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By J. E. Quinn, S. Wolstencrof, K. H. Soldenhoff

Ion Exchange (IX) using Strong Base Anion Exchange (SBA) resins is conventionally used to purify uranium from sulfuric acid pregnant leach solutions (PLS), particularly when uranium grades are relatively low. However, the presence of chloride in the PLS interferes negatively with conventional SBA based IX processes, by reducing the uranium loading on the resin. Chloride can be present in the PLS due to the use of saline bore or seawater in leaching, or chloride containing leach/IX reagents. ANSTO has been examining strategies to combat this problem for several years. ANSTO previously reported that a recently developed high-capacity SBA resin was capable of extracting uranium efficiently from saline leach liquors produced at Boss Resources’ Honeymoon in-situ recovery mine in South Australia. The resin was tested successfully in a 2017 Field Leach Trial carried out onsite in the existing wellfield area. While the piloting was extremely promising, the elution was more challenging, with eluate tenors limited to 2 g/L U3O8 using NaCl. This is due to the resin’s strong affinity for the uranium complex, which makes it difficult to elute efficiently by standard methods. In this paper, we describe a novel elution process developed for strong base resins that significantly improves upon conventional methods. The process, developed by ANSTO, is based upon conversion of the extracted uranyl sulfate species to uranyl carbonate, followed by elution with sodium chloride. The loading and elution process was demonstrated in continuous locked-cycle piloting conducted at ANSTO in 2019. The results were excellent, with eluate tenors of 8–9 g/L U3O8 achieved from Honeymoon PLS containing 50 mg/L U3O8, with very little transfer of impurities. In subsequent test work, the eluate was shown to be amenable to uranium peroxide precipitation. The results represent a huge step forward for the purification of uranium from saline leach liquors.

Jan 1, 2020

By A. D. Pittuck

Refractory minerals .containing uranium and columbium have been successfully treated at Queen's University, Kingston, to produce high-grade concentrates. Recoveries of over 90 per cent of the uranium and columbium have been obtained when treating concentrates containing euxenite, fergusonite, betafite, and pyrochlore. The processes ?consisted -of leaching the columbium with hydrofluoric acid, and the uranium with nitric acid, sulphuric acid, or sodium carbonate solutions. The leach liquors were extracted with organic solvents from which the values were stripped and precipitated, producing final products assaying 45 to 55 per cent Ob2O5 and 60 to 70 per cent U3Os.

Jan 1, 1958

By Wm. D. Jr. Sheldon

THIS paper presents practical data to aid in the selection of a mine ventilating fan, and outlines considerations to be made to ensure satisfactory operation and optimum efficiency of the fan. Much has been published on the general subject of mine ventilation, but the writer has found few specific data on factors and considerations which govern the selection of a fan-data which should be available to the operator if his fan is to give satisfactory service within the range of the high-efficiency portion of its performance curve and deliver the specified air capacity when operating against the anticipated range of resistance of the mine. The total quantity of fresh air furnished by the ventilation system must be adequate to provide, and to ensure at all times, safe and healthful working conditions in the mine. It is assumed that the mine operator is able to determine the air quantities required for the various parts of the mine.

Jan 1, 1941

By M. S. Diederichs, G. Walton

"Developments in understanding the brittle fracture of rock over the past two decades ultimately led to the acceptance of a cohesion-weakening-friction-strengthening model as an appropriate strategy for the modelling of spalling using a continuum approach. This strength model has been used to replicate observed failure depths and geometries for a number of case studies in the literature, most notably the AECL Underground Research Laboratory in Manitoba. One thing which these case studies typically ignore, however, is the influence of rock dilatancy on the evolution of brittle failure. Physically, this phenomenon is the volumetric expansion of the rock due to fracture opening; numerically, this phenomenon is captured by the flow rule, which is often characterized by the dilation angle, ?. Accurately modelling rock dilatancy in conjunction with strength evolution is necessary both to predict the magnitude and distribution of ground displacements, as well as the exact depth and shape of the fracturing zone. Both of these factors can have significant implications for support design. This paper is focussed on presenting some of the recent developments in this field in the context of a number of numerical modelling case studies. Initially, a new model for the dilatancy of brittle rock is presented, as well as some representative data and model parameters for different rock types. Next, several case studies of highly stressed tunnels and shafts are presented. The results of continuum numerical models are presented to demonstrate the ability of the back analyses to match observed in-situ measurements and obtained. The predictive capabilities of the material model are also highlighted for cases where sufficient “a priori” information (such as laboratory compression testing data) are available. The issues of model nonuniqueness and strain-localization/bifurcation are also addressed."

Jan 1, 2015

By A. H. Lang

"The name Barkc:rville district is applied loosely to the gold-bearing area around the historic town of Barkerville; the first mining camp in western Canada. The region is partly in the Cariboo mining division and partly in the Quesnel mining division. It contains two producing lode gold mines; the Cariboo Gold Quartz and the Island Mountain; and numerous other deposits. The regional structural pattern is outlined in this paper; the structural details of the producing mines are described in the papers that follow.The discovery of rich placer deposits in this district in 1860 was followed by the Cariboo gold rush. Placer mining in the area flourished until 1875 and then declined as the shallow diggings were exhausted, but important operations are still active. The total placer production amounts to about $50,000,000. An extraordinary number of quartz veins outcrop in the district, but many have only a small gold content. The miners soon recognized that the placer gold must have been derived from the erosion of these veins, and some directed their attention to the possibility of quartz mining. The erection of a 4stamp mill in 1876 was the first attempt at ore reduction in British Columbia, exclusive of arrastras. Efforts to mine the Cariboo lodes on a large scale were not successful, however, until 1933, when, due to the pertinacity of F. M. Wells and to the increased price of gold, the Cariboo Gold Quartz mine commenced production, followed by the Island Mountain mine in 1934. This success led to development work at many properties in the district, but the only ones that have reached production to date are the Columbia Tungstens, where scheelite has been mined intermittently since 1937, and the Cariboo Hudson, from which gold was produced in 1938 and 1939."

Jan 1, 1954

By A. R. Farkoosh

Al-Si based alloys have been recently used by automotive industry for highly stressed engine applications. Due to severe working conditions of the engine parts, existing alloys hardly endure high pressures at high temperatures. This necessitates alloy modifications to enhance the elevated temperature performance. In this study, the effects of trace nickel additions on the microstructural and mechanical properties of A356+0.5Cu alloy have been investigated at different aging conditions. Electron probe microanalysis (EPMA), scanning electron microscopy (SEM) and X-ray diffraction (XRD) are used to study the microstructural changes. Aging curves have been obtained by hardness measurement. It was seen that the presence of additional nickel introduced many complex intermetallic phases within the microstructure which led to improved high temperature mechanical and aging response.

Jan 1, 2011

By T. Plikas, L. Gunnewiek

Computational fluid dynamics (CFD) modeling was used to evaluate the performance and optimize the design of a potroom ventilation system in an aluminium smelter facility. The ventilation system must ensure the inflow of fresh air to the workplace by natural draft and the removal of heat and hazardous emissions generated from the pot cell process. A full-scale, three dimensional CFD model of the potroom was developed to predict the air temperature distribution and contaminant concentrations throughout the potroom for the purpose of verifying that the industrial workplace hygiene standards will be met by the proposed ventilation system design. The modeling work was used to optimize the size of the floor gratings around the pot cell and roof ventilator, as well as determine damper settings in the roof ventilator. The effects of outside air temperature and external wind on the performance of the ventilation system was evaluated to ensure the design performs adequately in response to seasonal variations in climatological conditions.

Jan 1, 2006

By J. E. Udd, S. Bharti

"ABSTRACTMonitoring of stability conditions in underground mines permits management to assess the response of the rock mass to mining strategies. Monitoring of movements, if sufficiently early, may also permit operators either to avert potential failures or to develop alternative approaches to extraction.The Falconbridge organization has been a leader both in the uses of rock mass stability monitoring techniques and in the development of instrumentation.In this paper, the authors review the Falconbridge approaches to monitoring, and present case history examples to illustrate the application of the various instruments used.RESUMELa surveillance des conditions de stabilité dans les mines souter-raines permet aux chefs d'enterprises d'évaluer les réactions de la masse rocheuse aux méthodes d'extraction minière. Si le contrôle des mouvements du terrain est effectué assez tot, l'exploitant pourra prendre les mesures qui s'imposent, soit pour éviter les détériorations possibles ou pour mettre au point de nouvelles méthodes d'extraction.Le groupe de la Falconbridge a ére le premier a utiliser des techniques de vérification des conditions de stabilité de la masse rocheuse et a mettre au point l'appareillage requis.Ce document présente une revue des méthodes employées par la Falconbridge pour assurer la surveillance active de la stabilité de la masse rocheuse et illustre au moyen de cas concrets la manière d'utiliser les divers appareils."

Jan 1, 1987

By L. J. Bryson, C. A. Biley

"Anglo American Platinum’s Rustenburg Base Metals Refiners (RBMR) produces Ni and Cu cathode from slow cooled converter matte after Platinum Group Metals (PGMs) are magnetically separated for further processing. In 2010, execution of the RBMR expansion project was commenced to increase the production capacity to 33 ktpa Ni. The expansion, which is currently still in a ramp-up stage, brought about several fundamental changes to the circuit chemistry, including the installation of a dedicated Pressure Iron Removal (PIR) autoclave. This provided an independent outlet for iron from the refinery, which previously deported to the residue from the leach circuit and was toll refined. At the same time as changes in the circuit associated with the RBMR expansion were being made, the plant experienced a significant increase in iron and copper units per nickel unit in the feed. The decoupling of the leaching and iron removal process steps has had significant advantages for the robustness and control of the overall circuit, in particular pertaining to the preparation of a nickel electrolyte of sufficient purity to produce LME grade nickel. This paper details the primary changes to the RBMR circuit chemistry with a particular focus on iron deportment and the benefits derived from the installation of the PIR autoclave.INTRODUCTIONAnglo American Platinum mines and refines Platinum Group Metals (PGMs) through a complex processing pipeline in its South African operations. Mined ore is first treated through several mineral processing stages, geared to the recovery of base metals and associated PGMs, followed by smelting and refining operations that aim to separate base metals from PGMs and recover the value components to purified, saleable products. The focus of this paper is the Rustenburg Base Metals Refiners (RBMR) complex which receives a PGM-containing converter matte, then physically separates PGMs and base metals, and recovers nickel and copper to cathode by utilising leaching, precipitation and electrowinning processes.With new mining operations coming online and the continued increase in PGM ore arisings, it was necessary to undertake an expansion project at the Base Metal Refinery (BMR) to increase production capacity from 21 ktpa to 33 ktpa Ni. Complicating the expansion project was the requirement of continued production through all stages of design, construction and implementation and, due to stringent capital constraints, the utilisation of all existing equipment installed during a previous expansion in 1981. Against this backdrop, the expanded BMR flow sheet involved significant changes to the chemistry, especially iron management. These changes in iron management allowed for the separation of iron and copper residues and significantly increased the robustness of the plant to changes in feed mineralogy as well as the potential to increase production duties of the existing equipment."

Jan 1, 2016

By Donald O. Downing

"IntroductionThis paper provides an overview of the coal mining industry in Canada with a description of current circumstances. The Canadian industry is placed in a global context and the future prospects of the industry are described. The export market is very important to the future of Canadian coal production and the essential aspects of the market are explained. Future prospects are very much tied to metallurgical coal exports and some key characteristics of that market are discussed, including major technological changes in the industry. Stability in 1996The Canadian coal industry enjoyed another strong year in 1996 continuing a trend established over the last four years. The strength of the industry is based on a stable domestic industry and a relatively healthy inter- national market. The figures bear out these statements. In 1996 total production reached 75 million tonnes and consumption was 52 million tonnes. The major markets for coal in Canada are electricity generating stations (Alberta, Saskatchewan, Manitoba, Ontario, New Brunswick, Nova Scotia) and the steel industry in southern Ontario. Approximately 11 million tonnes of coal were imported and exports reached a new record of 34.5 million tonnes, mainly from western Canada. Canadian Coal FlowsCanada represents a unique case in the coal world because we both import and export coal (Fig. 1). The reason for this apparent dichotomy is Canada’s geography. Eastern Canadian coal markets are located closer to the eastern United States coal fields and are basically served by them. This is true for both thermal and metallurgical coal. Major imported coal users are the steel industry, electricity generators and other industry including the cement industry in southern Ontario, Quebec, New Brunswick, with a little coal imported into Manitoba. Only about 2.2 million tonnes of western Canadian coal move into the east, including both lignite and bituminous coal."

Jan 1, 1997

By Yu-Min Cheng

Over the past two years, the construction industry has increasingly recognized the benefits and capabilities of building information modeling (BIM) for information integration, visualization and parametric design, reducing the duplication of work and complexity of interface integration, while significantly saving both time and cost. However, due to the variety of participants in engineering projects, the differences between data definition, data format, and data storage increase the difficulty of integrating data from diverse sources. Therefore, buildingSMART has developed a common data schema, called Industry Foundation Classes (IFC), that makes it possible to hold and exchange relevant data between different software applications, to increase the efficiency of BIM work and to ensure a consistent and high-quality output. This paper presents a novel methodology that assists in facilitating the import and export process for parametric BIM objects between heterogeneous BIM systems. This methodology is based on the IFC data schema and includes graphical and non-graphical description data. The objective is to retain the geometry, parameters, unit, texture and links of an object during exchange and sharing to ensure that data integrity is maintained. To sum up, this research addresses the issues of transferring parametric BIM objects between heterogeneous systems to increase data integrity and reduce transfer and integration times.

Aug 1, 2013

By Y. Wang

In this study, homogeneous (unseeded) precipitation of nesquehonite (MgCO3.3H20) by the reaction of MgC12 with (NH4)2CO3 in supersaturated solutions at 30 °C was investigated. Factors which influence the precipitation of MgCO3.3H20, such as initial concentration, temperature, stirring speed, titration speed, equilibration time, have been studied. SEM images show that the initial concentration and titration speed have significant effect on nesquehonite's crystal morphology and particle size. In addition, stirring speed and equilibration time also have some influence on its properties. With the optimization of operating conditions, the crystals can grow up to a length of about 40µm and a width of 5µm, indicating good filtration properties. High purity nesquehonite obtained in this study was calcined to produce highly pure MgO at 800 °C as shown by XRD results. The novel process may be used to separate Mg and Li from high Mg/Li ratio brines in Qinghai, China.

Jan 1, 2007

By D. R. Murray

"In 2017, Nutrien Allan Potash remediated a portion of the concrete liner in the production shaft. A set of underslung work platforms and collection boxes were used in conjunction with hydraulic splitters, jackleg drills and hand chippers to excavate and remove the broken concrete. New concrete was placed with the original pressure relief design, using a shaft slip form. Shortly after excavating, it was found that the estimated breaking rate and amount of original concrete in-situ was under estimated. Fifteen feet of excavated concrete (2719cu.ft) and ten feet (of replaced concrete was completed on April 28, 2017, and operation of the production shaft was returned to mine operations. During February 2019, Nutrien Allan Potash began remediation of a portion of the concrete liner in the service shaft. The project is different than the 2017 project, as the remediation has occurred during normal running operations and occurred only on night shift. Rather than hydraulic splitters and hand chippers, the new method includes a concrete saw and mechanical excavator from a working platform. The selected method is based on the lessons learned from the 2017 project in the production shaft. The service shaft project was scheduled to be completed in July, 2019. INTRODUCTION Nutrien Allan Potash is located approximated 75 km east of the city of Saskatoon, Saskatchewan, Canada. There are currently two shafts at Nutrien Allan Potash: the Production Shaft and the Service Shaft, transporting people and material from surface to a depth of 3,335 ft. The Production Shaft was completed in 1967, with one section of grey cast iron tubbing installed in the Blairmore formation between the 1605 and 2037 ft Levels. A second set of cast iron tubbing was installed in the Duperow formation between 2203 and 2463 ft Levels in 1999. The remainder of the concrete as of todays standards is designed as a pressure relief liner. The Service Shaft was completed in 1968, with one section of grey cast iron tubbing installed in the Blairmore formation between the 1600 and 2048 ft Levels. A second set of cast iron tubbing was installed in 1981, with 169 ft installed through the Duperow formation. The remainder of the concrete as of todays standards is designed as a pressure relief liner. PRODUCTION SHAFT REMEDIATION During the second quarter of 2015, the Mine Engineering team were notified of an area of concern in the production shaft. The shaft specialists of Golder Associates Ltd (Golder, formerly Alan Auld Canada) were contacted to complete an inspection of the production shaft liner with emphasis on the area of concern. Based on the inspection and documentation review, it was determined that the concrete at the 2804 foot elevation had been broken out for some time and was retained with #8 rebar bolts with resin encapsulation. The broken concrete was encroaching on the clearance to the conveyance."

Jan 1, 2019

By J. W. Reynolds

"The use of approved fire-resistant hydraulic fluids in equipment operating underground was made mandatory in British Columbia by amendment to the Provincial Mines Regulation Act effective January 1, 1975. This paper covers the action taken to achieve this, in the largest underground metal mine in British Columbia. Some evaluation of costs and effects based on experience to date is included.BackgroundAn amendment to the Mines Regulation Act of the Province of British Columbia was passed in July 1974 as follow s: "" Rule 111 (b) Hydraulic Fluids. After the first day of January 1975, all hydraulic fluids used in equipment operating underground shall be of a fire-resistant type accept able to the chief inspector.""Unquestionably, its intent was justified as a safety improvement measure. The list of fires in mines involving machinery where hydraulic fluid was a factor in the fires is long and sobering. In British Columbia, in a 22-month period from 1972 to 1974, there were six fires in metal mines resulting in extensive equipment damage and injury to four workmen. Nevertheless, no provision was made for research or development of systems modifications compatible with conditions encountered in B.C. and, as late as June 1977, the Mining Association of British Columbia continued to argue that fire suppression systems should be considered sufficient until a universal suitable hydraulic fluid could be developed. The sole concession was to issue permits for continued use of mineral oil in equipment bought prior to 1975 in order to allow producing operations to continue. The burden of developing the necessary technology was laid on the industry.The Sullivan Mine at Kimberley, the largest and longest established underground mine in the province, and Cominco's most important source of ore s for its smelter at Trail, B.C., was at the outset of a conversion from conventional to trackless mechanized mining methods in pillar recovery operation s. Introduction of fire-resistant hydraulic fluid s had to be done in a period of change, in many instances on equipment for which no data existed, and called for research which had to be done while retraining the work force.The introductory phase is complete. All equipment is on FRF, the requirements of Rule 111(b) are being satisfied, and a number of research and development programs continue."

Jan 1, 1980

By H. Staton, XPS Consulting & Testwork Services, T. Deng, M. Kelvin

"Lundin Mining’s Eagle Operation, located in Marquette County, northern Michigan consists of a mine and concentrator that processes a Ni-Cu-(PGE) ore. Mine production began in 2014 and is expected to achieve production of approximately 23,000 tonnes of Ni and 20,000 tonnes of Cu per year. The ore is trucked to the Humboldt Mill, where both a Ni and Cu concentrate is produced.XPS Consulting & Testwork Services (XPS) has assisted the team at Eagle since 2013. Prior to start up, the ore was piloted at the XPS lab in Sudbury, Ontario to demonstrate the concentrator flowsheet and establish flotation operating strategy. XPS consulting metallurgists worked closely with the Eagle team during the commissioning of the plant providing troubleshooting, sampling, metal balancing expertise and support. Finally, a series of monthly composites over a 6 month period was submitted for mineralogical characterization to assess plant performance, identify opportunities for improvement and to provide a baseline for the future operation.Lundin’s investment to test the ores ahead of mining and to team with XPS’s experienced mineral processing engineers to help commission the plant has led to the plant achieving concentrator production targets shortly after startup. The commitment to training and implementation of best practices, and a culture where ongoing testing is the norm, puts the Eagle Operation on sound footing for future operation.INTRODUCTIONLundin’s Eagle Mine is a subsidiary of Lundin Mining located in the upper peninsula of Michigan. The mine itself is an underground operation and the ore is trucked from the Eagle mine site 2 hours to the Humboldt mill.The ore is an ultramafic hosted high grade Cu Ni deposit and exists as either massive or semi massive sulphides. The high resource grade of Cu (2.49%) and Ni (2.93%) make this a valuable ore source. (Owen & Meyer, 2013) A metallurgical team was put together by Lundin to ensure the mill was designed and commissioned to optimize metallurgy in the shortest time from this valuable deposit. The commissioning plan targeted commercial production by Q1 2015."

Jan 1, 2016

By M. Gyenge, O. F. Coates, K. Barron

"It is suggested that artificial supports might be used to increase, with safety, the angle of hardrock open-pit slopes. Guidelines for designing such a support system, based on a simplified analysis, are given. The installation, construction and instrumentation of a trial support system is described and a breakdown of the construction costs is given. On the basis of this cost analysis, the economic benefits derived from reduced waste-rock excavation are compared with the support costs for a typical mine. In an example, it is shown that the slope angle in an open-pit mine 500 ft deep, with benches 50 ft high by 30 ft wide, could be safely increased from 37Yz degrees without support to an optimum of 53 degrees with support. In this case, the support costs would be approximately $900 per linear foot of pit wall and the savings due to decreased excavation of waste rock (at $0.34/ton) would be approximately $1,900 per linear foot, yielding an increased margin of profit of approximately $1,000 per linear foot of pit wall. This figure could be increased to $6,000 per linear foot if the steeper slope were used to extract more ore.More than 50 per cent of the support costs are accounted for by diamond-drilling the holes for the deep cable anchors. The use of percussion drills for this purpose would seem to offer a means of significantly reducing the support . costs and thus further increasing the profit margin available."

Jan 1, 1971

By V. G. Papangelakis, J. E. Dutrizac, G. Azimi

A new model capable of predicting the solubility of calcium sulphate solid phases in zinc sulphate processing solutions from 25 to 95°C was developed. The model uses the Mixed Solvent Electrolyte (MSE) model of the OLI systems software to calculate the mean activity coefficients of the electrolyte species. The model was tested using recently developed experimental measurements. It was shown to predict accurately the solubility behaviour of calcium sulphate in multi-component zinc processing solutions containing ZnSO4, H2SO4, MgSO4, MnSO4, Fe2(SO4)3, Na2SO4 and (NH4)2SO4. The model can also explain the complex effect of coexisting metal sulphates on the solubility of the CaSO4 phases. The model is a practical tool for assessing the process chemistry of a wide variety of complex aqueous processing streams.

Jan 1, 2008

By Lawrence Devon Smith

"This paper examines the impact of the various assumptions that go into an economic evaluation, and shows how these can be combined to show an exciting result that may not really exist. An example of an embellished case (the kind that one frequently sees when projects are being promoted) is developed and the cumulative impact is analysed to show the actual project underneath. The paper also points out some areas to watch for overly optimistic assumptions such as prices, inflation, and debt. The concept of a ""bare bones"" base case is proposed (constant metal prices, constant dollars, no inflation, no debt, no interest, on a project basis, after tax) as a common reference point.As well, the discount rate is examined as a fundamental means of reflecting risk in discounted cash flow evaluations. Current industry practice is discussed, and a methodology for the analysis of risk levels is proposed that assesses the constituent components of the discount rate: real interest, mineral project risks, and country risk.INTRODUCTIONOften, the first time that all of the technical and economic data for a mineral project comes together in one place is when the economic evaluation is developed. This typically happens when work on the project has progressed to a sufficient level of detail that the effort to produce a year-by-year cash flow is justified, usually at the pre-feasibility or feasibility study stage. The data involved will include:• production; tonnes waste and ore mined, ore grade, mining recovery, metallurgical recovery, metal sold• revenue; metal price, smelting & refining charges, marketing costs• operating Costs; mining, milling, administration, fees, royalties• capital Costs; exploration, development, construction, indirect costs (engineering, management), contingencies, start-up, inventories, working capital, replacement and sustaining capital, closure costs• taxes and royalties• exclusions; depreciation (this is not a cash item), sunk costs (only costs going forward)."

Jan 1, 2003

By Y. W. Pan, Y. R. Liu

The disturbed natural rock mass tends to equilibrium state accompanying with non-equilibrium evolution process which has significant influence on the long-term stability of engineering structure. The deformation development in the non-equilibrium evolution is determined by two intrinsic processes, trend to equilibrium and damage development, which can be illustrated by evolution of excavated tunnel. Thus the creep and damage must be taken into account in study of non-equilibrium evolution process. Within Rice’s irreversible thermodynamics with internal state variable (ISV), the conjugate force function which equals to zero is a convex surface which divide the stress space into two parts, called equilibrium and nonequilibrium stress space respectively. The concept of effective stress of non-equilibrium has been proposed, in which the stress difference (d - d ) are the effective driving forces of non-equilibrium evolution process with hardening and damage effective. The formulations of inelastic strain rate and energy dissipation rate have been recast in the form of effective stresses. The inelastic complementary energy (ICE) is proposed to measure intensity of non-equilibrium evolution of material system. The specific equations of conjugated forces and kinetic equations of internal state variables are presented. The ICE and rate of energy dissipation are all calculated to be used to evaluate long-term stability of geo-engineering. The results show that rate of energy dissipation may be more convenience and flexible than ICE for internal state variable constitutive equation of rock mass.

Jan 1, 2015

By A. Grimod

Rockfall drapery systems are commonly used as a simple, fast and cheap measure against the rock falling trajectories affecting very steep slopes. The system basically consists of a steel mesh, which is held on the top edge with a longitudinal cable fixed by means of a suitable number of anchors. The effect of this kind of intervention is to control the falls of the rocks, which are driven toward the bottom with slow velocity, or are stabilized on place. It can be used on any kind of slope to protect sensitive target in the mining industry, roads and railways, and inhabited areas. The falling blocks, typically smaller than 0.6 - 1.0 m in diameter, pile up into a trench (or into a ?pocket of mesh?) at the bottom. In comparison to other types of rockfall interventions, the simple drapery is cheaper, and its maintenance is easier, but on the other hand it cannot be considered the remedy for shallow instabilities, because it can only mitigate the effect of the falling trajectories. The design of simple draperies requires the analysis of several factors like the slope features (height, gradient, morphology), the geological and dynamic features (nature of the ground or rock, type of instability, erosion problem, blocks size), the environmental condition (presence of vegetation, aesthetical problem), the installation problem (accesses to the slope, safety for the workers, safety for the surrounding areas) and finally the performance required (temporary or permanent intervention, required maintenance, cost). Finally the most problematic design-step is the choice of the suitable mesh, the top longitudinal cable, and the top anchors type. Because of the highly variable nature of rockfall behaviour these structures cannot be standardized, but they have to be analyzed and designed for each case. Maccaferri has developed a new software application (MacRO 2) has a practical tool to define the mesh and the related supporting structure composed by up-slope cable and anchors. The software, based on the approach proposed by Muhunthan B. et al. (2005), allows designers to verify the top longitudinal cable, the anchors, and the mesh drapery, and to plan for maintenance procedures. Even if the method seems quite simple and rough, it is effective and lets the designer correctly foresee the materials and the geometrical features to be used on the interventions. This paper analyses the condition for the simple drapery installation, the main steps for the calculations, and it will present a case study in a U.S. mine. Nevertheless, even if the software allows a quick and simple calculation approach, onsite observations are always recommended in order to achieve a good design, with the ultimate goal of protecting property and human lives.

Aug 1, 2013