Search Documents

By Martin B. Hudson, John Yao, Matthew R. Crow, Yiming Sun, John T. Waggoner, Roozbeh Geraili Mikola

"The Wilshire Grand redevelopment project in downtown Los Angeles includes construction of a new 73-story tower. Construction required excavation up to 93 feet deep (28 m). The south side of the excavation, up to 57 feet deep (17 m), required placement of shoring within about 6 to 10 feet (1.8 to 3.0 m) horizontally away from a 400-foot-long (122 m) section of one of the existing Los Angeles Metro Red Line twin subway tunnels. These tunnels were constructed using a 22-foot-diameter (6.7 m) digger shield, and were initially supported with expanded, precast concrete segments, with final cast-in-place reinforced concrete lining. The temporary shoring system for the deep excavation consisted of soldier piles generally spaced at 8 feet (2.4 m) on center with multiple levels of tieback anchors extending above the subway tunnels. The lowest level of bracing consisted of rakers supporting walers attached to the soldier beams because installation of tieback anchors at that level would conflict with the tunnels. Numerical analyses were performed to predict tunnel movement caused by the excavation and its effects on the train operations. This paper describes the numerical modeling, tunnel and geotechnical instrumentation and monitoring program, and comparison of the computed and observed tunnel responses to the deep excavation and tower construction. With increasing urban redevelopment in major cities, the project is a valuable case history for excavation adjacent to existing tunnels. INTRODUCTION The Wilshire Grand redevelopment project includes the demolition of a 16-story hotel built in the early 1950s and the construction of a new 73-story tower in downtown Los Angeles (LA) that will be the tallest building in the western United States. The project site is situated on approximately 2.7 acres (1.1 Ha) of land bounded by Figueroa Street to the east, Wilshire Boulevard to the north, Francisco Street to the west, and 7th Street to the south (see Figure 1a). The new tower is being constructed by Turner Construction for Hanjin International Corporation. Construction of the basement and foundation of the new tower required excavation up to 93 feet (28 m) deep. Shoring was designed by Cefali & Associates and installed by Malcolm Drilling Company. Along 7th Street, an excavation up to 57 feet (17 m) deep required shoring to be installed within about 6 to 10 feet (1.8 to 3.0 m) horizontally from an existing 400-foot long (122 m) section of one of the LA Metro Red Line subway tunnels (see Figure 1b). The tunnels, extending from the 7th/Metro Station to the Westlake-MacArthur Station, were constructed in the late 1980s and early 1990s with an excavated diameter of approximately 22 feet (6.7 m). They were initially supported with expanded, precast concrete segments with a final cast-in-place reinforced concrete lining. The existing hotel was demolished in 2012 and 2013, with shoring installation and excavation for the new basement occurring as the demolition occurred. At the time of writing, January 2016, the structure of the building adjacent to the tunnels is largely complete."

Jan 1, 2016

By R. Fernández, E. Marczak, A. Collins

Newmont roasting plant in Carlin, Nevada commenced operating in December 1994. Over the years, refractory ores and pyrite concentrates from different gold deposits constituted the feed to the facilities. Historical plant performance indicated that the roasting temperature was the main variable that affected the structural characteristics of the calcine which, in turn, affected the recovery of gold by cyanidation. Gold recovery as a function of roaster temperature was closely monitored since October 2000. Original design temperature was 550oC. Lower roaster temperatures of around 500oC resulted in gold recovery increase by more than 6 percent. This increase was directly related to an increase of the surface area of the calcine. The implementation of an “intelligent” process control system helped significantly in achieving steady low roasting temperatures thus achieving high gold recoveries between 92 and 93 percent. Under those conditions, several roasting campaigns with high-arsenic-containing ores were conducted, which resulted in a significant decrease of gold recovery. The reduced gold recovery was caused by the loss of surface area (e.g. porosity) of the calcine as the arsenic content of the roaster feed increased.

Jan 1, 2007

By Bryce T. Tripp

Utah produces a wide variety of industrial rock and mineral commodities, valued in 1998 at $534 million (28 percent of the total non-fuel mineral production of Utah). Major commodities produced in 1998 include: halite; potash and magnesium chloride; Portland cement; sand and gravel; car- bonates including lime, limestone, and dolomite; phosphate; crushed stone; clays; perlite; gypsum; and sulfur and sulfuric acid. Commodities produced in lesser amounts include: diatomite; pumice; silica; lightweight aggregate; gemstones, ornamental stone, and mineral and fossil specimens; byproduct sulfur and sulfuric acid; silica; and building stone. The years 1993 through 1998 were a period of steady growth in industrial rock and mineral production. However, some commodities have grown much more rapidly than others. The robust western U.S. economy has stimulated production of construction-related commodities like sand and gravel, raw materials for Portland cement, lime, and building stone, resulting in exploration for raw materials, development of new quarries, and expansion of existing plants. Noteworthy specific developments include: (1) opening of new aggregate operations and buyouts of small aggregate operations by large national and international firms, (2) expansion of a lime operation and two cement plants, and (3) development of several new gypsum mines. The future of the industrial minerals industry in Utah looks promising despite a more restrictive regulatory environment and a growing anti-development attitude among its citizens. While Utah has become less pro-development than it was prior to the 1990s, it is still moderate compared to strongly anti-development states, so companies have some motivation to choose Utah in their strategic mineral development plans. As long as the western states' economies continue to grow, Utah's industrial minerals industry should thrive.

Jan 1, 2001

By Ataç Başçetin, Hasan Çelt, Hüseyin Onur Dönmez, Kürşat Hasözdemir

Phenolic foams, known for fire resistance, show broader industrial potential, particularly in mining, through property enhancements. Adjustments to the formaldehyde-to-phenol (F/P) ratio, bio-based additives like lignin, and nano-silica improve foam strength and thermal stability. Density modifications allow foams to range from flexible, low-density forms to rigid, high-density supports. In mining, enhanced phenolic foams could reduce coal ignition risks by acting as oxygen-blocking barriers. Current findings suggest these foams offer viable, sustainable solutions for safety in hazardous environments. Continued development could make them essential for thermal and mechanical applications under extreme conditions. This paper aims to provide a comprehensive overview of the mechanical characteristics of phenolic foams, current enhancement strategies, and standardized testing methods used to evaluate foam properties.

Feb 1, 2025

By Y. Wang, E. Forssberg, A. Johansson, B. Chan

A super-conducting high gradient magnetic separator with matrix vibration in dry separation mode is a powder purification device, which has been used to remove weakly magnetic impure particles from fine calcite powders below 53 µm in this study. A fundamental question concerned is the evolution of the matrix clogging under gas-solids loads. This paper presents the improvement of the separation selectivity using a method of mechanically based vibration on the matrix in the separator. The functions of the matrix vibration are discussed. The results indicated that the mechanically based vibration on the matrix within a high intensity magnetic field while a feed was introduced in an air stream, was found to be effective for the dry purification of fine powder materials.

Jan 1, 2001

Federal regulations require the use of methane monitors on all mining machines. All machine-mounted methane monitors currently used in underground coal mines rely on catalytic heat of combustion sensors. As a comparison, although not currently approved for use on underground mining equipment, instruments with infrared sensors are evaluated in this study. Potential advantages of using infrared sensors include faster response time, long-term stability, and reduced maintenance needs. Tests conducted in the laboratory and at a full-scale model mine compare the performance of catalytic heat of combustion and infrared sensors operating under test conditions designed to simulate airflow conditions underground.

Jan 1, 2009

By D. Arku

The increased use of sensors to facilitate automation has led to an explosion of data. As data sets grow in size, their use becomes more complex. Therefore, there is an incentive for reducing the size of the datasets, as long as this does not compromise information gleaning. With this in mind, this project explored basic aggregation as a viable alternative to amassing large amounts of data. The goal of the project was to determine if one would arrive at different conclusions had they analyzed aggregated data instead of raw data. In a mine, operational data is typically used for tracking process statistics, correlation between factors, autocorrelation and multivariate models (for a factor of choice). Therefore, this project compared results from such analyses when it was conducted with aggregated data (AD) with the results of analyses conducted with raw data (RD). The data consisted of one-minute-apart readings from a semiautogenous grinding (SAG) mill on the horsepower, feed rate (tons per hour), rotations per minute (rpm), noise, recycle (tons per hour), density (% solids) and bearing pressure (psig). This data was aggregated by averaging five and 10 continuous (one-minute) observations. Changes in statistical measures between the two approaches were typically within 5% of each other. Differences in correlation coefficients between RD and AD(s) were also within this range. Autocorrelations present within RD were preserved in AD, as long as the time lags were scaled for the amount of aggregation. Regression and neural network models were also developed for power consumption. The prediction performance of developed models was similar whether one used raw data or aggregated data. Overall, it appeared that aggregating the data based on 5- or 10-minute time spans would not have resulted in conclusions (from simple or complex analyses) being different from using raw data. In other words, whether one had used raw data or aggregated data, the conclusions would have been the same, suggesting that time domain aggregation, a common industry practice, is a good alternative to storing high-density data in this case.

By Matthew Wallin

A part of the East Bay Municipal Utility District?s Folsom South Canal Connection Project, 430 feet of raw water pipe was installed using micro tunneling beneath the Mokelumne River. The access shafts for this crossing were constructed 50 and 35 feet deep through very dense sands and soft sandstone and siltstone. High groundwater and the immediate source of recharge from the river required watertight shaft construction methods. The shaft contractor, Drill Tech of Antioch, CA, used a brand new Bauer cutter-soil mixing (CSM) rig to construct the large shafts. The structural concept is similar to secant piles, but instead of creating cylinders of soilcrete, the CSM rig creates interlocking rectangular panels. This technology has been used previously in Europe, Asia, and Canada, but this was the first project to use CSM technology in the United States. Cutter-soil mixing technology has other applications beyond shaft construction, including retaining wall construction and levee reinforcement.

By R. Oler

The mining industry?s traditional preference for protective coatings in corrosive environments, due to cost considerations, has been to apply galvanized and epoxy coatings. As a result of extreme pH levels and the limitations of current products, a new coating has been developed to withstand severe conditions. Harsh chemicals and corrosive groundwater pose added challenges to mines in maintaining long term ground support which demands continuous rehabilitation. This paper highlights the challenges and identifies a solution by applying a new economic coating to DSI?s Omega Bolt? that withstands the most corrosive of conditions. [ ]

Jan 1, 2012

By G. T. Adel, J. D. Miller, C. L. Lin

Washability analysis determines the maximum separation efficiency that can be achieved in the operation of coal preparation plants. Unfortunately, there are no on-line techniques for determining this most fundamental information. It now appears possible to determine coal washability on-line through the use of x-ray computed tomography (CT) analysis. This paper presents the results for the development of a CT-based, on-line coal washability analyzer. The development of appropriate hardware and software necessary to adapt a CT analyzer for use in determining coal washability is discussed. Testing of the analyzer using well-characterized coal samples is presented.

Jan 1, 2000

By J. T. Bartlett

Life-of-mine process simulation is an interdisciplinary effort and a useful means of thoroughly evaluating mining and minerals projects. Communication between geologists, mine planners, miners, metallurgists, and managers not only benefits each discipline but facilitates design of an efficient operation and allows for accurate forecasting of productions and cash flow. By focusing on the key areas: geology; mine design; waste dumps; stockpiles; metallurgy; weather data; tailings disposal; using contours, block models, mine plans, process flowsheets, design criteria, operating and control strategies, maintenance schedules, and operating costs to perform detailed daily simulation from start-up to shut-down; a comprehensive understanding for all disciplines is achieved. Construction of a METSIM model that includes all test work and project data from drill holes through net present value calculations brings the pieces together to achieve optimum process design, minimize operating problems and eliminate the term ?black box? from project meetings and discussions.

Feb 27, 2013

By William Stewart, John Tinkler, Gary B. Hemphill

Of the 345 km long Taiwan High Speed Rail Project, connecting the cities of Taipeiand Kaohsiung, the 23 km alignment on Contract C230 required the construction of5755 m of shallow mined tunnels ranging from 137 m to 1285 m in length. All nine of these tunnels were mined using NATM methodology. On September 6, 2002, a collapse occurred in Tunnel T08 that affected approximately 50 m of tunnel. There was little warning. However, the crew was evacuated approximately 45 minutes prior to failure and thus, no injuries or loss of equipment. This paper will discuss the mining methods, jet grouting ground support, and the instrumentation selected for the rehabilitation and monitoring of the tunnel.

Jan 1, 2005

By SH. Shahsavari, H. Akbari, M. Noaparast, M. Oliazadeh

Mejel valley zircon ore in Iran is located in north part of Iran and was sampled to evaluate its concentration. The aim of this project was to define the mineralogy of this zone and separating zircon from other minerals using gravity concentrators and magnetic separators. It is constituted of various valuable minerals, mainly zirconium, niobium-tantalum, titanium, rare earth elements particularly cerium-bearing minerals namely zircon, sphene and rare earth elements oxides. We used statistical method for designing of experiments. Yates method used for analysis of basic experiments results. The grade of zircon in primary sample was 1.1%. Different experiments were designed to optimize all required parameters. The final concentration with 75% zircon was produced and final recovery was 79%. Finally, lab-scale based flow sheet was prepared using experiments results.

Jan 1, 2005

By Steve Dubnewych

The Joint Water Pollution Control Plant, operated by the Sanitation Districts of Los Angeles County, treats wastewater generated by over three million people. A new tunnel and ocean outfall is being considered to meet future hydraulic demands and provide long-term redundancy for the Districts? existing tunnels, portions of which were constructed as early as the 1930s. The detailed process used to evaluate the feasibility of various tunnel and out-fall locations is described. Challenges include a geologic profile with mixed face and squeezing ground conditions; high water pressures; active fault crossings; gassy and contaminated ground conditions; and liquefaction, slope stability, and lateral spreading concerns in the area of the riser and diffusers.

The mining industry continues to experience a skills shortage and this is having an impact on the ability of mining companies to operate sustainably. Apart from a few exceptions, there is a dearth of geologists, mining engineers, metallurgists as well as environmental scientists and other professionals in the global mining industry. This relates to both quantity and quality. It makes good business sense for mining companies to employ local professionals rather than expensive expatriate staff. In some cases a mining company could employ more than 10 local mining engineers for the cost of one expatriate. However, in many countries local professionals are not always equipped professionally to work on mine sites. The result is that many companies are not operated optimally due to human resources gaps. In some cases, particularly in key areas such as mine planning, this threatens the sustainability of the operation or at the very least results in sub-optimal resource utilisation. This paper briefly presents some of the issues and strategies being implemented and that might be implemented to maintain a sustainable supply of quality minerals graduates to the industry in 2011 and beyond.

Jan 1, 2011

By R. T. Dec

A review is undertaken of existing mathematical models of compaction process in roll press. The example of plane-strain, plane-stress model is presented together with comparisons between computed and experimentally recorded pressure distribution in roll nip region. Next, the discrepancies between predicted and measured values are discussed and practical method based on experimental optimization of compaction process using laboratory roll press is proposed. Examples of the selection of optimum roll press operating parameters for calcium oxide fines, sodium chloride and iron oxide dust are presented to illustrate advantages of the method. Finally scale up procedure is discussed for estimating the performance of commercial size roll press based on the data collected on laboratory size equipment.

Jan 1, 2000

By W. Randall, Robert M. Leary

Twin 1250 m (4100 ft.) long highway tunnels through Cumberland Mountain near Middlesboro, Kentucky are planned to be completed in the early 1990's. The tunnels will be excavated in sandstones, limestones, and shales, dipping at 35 to 50 degrees and striking nearly perpendicular to the tunnel alignment. In 1985-86 a pilot tunnel was excavated as a crown drift along the alignment of the southbound tunnel. The benefits of the pilot tunnel in reducing uncertainties for main tunnel construction are discussed. The cost-benefits of the pilot tunnel are examined in view of estimated main tunnel costs.

Jan 1, 1987

By F. M. Doyle

Ion flotation shows great promise for recovering and removing metal ions from dilute process streams, either for environmental compliance or to recover values. This technique uses an ionic collector to concentrate non-surface active colligend ions of the opposite charge from a bulk solution at the solution?vapor interface. With a sufficiently large solution?vapor interfacial area (provided, for example, by sparging gas through the solution), the colligend can be concentrated and removed along with the collector in a foam phase. A key limitation on using the technique in the minerals industry, where many process streams contain a variety of ions and have relatively high ionic strengths, is the need to control which ions are interacting with the collector. Here the effect of three different chelating agents, namely dodecyldiethylenetriamine (Ddien), ethylene diamine tetraacetic acid (EDTA) and triethylenetetraamine (Trien), on the selectivity of copper, nickel and cobalt, or copper and alkaline earth metal ions, is reported. The results are discussed in terms of their implications for adoption in the minerals industry.

Jan 1, 2009

By F. N. Kissell, C. D. Litton

This study predicts the level of smoke that miners might meet while trying to escape a coal mine fire and describes how smoke would impede their safe escape. For this study, the authors assumed that miners exit through an escapeway adjacent to the burning entry, that some air would leak from the burning entry to the escapeway. The following conclusions were made: • A very low amount of air leakage to the escapeway can produce a critical level of visual obscurity from smoke. This shows that intake airways may be as susceptible to smoke visibility problems as return airways. • This critical level of smoke obscurity is reached much before a critical level of carbon monoxide is reached. • Small fires can cause a severe sensory irritation that further limits vision. Thus, reliable eye protection is very important. These results show that methods to guide miners through dense smoke will contribute greatly to saving lives during mine fires.

Jan 1, 1993

By W. Petruk

Imaging is a fundamental requirement when characterizing minerals, ores and related products. Images are used for presentation, texture analysis, characterization, image analysis, identification, etc. The image mode that is utilized is dependent upon the application, mineral properties and available instruments. Different instruments produce images that display different features; in order of increasing complexity they are: hand specimens, a non-polarizing microscope, polarizing optical microscope, scanning electron microscope (SEM), low vacuum SEM, microprobe, secondary ion mass spectrometer, staining, cathodoluminescence, tomography and others. Image analysis uses images produced with either an optical microscope or a SEM, but the SEM images are superior in this application.

Jan 1, 2001