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By Zhang S

A probabilistic approach is proposed for updating open pit slope sta- bility based on successful performance. The suggested approach is developed within the framework of Bayesian probability theory. In seeking solutions to geomechanics problems consideration must be given to inher- ent variability of shear strength parameters and to the errors in the esti- mation of these parameters. The latter can be significant and may lead to consistent overestimation or underestimation of the values derived from site investigation and testing. Conventional deterministic methods of slope stability analysis do not allow systematic modelling of uncertainties in applied loads or in shear strength parameters. Within a probabilistic framework indicators of stability may be calculated, e.g., the reliability index and the probability of failure. Based on observation of slope per- formance at any given stage of a project, the mean or the standard devi- ation (or both) of a shear strength parameter may be updated. Consequently the indicators of stability can also be updated. The appli- cation of such an approach is demonstrated by an illustrative example.

Jan 1, 1989

By Donald C. Moore

Asamera Minerals Cannan Mine has been producing a 170 g gold/tonne (5 oz gold/ton) siliciaus flotation concentrate since July 1985. Flotation concentrate is shipped to a smelter for gold recovery. Numerous processes have been investigated to economically produce bullion on site. This paper describes the laboratory and pilot plant test results of a bacterial assisted oxidation of the refractory minerals. Economic comparisons with autoclaving and roasting processes are included.

Jan 1, 1989

By C. J. Veal, C. I. House, S. R. Bellamy

INTRODUCTION Coal gold agglomeration (CGA) is a new concept in gold processing. It involves the recovery of oleophilic (oil-loving) gold grains by causing them to adhere selectively to the surfaces of coal oil agglomerates. Under optimum conditions very high recoveries of gold. can be achieved. The agglomerates are recycled to build up gold loading to typically 1000 - 5000 g/tonne. Bullion can be produced by burning the loaded agglomerates with subsequent recovery of gold from the highly loaded ash either by dissolution/electrowinning or smelting. A wide-ranging programme of laboratory testwork has been performed to investigate the response of different ore types to the process. This has shown CGA to be most applicable to ores in which the gold is liberated or easily liberatable, relatively coarse (ca 500 µm) and fine (<5 µm) gold grains being recoverable with equal ease. The best opportunities for CGA seem to be: • placers containing fine gold not recoverable by gravity concentration • low grade gravity concentrates to avoid multiple magnetic/gravity separation stages and amalgamation • free milling ores where the gold can be liberated at a reasonable ore particle size eg >d80 50 µm • tailings past or present from gravity concentration plants. CGA testwork ranging in scale from laboratory to pilot plant on tailings produced by gravity concentration in the 19th century Australian gold rush has already been reported (Bonney, C F, 1988; House, C I, Townsend, I C and Veal, C J, 1988). An economic appraisal for a Canadian free milling gold ore has also been published (Buckley, S A, House, C I and Townsend, I G, 1989). This paper describes results of a detailed laboratory programme to assess CGA as a means of recovering gold from a beach sand deposit in New Zealand. The area from which the samples were taken consists of quarternary interglacial marine, lagoonal, fluvial and eolian deposits. The heavy minerals present are predominantly ilmenite and garnet and small concentrations of gold. In certain locations the sands and gravels are consolidated by a limonitic cement. In the 19th Century some parts of the deposit were mined and the ore processed using stamp milling and gravity concentration. Gold recoveries were low, probably below 50%, due primarily to the fine size of the gold grains, the flaky nature of the gold and also imperfect liberation by the stamp mills. Our laboratory testwork was divided into three parts: i) Preliminary studies on an initial sample to assess the feasibility of treating the ore by CGA ii) Extended studies on further samples from various locations in the deposit to confirm predictions from (i) iii) Conventional gold recovery techniques. EXPERIMENTAL PROCEDURES All CGA tests were performed by agitating a slurry of ore in water in a 0.6 dm3 pyrex beaker fitted with four vertical baffles. When required, potassium amyl xanthate collector was added and the slurry conditioned for 5 min. Coal (ex BP Coal Australia&apos;s Tahmoor Colliery) previously ground to a d80 50 µm was added followed by a commercial grade of gas oil (density 840 kg/m3). The agglomeration time was 30 min. The agglomerates were separated from the tailings by screening, both were then dried and analysed for gold by fire assay. This test procedure provides a reasonably accurate estimate of gold recoveries that might be expected from our 1 tph pilot plant. Ore samples were ground either dry in an agate ring disc mill or wet in a steel batch tumbling

Jan 1, 1989

By G. Barbery, P. Dauphin

"In order to obtain reproducible and reproducible results in batch flotation, researchers have tried various approaches, from normalized testing, to modifying existing cells, and even designing new machines. The paper reviews the basic concepts that must be fulfilled in a laboratory flotation machine, and present the FLOTOMATEC design, which results from five years of testing and development. In addition to providing accurate measurements of air flowrate, power consumption, agitation speed, the cell eliminates most operator induced errors. Results of experiments comparing FLOTOMATEC to a conventional cell, as well as reproducibility tests are given. Introduction The use of batch flotation machines in mineral processing research and development is very common. These machines have been used for many years without almost any change in their design, instrumentation or automation. Various authors since Raffinot (1960) have criticized the available designs, especially with respect to the large errors that are introduced by the manual mode of operation. Barbery et al. (1986) have presented a review of the problems involved in laboratory testing in flotation research.Batch laboratory machines should have the following characteristics:"

Jan 1, 1989

By W. Wallace, T. Ong, M. Gautam, M. Keane, S. Xing, J. Harrison

"Diesel exhaust soots were assayed in the Ames Salmonella typhimurium histidine reversion assay system using TA 98, the soots being applied as the following preparations: dispersion in dipaimitoyl glycerophosphoryl choline (DPL), dispersion in dipalmitoyl phosphatidylethanolamine (DPP!), and dispersion in dipalmitoyl phosphatidic acid (DPPA) in physiological saline, and in physiological saline without added surfactant. The extracts of soots by dichloromethane / dimethylsulfoxide (DCM/BHSO) were also assayed. Studies were performed both with and without :IQ microsomal activation of the soot preparations. The DPP! and DPPA surfactants were chosen as phospholiridz with two palmitic acid moieties esterified to a glycerol as is the case with DPL, but with hydrophilic groups having different electrophilic characters. The soots, without S9 activation, showed mutegenic activity when extracted in the conventional procedure with DCM/DMSO. The mutagenic activity of soots dispersed in DPL was quantitatively comparable to, and in some cases greater than, the activity expressed by an equal mass of soot extracted by DCM/DMSO. Soots in other surfactantpreparations, DPP! and DPPA, also expressed positive mutagenic activity. Praincubation with S9 microsomal enzyme fraction reduced the activity of solvent extracted soots, and greatly diminished the activity of DPL dispersed soots. Initial sister chromatid exchange (SCE) assays using the Chinese hamster V79 cell line indicated DPL dispersed soot also can cause SCR in mammalian cells. Results thus far suggest that surfactant suspended or ""solubilized"" respirable soot particles could provide a mechanism for transport and expression of mutagens in the lung."

Jan 1, 1989

By E. Alaphia Wright

An accepted approach to open pit mining sequence planning is one of computer aided planning where: the planner works out his mining sequences by trial and error using interactive graphics; This approach gives results that could in- variably be improved given more time for the planning exercise. Increased emphasis on interactive planning reveals a need for simple formalized procedures for improving mining sequence planning practices. This paper discusses a case study in which Dynamic Programming (DP) is used in mining sequence planning. It is shown that DP can be applied to identify various intermediate, pit boundaries. These are then arranged in descending order of economic values and their material contents analysed with respect to tonnages, grades, production requirements, and equipment capacities. Those increments which best satisfy defined conditions are selected and the others discarded. The mining sequence is thus built up as a chain of best- economic valued mining increments satisfying given production requirements and constraints.

Jan 1, 1989

The molecular form of aliphatic amines precipitates in alkaline solutions when the amine solubility limit is exceeded and forms a typical colloidal system. The zones of mines precipitation and micellization are defined and it is shown that the appearance of a colloidal system in a certain pH range is a unique feature that makes weak electrolyte type surfactants differ from strong electrolytes. The formation of iono-molecular complexes reported in the literature is shown to be a pre-precipitation phenomenon. The zeta potential - pH curves for minerals and bubbles in the presence of amines in the pH range where the amine forms a colloidal precipitate are entirely determined by the precipitate. The pH dependence of the flotation of certain minerals using amines is discussed in the light of these findings.

Jan 1, 1989

By M. B. Wechsler

An analysis is developed for determining the maximum loading, as well as the potential uplift of the piles on bridge pier foundations. There are considered piers supported on two through seven rows of piles, and related to two simply supported collinear superstructures of any structural material. The study leads to different types of influence lines for various load combinations. For load combinations containing vertical loads only, the related influence lines are similar to those as for the bending moments of a virtual span covering the two actual spans, as well as the gap between the two superstructures; and, in this case, the heavier loads should be positioned in the vicinity of the pier. While, in the case when vertical loads are acting together with hori­zontal forces, the related influence lines will indicate where the heavier live loads should be positioned. And they will also indicate on which portions of the spans the live load should be avoided.

Jan 1, 1989

By Richard P. Killmeyer

In 1985 the Pittsburgh Energy Technology Center (PETC) of the U.S. Department of Energy (DOE) conducted a study to evaluate the emerging selective agglomeration processes (Killmeyer, 1985). This paper covers a recent similar study evaluating an associated technology, the emerging advanced froth flotation processes. This study has goals similar to those of the 1985 study: to evaluate the emerging froth flotation technologies collectively and determine how far they have progressed in their ability to clean ultrafine coal, and to assess the differences among the participants. The major concern again in this study was not the level of development, nor the economics of each individual process but only the current technical performance.

Jan 1, 1989

By Eric R. Bauer

The U.S. Bureau of Mines, in cooperation with a southwestern Pennsylvania coal mining company, BethEnergy Inc., Mine No. 60, Eighty-Four, PA, recently assessed the feasibility of using pre driven recovery rooms (open entry recovery) when longwall mining to increase the productivity of the coal extraction process. Two recovery entries, one 200 ft long and another 600 ft long, were supplementally supported with bolts, channels, and wire mesh, and either fly ash-cement piers or fiber cribs, then mined into by the longwall face. The recovery entries showed little deterioration as the supports provided adequate resistance to the front abutment loading. Compared with conventional recovery methods, the fullface recovery room allowed for panel extraction to be completed nearly 17 days faster and to reduce face equipment move time by 1-1/2 days. The potential productivity increase accompanying recovery rooms is greater than the cost of supporting a fullface recovery room. The fullface recovery room provided over 18 additional production days and the opportunity to mine nearly 68,400 st of coal per year per panel mined.

Jan 1, 1989

By J. A. Yeats

This paper describes the loading to 25MN of a 1.2m diameter bored cast-in-situ test pile founded in the Thanet Sand which was base grouted. The pile was sleeved over the major portion of its length to test primarily the base response of the pile. The results are presented and compared with similar pile load tests in Thanet Sand.

Jan 1, 1989

By E. Fahrenkrog, D. Sbartaro, E. N. Cifuentes

An intelligent supervisor using expert system tools and applied to a crushing plant has been developed with a structure based on a model of a human operator. It consists of a knowledge base containing a qualitative model of the process and a rules base with the heuristic logic used by an operator when supervising a plant. The simulation results obtained show the potential of this type of system to supervise the automatic operation of a plant. There has been very significant development in artificial intelligence over the last two decades. Within this development, two approaches can be distinguished, (Winston, 1984). The "model approach," in which the main objective is to understand and model the be¬havior of living systems. The second approach is the "engineering approach." Here, systems capable of performing tasks usually requiring human intelligence are created. As part of this latter approach, knowledge engineering and its main achievement, expert systems, have been developed. Expert systems arose from the need to incorporate the abilities of a human expert in solving realistic problems in which the conventional approach has great difficulties. The first successful applications of expert systems were in medical diagnosis, geophysics, and fault detection. However, since 1971, when Fu (1971; defined intelligent control as the inter action of artificial intelligence and automatic control, some significant developments in the use of artificial intelligence tools for process control have been achieved (Astrom, 1986; Pinto 1988; Fahrenkrog, 1988; and Porter 1987). The modern control theory has made important advances. And, although successful in some applications, it has failed to cope with the practicalities of many industrial processes. As a result, the automatic operation of a plant has been confined to a small region around a normal operating point and to periods without any great disturbance. One of the main reasons for this is the lack of accurate and structured knowledge of the processes involved. Despite this, operators applying their knowledge, experience, and a little intuition, often obtain good results controlling the plant in such situations. Considering the above, the next obvious step is to include similar reasoning capacities in a computational system. The development of such an expert supervisory system prototype applied to a mineral crushing plant is presented. Problem description The problem is to conceive a control system with the ability to handle quali-

Jan 1, 1989

By K. Rainer Massarsch

The effects of soil displacement caused by pile driving on adjacent piles and structures are discussed. A method is proposed to estimate the point of force equilibrium which makes it possible to calculate up-lift forces and pile head movements. For the case of pre-coring a method is proposed to estimate the stability of the bore hole, based on cavity expansion theory. Model tests were performed to establish the displacement pattern of the soil during the driving of a pile group. It can be concluded that at the ground surface, already installed piles have little influence on the lateral displacements, but reduce significantly the soil heave. During the driving of a pile group, the soil is displaced according to a complicated pattern, which is strongly influenced by the order in which the piles are driven. In clay the displaced soil volume corresponds to the total volume of driven piles.

Jan 1, 1989

By V. N. Kelly

The ability to link geological sections on a graphics screen to form three dimensional geology representation was implemented at Kidd Creek in 1987. This technique affords an opportunity to optimize metal estimation in ore at the Kidd Creek copper, zinc and silver mine, by applying enhanced interpretation methods. On a series of geological sections varieties of ore are outlined. These are linked from section to section to form polyhedra which closely simulate the three dimensional shapes of the different ore types referred to as mintypes. The orebodies are divided into zones, referred to as domains, that approximate the function of variograrns, for which&apos; preferential continuity of mineralization has been estimated for distances in the width, strike and dip directions. These distances define ellipsoidal volumes of influence. The domains are also linked into polyhedra. Both types, coded by ore variety and zone, are mapped into the block model. Tonnage and metal values are calculated for ten-foot cubical cells of the block model by any of several estimation methods under domain control. In estimating the metal grades for a cell the predetermined search ellipse is applied to select only those drill hole assays of the same mintype as the cell designation. Once grade estimations have been determined for the cubical cells comprising the model, a wide range of stored information can be viewed. For example, in plan at any row elevation or on vertical section at any azimuth, as either printed values for the cells or as contoured data. This flexibility is of particular value in checking and refining the geological interpretation to better conform to ore types and grades actually mined. Combined with three dimensional geological modelling, and correctly chosen domains, the use of mintypes implants essential geological control into the system and prevents assays for one ore type from affecting grade estimation in adjacent ore types. The three dimensional geological modelling and block model segments provide information which is effectively applied to the stope design, production, planning and control parts of the system.

Jan 1, 1989

By Y. Luo

A PC based computer model has been developed by the authors for predicting the surface subsidence due to underground coal mining. Its reliability, comprehensiveness and user friendliness demonstrate that it is a good tool for the mine operators, government agencies and scientific researchers alike.

Jan 1, 1989

Enhance hydraulic fragmentation technology by developing alternative grout sealing methods. Traditional grout scaling methods rely on chemical adhesion and require large contact areas to restrict high-pressure fluids. Fluid injection into rock requires economical and effective seals. With economical and effective seals, rock is easily fractured in tension by high-pressure fluid injection (fig. 1). Approach An innovative grouting technique was developed and tested by the Bureau. Slowly hydrating expanding chemicals are placed within a borehole and around a section of high-pressure tubing. Testing was conducted using 9/16-inch-OD smooth-walled injection tubes in 1.5-inch-ID holes. Seal lengths weir less than 10 inches and curing times were less than 24 hours.

Jan 1, 1989

Australia is not capitalizing on the raw gems and precious minerals that it produces in abundance. In particular, there is an unrealised value for diamonds due to lack of processing after mining. Australia could enhance the value of its raw jewellery products by developing and integrated jewellery industry. For instance, initiation of a diamond industry would require training programmes to educate people in the requisite skills, such as diamond sorting, cleaving, sawing, bruting and polishing. Equally important would be the training of people in design jewellery, manufacturing, and appropriate diamond grading and sales techniques. Future technological advances in diamond processing will decide where the major diamond processing centres of the world will be. Australia, for a relatively small investment, could develop a highly productive diamond processing capacity using the new technology available. Australia&apos;s geographical position, and advanced banking and communication facilities provide the potential for this country to become a major trading centre for diamonds. KEYWORDS: Argyle Diamond Mine, Diamonds, Diamond Production, Diamond Sorting, Jewellery Industry

Jan 1, 1989

By David G. Borg

"Although researchers have realized varying degrees of success in numerics modeling, computer blast simulations and small scale in-situ testing, most will agree that the greatest uncertainty in total success stems from the uncontrollable field variables. Given the diverse nature of field conditiorencountered, no reliable and proven method of evaluating fragmentation quantitatively, and the lack of adequate field controls found in many operations, it is unlikely that a universal plug-in model will be developed for all blasting in the imediate future. This does not imply that all research devoted to modeling should cease, for it is precisely here where more research efforts are desperately needed."

Jan 1, 1989

By Cousens DR, Benhamou M, French DH

Techniques appropriate to petrographic image analysis are being developed using digitized backscatter electron images of well characterized mineral assemblages obtained from a Cameca scanning electron microprobe. Emphasis is on developing descriptors for size, shape and association of mineral grains as these all convey important information concerning the nature of rocks and the processes that have operated upon them. Processes, for example, that could indicate the proximity of mineralization. For convenience, the work is being carried out on the PDP11/73 host computer of the electron micropt be, although it is recongnized that such a multi-user environment is not appropriate for practical image analysis. The eventual aim is to develop a low-cost microcomputer-based package for quantitative description of mineral textures and rock fabrics as an objective aid to the petrographic analysis of ores and host rocks.

Jan 1, 1989

By John E. Pahlman

The U.S. Bureau of Mines has continued its investigation of chemical additive drilling fluids that produce a zero surface charge (ZSC) on a rock to better define the boundary conditions of the phenomenon. Laboratory drilling tests were performed on Minnesota taconite, Tennessee marble, and Sioux Quartzite using diamond-impregnated coring bits or tungsten carbide spade bits. Drilling fluids were made from chemical additives such as inorganic salts, cationic surfactants, cationic polymers, acids, or nonionic polymers in either distilled, deionized water (DDIW), mine pond water, mine well water, or tap water. These additives were tested below, at, and above their respective ZSC concentrations. Penetration and bit life improvements obtained with ZSC concentration solutions ranged from 88 and 56 pct, respectively, to over 650 pct and over 400 pct, respectively, for the additives tested. Polyethylene oxide (PEO) was found to be the best additive for ZSC-controlled drilling because a continuous range of PEO solution concentrations produced the enhanced ZSC-controlled drilling performance.

Jan 1, 1989