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By L Mikhael Gurieff, D Baas

The Phu Kham Copper-Gold Operation (Phu Kham Operation) is located in the Lao People's Democratic Republic and is owned and operated by the Lao-registered company, Phu Bia Mining Limited (PBM). Australian-headquartered copper and gold producer, PanAust Limited holds a 90 per cent interest in PBM; the Government of Laos owns the remaining 10 per cent. The Phu Kham Operation was commissioned in 2008 with an initial concentrator nameplate throughput of 12 million tonnes per annum (Mt/a). Subsequent improvement projects, including the Phu Kham Upgrade Project (PKU), completed in 2012, and the Phu Kham Increased Recovery Project (IRP), completed in 2013, increased the design throughput to 18 Mt/yr. In 2016, the actual mill throughput exceeded 19 Mt/a, this throughput is budgeted to be maintained until the end of 2020.The concentrator flotation circuit upgrade, completed during the IRP, called for a non-selective bulk sulphide concentrate to be generated from the rougher circuit. This in turn caused the mechanical flotation cells in the cleaner circuit, particularly those in the second cleaner bank, to become volumetrically overload. The overload reduced the cleaner circuit performance to approximately 92 per cent copper recovery at a 23 per cent copper concentrate grade, below the expected 95 per cent recovery. This bottleneck restricted copper units entering the plant to approximately 14.5 tonnes per hour (t/h) due to uncontrolled recirculating load build-up in the mechanical cleaning circuit.Maintaining the operating methodologies would have led to a copper production shortfall beyond 2016, to address this shortfall the Phu Kham Operation looked to optimise the Jameson Cell and mechanical cleaner circuit performance. The work included fundamental application of flotation practice and modelling, mineralogical analysis, bubble size analysis, plant surveys and test work. The results were used to develop and implement an innovative automated control system strategy incorporating flotation theory and operating strategies. The automation has the ability to quickly adapt to disturbances in the circuit and maintain optimised performance with little or no intervention by flotation operators.Upon completion, cleaner recovery increased to 95 per cent at a final concentrate grade of 23 per cent copper, and copper units entering the plant increased to 17.5 t/h.CITATION:Baas, D and Mikhael Gurieff, L, 2018. Developing flotation circuit control and automation for the Phu Kham Copper-Gold Operation concentrator, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 37–58 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By L Thorburn

In 2009, the Queensland Government developed a series of amendments to environmental authorities (EAs) for mines throughout the Fitzroy Basin in response to studies that assessed the cumulative impacts of mine water discharges in the basin. One of the key amendments was the requirement for all mines in the Fitzroy Basin to develop and implement a receiving environment monitoring program (REMP). The intent of the REMPs was to provide baseline information on the condition of the receiving environments of the mines and any impacts resulting from release of mine-affected water. Since this time, the requirement to complete a REMP has been incorporated into new or revised EAs for mines (including metalliferous mines) in other regions, as well as for other industries that discharge to natural watercourses (such as coal seam gas). This paper discusses the approaches that can be used to incorporate biological monitoring and direct toxicity assessments into REMPs. It highlights the importance of collecting biological data using sound experimental design principles to investigate whether releases resulted in environmental harm; and the use of monitoring data, coupled with direct toxicity assessments, for setting more realistic, site-specific trigger values and release limits (compared to the default guidelines such as Australian and New Zealand Environment and Conservation Council (ANZECC), which may not be appropriate to the region). Implementation of a robust REMP can maximise outcomes for both the proponents and the environment.CITATION:Thorburn, L, 2013. Receiving environment monitoring programs - making the most out of biological indicators and direct toxicity assessments for monitoring of aquatic ecosystems, in Proceedings Water in Mining 2013 , pp 143-148 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 26, 2013

By P Klaric

Drive stability is critical in block/panel cave mining. The production levels of these mines are required to remain operational for the entire life-of-mine which can be in excess of 30 years. It is therefore necessary to produce high-quality drives to ensure sustainable mine productivity. In order to improve the quality of drives and pillars, this gold mine instigated a project to optimise their development blasting. The initial aim was to reduce the level of overbreak in development mining, which was averaging approximately 18 per cent. The benefits of controlling overbreak not only included an increase in the integrity of the drives but also a decrease in load and haul and ground support costs. Through focusing on the optimal blasting of the perimeter holes, overbreak was reduced to 4.5 per cent. The project’s focus then moved to drill and charge designs for development faces. In optimising these designs, it was anticipated that improvements in the development mining cycle would be achievable.CITATION:Klaric, P, 2015. Improving drive stability through efficient development blasting design and practices, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 327–332 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

The Morning Star diorite dyke has been subjected to two periods of mineralization. The earlier, genetically related to the dyke magma, gave rise to a weak chalcopyrite-pyrrhotite-pentlandite-gold mineralization in a narrow zone, up to 25 cm. wide, which parallelsthe nearby western (hanging) wall of the dyke. Subsequently a set of conjugate shears formed in the dyke as a result of tectonic movements. Gold-quartz veins formed in these shears giving rise to the classical "ladder veins" of the Morning Star mine. On either side of the veins ("floors") the diorite has been bleached for up to 3 ft. This involved introduction of much CO. and some K"O, and S with abstraction of SiO. and FeO, giving rise to carbonates, sericite, zoisite and pyrite. The veins consist of quartz with minor amounts of albite and carbonate, together with pyrite, arsenopyrite, pyrrhotite, chalcopyrite, sphalerite, tetrahedrite, galena, bournonite, boulangerite and gold. Spectrographic analyses of gold show that the suite of trace elements is consistent throughout the mine.INTRODUCTIONThe gold-quartz veins of the Morning Star Gold Mine, at Wood's Point, Victoria, are a classic example of the "ladder vein" type of deposit. The structure of this series of repeating quartz veins or "floors", some barren and some productive, occurring in a set of conjugate shears which transect a "dyke bulge" of diorite (Fig. 1), has been described on numerous occasions as mining has progressed and figures in the textbooks (Whitelaw, 1905; 1916; Junner, 1920; Lindgren, 1933; McKinstry, 1935; 1942; 1949; Kenny, 1949; Hills, 1952; Clappison, 1953) ; but there has been no study of the mineralization apart from that in Junner's (1920) general study of the Walhalla-Wood's Point Goldfield, made at a time when mining had not developed below the 400 ft. level,. and the mine was dormant.

Jan 1, 1958

By Gillies A. D S

The active history of foreign investment in the mining industry has resulted in Australia emerging as a major world producer of a range of mineral commodities. The current contribution to the national economy represented by mineral production and export revenues would not have occurred without both capital and expertise provided by foreign investors in the past. The initial foreign investment has led to the formation of Australian majority owned and controlled multi-national mining groups such as BHP Limited, CRA Limited and MIM Holdings Limited. These Australian companies, and others, are playing a significant part as foreign investors in the mining industries of Papua New Guinea (PNG) and Indonesia. The study examines issues of importance in foreign investment in each of the countries. It concludes that in Indonesia, the nationalisation of the Dutch mining industry in 1957 did much to deter foreign investment. The remarkable degree of policy stability brought about by the Contract of Works system since 1967 has gone a long way to restoring that confidence. The level of investment in the Indonesian mining sector is steadily increasing. Its attraction to Australian investors is a combination of policy stability, favourable fiscal terms, geological prospectivity for a range of commodities and proximity to Asian markets to the north. PNG has a stable policy regime which until recently has been free from political interference at the administrative level. As such, investors were developing confidence in the system and investment was progressively increasing as evidenced by growing exploration expenditures up to 1988. The 1989 Bougainville revolution caused a re-assessment of PNG's investment and country risk. The recent Mt Kare incident has further raised concerns over the government's ability to guarantee internal security. Foreign investors are faced with weighing concerns with the risks of operation in PNG against the undoubted geological prospectivity of the country. The fiscal regimes of Australia, Indonesia and PNG were compared by means of a simulated open pit gold mine in each country. The effect of taxation is examined by reference to the relative change in project internal rates of return (IRR). The comparison of the relative differences between pre-tax and post-tax IRRs provides a measure of the relative attractiveness of each fiscal regime.

Jan 1, 1994

By J Addai-Mensah, W Skinner, C Kelsey, J R. Kelly, E Baawuah

Comminution continues to be the most capital-intensive unit operation in mineral processing. The fundamental purpose of comminution is to liberate the valuable minerals so that they can be economically concentrated into saleable products. Declining ore quality characterised by lower grade and increased complexity requires significant energy consumption for comminution. Low-grade magnetite ores are typically fine-grained and require fine to ultra-fine grinding (P80 ~ 30 - 40 µm) to enhance its liberation from the typically siliceous gangue matrix. Historically, this has been achieved using multi-stage crushing and grinding technologies, which require high energy consumption with low energy efficiency. This motivated innovations in energy efficient technologies for comminution. Such technology has been developed in the IMPTEC super-fine crusher. It is an innovative, dry (with the potential to be operated wet), media-free, energy efficient crusher that can to reduce 10 mm feed particles to 19 – 30 µm with very low recycle loads. In this study, the mineralogical and physicochemical characteristics of crushed magnetite ore using the IMPTEC super-fine crusher have been investigated in comparison with those of rod milling. The super-fine crusher generated higher liberated magnetite minerals in the – 300 + 212 µm and < 45 µm size fractions compared to rod mill. Both comminution devices generated large low-grade hematite and goethite middlings. However, the rod mill produced higher locked/unliberated hematite and goethite compared to that of the super-fine crusher. Quartz mineral had the highest liberation irrespective of the comminution device used. The super-fine crusher generated higher entrapment of other minerals within the silica matrix compared to the rod mill. The breakage mechanism of the super-fine crusher which is predominantly through high compression with shear, generated improved mineral liberation in the coarse size fractions compared to the predominant abrasion and attrition breakage mechanisms of rod milling. The higher mineral liberation generated by the rod mill is potentially due to the prolonged batch milling of the ore compared to the single-pass open circuit of the super-fine crusher.CITATION:Baawuah, E, Kelsey, C, Kelly, J R, Addai-Mensah, J and Skinner, W, 2018. Mineral liberation studies of IMPTEC super-fine crusher – 130 crushed product, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 313–326 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By J Pan

This case study assesses the application of Mine-to-Mill optimisation combined with Whittle Consulting’s Prober<sup>®</sup> economic optimisation for the purpose of economic value uplift in open cut base and precious metal operations. The study extends the application of these optimisation methods to incorporate the recent practice of Ultra High Intensity Blasting (UHIB) developed by Orica Mining Services. The case study deposit known as “Marvin” is a copper/gold porphyry resource that is commonly used in optimisation software training and industry case studies. It has many similarities to Newcrest’s Cadia Hill open pit mine in NSW. Prior desktop research and industrial trials employed static assessments of Mine-to-Mill effects. No prior work other than a Whittle Consulting client study, has sought to assess the impact of variable fragmentation on enterprise economic value. This study examines the use of variable blasting intensity as a driver of economic value maximisation over the mine’s life.CITATION: Howe, S and Pan, J, 2018. Application of enterprise optimisation considering ultra high intensity blasting, in Proceedings Complex Orebodies Conference 2018, pp 14–20 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 21, 2018

By A G. L Pratt

The record for autonomous haulage systems in underground mining over the past 15 years is patchy, marked by many trials and attempts, with few examples of sustained operation until relatively recently. The drivers for the introduction of this technology are variously listed as the occupational health and safety of people working in underground mines, reductions in direct operating costs and increases in productivity.This paper reviews the trends for operation of semi-autonomous and autonomous haulage achieved by underground mines and the defining features of the technology currently available. The inclusion of autonomous haulage as part of mining studies and the fundamental conditions for its successful application is discussed in the paper. The components required for an autonomous underground haulage system are outlined and the key aspects that need to support its effective implementation are examined together with their associated opportunities and risks. Special note is made of the critical role people, including executive leadership, have in ensuring the successful introduction of this technology.The paper draws on published case study material, equipment supplier information and research findings. The aim is to offer a high-level insight into what is required for the application of autonomous haulage technology and its successful implementation in underground mines.CITATION:Pratt, A G L, 2016. Autonomous haulage systems in underground mining – what is required for success? In Proceedings International Mine Management Conferenc, pp 35-52 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jun 22, 2016

By J Johansson, J Lööw

Attractive mining workplaces are good, safe and healthy environments. They are also workplaces that the workforce of the future wants to work in. As skilled miners and engineers are already scarce, this is important both for today and for the future. However, the future of mining will also be subject to increased international competition. In attempting to become more competitive, many mining companies turn to rationalisation, looking to both rationalise their production and organisation as well as optimise their processes. Work organisation is important in both rationalisation and providing attractive mining work. As a result, this paper investigates a ‘lean production’ (LP) philosophy for the organisation of future mines. The aim of the paper is to investigate to what extent LP can be used to organise for attractive mining. It first defines what attractive mining work is and to what degree it can be influenced by work organisation. A short insight into the LP concept will be given as well as a review of how it is discussed and utilised in mining today. In conclusion, a summary of LP’s potential to realise future attractive mining is given.CITATION:Lööw, J and Johansson, J, 2015. Work organisation for attractive mining – lean mining and the working environment, in Proceedings Third International Future Mining Conference, pp 197–204 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 4, 2015

Carbon sequestration in planted forests provides an immediately available, low cost option to address the greenhouse impacts of coal mining and coal utilisation in a carbon constrained world. In addition, planted forests also offer the opportunity to address other environmental issues, particularly salinity and loss of biodiversity. Given salinity is characteristically associated with agriculture in the 500 to 700 mm rainfall belt, then where such forests can also produce commercial timber products, they offer the additional opportunity to establish new, diversified rural employment in both timber growing and processing. In the majority of Australian catchments affected by salinity, where rainfall is generally less than the 700 mm limit to conventional forestry, and where groundwater reserves are often saline, the objective of achieving economically viable forestry production presents a significant challenge. In 1996, Saltgrow commenced a collaborative breeding program to combine the salt and stress tolerance of E camaldulensis, with the growth rate, stem form and wood properties of the commercial species, E grandis and E globules. This program aimed to produce trees with the potential for commercial rehabilitation of saline landscapes. Results covering a range of site conditions from SaltgrowÆs network of over 100 trials around Australia are presented. The opportunity for commercial plantations integrated with agriculture in low to medium rainfall areas to address salinity and sustainability will be discussed. In addition, the significant potential for partnerships between land-rich, cash-poor farmers, catchment management authorities seeking to invest in public good projects that enhance environmental sustainability, and major carbon producing industries with either mandated or voluntary requirements to curtail net emissions will also be discussed.

Jan 1, 2005

By C Muñoz, N Ortega, J Vergara, D Avilés

Mass blasts have been the subject of extensive studies because of their potential benefits in mining operations. However, it has not been possible to advance due to the paradigm that states that the blasts near the designed final wall or to critical structures have to be low tonnage. Another reason is the absence of specialised simulation programs to more precisely determine the influence of the energy released by blasting to the rock mass. There are some studies that demonstrate the possibility of massive blasting that maintain the design of the final slope (Farias and Santander, 2014). It should be noted that these studies develop the concept that the size of the blast should not increase the peak vibration in the rock mass.The study was carried out in partnership with Los Colorados Mining Company. Analysis, reconciliation and wall control for two types of blasts were performed:blasting production: approximately 850 000 t, with special wall control considerationsblasting of approximately 950 000 t over the entire width of the bench.Monitoring systems were used in the near field and far field using examination of holes in order to obtain information to assess the impact on the rock mass and then to compare these to conventional blasting combining production and contour blasting.The results show that for a large blasted volume, production and/or those generated from toe to crest on the bench did not produce more impact in the rock mass than the conventional blasting.The conclusions drawn from this study are:an improvement in the excavation rate of 7500 t/h that is higher than the maximum rates normally obtainedthe peak vibrations of the P wave generated by both blasts did not exceed the peak particle velocity criteria (Vergara and Muñoz, 2014)holes examination indicating no difference in their entire length, in pre- and post-blast reviewover US$2 000 000 savings generated in the year (estimated by the client) (Avilés, 2014).CITATION:Vergara, J, Muñoz, C, Ortega, N and Avilés, D, 2015. Benefits related to applications of a mass blast in open cut mining, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 625–632 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

The introduction of a new mining method to Australia is not without its risks and challenges. This paper discusses the processes of planning a new operation, with particular emphasis on block caving and its Northparkes adaptation. As well as applying advanced technologies, here also is the opportunity to develop the art and science of block caving for its application to a wider range of geotechnical conditions than previously Envisaged.

Jan 1, 1995

By R Cunningham, P Duniam

Late in 2005 it became apparent that cave propagation at the Northparkes Mine was not progressing as planned. By mid-2006 sufficient Reserves were identified to warrant an extensive drill and blast program to assist in cave propagation. This program began late in 2006 and concluded early 2007. A significant challenge faced was the drilling and blasting of holes between 75 - 240 m in length in the South Wedge in Lift 2 at Northparkes Mines E26 orebody. The project set new benchmarks in production drilling and charging in underground metalliferous mining. This paper discusses the drill and blast designs, the challenges and the operational issues encountered with this project. Also highlighted are ways in which these were overcome.

Jan 1, 2007

In the UK during the 1990s the energy companies had developed a policy of æDash for GasÆ, building large natural gas power stations to produce more than 30 per cent of the UKÆs electricity demand. The price of imported thermal coal was dropping and the electricity generators were putting pressure on the UK coal producers to produce coal at a reduced cost. Imported coal from Columbia, South Africa, America and Australasia had increased their market share in thermal coal sales to over 50 per cent of a 55 Mtpa market. The pressure on the UK coal industry to reduce costs and improve productivity levels from an ever decreasing resource was high. Companies were benchmarking their operations on the imported coal producers and had to realign their organisations, productivity levels and costs to world best practice, not just technically, but in world class organisational management techniques.

Jan 1, 2005

By P Voulgaris

The Osborne Mine commenced production from an open pit in December 1994 with the first ore being hauled from underground one year later. Currently all ore is hauled up a decline by trucks until the shaft system is commissioned in early-1998. The mine is hosted within a multiply deformed and complex sequence of metamorphic, igneous and metasomatic rocks of mid Proterozoic age that are concealed beneath 20-40 metres of Mesozoic sedimentary cover. Epigenetic and largely hypogene copper - gold mineralisation occurs in a close spatial relationship with quartz - magnetite ironstones and is an important example of a significant mineralisation style in the Mt Isa inlier. Life of mine concentrator production, to year end 1997, totals 3.2 Mt of ore at 3.40 per cent Cu and 1.13 g/t Au. Total metal produced was 97 000 tonnes of copper and 2900 Kg of gold (95 600 oz) from some 348 000 tonnes of dry concentrates averaging 28.01 per cent Cu and 6.99 g/t Au. At the start of 1998 OsborneÆs total measured and indicated resource was stated at 11.38 Mt at 3.24 per cent Cu and 1.21 g/t Au with an ore reserve of 11.42 Mt at 2.90 per cent Cu and 1.09 g/t Au. Exploration efforts in and around the mine have been increased since 1996 and have resulted in an early success, with a 28 per cent increase in ore reserves since mine start-up, and the establishment of a 1.5 Mt inferred resource open to depth. During 1997 the performance of the concentrator has exceeded expectations with throughput having been increased to 1.45 Mt per annum. The Mining Cycle at Osborne has proceeded from discovery through feasibility and is currently seen to be in the latter part of the development stage and/or the early part of an expansion stage. This paper will describe the role of geology and exploration within these stages and will highlight how a number of key interpretations and decisions based on geology have both favourably and unfavourably affected the project.

Jan 1, 1998

The Que River and Hellyer polymetallic massive sulphide ore bodies are located 3 kilometres apart in the Cambrian Mount Read volcanics of Western Tasmania. Both deposits are classic examples of the Kuroko volcanogenic style. Base and precious metal rich hydrothermal solutions rose through a deep fracture system and vented on the sea floor, causing sulphides to accumu- late in adjacent topographic lows. Together the preproduction geological resource is approximately 23 million tonnes at greater than 18% zinc plus lead, with economically significant silver and gold. Exploration by Aberfoyle in the Mount Read volcanics com- menced in 1970. Que River was discovered in 1973 following a comprehensive data review, a regional stream geochemical survey and a helicopter-borne electromagnetic survey. Production began in 1981, and the mine is currently producing 300,000 tonnes per year. The ore is sold to the Electrolytic Zinc Company of Aus- tralasia Ltd mill at Rosebery. Ten years of extensive geological mapping, soil geochemistry, and induced polarisation, combined with continual study of the Que River orebody and its host rocks, formed a strong frame- work for the discovery of the Hellyer deposit, which was found as a result of drilling .a subtle time domain electromagnetic anomaly in 1983. Hellyer is currently being mined at a rate of 250,000 tonnes per year, with the ore being concentrated at Aber- foyle's converted Cleveland tin mill. Treatment of 1 million tonnes per year will begin in early 1989 at a new mill located near the Hellyer site.

Jan 1, 1988

By R G. Moreby

The purpose of this paper is to provide the rationale for decision making when considering the use of three heading gate roads in Australian underground coal mines.There are currently 30 underground longwall mines in Australia with all but two employing two heading gate road longwall layouts. The volumetric capacity of these two heading ventilation circuits is evidently viable in typical block lengths and in low to moderate gas regimes. However, in gassier regimes, potential longwall production rates of 10 Mt/a, and or where block lengths are being extended to well beyond historical norms, a conventional two heading U circuit may not be adequate. Other than seam gas emission, block length and production dependent heat loads together sealed area management requirements also have to be considered.The two mines currently employing three heading gate roads have the opportunity to revert to two headings at any time but, based on operational experience to date, have not done so due to the consequential reduction in gas management capacity and lower production rates associated with gas delays and limitations on tailgate access.Although there are a number of alternative two heading longwall circuits available and employed worldwide, the custom and practice of promoting inert goaf atmospheres in most Australian coal mines to mitigate the risk of catastrophic gas explosions and spontaneous combustion often prevents the use of gas loaded bleeder systems. In this respect, Australian underground coal mines may be considered the safest in the world.The current situation is that three heading gate roads have been proven successful in Australian conditions, albeit at additional cost, where two heading ventilation circuits cannot manage net seam gas emission to the ventilation system at the production rates required. In this respect, a further important driver for decision making is the short to medium term value of CO2-e emission taxation in Australia.CITATION:Moreby, R G, 2013. The rationale for use of three heading gate roads in Australian underground coal mines, in Proceedings The Australian Mine Ventilation Conference , pp 13-26 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

The Kalgoorlie Golden Mile is proposed as an Archaean volcanogenic-type deposit, modified and redistributed along later-developed structures. Rich pyritctelluride and Green Leader gold mineralization is associated with the end phase of basic volcanism and, in a general sense, is confined to a broad interface zone between the products of marine basic volcanism and later acid volcanism. There is virtualIy no ore associated with the main body of acid volcanics.Green Leader is the local name of a type of ore that occurs at some igneous rock contacts in association with graphitic sediments and layered acidic tuffs. It is characteristicalIy green, of various shades, and commonly yields very high gold assays, the reasons for which are not apparent in hand specimen.Carbonates, carbonaceous shales, tuffites, rich gold ores, and acid and intermediate dykes, alI indicating a common heritage, are features common to the main ore hosts, viz. the Paringa Basalt (Calc Schist) and theGolden Mile Dolerite ("Quartz Dolerite Greenstone").Several probably related fracture systems have reconstituted most, but not all, of the original deposits into a large number of steep tabular lodes.Includes two sets of discussions and comments from later Proceedings volumes.

Jan 1, 1974

By J Y. C Lo

The construction of two drainage tunnels and the associated subvertical drain system at the Po Shan area in Hong Kong was completed in December 2009. This project is the first of its kind to utilise drainage tunnels and a network of subvertical drains to regulate the groundwater table to enhance the long-term stability of the hillside of Po Shan area.The groundwater levels, monitored by preinstalled piezometers, once exhibited dramatic drops during drilling of the subvertical drains; however, have recovered from natural replenishment after effectively plugging of the drains. The level of groundwater drawdown is in line with the design function of the subvertical drains. In order to understand the groundwater flow pattern in the Po Shan area during and after construction and to set out operation schemes for the subvertical drain system so as to control the groundwater table in the Po Shan area, a post-construction review has been carried out to examine the behaviour of the drainage system and its impact on the surrounding subsurface groundwater flow.This paper presents a review of the groundwater monitoring data during and after the construction of the drainage tunnel system covering a period of over 3.5 years. A simplified conceptual hydrological model is developed, which has been verified by the monitoring data, to capture the key elements with regard to groundwater variations in different stages of the construction. The performance of the tunnel and subvertical drain system as revealed from these field measurements is discussed.

Mar 8, 2011

By A Minchinton

With blasting, all far-field phenomena including, but not limited to, stress wave propagation, fracture, vibration and muck pile formation are intrinsically and irrevocably dependent upon near-field phenomena or mechanisms that we describe using physics-based mathematics typically transcribed into computer codes. The energetics involved in such near- to far-field transitions are not fundamentally relevant as they are simply progenitors of these processes.The notion of explosive energy as a descriptor for explosive or blasting performance is a case in point. These energies, which are generally used in blasting tables, are almost exclusively based on ideal detonation theory alone and do not include the influence of the rock, charge diameter, blasthole length and the late-time dynamic expansion that can be predicted using codes based on non-ideal detonation theory.With decoupled charges in presplits for example, the pressure drop between the charge and the blasthole wall can be simply described to first order using the energy relationship associated with adiabatic expansion. However, a more realistic mechanistic solution involves interacting fluids and turbulence leading to dynamic processes such as the channel effect.CITATION:Minchinton, A, 2015. On the influence of fundamental detonics on blasting practice, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 41–54 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015