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By X. Cao, P. Wanjara, J. L. Fihey, X-T. Pham, F. Mirakhorli

Single-pass hybrid laser-arc welding of 10-mm thick cast plates of CA6NM, a low carbon martensitic stainless steel, was carried out in butt joint configuration using a continuous wave fiber laser at its maximum power of 5.2 kW over welding speeds ranging from 0.75 m/min to 1.2 m/min. The microstructures from the fusion zone to the heat affected zone and base metal were characterized after post-weld tempering at 600°C for 1 hour. From optical and scanning electron microscopy examination, the fusion zone was observed to mainly consist of tempered lath martensite and some residual delta-ferrite. The mechanical properties including microindentation hardness, ultimate tensile strength and Charpy impact energy were evaluated in the post-weld tempered condition and correlated to the microstructures and defects. The ultimate tensile strength and Charpy impact energy values of all the fully penetrated welds in the tempered condition were acceptable according to ASTM, ASME and industrial specifications. The failure mechanisms during tensile deformation and Charpy impact loading were examined by scanning electron microscopy, fractography and optical metallographic analysis near the fracture origin.

Jan 1, 2015

By Stephen B. Cheeseman

The quantity of data available and the rate at which we access such data are rapidly increasing. Electronic data capture systems, fleet management systems and a host of other technological advancements have created a constant stream of real-time, tactical data. However, are we taking advantage of this data? Are we converting data into useful information to aid in efficient decision-making? Mining operations are struggling with ?information overload?, finding it difficult to extract the benefits from vast stores of data. Without the necessary tools to facilitate a data filtering and information reporting process, most operations revert to old practises such as re-entering data into multiple spreadsheet reports. As a result, the ability to make effective use of data still eludes many mining operations. Some operations have taken audacious steps to rectify this situation. The De Beers Venetia mine in South Africa has implemented an integrated mining information technology solution that transforms their data into practical, usable information allowing staff and management to make decisions that improve efficiencies and reduce costs. In the absence of quantitative justification or ROI, De Beers took a risk in implementing change. Today, they are realising the benefits. This paper will unearth the information technology issues that surfaced during the Venetia implementation, then identify the benefits De Beers has obtained from deploying an integrated mining information technology solution at the Venetia mine.

May 1, 2002

By E. Wright

"INTRODUCTIONThe Ruttan Mine is located twenty-two km east of Leaf Rapids in northwestern Manitoba. The copper-zinc exhalative massive sulphide deposit is comprised of a series of individual and interconnected en echelon lenses which strike east 20 degrees north and dip south 70 degrees. The mine has been owned and operated by the Hudson Bay Mining & Smelting Company since July 1987. Sherritt Gordon Mines Limited began mining the orebody in 1973 from an open pit, but production has been entirely from underground since 1980. HistoryDuring the progression from open pit to underground mining, it was recognized that manual methods of ore reserve calculation were inadequate for responding to changing metal prices and evaluating alternative mine plans. The mine planning system that was developed is described in the paper, ""Computerization of Ore Reserves and Mine Planning Functions at Ruttan Mine"", presented by B.C.W. Haystead at the 1984CIM Annual General Meeting. At that time, programs for core logging, diamond drill hole plotting, grade interpolation, ore outline digitizing, and reporting had been developed by the Systems Department for use on Sherritt's UNIVAC 1100 mainframe computer. Telecommunications linked terminals at the Ruttan coreshack and office to the UNIVAC in Fort Saskatchewan, Alberta. The same mine planning system was also used at a second property.Operation of the mine planning system was expensive, and it was evident that increased use required a costly upgrading of the UNIVAC in order to maintain an acceptable service level to all users. The system was re-evaluated,' and it was concluded that: core logging was not easily adaptable to a new property, nor flexible enough for exploration; plotting, grade interpolation, and digitizing required considerable manual effort; and that the UNIVAC operating system was difficult to learn.It was recommended that a study should determine if: core logging could be redesigned and/or implemented on a microcomputer; interactive graphics be used to reduce the effort for functions requiring visual interpretation; and the creation of input processors would assist users in setting up parameters for guiding the programs."

Jan 1, 1989

By D. G. Macintyre

"Potentially economic stratiform barite-sulphide deposits have recently been discovered in Devonian basinal facies rocks of the Kechika Trough of northeast British Columbia. This new mineral district is over 180 kilometres long and includes nine major occurrences, namely Driftpile Creek, Bear, Mount Alcock, Cirque, Fluke, Pie, Elf, Kwadacha and Sika. The Cirque is the largest known deposit, with reserves of atleast 30 million tonnes averaging 10per cent combined lead-zinc and 47 grams per tonne silver. The footwall rocks for the Cirque and other strati/rom barite-sulphide deposits in the area are rhythmically bedded baritic and pyritic carbonaceous black shales, siliceous argillites and cherts of probable Mid to Late Devonian age. These siliceous rocks overlie a succession of proximal to distal turbidites which are the basinal equivalent of Early to Mid Devonian carbonate reefs to the east. The siliceous facies is overlain by deeper-water black shales of probable Late Devonian to Mississippian age.Preliminary stratigraphic and sedimentological investigations suggest that the strati/arm massive pyrite and bedded barite deposits formed in third-order euxinic basins within a northwest-trending structurally controlled trough which, in the southern part of the district, was bounded by carbonate reefs. The exhalative event, which appears to have been accompanied by synsedimentary faulting, took place during the early stages of a major eastward-directed marine transgression that was probably related to rapid crustal subsidence. Dewatering of metal-enriched shales and subsequent brine discharge along fault zones within the trough, with the exhaled brines accumulating in seafloor depressions, is the mechanism envisaged for formation of the deposits. Convective circulation systems may have been established about the more deep-seated faults, in response to elevated heat flow levels."

Jan 1, 1982

By J. Cayouette, C. Bolduc, P. Blatter

"The LaRonde mill was commissioned in 1988 and began treating ore from the Penna shaft in 2000. The mill has been expanded to accommodate 7,500 t/day, but ramped down to 6,000 t/day since the deep extension began. The process recovers gold, silver, and base metals. In 2008, the Goldex plant began trucking gold-pyrite concentrate to a treatment plant feeding pulp to the LaRonde mill, increasing gold output by 40,000 oz. In 2009, the high-grade Lapa ore processing facilities were annexed to the LaRonde plant, increasing gold output by 120,000 oz. This paper outlines the metallurgical considerations related to the treatment of different ore types.RÉSUMÉ Le concentrateur de la mine LaRonde a été mis en service en 1988 et a commencé à traiter le minerai du puits Penna en 2000. La capacité du concentrateur a augmenté afin de permettre le traitement de 7 500 tonnes de minerai par jour, capacité qui est retombée à 6 000 tonnes par jour (tpj) depuis le début de l’extension en profondeur de la mine. Ce procédé permet de récupérer de l’or, de l’argent et des métaux communs. En 2008, l’usine de traitement Goldex a commencé à transporter par camion du concentré de pyrite et d’or vers une usine de traitement alimentant en pulpe le concentrateur de LaRonde, augmentant ainsi la production d’or de 40 000 onces. En 2009, les installations de traitement du minerai à haute teneur de Lapa ont été annexées à l’usine de traitement de LaRonde, augmentant la production d’or de 120 000 onces. Cet article passe en revue les considérations métallurgiques liées au traitement de différents types de minerai."

Jan 1, 2017

By Larry M. Southwick

There have recently been executives at major metals companies who have recommended that Greenfield Projects not be pursued. Greenfield includes not only new geographical locations, but also new technologies and new types of feed materials. In the middle part of the 20th Century, two such projects were successfully commercialized to recover nickel from Cuban lateritic ores. One project (at Nicaro) used the Caron ammonia-ammonium carbonate leach and the other (at Moa Bay) a high pressure acid leach. How both of these projects dealt with these Greenfield issues will be reviewed, based on the original reports that described the research and development of the plants. This study will include a review of the critical ore characterization and sorting issues, as well as the extractive metallurgical, product recovery and equipment selection and sizing problems and how they were solved at each stage of project development, from laboratory through one or more pilot scale plants to start up and operation. In one case, a major revision of the plant was made after several years of operation to correct operating, equipment selection and materials of construction problems that hindered economical operation. These descriptions will provide a guide through the complicated and critical issues that in recent times have caused many companies to give up on similar development. Even with the more advanced analytical and computational tools available to today’s mineralogists, engineers and metallurgists, the basic concepts with which these projects successfully addressed their sets of problems are still required. In addition, upper management, now perhaps further removed from hands-on experience than was common then, will see how complicated problems require intense and detailed effort to avoid failure in the field and capital blowouts. Build it and we will make it run, kicking the can down the road and borrowing operating and design concepts incorrectly on technological issues, or nine year olds on a sugar high making financial decisions are not philosophies by which to succeed with Greenfield Projects.

Jan 1, 2014

By Ray Mason, Damien Label, Howard Bernier, Kevin McDermott, Kevin Coombs

"GeneralWabush Mines is an unincorporated joint venture of seven steel companies and Pickands Mather & Co. The mining and concentrating facilities are located in southwestern Labrador and the pelletizing and shiploading facilities are at Pointe Noire, 200 miles south, near the town of Sept-lies.The operation is based on a 5 ½ sq. mi. specular hematite deposit with a reserve of 375 million tons of concentrate. Annual production capacity is rated at 6 million tons of pellets per year. The final upgrading process utilizes high-tension separation of silica following wet autogenous grinding, spiral gravity separation and fluo-solids drying. The concentrate is railed in closed cars to Pointe Noire. The concentrate is reground dry and pelletized on Dravo Lurgi travelling grate machines to produce an oxide pellet with 65.5% Fe, 3.0% Si02, 1.95% Mn and 93.5% Tumble Index.HistoryPlant operations commenced in 1965 with a concentrator capacity of 5.3 million tons per year and a pelletizing capacity of 4.8 million tons per year. The original facilities for classifying the crude ore into fine and coarse fractions for storage purposes before reblending as autogenous mill feed were found to be unnecessary and were by-passed after plant startup. Capacity of the operation was increased to 6.0 million tons of pellets per year in 1968. This increased capacity required the installation of an additional160 cleaner spirals in the ore dressing plant, a new 5000 hp ball mill, three balling circuits and increased cooling air capacity in the pellet plant.In 1970, the regrind circuit in the pellet plant was converted to dry grinding and a significant reduction in grinding media consumption and maintenance costs was realized. A ninth grinding mill of 5000 hp capacity was installed to compensate for the reduced capacity in going from wet to dry grinding."

Jan 1, 2000

By CRO CRO

Elk Valley Coal?s Cheviot Project is located in the Alberta foothills south of the town of Hinton. The mine has been in operation now for the 3 years. The start up and subsequent operation of the Cheviot project has been directly influenced by the Cardinal River Mine. As the Cardinal River Mine was winding down due to reserve depletion in 2004, the price of seaborne traded metallurgical coal jumped to record levels and customers began aggressively seeking new sources of supply. Several months later, the owners of Elk Valley Coal decided to begin mining at the Cheviot mining area, extending the life of the area?s operations by over 25 years. The Cheviot Project had been delayed by low coal prices, ownership changes and a complicated and lengthy regulatory process fueled in large measure by stiff opposition from a number of major environmental organizations. Chief to the startup of the project was the construction of a 23-kilometer-long haul road that would connect the new coal measures to the existing Cardinal River processing and rail facilities. Construction of this road was completed with the first coal truck making its first trip in October 2004. This paper will look at some of original assumptions, the actual mining experiences and the lessons that were learned while moving from the drawing board to the current development as it exists today.

May 1, 2007

By J. B. Mawdsley

Introduction The writer was instructed to visit the Chibougamau region during the field season of 1927 and report on the mineral discoveries that had been made there since 1911. lt was deemed advisable to obtain detailed information regarding the rocks underlying the area in the vicinity of these recent discoveries. Accordingly an area 60 square miles in extent was mapped. The outcrops were studied along the water courses and along bush traverses spaced at half-mile intervals between these water courses. The completion of the rest of the summer's programme allowed only three weeks for this work. lt is from this small, mapped area, and this necessarily cursory survey, that the material for this paper was obtained. Location And Means Of Access The name Chibougamau district is applied loosely to an ill-defined area of about 1,000 square miles lying mostly north and west of Chibougamau lake in the Province of Quebec. The lake is approximately half way between lake St. John and James bay. It lies 150 miles north of the Canadian National railway and 40 miles south of Mistassini?lake.

Jan 1, 1928

In this paper we present the results of preliminary investigations into the applicability of new laboratory scale tests for the prediction of operating gap and specific throughput in high pressure grinding rolls (HPGR). The work is a part of the CAMIRO HPGR research program being conducted at the University of British Columbia, which aims to develop a suite of small-scale tests and procedures for the selection and sizing of HPGRs. A focus of the presented study is to test sample types in terms of their terra-mechanics based characteristics and relate them to specific throughput and gap results from pilot HPGR testing on the same samples.

Jan 1, 2012

By N. Saeidi

"For a mine section comprising 100 different stoping activities, there are ~10158 different possible stoping sequences to explore in the mine schedule optimization search and this figure is indicative of the challenge posed in maximising profitability through mine schedule optimization. Any viable excavation timetable must satisfy all conditions that will constrain feasible sequences. In general, consideration of additional constraint will tend to reduce profitability. Geomechanical constraints on mine schedules, introduced with the aim of avoiding excavation instabilities, can be established for underground mine schedule optimization processes but, currently, this is done only rather crudely; precedence relations between excavation activities (stoping or development) are encoded to produce particular stope sequence patterns (e.g. ‘chevron’ or pyramidal sequences).The work reported aimed to investigate automated processes for formulation of such geomechanical constraints. The timetable optimization approach to the problem precipitated a fresh look at time dependent, and excavation sequence dependent, deformation. Abundant evidence emerged that supported the notion that any methodology developed that failed to account for such time and sequence dependencies was itself bound to failure. Yet, it was also recognised that any deviation at all from an assumption of linear elasticity for geomechanical numerical modeling, adopted to inform geomechanical constraint formulation, would rapidly lead to impractical levels of computational effort.Thus the approach presented here represents a compromise: the elastic stress fields induced by individual mining activities are computed for each activity, independently considered within a computational domain identical to that of all other activities. These are stored in a database. Instability risk for a specific sequence of mine activities can be assessed through superimposition of stress fields drawn from the pre-computed database. Time stamps allocated to events corresponding to the excavation processes permit the conversion of the sequence of elastic stress fields into a time table of stress fields. For specific locations within the computational domain, the aggregate effect of the sequence of mine activities leads to stress-time histories having a castellated appearance, a result of the near instantaneous response of an elastic medium to the excavation perturbations. Time dependent deformation responses are crudely allowed for through the re-profiling these castellated histories through graphical construction of curved responses, where the curve gradients are related to a viscous parameter. Such curves form the basis for a geomechanical constraint formulation to be adopted for mine schedule optimization."

Jan 1, 2015

By Garry Biles, Ken Major, Raj Anand

"Prime Resources Group Inc. (Prime) commenced the Eskay Creek Mine operations in 1994 in northern British Columbia. The ore from the underground mine is crushed and shipped to smelters in Japan and Canada. The nominal production rate is 300 tonnes per day.Before commencing the above operations, preliminary evaluations for the high grade gold mine had indicated that an extremely complex metallurgical and chemical process flowsheet would be required to recover the economic metals. Subsequent to the metallurgical testing program, Prime identified markets for the untreated ore and initiated underground mining and ore transportation operations.Prime recently identified lower grade ore zones, which are less economic or uneconomic to mine and ship directly to the smelters. Test programs were initiated to evaluate processes for upgrading the ore to a marketable product. In 1997, Prime will complete the engineering and construction of a 150 tonne per day flotation plant to concentrate the gold and silver values for the NEX and 109 zones. The mine will then, in addition to the direct shipping of the shippable ore, ship concentrate from the millable ore. This paper discusses the development and design of the flotation plant.IntroductionThe Eskay Creek Mine is located in north-western British Columbia approximately 83 km north-west of Stewart, B.C. as shown in the location map Figure 1. Access to the site is provided by a restricted access gravel road from Bob Quinn Lake junction of highway 37, a distance of about 59 km. The work force at the mine is based on a two-week rotation schedule. Employees are flown from as far away as Vancouver to Smithers by commercial airlines and then from Smithers to the Bob Quinn airstrip by local charter. During poor weather conditions, transportation to site is by vans that take about six hours to travel the 450 km road distance."

Jan 1, 1998

By R. J. Labine, D. I. Brisbin, R. Roussain, P. R. Coad

"Abstract - The Owl Creek Mine is located near the west end of the Neo-archean Abitibi greenstone belt, 17 km northeast of Timmins, Ontario, and 4 km north of the Destor Porcupine fault. Gold occurs in epigenetic quartz veins and their pyritic wallrocks in two zones within a package of east striking, steeply north dipping, volcanic and sedimentary rocks. At the West Zone, 1 729 603 t of ore with a grade of 4.83 g/t Au (268 587 troy oz.) were produced from an open pit centered on a wedgeshaped unit of Tisdale Group basalt that occurs between two overturned, south facing units of Porcupine Group graywacke and argillite. Basalt/graywacke contacts are locally marked by graphiticcarbonaceous argillite, strike-parallel faults and massive quartz veins.Deformed quartz+/-ankerite veins occur along the graphitic sedimentary/volcanic contacts and in gently to moderately dipping fractures in basalts, and, to a lesser extent, in graywackes. Veins also occur sub-parallel to steeply dipping 070° foliation. Altered host basalts are composed of iron carbonate, sericite, quartz, carbon, chlorite and disseminated pyrite. Gold occurs as inclusions in pyrite, and less commonly as free gold in fractures and along graphite-quartz grain boundaries in quartz veins. Fractures preferentially developed in more competent basalts during pre- to syn-ore deformation are interpreted to have provided the permeability required for emplacement of mineralized quartz veins. Carbonaceous basalt/graywacke contacts further enhanced gold deposition by acting as chemical traps. The interaction of hydrothermal fluids with these carbonaceous sedimentary rocks led to the characteristic local darkening of host basalts due to carbon impregnation and chlorite development."

Jan 1, 1998

By James R. Kuipers

Center for Science in Public Participation CSP2 ? Organized in 1997 to provide technical assistance to public interest groups on mining and water quality issues ? 80%of effort devoted to direct support of grassroots groups and tribal governments ? 20% of effort devoted to public-oriented education for public, tribal, state and federal regulators, and for industry ? Board represented by public interest groups, at large citizens, and academia ? Professional staff with experience from mining industry, academia and government ? website: www.csp2.org CSP2 Mission Statement The CENTER for SCIENCE in PUBLIC PARTICIPATION provides training and technical advice to grassroots groups on water pollution and natural resource development issues, especially those related to mining. CSP2 seeks to focus the debate on factual issues, as brought to light by its technical analyses, and whenever possible to seek consensus and win-win solutions. CSP2 also performs policy related work with federal and state regulatory agencies on the implementation of water quality, waste disposal, and mining reclamation regulations.

May 1, 2002

By B. C. Legg, G. L. Tiley

"Many of the ore bodies presently being developed are in remote locations and are, or will be, served by electrical power supply systems of limited capacity.The largest single components of the electrical systems of an underground mine are usually the production hoist drives; the power demands of these drives vary continuously throughout each hoisting cycle.Before 1970mine hoists were driven by either wound rotor induction motors or DC motors in conjunction with motor generator sets.Static Power conversion equipment now costs less to purchase and install and is claimed to be more efficient than motor generator sets. On the debit side, however, it can adversely affect the hoist motors, it operates at relatively low power factors, and it produces harmonic currents.This pa per discusses the effects of static equipment on both DC motors and AC power systems, and evaluates the relative consumption of the three classes of drives."

Jan 1, 1993

By Jarret Thomson

An understanding of groundwater flow is essential for many aspects of mining. This is especially true for the process of shaft sinking through the sandstones of the Manitou Falls Group in the Athabasca Basin of northern Saskatchewan. Experience has shown that the hydraulic conductivities of these sandstones can be relatively high, especially in zones containing natural fractures. To develop a better understanding of the inflow potential into a shaft, a laboratory testing program was undertaken to investigate the hydraulic conductivity of fracture core samples from the Manitou Falls Group. This program involved the measurement of hydraulic conductivities under steady-state flow conditions, while cycling the effective confining pressure across a span that is representative of in-situ conditions. The change in fracture aperture was simultaneously recorded at each confining stress level. It was found that existing relationships relating aperture and flow did not accurately capture the behavior of the samples tested. The effects of fracture staining and infilling were also investigated, and were found to have a notable impact on the hydraulic conductivity.

Jun 1, 2012

By Jochen Petersen, Caroline Muzawazi

The technical feasibility of ammonia leaching of PGM bearing Platreef flotation concentrates was investigated as an alternative method for the recovery of base metals prior to precious metal recovery. The composition of the concentrates includes 2.02% Cu and 3.17% Ni, and the major base metal minerals are chalcopyrite and pentlandite. Optimal leaching conditions were initially established in shake flask experiments to be a solution containing 4 M NH4OH, 4 M (NH4)2CO3 and a pH range between 9 and 10. These were used as base case conditions in column and batch stirred tank reactor tests, where the effects of total ammonia concentration and operating temperature were explored further. At optimal conditions nearly 100% Cu and Ni extraction were obtained in the batch stirred tank reactor, and 95% Cu and 60% Ni extraction was obtained in columns. The activation energy for chalcopyrite and pentlandite was 36 kJ/mol and 16 kJ/mol, respectively, in both reactors, indicating different reaction pathways for the two minerals. Gas-liquid mass transfer appears to be the limiting reaction step in columns much more than in tanks, and the degree of ammonia loss to air is significant. This initial test work indicates the feasibility of using ammonia leaching for this and similar materials as an alternative route to conventional smelting and refining prior to PGM recovery, but a number of technical challenges still need to be overcome.

Jan 1, 2014

By Charles Tkaczuk

In order to remain competitive the mining industry must keep up with changes in technology. Many innovative technologies from the mining perspective are commonplace in other industries. A ?Global? review of technologies will often reveal existing technologies that can be innovatively applied in the mining industry. Industries, which are rife with proven solutions include, medicine, biotechnology, security, manufacturing, telecommunications, etc. This paper addresses the communications aspect of mining where greater productivity, lower costs and the ability to quickly react to mining related events is obtained through an increase in remote monitoring and operating control. A review of the communications systems in place globally reveals technologies that, with minimal modification, can be immediately applied to the mining environment. We discuss the concept, advantages and implementation of existing communications technology from an industry that is not usually associated with the mining industry. This technology will form the basis of a solid platform on which can be built a state-of-the-art process monitoring, control, and communication system. This lays the groundwork for providing one solution to the underground mining industry?s most difficult problem, establishing a reliable, maintainable and cost-effective underground bi-directional wired/wireless data, video and analog communications system. We need look no further than our own doorsteps to find such a solution. The cable that you see coming from the simple green or brown box on the boulevard into your home contains hundreds of television broadcast channels, FM radio channels and data channels. And if you have a set-top box, you are in control of it all. The Cable Television Broadcast Distribution System suppliers of today are at the leading edge of converging all the different methods of communications onto a common carrier, coaxial cable or fibre optic cable. There is no fundamental difference between providing a reliable communications network to a city/neighbourhood/home/personal computer than there is to a mining operation/underground level/equipment or person. The principle is the same. Only the application is different. Realizing this, we can capitalize on the efforts of other industrial sectors, to solve our communications problem. Where else can you find a solution to a problem that is mature, having been developed with the input of thousands of engineers, and having hundreds of millions of dollars spent on research and development, manufacturing, distribution, global presence and engineering support?

May 1, 2003

By Nicolas Gatelier, Sophie Laurent, Thierry You

Hard-rock caverns for hydrocarbon storage are a very particular type of underground facility controlled not only by local administrative and regulatory constraints that can be very specific, but also by the possible risks of geotechnical or geomechanical failure. Each such facility throughout the world is a prototype that needs to be adapted to very different site conditions. The straight forward application of design methodologies from relatively similar fields (mines, tunnels) can be very useful, but risks holding back the scientific and technical improvements needed by an engineering industry in full development. Here we look at various case histories and at problems that have been raised where recent attempts at standardization would appear to have been ill adapted, and where storage designers, through experience and judgment, may still provide innovative engineering solutions.

Jan 1, 2015

By M. Cai

"It is well known that Peak Particle Velocity (PPV) plays a critical role in triggering rockburst damage in burst-prone underground mines. To estimate the PPV distribution around excavations, advanced numerical modeling can be used. In wave propagation numerical modeling, velocity field is often assumed to be uniform around an excavation. However, it is observed that wave velocities near mine openings are not constant, but rather non-uniform. Wave velocity in a rock mass depends on many factors such as rock quality and confinement. In particular, confinement has a large influence on wave velocity. The confinement around an excavation is low at the wall boundary and increases gradually and reaches a constant value far away from the excavation boundary. Hence, stress redistribution due to excavation will have a profound influence on wave propagation in underground mines. A better understanding of the influence of excavation effect on wave propagation helps to interpret the field observation of rockburst damage and improve mine safety. For this purpose, a non-uniform velocity model need to be constructed and the influence excavation effect should be taken into account in numerical wave propagation modeling.In the present study, a non-linear velocity model is developed firstly by considering the influence of confinement on wave velocity. This model links wave velocity to confinement explicitly. A coupled numerical method is then developed and used to study the seismic wave pattern around excavations in underground mines. Two codes, FLAC and SPECFEM2D, are coupled in the analysis. The motivation of developing the FLAC/SPECFEM2D coupled approach is to take merit of each code, such as the stress analysis capability in FLAC and the powerful wave propagation analysis capability in SPECFEM2D. The coupling process is realized through three steps: (1) static stress redistribution around an excavation is analyzed in FLAC; (2) data for coupling analysis, such as non-uniform velocity field (based on the new developed velocity model), mesh, absorbing boundaries, etc., are generated by FISH functions in FLAC and passed to SPECFEM2D; and (3) wave propagation modeling is performed in the SPECFEM2D considering a fault-slip seismic source. Because stress redistribution around the excavation is considered, non-uniform velocity field for the SPECFEM2D model can be obtained and this is a notable feature of this study. Very large difference in the S-wave response in these two modeling approaches with uniform and non-uniform velocity fields can be seen from the modeling results.Using the FLAC/SPECFEM2D coupled modeling approach, accurate velocity models can be constructed and this in turn will help to produce accurate PPV distribution around the excavations. Accurate PPV contours can be used to identify high rockburst risk zones for improved dynamic ground support strategy."

Jan 1, 2015