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By Rakesh Raghavaraju, Bibhu Mohanty

The paper analyzes the decay of shock pressure as a function of distance from the borehole, and its implication on shock-induced fracture properties of the target rock as the first step in predicting fracture and fragmentation behaviour in a well-characterized rock.

Feb 1, 2020

By S. Gallagher, A. Mayton, R. Merkel

The prolonged exposure of equipment operators to shock and whole-body vibration (WBV) IS linked to cumulative back, neck, and abdominal disorders. In low-coal mines, space restrictions make seat suspensions difficult to use in isolating operators from shock and WBV. Researchers at NIOSH, Pittsburgh Research Laboratory, are responding to these issues by investigating viscoelastic foams. For the full-load case. an ergonomic seat with viscoelastic foams isolated the shuttle car operator from shock at 15 Hz. Researchers used results from additional foam testing with an analytical model to identify viscoelastic foams that provide shock isolation at a frequency below 5 Hz.

By A. Mayton

The prolonged exposure of equipment operators to shock and whole-body vibration (WBY) is linked to cumulative back, neck, and abdominal disorders. In low-coal mines, space restrictions make seat suspensions difficult to use in isolating operators from shock and WBY. Researchers at NIOSH, Pittsburgh Research Laboratory, are responding to these issues by investigating viscoelastic foams. For the full-load case. an ergonomic seat with viscoelastic foams isolated the shuttle car operator from shock at 15Hz. Researchers used results from additional foam testing with an analytical model to identify viscoelastic foams that provide shock isolation at a frequency below 5 Hz.

Jan 1, 1998

By Jaime Huidobro, Mervin Austin

The effect on an explosive column of the sharp transient stress waves generated during the earlier detonation of adjacent blastholes is of paramount importance to explosives users. Some explosives will sympathetically detonate under these stresses. Others may suffer a transient desensitization, arising from a temporary increase in the density of an explosive beyond certain limits and persisting until the explosive mass relaxes back to the original density. Some explosives are so adversely affected by these stresses that the product suffers immediate and permanent loss of sensitivity. These effects can be clearly seen while blasting in tough conditions such as burn cuts or wedge cuts and in materials, such as coals, that propagate shock waves well.

Jan 1, 1992

By John Hall

(New York Meeting, October, 1913.) THE Fremont test for measuring the energy consumed in breaking a notched bar of steel is not so well known in this country as it deserves to be. The test specimen used in this test is about 3/8 by 1/4 by about 11/4 in., notched with a hack saw on the lower side to cause the piece to break at a fixed point. A weight of 10 kg. falling 4 m., and provided with a knife or. chisel which strikes the specimen, breaks the test piece by impact. The residual force in the falling weight after it has broken the specimen is recorded by a suitable device, and the difference between the total energy and the residual energy of the weight (in kilogrammeters) is the force consumed in breaking the specimen. An experience of several years with the Fremont testing machine has shown its great value in readily detecting brittleness not revealed by tensile testing or slow bending testing. In this paper it is proposed to discuss (1) the supersensitiveness of the test as applied to cast steel and (2) its value in revealing the effect of heat treatment under certain conditions.

Jan 7, 1913

By John Hall

THE Fremont test for measuring the energy consumed in breaking a notched bar of steel is not so well known in this country as it deserves to be. The test specimen used in this test is about 3/8 by 1/4 by about 1 1/4 in., notched with a hack saw on the lower side to cause the piece to break at a fixed point. A weight of 10 kg. falling 4 m., and provided with a knife or chisel which strikes the specimen, breaks the test piece by impact. The residual force in the falling weight after it has broken the specimen is recorded by a suitable device, and the difference between the total energy and the residual energy of the weight (in kilogrammeters) is the force consumed in breaking the specimen. An experience of several years with the Fremont testing machine has shown its great value in readily detecting brittleness not revealed by tensile testing or slow bending testing. I this paper it is proposed to discuss (1) the supersensitiveness of the test as applied to cast steel and (2) its value in revealing the effect of heat treatment under certain conditions. .

Jan 7, 1913

Discussion of the paper of John H. Hall, presented at the New York. Meeting, October, 1913, and printed in Bulletin No. 79, July, 1913, pp. 1247 to 1256. WILLIAM 'R. WEBSTER, Philadelphia, Pa.:-I would like to call ,attention to the fact that the results of the ordinary tension and bend tests do not always give us the information we want even if we figure out the amount of work done. You want a bending test of sufficient width and full thickness. In the case of eyebars, for instance, I have had experience with a 10- by 1-in. eyebar which gave perfectly good results in a full-size test of the finished bar. The 10- by 1.5-in. and 10- by 1.75-in. eyebars from the same heats-of steel were absolutely worthless in full-size tests. The narrow bending tests from all these bars gave good results. Bat after going into the matter fully, we found that if pieces about 3 in. wide and full thickness were used for the. cold bending tests, the heavier material would not stand this test, but failed. That is, in order to check the quality of the rolled bar you should have a wide piece of full thickness for cold bending, as the narrow pieces give misleading results. J. E. JOHNSON, JR., New York, N. Y. :-I would like to ask if there have been any tests made to compare the results of Charpy tests with the true dynamic test similar .to the Wohler test, except that the piece is subjected to a tensile or compressive stress and to alternating stresses in addition, at the same time. This seems to me to approach more nearly than any other test to the conditions of actual service. where the piece is under a fixed initial stress plus a highly variable and often alternating stress. Some tests were made on this plan in England within a year or two. The test piece was Subjected to either a tensile or compressive stress of known amount and simultaneously to alternating stresses in addition. Such a. test as this gives information which we cannot get by a tensile test or even from the tensile strength multiplied by an. elongation. Such tests, however, are exceedingly tedious and require long periods of time in order to obtain valuable results. If material could be subjected to these dynamic tests and the same material to the. Charpy shock test, and if some reasonable qualitative relation could be established between the results of the two tests, then we could assume that the shock test, which is so simple and easy to make, was a measurably accurate test of the dynamic qualities of the material. At present it does not seem

Jan 12, 1913

By Joshua Hoffman, Philip Mulligan, Braden Lusk, Tristan Worsey

Blasters rely upon detonators to achieve the designed timing sequence to move material where it needs to go, minimize vibration, or optimize fragmentation. At times detonator inventory on seldom used delays may be slow moving. This can lead to detonators being used long after they were manufactured. This paper addresses the potential shelf life concern as it relates to timing accuracy of shock tube detonators. A recent study was conducted to study the timing accuracy of non electric shock tube detonator systems. A follow up study was then conducted to determine the degradation of the non electric shock tube systems accuracy with time. The follow up study is presented in this paper. Samples of detonators from the initial study were set aside for approximately one year and then tested. The results from the aged detonators were compared to those of the detonators that were tested in the original study. As an extreme case a third set of shock tube detonators was tested using detonators that were between eight and nine years old. The results from these tests are presented as well. Each system was tested at a short medium and long delay time. Statistical analysis was conducted to determine the effect of time on the detonators accuracy. This paper quantifies the importance of regular inventory cycling to help preserve manufactured timing when using non electric shock tube detonator systems.

Jan 1, 2013

By Per-Anders Persson

This chapter deals with the concepts ofshock waves aud detonation waves together, because a detonation wave is really a shock wave, supported by the explosive reaction that the shock wave ignites and propagates as it travels through the explosive material. In the context of rock blasting, furthermore, there is justification for treating shock waves and detonation waves together, because the mechanical effect of the detonation in an explosive in a drillhole in rock is propagated and its effects are spread throughout the surrounding rock by means of a shock wave The overall performance of an explosive in rock blasting or any other application is of course dependent on how much thermal energy is released in the chemical reaction that occurs when the material detonates, and on how much useful mrc!~amcal work the reaction products can do as they expand. A major portion of this chapter deals with the prediction and measurement of explosive performance, a subject which is now still in a process of rapid development.

Jan 1, 1994

By Joshua Hoffman, Braden Lusk, David McLane, John Rathbun

The dynamics of explosive detonations are understood; however recreating a real-world, to-scale scenario is costly. The use of a shock-tunnel allows testing to be done on a smaller scale, with the simulated effect of a large explosion. Analyzing explosive waveforms using this method can greatly reduce cost in testing blast-resistant products, such as anti-terrorism devices, mine safety products, and military equipment. The purpose of this project is to better the understanding of how the waveform dynamics of an explosive detonated within a shock-tunnel differ from those in an open-air arena test.

Jan 1, 2011

By S C. Alford

Explosive fracturing of metal is usually considered to be an imprecise process but, by careful consideration of shock-wave geometry, precise results are obtainable. The limited development of such charges is attributed to experimental difficulties. A charge configuration has now been devised in which a prismatic wave-shaping element is used to resolve the shock-waves entering a target plate into two convergent components. The extreme pressure caused by their collision initiates a diamond fracture in the proximal target face, and coincidence of reflected tension waves generates a fracture in the distal face. A combination of these effects breaks the target. An embodiment of S.R.T. is described which is flexible, magnetic and contains no cavities.

Jan 1, 1986

By Catherine T. Aimone

Specimens of copper-bearing quartz monzonite were subjected to a plane shock wave simulating high compressional stresses in the proximity of a borehole wall. Fragmentation was studied as a function of stress levels between 1.6 GPa (23 x 104 psi) and 7.3 GPa(105.8x104 psi) and pulse durations ranging from 1.1 µs to 6.9 us. Both explosive pressure and pulse duration were shown to have a strong effect on particle size distribution. While the effect of pressure is well recognized, the effect of pulse duration indicates that ultimate fragmentation increases with the time of application of a plane wave pulse. At high pulse durations, degree of fragmentation is more sensitive to changes in pressure than at low pulse durations.

Jan 1, 1984

By John W. Cloud

THE delivery of blows upon roadway structures by the locomotive engine at high speed, although long recognized, has, perhaps, not been a generally understood in severity, relation to speed, and cause as is desirable in matters of such importance. Some points of explanation, with illustrative diagrams, are, therefore, submitted to your attention, preparatory to a note on "Steel for Bridges," also submitted. In order that a locomotive may run at high rates of speed with-

Jan 1, 1881

By David Nemir, Jan Beck

A challenge in materials science is the production of a bulk solid material from a powder precursor. One solution is to use shockwave consolidation whereby a ductile tube is loaded with the powder of interest and then surrounded by an explosive. A detonator at the top of the explosive column initiates a symmetrical high-pressure pulse that moves inward and down the tube, causing the tube to deform and the interior powders to consolidate into a dense, well bonded bulk material.

Jan 1, 2016

By Jacob Miller, Phillip Mulligan

"Measuring the blast pressure associated with an explosion suspended above the ground (Free Air Burst)is a common research objective in Explosive Engineering. Theoretically, the shockwave from a Free Air Burst (FAB) configuration expands radially and the shockwave is assumed to have a smooth (uniform) shock front. The way in which the FAB explosive charge is suspended, packed, and the charge geometry can affect the shockwave expansion. These factors can generate a non-uniform shock front. As the scaled distance between the pressure sensor and the FAB increases, the shockwave expansion averagesnon-uniformities into a uniform shock front, at which point the FAB suspension system becomes less critical than when the scaled distance is “close-in” (Z <3)."

Jan 1, 2017

By Bob de Raadt

For a long time industrial underwater blasting has stood in need of a calculation method, for the determination of shockwave-proof as well as shockwave-effective charge distances to objects in water. After a brief discussion of the physical background of the shockwave mechanism in water, the author discusses an empirical theoretical computing method based on the "Bubble boundary" concept. The practical application of this model is finally shown in an account of a few underwater blasting operations in which charge weights of c.1-1000 kg were involved.

Jan 1, 1980

By Eric Brichler

Shaft Construction Using Diaphragm and Cement Bentonite Walls at Shoreline Storage Tunnel Eric Brichler, Senior Estimator, Major Projects eric.brichler@nicholsonconstruction.com Nicholson Construction Company, Denver, Colorado The Shoreline Storage Tunnel (SST) Project in Cleveland, Ohio is part of EPA-mandated Project Clean Lake, Northeast Ohio Regional Sewer District&rsquo;s program designed to reduce pollution in Lake Erie by 4&nbsp;billion gallons per year over the next 25&nbsp;years. &nbsp;The $3-billion program includes construction of large ‑diameter storage/conveyance tunnels, shafts at key combined sewer overflow (CSO) pick-up points, underground pump stations, improvements to wastewater treatment plant capacity and treatment, and expansion of green infrastructure.&nbsp; When completed, SST will comprise over 2.5 miles of 23-ft-diameter tunnel installed 87 to 135 ft below ground.&nbsp; The storage tunnel will manage higher flow volumes and keep stormwater out of the combined sewer system to reduce overflow occurrences.&nbsp; As part of the project, three deep shafts (SST-1, SST-2, and SST-3) were constructed to provide access to the tunnel, launch and retrieve the tunnel boring machine, and provide ventilation. &nbsp;Several additional structures will serve as diversion structures, drop manholes, gate structures or gate control structures.&nbsp; A short connection tunnel will connect the SST to the Dugway Storage Tunnel, which was completed earlier in the Project Clean Lake program. The shaft support of excavation system was designed using diaphragm wall methods. &nbsp;This innovative solution provided watertight, continuous shafts keyed into rock that significantly reduces risks as compared to traditional secant piles combined with a rib and liner plate system.&nbsp; Unreinforced concrete diaphragm walls were constructed using mechanical clamshells for shafts SST-2 and SST-3, and clamshell equipment and a hydromill were used for SST-1.&nbsp; All the SST shafts were lined with reinforced cast-in-place concrete and include baffle drop structures. Outside of the SST-1 and SST-3 shafts, several ground improvement blocks were installed using overlapping cement bentonite panels. These ground improvement zones were created to provide increased strength and water cutoff in the soil at locations where the TBM broke into and out of the shafts. A gate structure attached to both the SST-2 and SST-3 diaphragm wall shafts was supported by a soldier pile reinforced cement bentonite wall.&nbsp; The design of the gate structure SOE was handled collaboratively with the owner and their engineer, McMillen Jacobs Associates.&nbsp; The team worked together to resolve challenges surrounding tying in the originally designed bracing scheme to the new SOE method and methods for exposing and supporting a 100-year-old existing brick sewer, as well as excavating through an abandoned brick sewer. This case study will present the design for the shafts and gate structures, the diaphragm wall construction methods, the unique challenges overcome for each shaft, and the benefits of the final solution to the overall project.

Oct 7, 2024

By Dawn C. Tattle

[ ] Panoramic View of Completed Facade Supports The following case history describes the installation of earth retention systems, historical facade supports and structural caissons by Anchor Shoring & Caissons Ltd. at the Air Canada Centre/Raptors Stadium Project in Toronto, Ontario, Canada. The Air Canada Centre/Raptors Stadium project includes a 140,000 square foot office tower, a 20,000 seat basketball arena and their support facilities. The arena within the complex will also have the ability to host hockey, ice shows, concerts and family events.

Jan 1, 1997

By Babak Mamaqani

The Regional Connector Transit Corridor (RCC) is the Los Angeles Metro area's ambitious light rail project, running under the city's main thoroughfares, Flower and 2nd streets. When com- pleted, it will alleviate traffic and parking congestion downtown, while connecting thousands of residents living in the bedroom communities of Inland Empire and Long Beach to their jobs there. The rail line of 1.9 mi (3 km), which involves a $1.756 billion (€1.545 billion) budget to construct the under- ground rail line, including three new stations. They are the Grand Av Arts/Bunker Hill station at 2nd and Hope streets, Historic Broadway Station at 2nd Street and Broadway, and Little Tokyo/Arts District Station at 1st Street and Central Avenue, which will offer riders their first "one seat/one fare" ride option from Azuza to Long Beach. Regional Connector Constructors JV is led by Skanska USA Civil West California District Inc. (Skanska), in partnership with Traylor Bros., Inc. (Traylor), to deliver RCC to the Los Angeles County Metropolitan Trans- portation Authority (Metro). PB&A was the structural engineer of record (SEOR) responsible to design the shoring systems for the Grand Av Arts/Bunker Hill Station at 2nd and Hope streets, and Historic Broadway Station at 2nd Street and Broadway. The temporary shoring design for Historic Broadway Station is the focus of this article, and why the project received special recognition as a runner up for DFI's 2021 Outstanding Project Award. Two main challenges are discussed in particular: design of the shoring system considering all construction stages, and design of an underpinning system where the Los Angeles Times Building (Times Building) protruded into the station footprint.

Apr 1, 2022

By Eric Lindquist, John Compagnone, Gabriel Carvajal

"Condon-Johnson & Associates, Inc. (CJA) with the assistance of design consultant, Brierley Associates, designed and installed a water tight shoring system utilizing several ground improvement techniques jointly. Prior to the installation of the shoring system, a test program consisting of the installation and testing of 7 jet grout columns; 1 soil mix panel; 7 soil anchors and 3 tie downs was performed to verify design assumptions. State-of-the-art quality control measures were employed throughout the project.The shoring system consisted of:•,Deep Soil Mixing (DSM) wall utilizing triple axis tooling to install overlapping columns along the perimeter of the proposed excavation to a treatment depth of 54 feet.•,Installation of steel piles in DSM to provide rigidity to the wall.•,Installation of a jet grout bottom seal, installed from surface to a depth of 58 feet below existing grade.•,Installation of 153 soil anchors, 1-1/4” diameter and 47’-6” length, to tie the jet grout bottom seal to the native soil below to resist hydrostatic uplift, installed from existing grade to a depth of 91 feet.•,Installation of walers and pipe struts for internal bracing•,Installation and stressing of 117 tie downs, 1” diameter and 16 ft length, to tie the pump station mat slab to the jet grout bottom seal, installed from inside the excavated pit.Subsurface conditions at the site consist of uncontrolled fill materials to a depth of 20 feet comprised of sandy silt and clayey sand. The native soils underlying the fill generally consist of soft and compressible lean clay and silt with varying amounts of sands to a depth ranging from approximately 44 to 54 feet below ground surface, which in turn are underlain by dense to very dense silty sand. The groundwater elevation at the site is approximately 8 feet below ground surface.This paper covers the design aspects, construction, and quality control measures undertaken by the geotechnical contractor, with supporting figures.INTRODUCTIONThe owner, County Sanitation District No. 2 of Los Angeles County, designed upgrades to their existing Long Beach Main Pumping Plant Facility. The upgrades consist of a new pump station that includes a reinforced concrete below-grade wet well and dry well, a two-story operations building, two 78-inch diameter pipe inlets, two 42-inch diameter discharge pipelines connecting the existing manifold, two pipe junction structures, two insert-type junction structures, and electrical transformers. This paper focuses on the excavation shoring for the new pump station. The original shoring design concept for the pump station excavation illustrated on the contract plans consisted of pressed in sheet piles, a jet grouted bottom seal with soil anchors, 2 levels of internal bracing, and tie-down anchors to resist hydraulic uplift forces on the buried pump station."

Jan 1, 2017