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By Abdalla MH

The deformation resulting from the presence of a tunnel may signifcantly affected, nearby structures and need to be considered during design of both tunnel and structure. The aim of this paper is to study the effect of different factors which may affect the interaction between the tunnel and the str- ucture. These include; the depth of both tunnel and foundation level of the structure ( z and t ), distance between C.L. of tunnel and loads, breadth of the loaded area, Diameter of tunnel and lining of the tunnel. The problem is studied as a two dimensional plane strain model by the boundary element technique. The results of this study indicated that the presence of a cavity/tunnel increases, in general, the vertical displacement on the ground surface and at the foundation level as well as the horizontal and vertical stresses in the cavity/tunnel level. The effect of eccentricity is increasing as e/D decreasing. For pile foundation there is a quite different- influence of the presence of cavity/tunnel in both cases of friction pile and end bearing pile type of foundation.

Jan 1, 1987

The task of designing stable high walls and spoil piles in strip coal mines, and stable openings with controlled roofs and floors in underground collieries - within the constraints normally imposed by economics - depends upon a reliable assessment of rock mass strengths and rock mass reactions under a variety of stress conditions. Of the geological factors influencing internal friction and cohesion within rock masses, many may be determined qualitatively or empirically from bore-hole evidence. Rock types, descriptions and properties of intact rocks, location of boundaries, limits and degrees of weathering, potential for slaking or decomposition of rocks when exposed, bedding characteristics, the nature of rock anisotropy and the likely effects of water on rock mass properties can be assessed from bore- hole data. Discontinuities, whether they be major such as faults and dykes, or minor such as joints and fractures, present a greater problem, and in most instances the mine geologist must resort to additional techniques to describe or predict their occurrence, nature, frequency, intensity or physical properties. Information on ground water and seam gas is available from bore-holes within certain levels of reliability.

Jan 1, 1977

The limitations of the conventional practices, and their effects, in prospecting for and in the evaluation of alluvial gold deposits are briefly reviewed. Geophysical prospecting methods have demonstrated their complementary role in the delineation of deposits by reducing the number of boreholes which are primarily of a 'probing' type. Larger diameter boreholes, although more expensive on a linear basis, are much cheaper on a volume recovered basis. The need to have sufficient volume as well as number of samples is stressed. Classical statistical methods are not appropriate for such deposits as there is sufficient structure, or spatial correlation, to require the application of geostatistics. Quite reliable semi-variograms, but not in all cases, of the spherical scheme have been obtained. Subsequent kriging has, to date, been confined to unworked deposits: retrospective estimates to compare to production have not therefore been produced. However, the technique shows promise but indicates a considerably greater borehole density (of the conventional diameter) may be necessary to produce confident estimates. Used in conjunction with larger diameter boreholes, a lesser borehole density may be sufficient, through radical reductions of the sampling error.

Jan 1, 1977

The torsion test is considered as the best test used when the part is subjected to static or dynamic torque. Many published papers have investigated the torsion of non-heat treated metals. However, very few published papers dealt with the torsion behaviour of heat treated metals. The aim of this work was to study the effect of heat treatment on the torsion behaviour of steel alloy (AISI 01), which can be used for manufacturing small and medium drills, taps and reamers. The diameter of specimens used was 15 mm. The metal used was heat treated under different conditions, then torsionally tested. The results of torsion test were divided into two groups: results obtained during elastic limit from which the shear stress, shear strain and modulus of rigidity were calculated, while from the results obtained during plastic limit the plastic depth was calculated by applying derived equation when the angle of twist was more than yield value. The results obtained indicated that the value of hardness alone is not sufficient to establish heat treatment conditions. Rather, it was found that the determination of plastic depth together with hardness can help in the establishing of the optimum condition which was hardening temperature of 820¦C, hardening time 20 minutes and tempering temperature 220¦C. This condition produces hardness of 60 HRc and plastic depth of 2.5 mm.

Jan 1, 2003

By Emerson D. W

The search for economic mineral deposits is becoming more difficult as exploration goes deeper in the established mining camps and spread out to the surrounding covered areas, which may have an `overburden' some hundreds of metres thick. Geophysics is finding an ever increasing role in such exploration. When the target is zinc, the task often becomes even more difficult since sphalerite, the most commonly mined mineral, is non-magnetic, resistive, and relatively light compared to other sulphides. Fortunately, sphalerite commonly occurs in association with other sulphides, which are magnetic and/or conductive and/or heavy, thus most zinc-rich orebodies have at least one contrasting physical property to aid exploration. This paper presents the physical properties of sphalerite and other potentially important zinc minerals. Results of petrophysical measurements of samples from various zinc-rich ores are presented together with examples of geophysical surveys over a number of zinc deposits. The results show that the physical properties are not merely dependent upon the properties of the orebodies' constituent minerals. For example, the small (0.4 Mt) and low-grade (five per cent Zn + three per cent Pb + two per cent other sulphides) Flying Doctor deposit at Broken Hill, New South Wales (NSW) is much more conductive than the large (3+ Mt) and high grade (14 per cent Zn + five per cent Pb) Cadjebut deposit in Western Australia (WA). In the former case, tectonic stresses have

Jan 1, 1993

The planning, design and construction of a service tunnel, under a major arterial road between two hospitals are described. The multiple uses of the tunnel combine to provide a favourable cost-benefit ratio for the tunnel as part of a rationalisation of services between hospitals. The driven tunnel provides economic, program and approval advantages over that of a cut and cover construction. The cross sectional shape of the tunnel was determined during feasibility studies by the degree of weathering of the Silurian mud- stones, the shallow cover and the proposed excavation equipment as well as the functional requirements. The site investigations covering geotechnical, building, noise and level surveys provided input to the design documentation and construction phases. Monitoring of settlement levels and primary support stresses during early construction stages confirmed the adequacy of the proposed tunnelling methods and support to be used adjacent to the major building foundations. The 140 metre long tunnel was success- fully completed in April 1980 at a cost of $650,000.

Jan 1, 1981

A study was conducted to evaluate the effectiveness of the three types of sample grinders routinely used in the mining industry for the sample preparation of gold ores with particular emphasis placed on testing their capacity to produce a representative assay sample of coarse gold ores. The grinders used in this study are the Labtechnics LM5, the Mixermill 4010 ringmill and the Keegor vertical spindle pulveriser, commonly called a Keegormill. The study was based on the preparation of samples from two sources of known coarse gold ore, the Union Reefs Gold Mine and the Brocks Creek Gold Mine in the Pine Creek region of the Northern Territory of Australia, and a fine gold ore which was from the Macraes Gold Mine in New Zealand. The Union Reefs Mine contains visible coarse gold with 30 per cent to 40 per cent of the gold in the plus 75 μm fraction of milled ore. Discreet particles up to 5 mm have been recorded, Hellsten (1994). Union Reefs Gold Mine recovers 40 per cent of its bullion production through a gravity circuit, Riches (1997). Brocks Creek ore contains visible coarse gold with gravity bullion production fluctuating between 50 per cent and 65 per cent, depending on the mill feed. Average gravity bullion production from the Brocks Creek Mine is 55 per cent, Wilke (1997). The average gold grain size of Macraes Mine ore is 20 μm with 40 per cent of the gold in sub 10 μm particles. No gravity bullion is produced from the Macraes Mine, O'Keefe (1997). The testwork demonstrated conclusively that it is possible to prepare a representative sample for assay, of a coarse gold ore, when a Keegormill is used to pulverise the sample to a nominal 100 μm particle size (90 per cent passing a 100 μm screen by wet sieving). Both the Mixermill and the Labtechnics LM5 failed to prepare a representative sample, even when ground to a nominal 75 μm particle size.

Jan 1, 1998

Study on Preparation and Gel Performance of High Purity Montmorillonite In order to research the colloidal and thixotropic performance of the inorganic gel prepared by high purity montmorillonite, this study uses the moderate grade bentonite ores from Weifang (China) as raw material. Two-stage hydrocyclone classification was applied to obtain the high purity montmorillonite with its content of 94.8 per cent. In contrast to other methods of montmorillonite purification, two-stage purification by hydroclone has the advantages of larger throughput and easily achieving auto-control in industry, and purified products with different montmorillonite content can be obtained by this method. And then the inorganic gel was prepared by the prepared high purity montmorillonite and its colloidal and thixotropic performances by measuring the flowability and thixotropy were further studies. Research results show that the inorganic gel has plastic body liquidity, the viscosity decreases with the increase of the shear rate, the static and dynamic shearing stress values are 33.98 Pa and 91.89 Pa, respectively, and the thixotropic value is 95.2 dyne+s/cm2, which indicates that it has preferable colloidal and thixotropic performance. Montmorillonite inorganic gel prepared by bentonite with high montmorillonite content and low-layer charge has better gel performance.

Sep 13, 2010

Teller Underground Mine was established to extract ore from the Middle Vale Reef located on the eastern flank of Telfer Main Dome.The mine is located below a 150 m deep open pit operation. The ore body is shallow dipping highly structured, and is a main aquifer in quite difficult ground conditions.In respect of these conditions it was determined to access the orebody using an adaptation of coal mining and hard rock mining methods, with support being achieved using a combination of island pillars, rock bolts and timber stalls.The paper will describe these methods in more detail, then discuss the successes and failures of these methods when put into practice. As well, it will detail several factors whose influences were found to be greater than previously expected and stress the importance of good geotechnical advice.

Jan 1, 1993

By S Planeta

The use of explosives in underground mining has its drawbacks, particularly in the case of thin or narrow vein type deposits. Due to that, there is a need to develop more discriminative and safe rock-breaking technologies. Mechanical rock splitting seems to be one of the most promising avenues in this respect. This paper describes briefly principles and features of radial-axial splitters. It reviews a feasibility study done to evaluate a potential of this technology in selective mining. It was intended to compare productivity and cost of ædrill-splitÆ mining with conventional cut-and-fill method. Hypotheses and assumptions adopted, methodology used and the obtained results are presented and discussed. The study has confirmed an interesting potential of radial-axial splitters in mining thin and narrow vein deposits. In conclusion, it is stressed however, that it will take more R&D work to corroborate the results obtained. Some suggestions concerning future research in this field are also given.

Jan 1, 2003

By Kitzinger F

The economic climate of the Canadian mining industry forced an increased interest in rapid, continuous excavation techniques for hard rock formations. The potential applications and advantages of continuous mining over the present drill- blast-muck labour intensive cyclical methods are considerable. Noranda investigated an electrical technique, Plasma Blasting showing considerable promise for mining hard rock. The background of the technology and the theory of blasting rock with electricity is described. The Plasma Blasting process is based on the fast discharge of stored electrical energy into a small amount of electrolyte, suitably located in the rock. The electrical energy converts the electrolyte into high pressure plasma, which expands very quickly, thereby, generating a shock wave. This shock wave produces a stress field inside the rock, resulting in a blast similar to that made by chemical explosives, but without the deleterious fumes. Noranda is currently blasting boulders of 4-5 tonnes and is at present constructing a mobile, autonomous secondary rock breaker for underground and open pit applications. Tests on in situ hard rock formations will lead to the development of a continuous mining machine. Production rates of 500 tonnes per man-shift could be obtained with such a machine.

Jan 1, 1990

By J Nemcik, E Baafi, I Porter, G Spinks

Spray-on liners used in the mining industry for ground support and stabilisation applications are either cement based (æshotcreteÆ) or polymer based (æthin spray-on linersÆ). Some thin spray-on liners are a blend of both polymer and cement (eg Tekflex). A small number of thin spray-on liners (TSLs) have been trialled in Australia as potential replacements for steel mesh in roadways and other underground mining applications; however, they were found to cure slowly and the cured coatings became brittle after an extended time in place. The University of Wollongong in collaboration with the Australian coal mining industry has shown that a viable polymer-based alternative to steel mesh in underground roadway support applications can be developed to eliminate the use and handling of steel mesh. The work to date has: established the feasibility of developing polymeric alternatives to steel mesh in underground roadway support applications; identified the physical and material constraints to be endured by any new polymeric skin reinforcement system by measuring the mechanical properties of steel mesh; identified materials that can be spray applied; and demonstrated that polymer mechanical properties can be optimised to produce similar mechanical properties (elastic modulus, yield stress, elongation-at-break, etc) to steel mesh. The identified materials will: allow the face support cycle to be fully automated, or at least remotely operated and installed; remove personnel from the immediate face area; and substantially improve underground roadway development rates.

Jan 1, 2008

By McNabb KE, Ward B, Dyer G

Roof conditions at Southern Colliery, the second longwall mine to be established at German Creek, were found to be much stronger and more massive than at the earlier longwall mine on the lease. Investigations were made to ascertain the level of face support required for longwall extraction under the changed geological conditions. Geotechnical information was provided from drillholes and highwall exposures. Downhole geophysical logs, notably the sonic velocity log, were used to obtain a distribution of the major lithological units over the mine area. A representative type section of the strata and geomechanical properties was compiled to form the basis for numerical modelling. Two-dimensional finite element methods were used to predict strata movements and chock loads under cantilevered roof conditions. The model incorporated a 6.3 in thick roof beam either bonded or detached, with either a 2 in or 5 in overhang. The solid rib, immediate roof, chock support and goaf were modelled as distinct parts, in addition a front abutment stress profile, derived from three-dimensional displacement-discontinuity analysis, was superimposed on the model.

Jan 1, 1992

By McDonough RJ

Mechanical agitation is the preferred system for Carbon-in-Pulp processes. Agitator design requires an understanding of the relationships between energy, shear and flow and the nature of shear rates and shear stress distribution in an agitated tank. Laser techniques are useful when studying these phenomena. The alternatives are open impeller agitation or draft tube circulation. Each has advantages and disadvantages but both require careful choice of impeller and system geometry. Overall the draft tube circulator is the more attractive in many cases. Open impeller agitators are designed in accordance with established procedures for mineral slurries taking due account of shear effects in tanks containing carbon. Preferred tank proportions are 1:1. Circulator design methods were developed in the alumina industry before being applied to CIP processes. Optimum draft tube diameter is critical to power requirements. The overall system must be designed as an axial flow pump operating in a closed circuit. Such a system exhibits quite characteristic behaviour which requires an impeller of varying pitch angle and aerofoil section for best stability and efficiency.' Tank height may be 2 or more times diameter. Resuspension of settled solids can be assisted by a series of slots in the draft tube. These slots have the secondary effect of stabilizing hydraulic behaviour and reducing installed power requirements.

Jan 1, 1982

By Seneviratne SP

The excessive displacement of the seam floor in headings (i.e. roadways) called 'floor-heave' is often experienced in the underground mines of the Southern Coalfield of New South Wales. Apart from interfering with the mining operations, the phenomenon could be detrimental to the stability of the pillars left for support leading to an unpredictable increase in the subsidence of the overlying strata. The latter could pose a serious problem, particularly in the design of partial extraction layouts of mining for areas where subsidence is to be controlled. The susceptibility of the floor of different rock materials and thicknesses in a given `panel and pillar' partial extraction geometry was examined by two- dimensional Finite Element Modelling of the displacements, stresses and failure zones around the excavations. The modelling, assuming elastic behaviour of the materials, indicated that the maximum vertical displacements of the floor increased substantially as the Young's Modulus of the material decreased to less than 7GPa and the thickness of the layer increased. The results also discount the possibility of a properly designed panel and pillar geometry in the Southern Coalfield of New South Wales being unable to adequately control surface subsidence through the pillar, or its core independently of the yielded ribs, penetrating the floor.

Jan 1, 1992

By Marshall GA

Structural fatigue damage of haul truck frames is a costly problem associated with the operation of large mine haul trucks. A monitoring programme is described which has been instigated to measure stresses in the frames of haul trucks under actual mine operating conditions. The instrumentation used and methodology employed in the computer analysis of the results is briefly described. The results of the monitoring programmes are reviewed, and the effects of various factors affecting structural fatigue damage of three common types of rear dump truck are considered. Factors discussed include the effects of haul route features (for example shovel, dump and crusher areas); the effect of operations such as turning, braking, loading and dumping; the influence of payload; the effects of malfunctions in suspensions; and the influence of haul route surface quality. It is shown that with respect to payload, while structural fatigue damage is increased with payload, the structural damage per unit of payload does not change significantly for moderate increases in payload above the nominal value. Finally, on the basis of these results, recommendations are made for haul route design and operational practices which will increase the structural fatigue life of haul truck frames.

Jan 1, 1986

Depletion of shallow ore reserves is forcing the South African gold mining industry to exploit reefs at ever-increasing depths. By 2010 around 30 per cent of South African gold production probably will come from depths greater than 3 km (Johnson and Schweitzer, 1996). At such depths, virgin stresses will rise significantly, producing complex rock engineering problems (Malan and Basson, 1998). Concern over structural instability at depth has led planners to seek a technology capable of ædetection of geological structures with a displacement of 2 m or greater (or as appropriate to the mining technique) 200 m ahead of mining at an acceptable costÆ. Borehole radar probably is such a technology. Cover holes are drilled routinely ahead of development. The evaluation of its candidacy for a tactical role in ultra-deep gold mining dependsùamong other thingsùupon establishing the electromagnetic characteristics of the environment hosting significant gold reefs. The Ventersdorp Contact Reef (VCR) is one such reef. Recent borehole radar field trials, presented here, suggest that the VCRÆs overburden is a remarkably translucent, clutter-free dielectric with a Q of ~35 and that the VCR itself is the dominant radar reflector.

Jan 1, 2002

By T Alexieva

Since the early 1900s the geotechnical community has investigated every significant failure of a tailings dam, improved our knowledge of the behaviour of the tailings storage facilities, developed analysis methods, compiled lessons learned, and committed to zero failures. The rate of occurrence of tailings dam failures has reduced since the 1980s, however, failures continue to occur and continue to surprise us. At BHP, we have decided to take an approach to the tailings management that is similar to the approach to safety. We are looking at ways to eliminate, substitute, separate or engineer around the hazard (tailings dam failure). As such, our ultimate long term goal would be to eliminate the need for new tailings facilities. Unfortunately, we have not developed yet technologies for extracting many of the common metals and minerals without producing tailings. Our shorter term goal is to substitute the current conventional slurry tailings facilities with less risky dryer facilities. We are working with vendors and research organizations to develop technologies that can be efficiently applied on a large scale. At the same time, we are committed to using the best available engineering to reduce the risks associated with our existing and new conventional tailings facilities. The best engineering can be achieved by people with the appropriate education, experience, attention to detail, discipline and authority. We have implemented a system of governance to make sure, we have the best engineering applied to all our facilities, considering the specific conditions at each site.This paper presents the current tailings governance process at BHP, and the initiatives that were undertook towards achieving a zero failure goal. CITATION:Alexieva, T, 2018. Tailings governance, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 2–7 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

The seam gas content at Westcliff Colliery is 12-15m3/tonne of coal.Composition ranges from 99% CH4 to 52% C02 in one area. Desorption rates are proportional to gas contents and CH4 is preferentially desorbed. A crushed zone of reduced permeability advances with the face - at Westcliff ribside crushed zones are 2.5 to 6.5m wide. Poor strata control widens crushed zones. 12 months of pre-drainage allowed 2 heading development and longer pillars to be used in a virgin area instead of 3 or more headings without drainage. Machined coal may lose as much as 1.6m3/tonne being conveyed out of Westcliff Colliery. Experience differs from mine to mine. Permeation is affected by time, strata movements, changing water content, and changing stress. Permeabilities vary from lOmd for Pittsburgh Seam to less than 1 and for the Bulli Seam. All these data and differences await further investigation.

Jan 1, 1982

This paper describes the application of a three-dimensional finite element modelling tool to help assess the stability of a highwall at a Central Queensland mine following the weakening of its base due to highwall mining. With traditional stability assessment techniques, likely failure modes are identified on the basis of previous experience and structural, sedimentological and geomechanical data and a mechanistic analysis of these individual modes is performed. The value of the full three-dimensional model over these traditional techniques is that it provides a coherent approach to assessing highwall stability without the necessity of initially deciding upon the dominant failure mechanism and gives a useful adjunct to the traditional tools. The three-dimensional model assumes the rock mass is made of elasto-plastic blocks, incorporating possible planes of weakness, separated by near horizontal joints. The model includes the relaxation of stresses due to the excavation of the highwall and incorporates estimates of blast damage near the highwall surface

Jan 1, 1995