in the construction industry as to what intensity of shock vibrations green, or fresh concrete can tolerate. Peak particle velocities are often arbitrarily chosen, or are simply based on materials such as plaster and drywall that have been more thoroughly studied in relation to damage. Previous research on green concrete has used the concrete’s static strength subjected to shockwaves at different ages as the primary damage criteria. In addition, the static strength tests have been based on curing time. However, changes in temperature or humidity can dramatically alter the hydration rate, which affects strength development of different cements. To account for temperature changes and humidity the concept of concrete maturity is commonly used and allows the researcher to see where the concrete was in terms of hydration progress. In general, static testing determines the failure stress that the concrete’s macrostructure can handle, and often failure occurs in the natural materials first or along large defects in casting techniques. Dynamic testing or high strain rate testing, on the other hand, loads materials at such a high rate that larger defects do not have time to react and instead the microstructure is more highly stressed leading to higher strength and stiffness values. This is known as the material’s strain rate sensitivity. Since dynamic testing better tests the microstructural strength, it is believed that it may provide a better way to assess damage to green concrete. Testing includes both static and dynamic compression as well as static and dynamic splitting tensile strength to assess whether damaged has occurred to the concrete. No significant statistical evidence was discovered that damage to the concrete occurred at five different “green” maturities from peak resultant velocities ranging from 10.66 in/s (271mm/s) to 4.40 in/s (112 mm/s) with average intensity of 6.7 in/s (170mm/s).

Jan 1, 2003

By G. C. Naveen

Punatsangchu Hydroelectric Project Authority is constructing 1020 MW underground hydroelectric project in Bhutan. The project envisages construction of concrete dam, Desilting Chamber, Head Race Tunnel, Power House Complex and Tail Race Tunnel. Tunneling is one of the major activity in any underground projects as they are driven for multiple activities. By and large the tunnels are a major part of connecting networks from surface to caverns/underground working sites. Many tunnels in hydropower project are part of water conducting systems and one such important tunnel is the Tail Race Tunnel in this project and had to be excavated in thinly foliated rockmass conditions by D&B method. The rockmass is traversed by three to four joint sets and few minor shear seams. Rock Class “Q” values were between III and IV. Tunnel was excavated by full face parallel hole drilling blasting method. The adopted blasting method consisted of drilling 45mm (1.77 inch) diameter holes to a depth of 2m and the drilled holes were charged with 40mm (1.57 inch) diameter cartridge explosives and charges were initiated with half second non electric initiators. The perimeter holes were drilled at closer spacing of 30cm (1 feet) and alternate holes were charged using 32mm (1.23 inch) diameter cartridges explosive. Low dipping foliation joints present in the rockmass tend to slab in crown portion and erratic occurrence of intrusive bodies lead to unpredictable behavior of rock mass posing a major challenge for the safe excavation. Stability was a major issue through controlled blasting under constant supervision too could not limit the overbreak in certain weak rockmass conditions thereby exposing cavities of about 2.5m (8.2 feet). The stabilization of these cavities and handling the overbreak due to rockmass condition was time consuming and warranted additional supports. With systematic measurements and controlled blast designs the Horse Shoe Shaped Tail Race Tunnel of 9.1 m (29.85 feet) diameter and 304m (997.37 feet) length to connect with Downstream Surge Gallery of 314m (1030 feet) length, 18m (59 feet) wide and 58.8m (193 feet) height in thinly foliated and jointed biotite gneiss rockmass was successfully excavated.

By Jason Baird, Braden Lusk, Dominique Nolan, Allen Stults

Conical shaped charges have been used to penetrate rock for many years now. Examinations have been made looking at shaped charge liner geometry, material, and standoff, as well as explosive composition, confinement and initiation. Most of the testing conducted towards penetration rather than cratering has fallen within the realm of the petroleum industry and as such been confined to specific rock types, with test apparatus that include simulated down hole (subterranean) environments. The testing conducted within this experimentation is conducted at ground level, in small scale samples, using a single standoff, against multiple rock types. The data collected from that testing is examined here and relationships between physical properties of the rock and the liner are analyzed. The analysis of that data raises the possibility of a relationship that may lead to new empirical methods of penetration prediction in rock.

Jan 1, 2012

By P D. Kasbanis, Lyall Workman

"The energy output of an explosive is typically calculated using an equation of state and computerapplications. Results are reported as weight and bulk strength, either in absolute terms or relative toANFO. The effect of the equation of state selected and the assumptions regarding the energy calculation are considered and interpreted for the purpose of blast design. It appears that variations in the heat of detonation which result from the selection of the equation of state and parameters associated with it are not sufficient to significantly affect blast patterns, explosive consumption and costs. However variations stemming from the use of “available energy” associated with a cut-off pressure are significant, suggesting in many cases large pattern expansions. The validity of the various approaches is discussed and blast design results based on the energy calculated by the different approaches are presented and evaluated."

Jan 1, 1996

By Randy Wheeler

One of the more difficult topics to address concerns the effects of vibration on historic structures. Not only blast induced vibration, but also vibration from other transient and semi-continuous sources like, traffic, human activity, and environment forces. A common question might be, “What level of blast-re l a ted PPV is considered safe?” A review of some of the papers available from the ISEE Explosives Reference Database on CD ROM shows that 0.50 inch per second was often used. It was not clear on what basis this value was selected except that it represents the low frequency limit for plaster developed by the United States Bureau of Mines in RI 8507. In another case, a limit of 0.20 inch per second was mentioned, apparently simply because it was ten times less than 2.00 inches per second.

Jan 1, 2004