Search Documents

By David Mast, Irwan Halim, Brian Hagan, Kaveh Talebi, Jason Edberg, Amanda Foote

On June 14, 2023 Jay Dee Contractors’ Tunnel Boring Machine (TBM) “Phoenix” holed through and completed mining the second drive of the I-75 Segment 3 Storage and Drainage Tunnel. Completion of the tunnel came only after overcoming several challenges, including a groundwater intrusion event which deposited thousands of cubic yards of wet ground material into the tunnel. This paper will discuss the events which delayed completion of the tunnel by over nine months, the risk management and construction approaches assumed by the Design-Build team during bid, several challenges faced by Design-Build teams when building stormwater resilience tunnels using traditional Department of Transportation standards, and recommendations for improving risk allocation and proposal documents for future similar Design-Build tunnel projects.

Jun 23, 2024

By Jahnavi Parmar, Pranav R. T Peddinti, Saloni Pandya, P. S. Prasad

Coastal cities are in desperate need of suitable land to meet the ever-increasing demand for urban infrastructure to support commercial, residential, tourism, and off-shore activities. Countries with a lengthy coastal line, such as India, possess significant areas of wide spread highly saline soils subjected to periodic seawater intrusion. One such soil stratum was encountered at the Gulf of Cambay, Bhavnagar district, Gujarat, India. Due to the high volume of river runoff, the Gulf has a positive water balance. The relative humidity ranges from 65 to 86 percent, making the climate semi-arid to sub-humid. The high salinity, mineral content, basaltic origin, and deeper water table offered the impetus to investigate applicability of various soil treatment options for such saline soils. Admixture stabilization techniques have been shown to help with problematic soil features. The Current study aims to determine effectiveness of addition of locally available lignite fly ash (10% - 30% by weight) and cement (6% - 9% by weight) to Bhavnagar saline soil in respect of strength, electrical conductivity and CBR. In this assessment, a comparison of stabilized and unstabilized saline soil mixtures is expected to highlight the need of understanding influence of treatment on instinctive performance of stabilized saline soils, as well as assist practitioners in efficacious treatment of extreme saline soils for diverse geotechnical and construction applications.

Sep 1, 2022

By L. S. Gertsch, M. Z. Abu Bakar

The research presented here is part of a project to quantify the differences in the mechanical excavatability of rocks in dry and water-saturated conditions. A series of full-scale laboratory linear rock cutting tests were carried out with a long-bladed single disc cutter on dry and water-saturated sandstone blocks. The muck collected from the cutting tests was analyzed to establish a link with the specific energy (SE) of the operation. The coarseness index (CI), a non-dimensional parameter, was found to be a useful indicator of the relative efficiency of the cutting operation. An inverse relationship of the form SE = k CI-n was observed between SE and CI. The power n of the relationship for both dry and saturated rock was much lower than found in previous studies. The exponent n is believed to be dependent on the strength of the rock and the cutter type used. Although the average CI was lower for saturated rock than for dry rock, at the same time, saturated rock cutting was found to be less energy-intensive (in terms of SE) than dry rock cutting. Moderate correlation exists between the production rate or yield and the SE of the cutting operation for both dry and saturated rock, which can provide some useful information about the field production rate, discounting the effect of discontinuities in the rock mass.

Jan 1, 2012

By D. A. Douglass

This report describes the tri-n-butyl phosphate extraction of cerium (IV) from a sulfate leach liquor prepared from a bastnaesite concentrate as well as from pure eerie nitrate solutions. The work was done on a laboratory scale using separatory funnels. Extraction from pure cerium solutions entailed no great difficulties; however, extraction from the bastnaesite solution proved more difficult, mainly because of the inhibiting effect of the sulfate ion. Despite this, procedures were developed for obtaining good single-state cerium extraction (95+ percent) and a high-purity product (99+ percent), although the maximization of both cannot be achieved simultaneously. This necessitates a compromise in any extraction scheme.

Jan 1, 1959

By J. Dennett, M. Faris, M. Antonio, M. Collins, N. Tuffrey, R. Ellenwood, V. Reddy

"In January 2012, AngloGold Ashanti Córrego do Sítio Mineração, with assistance from Sherritt International Corporation, commissioned a new autoclave for pressure oxidation of refractory gold concentrate at the Córrego do Sítio operation in Brazil. Start-up of the plant occurred in a few weeks and enhanced gold recovery was realized almost immediately, with 94% gold extraction achieved in carbon in leach (CIL), compared to less than 70% without pressure oxidation. This paper describes start-up and commissioning of the plant and provides an overview of plant performance over the last five years.INTRODUCTION In 2008, AngloGold Ashanti purchased the former São Bento property from Eldorado Gold, which, along with AngloGold Ashanti’s existing Córrego do Sítio mine, was renamed AngloGold Ashanti Córrego do Sítio Mineração (AGA Mineração). Later that year, the Sherritt Technologies division of Sherritt International Corporation (Sherritt) was contacted to begin batch and continuous pilot plant tests to determine the amenability of the AGA Mineração refractory gold concentrates to the pressure oxidation process. Based on the results of the batch and pilot plant tests, AGA Mineração requested basic and detailed engineering studies to be conducted by Sherritt, eventually leading to commissioning of the plant in January 2012. AGA Mineração’s plant is located in southeastern Brazil in the state of Minas Gerais, near the city of Belo Horizonte. AGA Mineração`s Phase 1 mine plan covers three sites in the Laranjeiras, Carvoaria Velha and Cachorro Bravo ore bodies, and is designed to process 60,000 tonnes of refractory gold concentrate per year to produce 140,000 ounces of gold per year with an 11 year life of mine (AngloGold Annual Financial Statements, 2010). Recovery of gold at AGA Mineração is based on Sherritt`s pressure oxidation technology for refractory gold concentrates (Berezowsky et al., 1991; Collins et al., 2011a; Collins et al., 2011b). This process had previously been applied to the recovery of gold at the São Bento site (Carvalho et al., 1988; de Silva et al., 1989), in a plant that was operational between 1986 and 2007 (Silva et al., 2004)."

Jan 1, 2017

By William Watson

Coal production in the United States in 2010 increased to a level of 960 Mt (1,085.3 million st), according to preliminary data from the U.S. Energy Information Administration (EIA), an increase of 1 percent, or 9.43 Mt (10.4 million st) above the 2009 level of 975 Mt (1,074.9 million st) (Table 1). In 2010, U.S. coal consumption increased in all sectors except commercial and institutional, while total coal stocks fell slightly for the year. Coal consumption in the electric power sector in 2010 was higher by 4.5 percent, while coking coal consumption increased by 37.9 percent and the other industrial sector increased by 7.1 percent. The commercial and institutional sector, which prior to 2008 had been called the ?residential and commercial? sector and is the smallest of all the coal-consuming sectors, declined by 3.1 percent in 2010. (Note: All percentage change calculations are done at the short tons level.) U.S. coal exports increased from the 2009 levels due mostly to higher demand for metallurgical coal, while coal imports decreased for a third year in a row. The increase in coal consumption for electric generation during the year was the consequence of improving domestic economic conditions further bolstered by a cold winter and warm summer in important coal-consuming regions. Preliminary data show that total generation in the electric power sector (electric utilities and independent power producers, including useful thermal output) in the U.S. increased in 2010 by 4.2 percent. Coal-based generation also increased, resulting in a 38-Mt (42-million st) increase in coal consumed in the electric power sector. Coal use in all the sectors other than the electric power sector increased by 13.9 percent to a level of 65.9 Mt (72.7 million st).

Jan 1, 2011

By J. C. Gerdeen

A new analytical model for the shear stiffness at a joint of the fully-grouted resin roofbolt is developed using the Theory of Elasticity and an analogy to a beam on an elastic foundation, Gerdeen [2]. The model developed in this study treats the elastic foundation modulus of the resin as being composed of both an elastic rock and an elastic resin. All previous attempts have neglected the elasticity of the rock and treated only the resin. A three dimensional finite element model of the bolt-resin-rock system is developed also and comparisons are made between the predictions made by it and the analytical solution. It is found that the agreement between the two representations ranges between 1.2% and 10.5%, with the greater differences being observed for systems of very large or very small bolt diameters and resin annulus thicknesses. Since such configurations are not the rule in practice parameter studies are performed using the analytical solution with the finite element solution being used as a check. For a 0.75 in. bolt, a resin annulus thickness of 0.1375 in., a resin with E = 7 x 105 psi and -1) = 0.210, and a rock of modulus E = 6.8 x 106 psi and V = 0.159 the shear stiffness is found to be 1.220 x 106 lb,/in, from the analytical solution and 1.245 x 106 lb,/in, from the finite element model. Applying the finite element model to the problem of the axial stiffness of the fully-grouted resin roofbolt a value of 6.002 x 106 lb./in. is obtained which proves to be at least 50% higher than any of the now existing analytical predictions.

Jan 1, 1976

By Jasinder S. Jaspal

In underground room-and-pillar mining methods, the sectional conveyor belts are extended or retracted periodically to maintain shuttle car tramming distance to a minimum. A conventional conveyor belt extension or retraction is a heavy, arduous job that if mecahnized, has the potential to improve productivity and safety. To reduce the burden of heavy work of this activity and mechanize it, the Bureau of Mines developed a conveyor belt service machine (CBSM) through a research contract with Tractor MBA. The CBSM is a self-contained, battery-powered, rubber-tired vehicle capable of handling, storing and transporting conveyor belting, wire rope, and associated belt structures in seams as low as 48 in. Belt extensions and retractions are accomplished by moving the tailpiece of a belt conveyor with the CBSM to the next position while dispensing or retrieving the belt, wire rope, and associated belt structures. The CBSM improves the belt extensions and retractions by making them easier and faster, and it utilizes fewer workers. The CBSM was surface tested at the Bureau's Mining Equipment Test Facility (METF) to evaluate its performance and reliability. Modifications were made to the CBSM to correct deficiencies found during surface testing.

Jan 1, 1988

By Sergey Ulianov, Arkady Senchenko, Alexey Shvets, Arkady Bakotin

"This paper contains description of research results of technology development for copper recovery from weathered tails of iron processing plant. The predominant host mineral that contains valuable component is chalcopyrite occurring in its free form and in associations with ore and rock-forming minerals. Copper grade is 0.26-0.30%. Emulsion inclusions of chalcopyrite in pyrite and sphalerite were noted. Major problem is low copper recovery (30-35%) by flotation. When studying chalcopyrite in primary concentrate it was determined that the surfaces of many chalcopyrite grains are covered with oxide films which prevented collector attachment onto them. Second issue was deep association of chalcopyrite with pyrite and sphalerite. Sulfidizing reagent addition did not help to reach the required level of copper recovery to concentrate. In the result of research performed the technological flowsheet was developed including preliminary treatment of head material in a special unit aiming at oxide films removal, followed by copper rougher flotation on head size tails, crude concentrate regrinding and a number of cleaner flotation operations. After the treatment of weathered tails according to the flowsheet developed, copper recovery to flotation concentrate became 71.53%, at 23.46% copper grade. The suggested technology allows one to solve the issue with treatment of technology-related copper-containing stockpile material, as well as to include the ores where copper is represented by sulfide minerals covered with oxide films into processing."

Jan 1, 2014

By H. Mullani

We have in southeast Kansas a variety of soils underneath which are a variety of subsoils compressed into what is commonly called “ hard pan.” These soils are of six types, ranging from a clay to a sandy loam. The surface soil in Cherokee County and Crawford County, of whatever quality or type is, generally speaking, from 6 to 12 inches in depth. The so-called “hard pan” ranges from the native grass roots to a depth of from 2 to 12 feet, and in some places even deeper than that.

Jan 1, 2010

By Roberto A. Lopez, Eric Lindquist, Jon Bussiere, Dean Iwasa

"The new 11-story U.S. Federal Courthouse building in downtown Los Angeles demanded a cost effective foundation system capable of attaining a strict total settlement criterion of 0.5 inches (12 mm) under high applied loads. A design-build ground improvement system consisting of 3 ft (0.9 m) and 7 ft (2.1 m) diameter deep soil mix (DSM) columns embedded into the relatively soft Fernando Formation bedrock was selected for the project. The DSM columns support applied stresses of up to 8,800 psf from four large concrete core elements that transfer concentrated building loads to a 3 to 6 ft (0.9 to 1.8 m) thick reinforced concrete mat. The soil mixing ground improvement solution provided flexibility by allowing installation of the DSM columns around existing belled caissons left in place from prior structures, and by allowing repositioning of some of the DSM columns to avoid other existing obstructions in the fill. DSM spoils were used to construct a 2 ft (0.6 m) thick load transfer platform on top of the DSM columns. Quality control measures included utilizing equipment outfitted with automated data acquisition systems, performing three full scale load tests, performing daily wet-mix sampling and compression testing, performing full-depth coring and unconfined compression testing on core samples, and using a borehole acoustic televiewer to evaluate the uniformity of the DSM columns where core recovery was problematic. The results of subsurface investigation and the load tests were used to develop 3-dimensional finite differences models for evaluating stress distribution and deformation of the foundation system.INTRODUCTIONThe new U.S. Federal Courthouse building is currently under construction in downtown Los Angeles, California. The new courthouse will be 11 stories tall with one partial below-grade B1 basement level. The building will have four structural core elements that extend from the main building foundation at the B1 level to the top of the structure. The majority of the building loads will be transferred through the structural core elements to a new 3 to 6 ft (0.9 to 1.8 m) thick reinforced concrete mat beneath the central portion of the structure. The foundation pressures beneath each of the core element locations will be approximately 6,200 to 8,800 psf (300 to 420 kPa) with lower foundation pressures at locations farther away from the central core area."

Jan 1, 2015

By John C. Niedzielski

The PHX Sky Train is a five mile long automated people mover system located at Phoenix Sky Harbor International Airport. Phase I of the PHX Sky Train includes the design and construction of 227 drilled shafts supporting three stations and approximately 9,000 feet of elevated guideway. The guideway includes a 100 foot high, 330 foot long span extending over an active taxiway, which will be the first system of this kind over an active taxiway in the world. The soil conditions in this area generally consist of alluvial Sand, Gravel and Cobbles (locally known as SGC) deposited by the nearby Salt River. The foundation system will support relatively high axial loads, lateral loads and moments due to the height of the guideway above the ground surface, where it needs to pass over existing concourse walkways, bridges, a taxiway and buildings. Drilled shaft design involves designing 4.5-foot to 9-foot diameter drilled shafts within the SGC deposits, most of which extend well below the groundwater table. There is a high potential for collapse of drilled shaft excavation sidewalls within this material. Such extreme design loading conditions, together with difficult ground conditions at the site, result in several challenges for the design and construction of the deep foundation system for the guideway and stations. A load test shaft was designed and constructed as a means to provide site-specific measurement of axial performance under these difficult conditions. Results from the load test were used to reduce the size of the drilled shafts. This paper provides an overall description of the PHX Sky Train project, a summary of the ground conditions, design requirements, load test results and construction methods and equipment used to successfully install the drilled shafts for this project.

Jan 1, 2010

By H. Maleki

The U.S. Bureau of Mines pioneered the use of borehole deformation gauges and overcoring techniques to measure in situ stress. These measurements provide input to structural mine design and support selection for specific geologic conditions. This paper presents recent stress measurements in a western U.S. coal mine where the orientation of the stress field remained relatively unchanged over distances of several kilometers. The horizontal stress magnitude increased with depth of cover and in relation to major geologic structures. Local variations in roof stress profiles were used to develop generic models relating stress arching to strata stiffness and the inelastic behavior of mine roof.

Jan 1, 1994

By B. T. Darnton

Gravity concentration at the Pegasus Gold Montana Tunnels Mine was initiated in late June, 1991 with the commissioning of a coarse gold scalping circuit that processes a small portion of the ball mill circulating load. The primary objective for the circuit was to reduce the risk of gold particles advancing to flotation that are too coarse to float. The secondary objective was to enhance overall gold recovery and payable gold ounces in a cost effective manner. The gravity circuit has proven itself to be a major success. The above mentioned goals have been achieved, and they have been maintained at record throughput rates that are 30% higher than when the circuit was commissioned. A number of modifications and improvements were made over the last three years which allowed the gravity circuit to keep pace with the higher tonnage, these are discussed in detail in the body of this paper. The overall approach to gravity concentration at Montana Tunnels has always been to optimize production rather than maximize the gold ounces produced. This philosophy has now yielded a circuit expansion and relocation project which will allow for an estimated 50% increase in gravity gold production, while reducing the overall unit costs of production significantly. This paper will review historical gravity circuit performance, improvements, and the current relocation and expansion project.

Jan 1, 1995

By Mingyu Ma, Lingling Liu, Liqing Chen, Houlong Liu

In this article, a 444-type heat-resistant ferritic stainless steel containing 0.05wt% Ce and 2wt% (Mo+W) was used as an experimental material and a study was carried out on the effect of rolling processes on the microstructures and texture evolution as well as on the mechanical properties and formability. The rolling processes contain hot rolling at different hot rolling finish temperatures, annealing after hot rolling, cold rolling and subsequent annealing. As for the hot rolling process, two hot rolling finish temperatures, 860 C and 770 C, were adopted, and their influence on the microstructures and mechanical properties was comparatively studied. The results showed that the microstructures after hot rolling and subsequent annealing could be refined by lowering the hot rolling finish temperature. The resultant microstructures after cold rolling and annealing were hereditarily refined. Lowering the hot rolling finish temperature can weaken the -fiber texture in hot rolled or cold rolled ferritic stainless steel strip. However, the -fiber texture was homogeneously strengthened by annealing the cold rolled ferritic stainless steel strip. Enhanced mechanical property and formability in terms of strength and average plastic strain ratio could be obtained by lowering the hot rolling finish temperature of ferritic stainless steel.

Oct 1, 2019

By J J. L du Plessis

Escalating energy and electricity costs have become one of the biggest expenditure drivers in mining operations. During the last eight years, energy costs have trebled when expressed as a percentage of total running cost in South African mines. Power consumption on mines is controlled by three main strategies, namely load clipping where energy use is reduced for parts of the day, load shifting where energy use is shifted to other parts of the day, and energy efficiency where energy use is reduced permanently.To reduce the operating costs of ventilating and cooling underground mines continuously, system optimisation studies must be completed. A part of this paper describes methods that can be used to reduce energy usage by optimising cooling and ventilation systems during planning and in existing operations using network simulation models that accurately reflect the current and planned ventilation conditions. These models are used to examine various options for improving the overall ventilation and cooling efficiency. Furthermore, an overview of refrigeration and cooling practices, and ventilation strategies is presented.Ventilation-on-demand and cooling-on-demand strategies have the potential to reduce both the capital and operating costs associated with mine ventilation and cooling systems. In addition, it has been proven that modern strategies and energy-efficient tactics are technically feasible.It is also important that the correct equipment selection is made. This must be based on the best technology with the highest energy efficiency. Where equipment replacement is being considered, energy efficiency must be one of the key decision drivers.In this paper a number of studies were presented and from the experience and the data presented it is clear that a large financial benefit is possible through optimising ventilation and cooling during the planning of mines or within an existing operating mine.CITATION:du Plessis, J J L, 2015. Strategy and tactics implemented to achieve energy-efficient ventilation and cooling of mines, in Proceedings The Australian Mine Ventilation Conference, pp 9–18 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By Du Sichen, S. Seetharaman, A. Jakobsson

"In the Present paper, the principles of oxygen potential measurements have been discussed along with the design details for oxygen sensors that are used in copper industry. A description of some of commercial probes is presented along with their salient features. The application of these sensors in flash smelting, converter and casting sections of copper production are discussed along with their implications on process optimization.I. IntroductionThe high temperature galvanic cells have come into prominence on account of their numerous applications in both fundamental as well as applied measurements. Since the inception of the oxygen-ion conducting electrolytes like ZrOrCaO·by Kiukkola and Wagner [1], the oxygen concentration cells have been extensively used in laboratories as well as in industries. In metal-production technology, these cells have been used to monitor the oxygen potentials in metallic, slag as well as gas phases and also to control and styr metallurgical processes. The pioneer among the various industrial users of such cells is the copper industry. To-day, high temperature solid electrolyte cells involving oxygen ion conducting electrolytes have become an integral part of copper pyro-refining and continuous casting. In the present paper some of the applications according to the industrial processes are described including the developments that are going on in the European scene."

Jan 1, 1997

By Paul Weir

FOR the first time in 1938, bituminous coal production for the week ending Nov. 19 surpassed that of the corresponding week in 1937, and indexes of industrial activity indicated the possibility that the remaining weeks of 1938 would run ahead of the corresponding weeks of the preceding year. But regardless of this year-end pickup, total production in 1938 was approximately 25 per cent less than in 1937. The estimate of 340 million tons for 1938 places the bituminous industry slightly above the production level of 1933 and approximately 10 per cent above the modem low of 1932. Anthracite production is not subject to the same extent as is bituminous coal to fluctuations arising out of the rate of industrial activity, hence the decline from 1937 has not been so great being approximately 14 per cent under 1937. The estimate for 1938 production is approximately 45 million tons, but this represents the lowest level reached in the last fifty years with the possible exception of several strike years.

Jan 1, 1939

By Ke Yang, Robert Liang

"Drilled shaft foundations are widely used for many types of structures, especially for highway bridges, high rise buildings, and costal structures. The lateral design considerations are crucial for those structures that are subjected to lateral thrust forces, winds, waves, and earthquakes. The p-y analysis is the most widely used method for the analysis and design of drilled shafts for lateral load applications in soils. However, existing p-y criteria were developed based on the lateral load tests on small diameter drilled shafts in soils. Although, a lot of lateral load tests have been conducted, there are a limited number of lateral load tests on large diameter drilled shafts embedded in clay. In this paper, a lateral load test on 2.44 m diameter fully instrumented drilled shafts in clay is presented. The site specific p-y curves are derived based on strain gage readings. The existing p-y curves are found to be much softer than the site specific p-y curves. Correspondingly, the deflection at the top of the test shaft under the maximum applied load is predicted to be eight times larger than the measured value using existing p-y criteria. A new p-y criterion is proposed in this paper. The proposed p-y criterion is proven to be able to capture the site specific p-y curves of the load test and to predict closely the deflections at the top of the test shaft. INTRODUCTIONDrilled shaft foundations are widely used for many types of structures, especially for highway bridges and costal structures. The lateral design considerations are crucial for those structures that are subjected to lateral thrust forces, winds, waves, and earthquakes. Although efforts have been made on studying lateral response of drilled shafts; nevertheless, only limited studies have been published on the behavior of large diameter drilled shafts under lateral loads and the corresponding design methods."

Jan 1, 2005

By D. M. Dabbs

A static dew point technique has been used to evaluate the solubility of arsenic in ?slag and its dependency on P02 at temperatures of 1458 and 1523K. The ferrous-ferric ion ratio of the slags ranged from 3.9 to 23.8. These values correspond to partial pressures of 02 ranging from 10-8 to 10-12 atm. The solubility of arsenic in slag was found to be independent of? P02? The data indicate that elemental arsenic exists in silicate ?slags. This result was further substantiated by mass .spectrometric analysis of doped slag specimens.

Jan 1, 1983