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By Regina Rocha, Miguel Humpire

One of the challenges within unitary mining operations is blasting, which has a significant downstream impact on the following processes, which is why mining companies ensure the results of the blasting process through joint work with explosives specialists’ companies.

Feb 6, 2023

By Stephan A. Jefferis, Adrian H. Bath

"This paper draws together some themes on the durability of barrier systems, and particularly cementitious systems. For contaminated land and water retaining structures, durability can be poorly addressed at all stages of a project, from specification, to barrier material selection, barrier design including toe-in and through to performance assessment in operation. Permeability (hydraulic conductivity) is a dynamic property which will vary over time as reaction processes propagate through a barrier. However, laboratory testing, when undertaken, tends to be focused on short term tests with aggressive chemicals so that the effects of longer-term processes such as carbonation and leaching by permeating water are missed. For water retaining structures, carbonation and leaching actually may be the most significant processes affecting barrier performance as the groundwater adjacent to many water bodies can be otherwise rather benign (as regards bentonite and cementitious systems). These and other reaction processes have been modelled in the arena of nuclear waste repositories and procedures are well recognised. However, such procedures have yet to be widely adopted for the assessment of other barrier systems.INTRODUCTIONOver the last few decades there has been an enormous amount of laboratory research on the durability of barrier materials or more specifically papers reporting the results of permeability tests. Unfortunately there is a much smaller literature on scaling test results to barrier dimensions in the field or to required design lives. Although in the geotechnical industry durability research has been largely laboratory based, in the nuclear industry where relevant timescales are multi-millennia rather than decades, research has been heavily underpinned by geochemical modelling. A significant purpose of this paper is to examine the tools that may be used to analyse the results of tests on barrier materials used in geotechnical engineering, for example, for water retaining structures and contaminated land and draw the attention of the construction industry to the potential of the modelling procedures developed for nuclear repository assessments. Modelling can help to identify underlying processes and so augment information from laboratory testing focused on changes of physical properties such as permeability and strength."

Jan 1, 2016

By AIME AIME

ON JULY 12, 1921, S. S. Arentz, representative at large from Nevada, introduced in the House of Representatives, under the number H. R. 7736, a bill to revise, amend and codify laws of the United States relating to the location of mining claims on public domain, and other purposes. This bill had been drafted by a committee of consulting engineers of the U. S. Bureau of Mines. The immediate purpose of this introduction in Congress was to make it avail- able for general information and discussion. In pursuance of this purpose Mr. Arentz issued the following circular: This proposed codification and revision of the mining laws of the United States as received from a committee of mining and metallurgical engineers appointed by the Director of the United States Bureau of Mines was introduced in the House of Representatives by the undersigned (who has operated and developed mines throughout the West for many years). It is submitted to prospectors, mine operators and mining engineers, all of whom are affected and vitally interested in the subject with the hope that they will give this bill their careful consideration and study.

Jan 1, 1921

By Alejandro Sanz, Juan Luis Magro, David Mazeyrie

The Hampton Roads Bridge-Tunnel Expansion Project (HRBT), initiated by the Virginia Department of Transportation (VDOT), will add two new 1.5-mile TBM bored tunnels to the two existing immersed-tube tunnels between artificial islands, part of the connection between Norfolk and Hampton under the Hampton Roads Harbor in Virginia, USA. The new bored tunnels will be built by Hampton Roads Connector Partners (HRCP), a joint venture of Dragados USA, Vinci Construction, Flatiron Constructors and Dodin Campenon Bernard. This paper covers technical discussions that led HRCP to select a Variable Density TBM to address the challenges of this tunnel project, including but not limited to (i) the diameter of the bore: a 46 feet (14.04 m) diameter machine that constitutes the second-largest TBM ever used in the United States; (ii) shallow ground-cover under the water table; (iii) challenging and varying geology along the alignment, with mixed-face conditions and different types of ground modification zones; and (iv) the high TBM operating pressures required—all these and other challenges in a sensitive marine environment.

Jun 13, 2021

By Brian Young, Ben Pantony

Interferometric Synthetic Aperture Radar (InSAR) has played an integral role in many large scale tunneling projects globally. Until recently, it has been regarded as a complementary monitoring tool. On the Los Angeles Metro Purple Line Phase 1, InSAR was proposed as a primary means to replace weekly and bi-weekly surface monitoring requirements on surrounding critical infrastructure. This paper will summarize the statistical analysis approach engaged in order to compare and contrast a year of historical InSAR data to known geodetic survey data, in order to utilize InSAR as an operational monitoring tool on this project.

Jun 13, 2021

By G Williams

Discussing equipment, systems of work, the need for updated programmes of local seismic exploration, and developments within the South Wales coalfield.

Jan 1, 1993

By L. Wade, R. Wang, M. A. Horton

Laboratory methods to find the mechanical properties of rock are inherently biased towards stronger strata, which best survive the sample preparation process. Geophysical techniques are not subject to such bias and may be used to predict mechanical properties rapidly and cheaply. Samples (151) were obtained from a borehole that had been comprehensively geophysically logged. The mechanical properties of the samples were established in the laboratory and correlated with the geophysical responses of the strata from which they came. The results indicate that, for homogeneous strata at least, it is possible to predict the unconfined compressive strength reasonably well from sonic travel time measurements made in the field. Predictions of static Young's modulus may also be made from this data source, but with a lesser degree of confidence. A multivariate regression equation is presented which relates down-hole sonic travel time to unconfined compressive strength, depth and the frequency of fractures in the rock mass. This equation may offer potential for the prediction of the mechanical rock properties of fractured and layered strata.

Jan 4, 1993

By Giuseppe Gaspari, Xiangrong Wang

The pandemic emergency is forcing transit agencies to define strategies allowing social distancing, which are more challenging in underground interchange stations in crowded downtown cores. Toronto Transit Commission’s (TTC’s) Bloor-Yonge Station Capacity Improvement Project in Toronto was approved to meet increasing demand and represents an opportunity to fight COVID-19. This paper discusses cost-effective solutions in expanding the cut-and-cover station box over the existing Toronto Subway Line 2 and connecting it through ventilation openings in the cast-iron tunnel liner. Potential uplift risks and structural damage due to minimal vertical clearance were analyzed via three-dimensional finite element analyses with advanced constitutive laws to simulate the multi-stage construction process. Based on the simulation results, a series of countermeasures, including excavation support systems, king posts, ground-consolidations, and liner reinforcements were integrated into comprehensive design options to ensure the serviceability and structural integrity of the subway tunnels.

Jun 13, 2021

By John Newby, Ulf Gwildis, Fred Marquis

From the Brightwater Conveyance System in Seattle to the Second Narrows Water Supply Tunnel in Vancouver, BC, the design and construction of deep-lying tunnels in the Pacific Northwest often require the incorporation of deep portal shafts. Alluvium overlying marine and glacial deposits combined with the high regional seismicity is the common geologic setting. The latest example illustrating the development of shaft design for this scenario is the 40-m-deep shafts of the Annacis Island Wastewater Treatment Plant New Outfall System. The main components of the shafts include the initial lining, providing the excavation support system to be used for launching and receiving a 5-m-diameter TBM; and the final lining, designed to withstand all static and seismic loads and to remain viable for the intended design life. This paper presents design and construction considerations for these shafts against the background of and lessons learned from past project experiences.

Jun 13, 2021

By Andrew T. McBride, Malcolm S. Powell, Indresan Govender

"Current empirical Semi Autogneous Grinding (SAG) mill models contain assumptions concerning the amount of energy available for particle breakage, how this energy is distributed in the mill media and the rate at which the energy is transferred. Despite these assumptions the JK SAG model is highly functional with a proven track record. DEM provides a numerical framework to greatly improve on these assumptions that were necessary due to a lack of available input data.This paper identifies key outputs of the Discrete Element Method (DEM), such as energy spectra and impact probability distribution. It describes how they can be incorporated into current mill models utilising practical rock breakage data. The rate at which energy is transferred is shown to be dependent on particle position and mill rotational speed and not once per cycle as previously assumed. Based upon this an improved energy transfer methodology is presented. The fundamental outputs of the DEM are validated against experimental three-dimensional particle tracking data, so as to establish whether the DEM produces correct energy transfer predictions on the inter-particle level, which is crucial to this work."

Jan 1, 2003

By K, J. MAUNDERS

This paper briefly describes a computerised model of the South African electricity system which has been developed jointly by the Atomic Energy Board and the Electricity Supply Commission. The results of an analysis of this system have been subjected to a fairly extensive sensitivity analysis which reveals that up to the year 1990 between 680 and 700 million tons of coal will be required for electric power generation, together with between 7 000 and 10 000 tons of uranium. This result is fairly insensitive to data variations, but the prediction of a cumulative requirement up to the year 2000, of between 1 300 and 1 800 million tons of coal and 25 000 to 70 000 tons of uranium, proves to be very data-sensitive.

Jan 1, 2014

By de Vaux. Deryck, Natalie J. Shackleton, Vratislav Malysiak Cyril T. O. Connor

"The major losses of PGM and base metals in the beneficiation of platinum group deposits occur during the separation of gangue from the value minerals by selective flotation. A number of studies have shown that this negative impact on flotation is due to surface passivation, caused by various ions that may originate from the external water supply or, as is likely in the majority of cases, from the oxidation of the mineral surfaces and the grinding media. This investigation aimed at reducing surface passivation of pentlandite and inadvertent activation of pyroxene, thereby improving ultimate valuable mineral recovery and selectivity. Both synthetic minerals and plant ores were studied in order to determine the effect surface passivation and inadvertent activation have on mineral surface alteration and floatability. Zeta potential determinations, microflotation, ToF-SIMS (Time of Flight Secondary Ion Mass Spectrometry) analyses, laboratory batch flotation tests and continuous flotation testwork were used as tools to study the surface alteration and/or floatability.Zeta potential determinations and ToF-SIMS analyses showed that copper adsorption is non-selective. Both pentlandite and pyroxene become copper (II)-activated in the presence of copper sulphate and subsequently, in the presence of xanthate, adsorption of the collector will occur onto copper activated mineral surfaces. Zeta potential determinations also showed an alteration of the surface charge in the presence of polyphosphate, thereby inhibiting surface passivation of sulphides by slime coatings due to surface repulsion.The addition of diethylenetriamine (DETA) reduces the copper concentration on both minerals, predominantly on the pyroxene surfaces and polyphosphate further enhances the selectivity at pH 6.The microflotation and batch flotation data obtained has shown a significant improvement in the ultimate flotation response of valuable mineral recovery and concentrate grade compared to the standard reagent regime, while the continuous flotation results significantly improved the selectivity, however, at a similar ultimate recovery."

Jan 1, 2003

By A. Boulton

Low molecular weight synthetic polymers substituted with hydroxyl, carboxyl or sulfonate functional groups were used to improve the flotation separation of zinc or copper sulfide minerals from iron sulfide gangue minerals in three massive sulfide ores of different mineral composition. These polymers produced significant improvements in zinc or copper grades as a result of a selective depression of iron sulfide minerals. It was shown that this selectivity was the result of preferential adsorption of the polymer on the surface of the iron sulfide minerals. The different types of interaction between the functional group on the polymers and the sulfide mineral surfaces could explain the trends observed in the flotation results.

Jan 1, 2003

By N. Rouse

Underground raises and slots are a vital part of underground blasting operations. Raises and slots are vertical shafts or openings used for ventilation, ore passes, or creating voids in stopes. In the author’s experience, raise and slot designs can vary significantly from operation to operation or even within a single operation, sometimes for reasons unknown. The results of the various designs can differ depending on drilling accuracy, geology, and the explosives used in the design. The purpose of this paper is to summarize the recommendations found in published literature on raise and slot design in one document, while incorporating some of the author’s own experience with optimizing raise and slot designs in underground operations. Some inspiration is also included from burn round designs; small versions of raises drilled horizontally in development blasting rounds. This document includes discussion points on drillhole diameter and depth, pattern design and relief requirements, explosive types and loading recommendations, and timing. Ultimately, this document can be useful to those looking to design a raise or slot blast for the first time or for those looking to improve on the results from the raise and slot blasts used at their operations.

Jan 1, 2024

By X. Chen, F. An, H. Chen, Z. Wang

The bottom drainage roadway plays a crucial role in preventing coal and gas outbursts by using underground gas drainage methods. Therefore, it is essential to select the ideal position of the bottom drainage roadway. In this paper use a combination of geological data and numerical simulation to study the ideal position of the bottom drainage roadway, we taking the gas drainage of the first workface of No. 3 coal seam in the Yuxi coal mine in China as an example. The geological study showed a limestone marker layer at an average vertical distance of 14 m from the first mining face. Using this marker layer, the bottom drainage roadway could be excavated without the risk of accidentally exposing the coal seam, and less crosscutting borehole drilling from the bottom drainage roadway would be required. Based on the needs of gas control, the layout of the bottom drainage roadway was selected as an external stagger type. Combined with the numerical simulation results, when located 20 m outside of the mining workface ‘footprint’ on the horizontal projection, the bottom drainage roadway was a sufficient distance from the stress concentration area during mining of workface 1301, which facilitated roadway maintenance. Furthermore, the length of the crosscutting boreholes is also relatively short, which reduces the amount and cost of drilling. The results of this study are expected to provide a reference for the selection of an ideal position of the bottom drainage roadway in field engineering.

May 2, 2022

By Enir da Silva Fonseca

Este trabalho tem como objetivo principal analisar os dados obtidos através dos ensaios a flexão em 40 corpos de provas cerâmicos preparados de acordo com a NBR 13818:1997 e aplicar uma probabilidade estatística para cálculo da resistência à fratura. O modulo de resistência à flexão para a ruptura de cada corpo de prova foi calculado de acordo com a fórmula apresentada no anexo C da norma citada, e aplicada posteriormente no lote à estatística para distribuição de Weibull. Os resultados obtidos não apresentaram uma variação significativa na resistência mecânica à flexão para os corpos de provas sem umidade em relação aos submetidos à imersão em água.

Aug 16, 2017

By Eddy Dierckx

Modernization of flat rolling plants is essential to sustainably fulfill increasing market demands and to improve competitiveness. Intelligent modernizations ensure getting maximum prime yield of existing mills, even if they have gone through half a century of operation. Existing mills were designed based on former production, consumption and quality targets. Ever increasing requirements such as increase of productivity, change of product mix (e.g. new steel grades), reduction of energy consumption and improvement of product quality lead to the necessity to adapt the existing equipment to the new target. SMS group provides, besides the reliable equipment and automation solutions to successful upgrades of existing mills, also a systematic approach to develop technical and economical solutions together with our customers (conceptual engineering). This paper describes the SMS group approach to modernizations / upgrades, introduces powerful performance modules and provides a number of successful examples that have been implemented recently.

Aug 17, 2017

By Alfonso Núñez

The adoption of digital technologies can lower the costs and risks for construction, commissioning, hand-over and transfer to operations eliminate many of the costs and delays associated with handovers and ensure fit for operations deliverables. In Mining, future projects could have 50/30 % less CAPEX/OPEX due to unmanned platforms, remote operations centers, and automated data collection lowering headcount. Additionally, these strategic investments can ultimately become profit centers beyond the traditional ROI paradigm, resulting in a greater return to shareholders/stakeholders for our customer organizations.

Sep 29, 2023

By Caio Moreira, Saulo De Rezende, Nelly Ruíz

The present project sought alternatives for this material through the Mining Lab Beginnings program, which was developed by Nexa in partnership with Escalab to find solutions for the company's highly complex challenges. Through the program, several solutions were evaluated, with additives for the construction market being the most prominent. Tests were conducted to confirm the efficiency of jarosite in the mixture that composes this material. With successful laboratory tests, the technology was tested on an industrial scale, where it also demonstrated its technical and economic viability. The project is now moving into the operational phase, demonstrating that circular economy is the best solution for disposed tailings.

Sep 29, 2023

By T. Bhambhani, J. Jankolovits

Sphalerite flotation using copper sulfate has been performed in the industry for decades and the mechanism of Cu activation is well established. Despite its ubiquity, many practical questions surrounding copper sulfate persist. It is not clear how iron selectivity is achieved in zinc circuits given the propensity of iron sulfides to be activated by copper. Also, the large variation in copper sulfate dosages across different plants and ore types cannot be explained. Lastly, Zn flotation with greatly reduced copper sulfate dosages attracts significant interest and has been demonstrated in certain laboratory settings, but no information is available on why those laboratory solutions have not been adopted in plant practice. Flotation studies are presented that demonstrate that Zn flotation with very low copper sulfate dosages is possible when using certain novel collectors that are not practised in the industry. However, these reagent schemes are impractical because of a heretofore unappreciated and critical role that copper sulfate plays in Fe rejection. With both very low and standard copper sulfate dosages, copper sulfate influences both Zn flotation and Fe rejection. The results highlight the multifaceted role of copper sulfate in zinc flotation and the need to holistically consider complex systems’ behaviour to understand flotation reagent mechanisms and optimise plant performance. Keywords: Sphalerite flotation, metal activation, copper sulfate, iron rejection

Jan 1, 2020