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By David Miller, James Santoro

Blasting is often required in urbanized areas to allow for economical execution of construction, demolition, and mining. Several examples of operations that require blasting in built up areas include: rock blasting for foundation and utility excavations; surface and underground mining for mineral extraction; and explosives demolition. Although explosives demolition is an engineering discipline, not at all like rock blasting, it still uses explosives for the felling of structures that have outlived their usefulness. Through the use of modem technology and implementation of extra safety precautions, explosives are used safely in congested areas to make the performance of critical work economical and feasible. This paper discusses several precautions required when undertaking various types of rock blasting and explosives demolition in congested areas. It also presents the adverse effects that must be considered when blasting in congested areas. The effects identified include flyrock, vibration and airblast, fumes, and non-elastic (permanent) ground deformations/overbreak. Measures for mitigating and controlling these adverse effects to provide on-site and public safety are presented.

Jan 1, 2000

By Timothy J. Myers

Expansion and the economic growth in the southwestern region of Missouri necessitated the expansion of State Route 249 and the construction of a new interchange to provide service to the Joplin, Missouri area. The project is located above a former lead and zinc mine in Jasper County, Missouri and includes a five bridge interchange connecting State Route 249 and US Route 171. The variable subsurface conditions, both natural and manmade, prompted the design team to use ground improvement via grouting and small diameter micropiles to provide support for several of the bridge foundations on the project. The scope of work included mine shaft closures, 56,000 ft of overburden and rock drilling, 11,139 ft of micropiles, 524 cy of balanced/stabilized high mobility grouts, and over 8,700 cy of low mobility grout. The selection of the grout used was based on the actual subsurface conditions. Low mobility grout (LMG) was used in voided conditions and for closure of the mine shafts encountered during the excavation. High mobility grout (HMG) was used in fractured rock with the goal of improving the mechanical properties of the rock underneath the future bridge footings and controlling grout volumes during micropile installation. The split spacing method was utilized for both LMG and HMG holes. Geology of the project site subsurface consisted of extremely variable bedrock with strong to very strong limestone, chert, breccia, extremely weak shale, and weak to strong sandstone. Previous activities associated with the mining disturbance (such as partial filled vertical mine shafts, shallow and deep mine horizons, modified hydrology including artesian conditions) further complicates the site subsurface conditions. Real time monitoring and recording of all drilling and grouting parameters was conducted to assist in the evaluation of in-situ geological properties of the site in order to modify the ground improvement and micropile program as necessary. This paper will discuss the design and execution of the ground improvement and micropile program. The project is an excellent example of the use of multiple ground improvement and foundation support techniques combined with real time data analysis to provide a foundation support solution for a complex geological environment.

Jan 1, 2009

By Glenn Norris, Tyler Buckingham

"Gold recovery gains in the order of one to two percent have been realized in 2009 due to changes in the operation of the grinding circuits at Barrick Gold Corporation’s Hemlo - Williams Mill. The initiative known as “split milling” involves milling low grade open pit ore in one grinding circuit and higher grade underground ore in the other grinding circuit under different conditions.The philosophy of split milling involves processing higher grade underground ore at a lower throughput rate and a finer grind while milling lower grade open pit ore at a higher throughput rate and a coarser grind. Bench scale tests showed that the recovery relationship for underground ore sources was much more grind sensitive than that of open pit ore. This relationship proved to hold in the plant. The gold recovery gain due to finer grinding of the higher grade ore is much greater than the recovery loss due to coarser grinding on the lower grade ore. Since the majority of gold is being recovered at a higher rate, this results in higher overall plant gold recovery when compared to the traditional operation philosophy of blending the ore sources.The challenges for achieving the maximum benefits of split milling were two fold; the need to increase throughput on the open pit ore milling circuit and a means of grinding finer on the underground circuit. The former was met with an increase in SAG (Semi-Autogenous Grinding) mill ball charge, a basic “drill to mill” blasting campaign and changes to the primary gyratory crusher. The latter was met with a reduced SAG mill ball charge and a higher milling density. The resulting benefits in additional gold recovered are in the order of $3-5 million per annum.INTRODUCTIONThe Williams Mill processes ore from three different ore sources, the David Bell Mine (DB), the Williams Underground Mine (WUG) and the Williams Open Pit (OP). All three ore sources are located within the Hemlo camp in Northwestern Ontario adjacent to the Trans-Canada Highway. The Williams Mill was built in the mid 1980’s at which time it was designed to process 3,000 dry metric tonnes per day through a 22’ SAG mill in series with a 16’ ball mill. In 1988 a Mill expansion doubled the mill capacity by adding a second identical grinding circuit. A photo of the current grinding circuit can be seen in Figure 1. Today the Williams Mill processes an average of 8,000 tonnes per day of which approximately 60% is from the Williams Open Pit."

Jan 1, 2010

By J. Wiese

Recently the operating philosophy at concentrators processing platinum bearing ores has started to move from a recovery dominated system to one in which the production of high grade concentrates at the expense of some recovery would provide greater benefits in the further upgrading of the platinum group minerals (PGM). The low grades usually obtained are associated with the presence of naturally floatable talcaceous gangue minerals in all PGM ores. Polysaccharide depressants such as guar gum and carboxymethyl cellulose (CMC) are used to improve the grades of the concentrates. Recent testwork has shown that the use of high depressant concentrations can prevent any naturally floatable gangue from reporting to the concentrate. The only gangue present in the concentrates would be due to its entrainment in the froth. Under these conditions much higher grades can be achieved. The sulphide minerals themselves, however, become susceptible to depression at high depressant concentrations. This work examines how the recovery of sulphide minerals in two Merensky ores was affected by the type and concentration of the collector in the presence of high depressant concentration (500 g/t) and that the response of the sulphide minerals was also dependent on the type of depressant used (guar or CMC).

Jan 1, 2009

By Michael W. Neill, O&apos

Drilling slurry has become an effective aid to the construction of drilled shafts in caving and/or waterbearing soils. Historically, drilling slurry made of bentonitic clay and water was first used in the US in water well drilling as early as 1889. In coastal Texas drilled shaft contractors began using slurry, often made of on-site clay mixed with potable water, in the years following World War II, on a relatively routine basis. This type of slurry was used to "process" boreholes, in which the borehole was drilled "in the dry" until water or unstable soil was encountered, after which water and on-site clay were introduced into the borehole and mixed in place with the auger or other drilling tool. Drilling then continued under a slurry consisting of the uncontrolled mixture of clay and water until the excavation had reached a relatively impermeable and cohesive material. At this point, a steel casing was dropped into the hole and sealed into the lower stratum of impermeable geomaterial (soil or rock). The slurry inside the casing was bailed or pumped out, drilling continued to plan depth in the dry, a reinforcing cage was set in the partially cased borehole, concrete was placed and the casing was withdrawn. Some soil-slurry was undoubtedly trapped between the casing and the borehole wall, but the quality of that slurry was usually of no concern, because engineers of the period usually viewed drilled shafts as nothing more than deeply buried footings. Any unejected slurry would only serve to lower side shearing resistance, not yet considered in design, but would have no effect on end bearing. In the 1960 's the effectiveness of soil-slurry came into question because it was often ineffective in maintaining borehole stability at marginal drilling sites and because the economy of using shaft resistance, in addition to end

Jan 1, 1991

By J. Geisler

When addressing Germany’s resource supplies, we need to distinguish between those domestically available and imported ones. Resource extraction ostensibly competes with the designation of protection areas. However, the parallel existence of wildlife and plant life, and operations in the areas used for resource extractions is continually underestimated. The European Commission has compiled guidance documents facilitating the extraction of resources from protected areas. With regard to resource productivity, the market appears to be the appropriate instrument for minimising resource consumption. Policy makers are now called upon to create a legal framework leading to a consensus accepted by society.

Jan 1, 2011

By Tim O’Neil

Tire companies have historically used the mining industry as a platform to launch new technologies. And the mining industry has been receptive to that. So, while developing its Two Piece Assembly, Goodyear noted a number of trends in the mining industry: •The global market sophistication of equipment and operations requires the packaging of products and services to provide the best return on investment. •Industry consolidation and growth have resulted in fewer, more powerful mining houses, leveraging purchasing power in the marketplace. •User productivity demands continue to drive original equipment manufacturers to develop higher pay-load equipment. •Technology needs include improved ergonomics, to reduce fatigue and increase operator productivity. •Increased laws and environmental regulation prohibit on-site whole tire disposal practices.

Jan 1, 2003

By Jack Magtoto, Lysa Voight, Tom Martin, John Forero

SUMMARY Commitment by all parties to partnering goals established early in the contract aided Affholder, Inc. in constructing 2,360m (7,700') of soft ground tunnel in Rancho Cordova, CA. Despite two zones of known contamination, encountering a zone of loose cobbles and boulders in a matrix of flowing sand, some perched water tables and a flooded tunnel after 2 upstream safety plugs failed, the Contractor finished the work 33 days early and only 1.91% over his original bid.

Jan 1, 2007

By P J. Fourie, J R. Walklate

Gravity separation techniques have been in use in the mineral sands industry for decades; from the Reichert cone to Wilfley tables, Wright sluices and the Kelsey Jig, all attempting that elusive perfect gravity separation. Just as the gravity separation industry evolved, Richards Bay Minerals also evolved in their use and approach to gravity separation. This paper discusses the history of gravity separation at Richards Bay Minerals and briefly comments on future developments. History Primary Concentration Richards Bay Mineral?s (RBM) first mining concentrator and mineral separation plant commenced operation in 1977 to process ilmenite, rutile and zircon bearing dunal deposits along the northern Natal coast. The orebody contained a greater proportion of non-valuable magnetic heavy mineral in the SG range of 3 to 4 compared to West Australian and Florida USA deposits, making mineral separation more difficult(1). The deposit was mined using two dredges feeding a floating 2000 tph concentrator. Concentrator feed was screened and fed to two four-stage circuits consisting of primary, scavenger, cleaner and recleaner Reichert cones [see Figure 1]. The primary units were fed at a rate of 80 tph and a density of 60% solids by weight.

Jan 1, 2006

By John G. Henning

The Hoyle Pond underground mine is located in the Porcupine Gold Camp, 18 km east of downtown Timmins. Since the initiation of production in 1985, the operation has produced in excess of 1.9 million ounces of gold at a grade of 15 grams per tonne. Currently, Hoyle Pond ranks 8th in total ounce production for all past and present producing mines in the camp, with the highest head grade of any of the significant past, or present producing mines in Timmins. Cut and fill, shrinkage, longhole and panel mining methods are employed to excavate the narrow gold bearing structures. Using illustrative examples, this paper provides an overview of factors, such as geologic setting, rock mechanics challenges and mine infrastructure, which influence mine design at Hoyle Pond.

Oct 1, 2004

By Robert T. MacMillan

An essentially chemical technique has been developed on a small scale for the efficient utilization of certain domestic titaniferous iron ores. Three main steps are involved: (1) Sintering the ore at 1,050° C. with carbon and soda ash to reduce the iron to metal powder, retaining the titania in the slag, (2) separating the powdered iron from the slag, after wet grinding, by magnetic or gravity methods, and (3) sulfuric-acid decomposition of the titania fraction to produce pigment and certain byproducts. The technique was first applied to the tailings from the Bureau of Mines bauxite-concentrating plant at Bauxite, Ark. A good grade of powdered iron was produced from this material. Subsequently, the work was diverted to the study of the titaniferous magnetite from the MacIntyre Mine at Tahawus, N.Y., because of the potentially higher recoveries of iron, titanium and vanadium. Ninety percent of the iron in this ore has been recovered as an iron powder analyzing 90 percent metallic iron and containing 2 to 3 percent TiO2. The remaining titania was found in the slag and was recovered as pigment-grade TiO2 by application of a suitable technique. The vanadium was distributed between the TiO2 fraction and the alkaline liquor resulting from the wet-grinding and magnetic-separation operations, with only a minor proportion retained by the metallic iron.

Jan 1, 1950

Coal Preparation Research at Turkish Coal Enterprises (TKI)

Sep 13, 2010

By Brian Zelenko, William H. Hansmire

"By the time the latest expansion of the Washington Metropolitan Area Transit Authority (WMATA) system, known locally as Metro and which opened in 1976, is completed in 2020, the system will serve 97 stations and operate on 188 km (117 miles) of track on six interconnecting lines. Metro provides a critical transportation link to a population of approximately six million people within a 3,900-km2 (1,500-sq-mile) Washington Metropolitan area and has allowed job growth to expand to all corners of the region. In the 1950s and 1960s, when the system was first conceived and construction began, most jobs were centered in downtown Washington, and most of the workforce commuted by bus or car. Today, transit-oriented development has increased residential, commercial and government facilities near most of the existing 91 stations increasing the importance of the Metro system as a critical transportation link for the region. According to recent American Public Transportation Association (APTA) data, Metro is the second busiest transit system in the United States (after New York City’s transit system).During the nearly 50 years of construction on the Washington Metro system, technology improvements and lessons learned from the global tunneling industry were implemented. Portions of this background and history have been adapted from other work by the authors Roach et al. (2017) and expanded for use herein. For soil tunnels, these improvements included the change from a “two-pass” tunnel lining with a typical initial lining of steel ribs with wood lagging or segmental precast lining erected within the tunnel shield followed by a final lining of cast-in-place concrete to a one-pass lining system of pre-cast concrete gasketed segmental lining. Soil tunnels were originally excavated using open-face tunnel shields, but changed over time. By the late 1980s, tunneling using closed, pressurizedface tunnel boring machines (TBMs) using a one-pass tunnel lining consisting of segmental precast concrete permitted tunneling in a wider range of soil conditions with much less risk of damaging overlying utilities or structures, greater safety for tunnel construction personnel and without the need to dewater the soils. However, due to concerns about conditioning clays with earth pressure balance (EPB) TBMs, open face machines were still favored by contractors for their better advance rates, lower cost and ability to deal with boulders that were occasionally encountered in the Coastal Plain Terrace Deposits."

Jan 6, 2018

By Alexandra de Almeida Diego

O controle da transferência de calor é uma das principais funções que o fluxante exerce durante aplicação no molde de lingotamento contínuo. O fluxo de calor na interface placa / molde deve estar adequado aos parâmetros de processo e ao tipo de aço, caso contrário pode provocar preferencialmente alarmes de agarramento em aços baixo carbono e trincas longitudinais em aços médio carbono, podendo levar até ao breakout. Este trabalho tem o objetivo de caracterizar os filmes de escória aplicados em aços baixo (Filme BC) e médio carbono (Filme MC), ambos comerciais, utilizando as análises de Microscopia Eletrônica de Varredura (MEV) com Energia Dispersiva de raios-X (EDS) acoplado e Difratometria de raios-X (DRX). As diferenças entre os filmes de escórias foram discutidas e relacionadas aos dados presentes na literatura.

Aug 16, 2017

By Stephen Gerard Sawyer

This report presents a Fortran IV computer program for the structural analysis of space-frame protective canopies used in underground mines to protect equipment operators from falls of roof, face, or rib. This program entitled CANOPY permits rapid calculation of the elastic strength of a canopy for a variety of static loading conditions. Stresses in, and displacements of each structural member are computed and printed out. Additionally, identification of all members that have commenced yielding, weight of the canopy, total loads on the canopy, and maximum loads that the canopy can sustain elastically are output. Program description, input instructions, program listing, and two example problems are included.

Jan 1, 1972

By Emmanuel Portilllos

Every paste backfill system is typically unique, this being due to the particular tailings characteristics, the backfill recipe and requirements of mine planning. Key to successful transport to the underground workings through the boreholes and the distribution pipelines is the quality of cemented paste, being free of lumps and recipe components uniformly mixed. Certain types of mixer require that the mixing environment is required to be intensive as possible. In this sense, the present paper point out some of the general aspects of paste plant design, a short discussion on paste recipe and process equipment, followed by a technical comparison between a batch mixing and a continuous mixing process, currently applied to the production of cemented paste tailings for mine backfill.

Sep 9, 2007

By A. Noble

The design of separation circuits can be a complex, labor-intensive and costly process. While the engineer?s experience along with extensive data sets and simulation are crucial tools for determining the final solution, a more fundamental approach is suitable to compare preliminary options and reduce the number of potential alternatives. In light of this need, the authors have developed the Circuit Analysis Reduction Tool (CART?). This software package relies on the fundamental principles of linear circuit analysis; however, the solution methodology has been streamlined to automatically incorporate stream splitting and unique separation performance for each unit. The resulting tool allows preliminary analysis of circuit designs without the need of detailed feed characterization. In addition to the basic analytical approach, this paper supports the veracity of the methodology with several simulated examples for various separation models.

Feb 27, 2013

By Chase E. Sutton

The porosity of a sand is usually the measure of its capacity for holding fluid, although porosity is sometimes selective; that is, a small percentage of the actual pore space (voids), particularly in fine-grained sandstones, may be isolated by the cementing material which prevents the entrance of fluids under normal conditions. Obviously, however, porosity determinations are essential to an engineering study of underground conditions of an oil field, and a simple and reliable method of obtaining a reasonably accurate figure for average porosity is desirable. This report describes a method suggested by Ruasell,3 which was used by the writer in the preparation of a report on the Texhoma-Gose pool, Archer County, Tex.4 The conditions in this pool were particularly favorable for obtaining an average porosity figure, in that some 30 to 35 core samples of the pay sand were available for analysis.

Jan 1, 1928

By William F. Hahn

The Bureau Of Mines recognized the desireability of illuminating working places in trona mines. This report describes two illumination system designs, their demonstration and evaluation on a Jeffrey 120HR continuous mining machine in an active working trona mine in Wyoming.

Jan 1, 1980

By W. G. Pariseau

Conventional barrier pillars in underground coal mines are intended to protect mains and sub-main entries for relatively long periods of time. Inter-panel barrier pillars that may be used in especially deep coal mines, say, below 800 m (2,400 ft), are intended to protect longwall panel faces and adjacent panel entries for the life of nearby panels. Barrier pillar failures have serious consequences, especially when failure is sudden and catastrophic. Design of barrier pillars is thus of considerable importance to safety and efficiency of operations. Locally, failure occurs at the limit to elasticity when stress tends to exceed strength. Strength of rock is stress dependent, so an analysis of stress is central to rational design of barrier pillars. There are several approaches to stress analysis for coal mine pillar design that range from the simplified but popular tributary area method including variations that use empirical definitions of the tributary area (volume) to more sophisticated numerical methods such as the boundary element method and the finite element method. Despite ease of use, empirical methods are limited and always suspect when applied to conditions beyond their scope of definition, while boundary element methods do not generally include pillars in the solution domain. The finite element method is not so restricted and thus is a natural choice for conventional and inter-panel barrier pillar safety analyses. Caving of roof strata certainly affects the distribution of stress about longwall faces and nearby barrier pillars. Conventional wisdom that considers roof strata to respond as cantilever beams indicates the longer the span the greater are loads on longwall faces and face supports. Failure of roof beams, caving, shortens spans and relieves face and support loads. The same view is applicable to barrier pillars in that long roof spans outside of barrier pillars leads to higher pillar loads than short spans. Hence, caving should be beneficial to barrier pillar safety. However, the benefit may be small depending on the extent of caving and only in the form of a slight reduction in overburden weight transmitted to the barrier pillar, especially in case of inter-panel barrier pillars. FINITE ELEMENT MODEL Finite element models for stress analysis in rock mechanics are formulated in consideration of physical laws, kinematics, and material laws. These models meet the essential requirements for equilibrium of stress, satisfy strain displacements relations, and in a general sense, relate stress to strain through material laws, often referred to as constitutive relations. The last may be complex and replete with nonlinearities. A de facto engineering material law is the elastic model in the form of Hooke?s law for linear, homogeneous materials that may be anisotropic. A limit to elasticity is imposed by strength in the form of a failure criterion or yield function that accommodates triaxial stress states. Examples used in rock mechanics are the well-known Mohr-Coulomb (MC)criterion, the popular Hoek-Brown (HB) criterion, and the Drucker-Prager (DP) criterion. The first is linear in stress, while the second is nonlinear. Both do not include any effect of the intermediate principal stress. The last is also linear in stress but includes the intermediate principal stress. All show an increase in the major principal stress at failure with confining pressure. In the UT2/3 finite element programs, the failure criterion Y is a nonlinear, anisotropic form and is also the plastic potential [1]: [YJI=+ 11NYJI=+- (1) ] where N is an exponent, usually 2, and J2 and I1 are nonlinear anisotropic forms of the second invariant of deviatoric stress and the first invariant of principal stress. The form (1) reduces to DP when N=1and isotropy prevails. When Y = 1, the limit to elasticity is reached and plastic deformation is possible. The material constants that enter (1) are all computed from unconfined compressive, tensile, and, in case of anisotropy, shear strengths. These latter strengths may be estimated from conventional laboratory test data. Of course, joints in field-scale rock masses induce different values. How different is often a matter of conjecture. For comparative studies, laboratory rock properties seem adequate. Inelastic, that is, plastic behavior occurs with strain beyond the elastic limit. Strain hardening, ideal plasticity, and strain softening are possibilities. Ideally brittle behavior with complete loss of strength is an extreme form of strain softening [2]. Caving may also be considered as strain softening with a less drastic reduction of material properties. As intact roof strata fail, fall, and form a rubble pile below, a new material is formed with greatly reduced elastic moduli and strengths, say, 1/100th of the original intact moduli and strengths. From another viewpoint, caving is simply a natural cut and fill process. Input for stress analysis by the finite element method includes: 1. Preexcavation stress state 2. Geology (stratigraphic column) 3. Structure (major faults, joint sets) 4. Elastic moduli 5. Strengths, and specific gravities of each rock type 6. Excavation sequence Output from an analysis includes distributions of: 1. Stress 2. Strain 3. Displacement 4. Local factor of safety (element fs) The last is defined as the ratio of strength to stress and in view of the failure criterion (1), is the ratio [fsJstrengthJstress=] where the numerator is the maximum possible value and the denominator is the actual value of the square root of the second invariant of deviatoric stress. This invariant is a measure of shear stress intensity but also reduces to uniaxial tensile and compressive strengths as the case may be. An fs greater than 1 indicates an elastic state of element stress; a value of 1 indicates the limit to

Jan 1, 2009