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By R. Brändle, R. Luis-Fonseca, R. Cornejo, G. Fischer, G. Von Rickenbach, J. Jarufe

Rock damage around underground excavations has been an important hazard in mines and tunnels. Rock dilation generates buckling that needs to be contained before it causes damage to equipment or safety concerns to mine workers. In seismically active mines, rockburst occurrence has been widely recognized as one of the most important hazards in deep mines and tunnels. While there is a wide range of cases where rockburst hazard can be mitigated through dedicated excavation sequences, reentry procedures or exclusion zones, there are still many situations where large unexpected rockbursting may occur, relying only on rock support as the last mitigation measure to prevent production and safety losses. Considering the previous situations, surface support as mesh, plays a major role containing the failed/ejected rock and providing a safe working environment to the underground operations. While there have been considerable achievements in improving mesh resistance, with more than 26Kj/m2 of energy dissipation capacity, there is still a lack of research in the overlapping mechanism and load transfer between contiguous mesh elements. This paper presents the state of the art in static and dynamic analysis of welded and rolled mesh overlaps, based on experimentation carried on by Geobrugg in their Research Center, leaving clearly established that the difference in meshes is not only in levels of energy absorption, but also concluding that in the case of high resistance rolled meshes overlapping is not necessary and the transmission of stresses can be fully guaranteed by using suitable connecting elements. All these characteristics, supported by operational advantages as light weight and mechanized mesh installation, provides a considerable improvement in safety and productivity, improving the economic value of the project

Apr 26, 2022

By Humberto Almeida de La Serna, Kayleigh Meneghini, Gabriel Rubio Pirillo, Maurício Guimarães Bergerman

The Mining Annual Report (RAL) is an obligation for every current owner of a brazilian mining process which is already undergoing extraction. This document is basically composed by the company’s annual book balance, where is possible to educe informations that allow to evaluate the mineral market behavior. This research gathered filtered data linked with RAL production and technical responsability between 2010 and 2017, gotten by the Information Access Law, without the real CNPJ of each company, in order to preserve their identity. The results allow to quantify the Brazilian mining production during the period, illustrating that approximately 46% of the companies can be classified as micro, 30% as small, 20% as medium and 4% as large mining companies. It was observed that the micros concentrate the most part of technical responsibles who sign for more than three mines.

Oct 3, 2019

By L. S. Bbosa

Single particle impact breakage experiments provide essential data to aid in understanding of rock fracture in comminution. Such experiments, conducted using devices such as the drop weight tester, split Hopkinson bars and more recently the rotary breakage tester, have been successfully used to characterize ore breakage properties in relation to measured fracture energies. The work presented in this paper highlights the techniques behind the calculation of impact breakage properties from each of these three devices. The breakage parameters that can be calculated from experimental data from each of these are to be described. Drop weight tests are used to calculate A and b hardness parameters using the standard JK breakage model. Split Hopkinson pressure bars are used to establish the ultimate compressive stress of particles through single impact breakage tests and the fraction of impact energy utilized to cause particle fracture. Low energy breakage tests using the rotary breakage tester are shown to be used in calculating particle breakage probability. Methods to calculate parameters related to particle breakage probabilities such as E0 and Ecrit are also discussed.

Jan 1, 2014

By V. V. Morozov, I. S. Barmin, A. V. Tugolukov, V. V. Polivanskaya

"It was presents the results of research on improving reagent regime and scheme of enrichment of slime classes of Apatite-Staffelite ores and tailings stockpile of Kovdorsky enrichment plant. It was investigated the regularities of flocculation in the processes of thickening and selective flotation apatite-bearing ores. It was established character of the influence of flotation reagents on the flocculation process. It was shown that the sodium silicate and soda ash have a stabilizing effect by thickening of sludges. Neonol and oleic acid have a coagulating or flocculating effect. It was tested the new regime flotation, involving an initial conditioning with using of reagent - dispersants before feeding the pulp into the flotation and subsequent conditioning with reagents having a coagulating effect. The flowsheet and reagent regime for enrichment of fine-grained tailings stockpiled was developed, which providing production of standard apatite concentrate and increasing the recovery of valuable components. There are presented results of the research of activities of strong organic surfactant on solubility of colloidal form fatty acid collector and aggregate stability of fine minerals in the process of thickening and flotation. Surfactants such as Neonol have been investigated for increasing the activity of the collectors. When using the process of thickening sludge fraction with flocculant Praestol 2540 and stadial conditioning of sludge were obtained concentrates containing up to 38.1% P2O5 at recovery. INTRODUCTION A feature of the Apatite-Staffelite ores of the Kovdorsky deposit is the presence of a large number of fine mineral particles and a reduced hardness of phosphate minerals (Beloborodov et al., 2010, Tugolukov et al., 2012). Formed in the ore-preparation process, sludges are lost with a discharge in the thickening operation. Sludge is characterized by an increased content of phosphorus pentoxide (P2O5). Losses of P2O5 at enrichment of the stale tailings of Kovdorsky GOK reach 14.0%. The high losses of P2O5 caused a profound study of the behavior of thin apatite classes under conditions of thickening and flotation."

Jan 1, 2018

By J. Méndez-Nonell

The thermodynamic and chemical properties of SrSO4 and SrS in a gaseous flow of CO and CO2 at high temperature are discussed. The thermodynamic analysis of the system was made using data from the literature. The results obtained from the thermodynamic analysis were experimentally verified using the thermogravimetric technique. The experimental results suggest the formation of a complex compound between SrO and SrSO4. It was also found a change in the chemical mechanism of the process between SrSO4 and CO-CO2 and in the chemical mechanism of the process between SrS and pure CO2.

Jan 1, 1995

By Charles S. Barrett

NUMEROUS determinations1-7 of the tex-ture of cold-rolled polycrystalline iron, steel, and ferritic alloys have been made with good agreement among the various observers as to the principal features of the texture common to all, but there has been no adequate explanation of the texture in terms of the behavior of individual grains. This study presents an explanation of the texture based on the observed rotation of single crystals when deformed in a manner similar to a grain in the aggregate, a method we have found useful in leading to a better understanding of compression and tension textures;8,9,10 in particular, the aim has been to determine experimentally the end orientations of rolled single crystals of iron. These are discussed in connection with the point of view of Wever1 and of Boas and Schmid2 that the rolling texture is a simple compression texture (compression normal to the rolling plane) superimposed on a simple tension texture (tension in the roll-ing direction), and the point of view of Kurdjumow and Sachs3 that three ideal end orientations exist.

Jan 1, 1940

By Silvano Morelli, Giovanna Cassani, Renzo Bindi, Antonio Nicola

More than 70 km of main line and service tunnels have been excavated to date for crossing the Apennines between Bologna and Florence. A new design and construction approach, known as Analysis of the Controlled Deformation in Rock and Soils, (ADECO-RS), was adopted to tackle the extreme heterogeneity of the ground and the particular stress-strain conditions. The goal of this system is to obtain constant and predictable full section advance rates, even in very poor geology, with the highest possible level of safety and reliability. The execution of this gigantic project required the mobilization of 21 job-sites, with the concurrent operation of 30 excavation headings. The global production rates confirm the high quality of the design and the high level of industrialization reached during the construction stage, levels not previously obtained in similar conditions, using other approaches such as NATM.

Jan 1, 2003

By C. A. Garzonio, A. M. G. Affuso

The paper describes the analyses and the tests carried out on representative slabs of white Carrara marble which have highlighted the correlation between the micro fabrics and physical and mechanical parameters. The aim is to determine the conditions which indicate the triggering and evolution of the deformation phenomena. La note écrit l’analyse et les epreuves effectuée sur un echantillon représentatif de nombreuses dalles en marbrede Carrara. Les études montrent la correlation entre la minéralogie et les paramètres physiques et mecaniques. Le but est déterminer les conditions qui indiquent l’amorçage et l’evolutions des phénomènes de déformation. Diese Arbeit gibt eine Beschreibung der experimentalen Untersuchungen und der Analysen über die Marmorplatten von Carrara. Daraus resultiert, dass die Charakterisierung der Mineralogie und die Porosität der Gesteinsmaterialien die physikalische mechanische Degradation beurteilen und die Krümmungen bestimmen.

Jan 1, 2003

By J C. Small

Time-dependent deformation occurs when geo-materials are under an applied load; this may lead to additional deflection of a tunnel structure and the stress redistribution in the surrounding rock, shotcrete lining and rock bolt support system over time. A better understanding of this creep behaviour can improve the reliability of design, construction and maintenance of tunnels. Hence, the present investigation was carried out on the time-dependent properties of rock, shotcrete and the combined tunnel support system. Tunnels constructed in different ground conditions were modelled. The closure changes of the tunnel with time and the redistribution of stress in the surrounding rock, shotcrete lining and rock bolts due to the creep deformation were analysed. Results of the present analysis were compared with the results from the commercial program ABAQUS.

Jan 1, 2008

By Timothy Batchler

"Pumpable roof supports are currently being used to provide a safe working environment for longwall mining. Because different pumpable supports are visually similar and installed fundamentally in the same manner as other supports, there is a tendency to believe they all perform the same way. However, there are several design parameters that can affect their performance, including the cementitious material properties and the bag construction practices that influence the degree of confinement provided. A full understanding of the impact of these design parameters is necessary to optimize the support application and to provide a foundation for making further improvements in the support performance.This paper evaluates the impact of various support design parameters by examining full-scale performance tests conducted using the National Institute for Occupational Safety and Health (NIOSH) Mine Roof Simulator (MRS) as part of manufactures' developmental and quality control testing. These tests were analyzed to identify correlations between the support design parameters and the resulting performance. Based on more than 160 tests over 7 years, quantifiable patterns were examined to assess the correlation between the support dimensions, cementitious material type, wire pitch, and single-wall vs dual-walled bag designs to the support capacity, stiffuess, load shedding events, and yield characteristics.INTRODUCTIONDeveloped in the 1990s, the first major use of pumpable supports systems in U.S. longwall operations was in the support of bleeder entries (Barczak, Tadolini, 2008). Since then, they have been utilized as yieldable concrete supports to provide a safe working environment for longwall mining gateroads, bleeders, and emergency escapeways while also maintaining adequate ventilation pathways. The basic structure of pumpable roof supports has remained unchanged over the years. Formed in place with a twopart fast-setting grout, the support material can be pumped into a containment bag from several thousand feet away often through surface boreholes. The containment bag then acts as a form to fill the support and provides confinement to the grout during loading and after failure. Pumpable roof supports provide full contact with the mine roof and floor, which eliminates the need for secondary material to establish proper roof contact (see Figure 1). They provide a high peak load capacity and a sustained, confinement controlled yield behavior while maintaining stable ground conditions, which is essential to underground mining operations."

Jan 1, 2016

By S. K. Nandy, K. F. Unrug

The behavior of the immediate shaly roof within a drift mine in eastern Kentucky, operating in the Coalburg seam, was monitored with roof bolt dynamometers. The dynamometers used were capable of providing readings up to a maximum load of 66.72 kN (15,000 lbs), + 0.022 kN (5 lbs). To observe the influence of moisture on the rate and extent of roof deterioration, 57dynamometers were installed on roof bolts anchored in intake and neutral airways. Monitoring was conducted during the period January 1985 through January 1986, in order to cover a full cycle of dry and wet mine conditions associated with seasonal changes. Analysis of the data showed a trend of roof deterioration induced by condensation and eventual penetration of moisture within the immediate roof bedding planes, leading to rapid disintegration of the mine roof.

Jan 1, 1987

By K. F. Unrug

The research work reported in in this paper deals with the monitoring of roof behavior in a drift mine located in Eastern Kentucky operating in the Coalburg Seam. The thickness of the seam at the monitoring site ranges between 9 and 10 feet with the immediate roof changing from sandstone to shale then back to sandstone. Shale thickness varies between 0 and 2.5 feet. The characteristics of the immediate shaly roof were monitored with 38 dynamometers which were set up in three survey lines to cover the entire range of shale distribution. The dynamometers are capable of providing accurate load readings in the range of +/- 5 pounds. To closely observe the contribution of moisture toward roof deterioration the dynamometers were set up in intake and neutral airways. A television borescoping camera was used in conjunction with the dynamo- metric instrumentations at pre- determined observation holes to physically observe and record the separation process of the shale and sandstone stratum with respect to time. Monitoring took place between January 1985 through January 1986 in order to cover a full cycle of dry and wet mine conditions associated with the seasonal changes. Analysis of the data show a trend of roof deterioration induced by condensation and eventual penetration of moisture within the immediate roof bedding planes, leading to rapid disintegration of the mine roof.

Jan 1, 1986

The additive property of dispersion variances was found experimentally by D.G. Krige using data from the gold deposits of the Witwatersrand. In this property, called ?Krige?s relationship?, the dispersion of a small unit, v, within the deposit is equal to the sum of the dispersion of v within a bigger unit, V, and the dispersion of these units, V, within the deposit, D. It is known that the variance of the grades decreases as the support increases, the so-called volume-variance relationship. To analyse volume-variance and Krige?s relationship, the methodology herein proposed combines blending piles and geostatistical simulation to simulate the in situ and the pile grade variability. Variability reduction in large piles is based on the volume-variance relationship, i.e. the larger the support, the smaller the variability (assuming perfect mix). Based on a pre-defined mining sequence to select the blocks that will form each pile for each simulated block model, the statistical fluctuation of the grades derived from real piles can be simulated. Using this methodology, one can evaluate within a certain time period the expected grade variability for various pile sizes, and also calculate the Krige?s relationship between the small blocks and the piles of different sizes. A real case study using a large Brazilian iron ore deposit illustrates the methodology and demonstrates the validity of the results.

Jan 1, 2014

By T. Feroze, B. Genc

"The effect of some of the system variables in forcing and exhausting ducted fan systems on ventilation in an empty heading was investigated using computational fluid dynamics(CFD) and comparative analyses. The diameter of the duct, duct mouth to face distance, and the power of the fan (quantity delivered by the fan) were varied and their effect on ventilation determined through a comparative analysis of the flow rates calculated close to the face of the heading. Estimation models were developed, which can be used to calculate the flow rate close to the face of the empty heading for different settings of the system variables studied.The study showed that recirculation for a forcing ducted fan system can be reduced by increasing the duct diameter or increasing the duct mouth to face distance. For the exhausting ducted fan system, higher flow rates were achieved by reducing the duct mouth to face distance, andincreasing the fan design flow rate and duct diameter.The outcomes of this investigation will help ventilation engineers in deciding the optimum duct fan system required for sufficient ventilation.IntroductionThe ventilation of underground mines, irrespective of the type of mine and mining method, is divided into two broad branches, the primary ventilation and secondary or auxiliary ventilation. The primary ventilation is responsible for the total volumetric flow through the mine and the auxiliary ventilation is responsible for the ventilation of the development ends, production areas, and facilities disconnected from the main circuit with no through-ventilation connections. Auxiliary ventilation is the more difficult to achieve (Bise, 1996), and the disruption of this ventilation system is considered to be one of the primary factors contributing to methane and coal dust explosions (Creedy, 1996). A number of causalities have been recorded by many authors due to these explosions (Phillips and Brandt, 1995; Dubinski et al., 2011; Phillips, 2015). The ventilation of short headings, less than 10 m in depth, can be carried out without the use of any auxiliary equipment (Feroze and Phillips, 2015). However, for headings deeper than 10 m, auxiliary ventilation systems are required. These are generally classified into the three basic types, namely line brattice (LB) ventilation systems, ducted fan systems, and jet fans (Figures 1 through Figure 3 respectively)."

Jan 1, 2017

By Peter Cain

In 1993 an opportunity presented to monitor the effects of undermining an abandoned roadway by a longwall panel in the Sydney. N.S. coal field. Interaction subsidence data was collected by survey leveling to benchmarks in the undermined gateroad as well as by a standpipe system equipped with 15 vibrating wire piezometers measuring changes in elevation in the gateroad relative to an outby header tank. The piezometers were monitored at 30 minute intervals using a datalogger. while the leveling surveys were conducted weekly over the life of the project. The monitoring program resulted in the collection of a very large both of data. relating vertical subsidence to the relative position of the underlying face. The most basic analyses derived a travelling subsidence curve from the leveling data only. which hinted at a relationship between rate of extraction in the panel below and the amount of strain developed in the undermined strata. The complexity of the relationships between the amount of subsidence obtained, the location of' the individual monitoring stations, the rate of face advance below and the potential for "periodic" subsidence due to geological conditions has made analysis difficult. and the amount of data has compounded this problem. Recently. an analytical approach using a commercial neural network analysis package has been applied. which appears to have resulted in the ability to draw sonic meaningful conclusions from the data set. In this paper a short history regarding the collection of the data set is followed by a brief' description of neural networks. This is followed by a description of the several analyses performed. some of the results obtained, and conclusions drawn.

Jan 1, 1998

By S. Klingmann

ABSTRACT In this paper, we used data collected from the Gibraltar mine to analyze the effect of the TyreSense tire monitoring system on tire performance by reducing tire wear and preventing premature tire failure or damage. We analyzed the relationship between tire temperature, tire pressure, and tire failure or damage to help better understand the importance of controlling high tire temperature and pressure. The results enhance and expand the knowledge of the management of tire operational pressure and temperature.

Jan 1, 2014

By R. L. Grayson, S. Yuan

A stochastic model for evaluating the impact of the reliability and maintainability of shovels and trucks on the operational effectiveness of shovel-truck mining systems is presented. In the model, the Markov modeling technique is used to analyze the operating status of a shovel-truck mining system. Then, simulation is used to study the productivity of a shovel-truck system in a particular state. Finally, the relationship between the effectiveness of a shovel-truck system in terms of productivity and the reliability and maintainability of equipment is established. This relationship may be very useful to mine managers in making decisions in surface mining (e.g., regarding production process control, equipment replacement, and maintenance planning). A quantitative study is given to demonstrate how the reliability and maintainability of equipment affect the system effectiveness and how to pinpoint the parameter that has the most significant effect on the system effectiveness. The quantitative study indicated that in order to improve the system effectiveness significantly, the reliability and maintainability of the equipment need to be improved simultaneously.

Jan 1, 1995

By M. Board, R. Pakalnis, S. Seldon, R. Brummer

The Kidd operation mines roughly 10 000 tpd of copper and zinc ore from underground and employs about 700 personnel. In the late summer and fall of 1997, major movements in the proximity of the east wall of the Kidd open pit had been observed. The Kidd pit had been mined from 1965 to 1977 to depths of 260 m (850 ft), followed by subsequent mining by underground methods to current depths in excess of 1830 m (6800 ft). The No. 1 Mine (2600 Level to pit bottom) is approximately 90% extracted, with most of the remaining reserve between 2000 and 2500 levels. Although initial concerns centred on the stability of the pit walls, the potential ramifications of the movements to the underground were recognized and measures were implemented to ensure the safety of personnel as well as to minimize the potential damage to existing operations. In late October, damage to underground operations was observed as deep as the 2000 Level. In the final assessment, the global mobilized mass was a “wedge”-shaped hangingwall block extending from surface to about 610 m (2000 ft) below surface. The “wedge” boundaries are defined by a fault and shear zone which have continuous lengths in excess of 1070 m (3500 ft); its base by shearing through the host rock mass; and its eastern face by deep tension cracks (Fig. 1). Mined and filled excavations at the western face of the “wedge” allowed mobilization of a mass in excess of 30 M tonnes. Movements in excess of 75 cm (30 in.) per day were recorded on the surface stations that preceded the complete shutdown of operations on October 29, 1997. The evaluations in the days following the shut-down were centred on mitigation of immediate and future possible negative impacts on infrastructure and mining of the remaining No. 1 Mine reserves while ensuring the safety of the operators. This effort required the rapid assessment of the potential damage of the block movement on underground infrastructure, stope access, drainage and ventilation, as well as airblast potential due to the falling of a large block into the pit near the ventilation intake at the base of the pit. These assessments were presented in a previous paper (Seldon et al., 1999). In total, the lateral movement of the block on the ground surface was over 4.3 m (14 ft). This paper describes the detailed studies performed to understand the failure mechanism and to assess the impacts on future mining in No. 1 Mine.

Jan 1, 2000

By J. Alexandre

The use of bricks of soil-cement is proving to be an important constructive methodology due to low environmental impact in the production process of these blocks comparing with conventional bricks are burnt, besides being easy to produce. However during the process of production of bricks, which are compressed, knowledge of the properties of the soil used is critical to the quality and durability of the blocks. The objective of this work is to evaluate the feasibility of using soil from the municipality of Goytacazes for the production of soil-cement bricks. Assays were performed the compaction, liquid limit, plastic limit, particle size analysis, EDX and X-Ray diffraction for later pressed blocks and analyze their compressive strength and water absorption.

Jan 1, 2015

By M. K. Patel, K. C. Wade, M. Cross

In the past decade a good deal of effort has gone into the computer simulation of the heat distribution of pellet induration systems. The major uncertainty in the analysis of such systems is the gas flow distribution and, in particular, the role of leakage. Evaluation of the leakage into or out of a zone has proved to be very difficult, as has the cross-flow from one zone to another when adjoining zones have gas flows which change direction from up draft to down draft for example. This paper describes an initial model to calculate the gas flow distribution in a variety of practical situations of interest to those involved in pellet induration. The model is based upon a multiphase CFD code called CASCADE which is used in conjunction with the pellet induration simulation INDSYS.

Jan 1, 1990