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By R. Bellotti

The theory of cavity expansion in an infinite frictional soil mass whose strength is represented by a curved Mohr-Coulomb failure envelope has been used to predict with some confidence the cone resistance of a clean dry sand. Experimental data were obtained from cone penetration and pressuremeter tests on two sands, conducted in a large calibration chamber (CC) under carefully controlled placement and boundary conditions. A plane strain bearing capacity theory was developed, and to convert the results to axi-symmetric conditions, an empirical "shape factor" was used. In the paper, the theoretical background, experimental data, calculation procedure, and the results of the analysis are presented. In general, a reasonable validation of the cavity expansion approach to the bearing capacity of deep foundations has been obtained.

Jan 1, 1987

By Ramin Motamed, Joseph A. W. Toth

Evaluation of the capacity of large-diameter drilled shafts using current load test methods present challenges when considering the magnitude of loads required to fully mobilize their capacities. Often, these full scale tests do not fully mobilize the capacity through side resistance. Therefore, the need for innovative solutions to extrapolate side resistance and interpret nominal capacity are of key interest. In this study, we evaluate three methodologies for extrapolating unit side resistance based on bi-directional load test data. Fellenius (2001) presented these methods for interpretation of pile capacity using static load tests. Our interpretations are based on the evaluation of 116 load tests. Unit side resistance was calculated and reviewed for each load test and categorized using three criteria of mobilization; (A) full, (B) partial and (C) linear. This study specifically focuses on load tests that showed fully mobilized unit side resistance behavior (Criteria A). The three methodologies were applied assuming Criteria (A) load tests were mobilized to 50% of their measured values. Subsequent comparisons of each extrapolation were then compared against the full measured values for each test and generally showed good agreement. INTRODUCTION It is widely accepted that conducting load tests such as standard top-down tests or bi-directional (i.e. O- cell) tests can help designers understand load-settlement behavior and the nominal resistance of drilled shaft foundations. These load testing methods provide the advantage of confirming design assumptions as well as improving the reliability of the foundation design. The potential cost savings from the application of these methods for mid to large size projects is self-evident. For example, in a recent project in Northern Nevada, an O-cell test on a 6.9 ft diameter, 114.8 ft length drilled shaft imposed an initial cost of $125k to the project, resulting in a 15% reduction on the total foundation cost; equivalent to $1.3 million in overall savings (Pease, 2014). However, the costs of implementing such methods on smaller projects can be prohibitively expensive (Hagerty et al, 2016). Despite the clear advantages of drilled shaft load testing, the current practice is not without limitations. Performing load tests on large-diameter drilled shafts with high capacities is a challenge considering the significant loads required to fully mobilize the capacity of such foundations. In some cases, the feasibility of these tests is impractical because the associated initial cost is not guaranteed to outweigh the final savings. As a result, large scale load tests are sometimes ruled out from the design phase of projects. Furthermore, in the majority of load tests the magnitude of loads applied are specifically selected to not approach failure, so the shafts can be used in the future foundation system (i.e. production shafts). This practice of field testing restricts our knowledge of the true capacity of the drilled shaft at failure; hence the nominal resistance remains unknown.

Jan 1, 2018

Geological maps, data, and prospectivity analysis relevant to mineral exploration in New Zealand have recently been released. Regional-scale geological mapping is increasingly available for the country through the QMAP 1:250 000 Geological Map of New Zealand programme. Published QMAP sheets Greymouth, Wakatipu, Waitaki and Dunedin cover large areas of interest for mineral exploration companies. The QMAP geological data are also available in digital form for use with other digital datasets using GIS software. Crown Minerals, in cooperation with GNS, have completed two gold prospectivity studies; the first covering mesothermal gold in the South Island, and the second encompassing epithermal gold in northern New Zealand. These studies have defined areas of interest for these two mineralisation types and assembled geological, mineral occurrence and production, geochemical, geophysical, topographic and cultural data into projects for use with GIS software. Included are the results of prospectivity modeling for gold using these data and specific mineralisation models. The prospectivity studies and relevant data are freely available on CD through Crown Minerals and are intended to encourage mineral exploration in New Zealand.

Jan 1, 2003

Although AustraliaÆs coal mining industry is currently experiencing a pleasing period of price relief, long-term trends toward lower real prices will surely continue. Higher price levels attract expansion by existing operators and market entrance by new operators. History clearly demonstrates the relentless long-term march toward ever lower real prices. Therefore, the need for economic returns applies constant pressure to improve productivity. To be sustained, high productivity requires a systematic response based on a solid understanding of critical productivity determinants. The most powerful determinant of productivity is now widely understood to be workplace culture. Culture largely comprises a combination of behaviours, symbols and attitudes. This paper will examine and review scienceÆs latest discoveries in human behaviour. It will provide a proven, practical framework for understanding behaviour and applying this knowledge. Significantly, it will highlight why conventional approaches toward improving productivity often provide disappointing economic returns. The modern understanding of behaviour factors will cover coal face operations. More importantly, because executive and managerial levels in coal mining have significantly greater impact on industry and mine productivity the paper will concentrate on leadership. Particular emphasis will be placed on use of modern systems and in particular use of what are by far the most powerful drivers of behaviours û measurement, analysis and reporting systems. The paper and presentation will show how conventional systems rooted in antiquated American legislation from the early 1900s stifle productivity improvement and drive suboptimal and even counterproductive behaviours. These commonly used systems will be compared with accurate and effective modern methods for assessing performance to improve productivity. These principles are proven in all industries and effective application in mining will be highlighted. Actual results will be used to demonstrate practical approaches successfully applied in both metal and coal mining in Australia and overseas.

Jan 1, 2005

By Ali Nazem, Rennie Kaunda, Zoheir Khademian, Fei Wang, Raymond Henn, Alex Peretiatkol

"The field demonstration portion of the Underground Grouting and Ground Improvement (UG&GI) short course offered by the Colorado School of Mines was held on May 18, 2016 at Baski Inc.’s Yard in Denver, CO.Numerous full field scale demonstrations of grouting methods and equipment were conducted under various field conditions. As part of these field tests, permeation grouting testing and demonstrations were also conducted. Various cement grout mixes were injected into 1.5-m (60-in.) tall transparent sand columns under controlled conditions (Fig. 1). The objective of the sand column permeation grouting demonstrations in the study was to show students the effects of ordinary Portland cement versus ultrafine cement on the engineering properties of the grout, and the permeation height through various types of soil stratigraphic layers in the sand columns. Similar previous demonstrations have had a specific focus on various brands of Type I-II Portland cements and ultrafine cements with a range of water cement ratios and injection pressures. More detailed information about these previous studies can be found in published proceedings (e.g. Henn et al., 2009 -2011).Equipment and material usedThe five clear plastic sand columns were 191 mm (7.5 in.) inside diameter and 1,524 mm (60 in.) tall. Each sand column had a 19 mm (0.75 in.) diameter hole drilled at the base (bottom) of the blind flange for injection of the grout. A perforated plate and/or screen at the base of the sand columns helped to prevent sand from plugging injection port. A ChemGrout grout plant was used for the demonstration consisting of 0.36 m3 (97 gal) high shear (colloidal) tank mixer, a 0.36 m3 (97 gal) agitator tank and a progressive helical cavity pump with maximum output capacity of 77 L/min (20 gpm) at a maximum discharge pressure of 265 psi (18 bar) (Fig. 2). A simple grout header arrangement consisting of control valves, pressure gauges, flow meter, grout delivery and return line, and a short injection line was also custom built. Also used were infra-red thermometers to measure the temperatures of the grout mix batches, CRD and marsh funnels to measure viscosity, baroid mud balance to measure specific gravity, and a digital scale to measure weights. The grout materials used were Holkim Portand cement (Type I-II), Nippon Steel Sumikin superfine cement and U.S. grout ultrafine cement."

Mar 1, 2017

In 1984/85 financial year Australia produced 529 thousand barrels per day (kbd) of crude oil. By far the major contribution (453 kbd) was light waxy oil from offshore Gippsland, Victoria. When these discoveries were made in the latter 1960s, imported oil was available in abundant supply and at low prices. Because of this, the Gippsland producers persuaded Government to control the marketing and pricing of their crude, and thus provide the required security of offtake. Political events in the middle East created supply shortages during the 1970s, and dragged up government selling prices for OPEC crude oil. Thus Arab Light crude that sold for less than US$2/barrel (bl) in 1970 reached $34/bl in 1981. Following the consequent decline in world oil demand, in 1982, Australian refiners sought to evade their obligation to lift Gippsland crude. Hence, in 1983, the Government was forced to introduce a floor quota of 385 kbd of Gippsland crude liftings and to allow producers to export any additional production refiners did not require. On expiry of the old arrangements, Government introduced a partial free market from January 1985, whereby the balance in excess of 350 kbd may be sold to Australian refiners at negotiated prices, or exported as before. In 1984/85 exports were some 90 kbd and will be higher in the current year. About half this total has been exported by BHP, providing valuable experience and lessons which are described in the paper.

Jan 1, 1986

By Mark A. Williams

"This paper was originally intended to be a presentation of a case study of two surface bituminouscoal mines in the southern Appalachian coal fields located within five miles of each other. These mines were nearly identical in every aspect from geologic setting to equipment application. Althoughrepresentatives from each mine desired to participate in the preparation of this paper through support in providing background information and in review and editing, it was later concluded that, due to the environmental sensitivity associated with each mine, it may not have been a good decision to present this case study in a public forum."

Jan 1, 1994

By Andrew R. Marchbank

The application of biologically assisted methods for metal extraction in the mining industry has a long history, but development of modern techniques has been relatively slow. There is, however, a resurgence of interest in the industry with the recent development of methods to successfully treat base metals concentrates. Two major pilot plant programs for treatment of chalcopyrite concentrates have been initiated in the past year and results from one are beginning to be released. This paper provides an overview of methods that have been applied in the past; from the earliest deliberate applications of the technology, through the copper and uranium heap and dump leach applications, the more highly engineered agitated tank leach gold applications and the developments currently taking place in the industry.

May 1, 2002

By H. Chaouki

The aim of this work is to simulate the forming process of a green anode. For this purpose, a nonlinear compressible viscoelastic constitutive law is presented. The concept of natural reference configuration is considered. Within an isothermal thermodynamic framework, a Helmholtz free energy is proposed to take into account the nonlinear compressible deformation process occurring between natural reference configuration and current configuration. A dissipation potential is introduced in order to characterize the irreversible aspect of compaction process. Thus, the constitutive law is formulated through two equations: 1) an expression of Cauchy stress tensor and 2) a differential equation characterizing the evolution of the natural reference configuration. Material parameters are assumed to be a function of the bulk density. This allows capturing the micro-mechanical phenomena within the chosen macroscopic approach. An experimental study based on compaction tests is carried out in order to characterize the mechanical behaviour of the anode paste. A user's material VUMAT subroutine for finite element dynamic explicit analysis has been developed and implemented in the ABAQUS commercial software. To evaluate the model predictive capability, numerical simulations of the compaction forming process of anode paste were performed. Simulation results show that the constitutive law predicts the experimental trends and gives interesting physical responses. This constitutes a first step toward making a benchmark with experimental results on the forming process of anode paste.

Jan 1, 2011

By Barry D. Lichter, Pierre Sommelet

High-temperature heat contents of InAs and GaAs were measured over the temperature range 400°K to temperatures above the melting points using a di-phenyl ether drop calorimeter. Smoothed values of the thermal properties have been derived and tabulated at even temperature interuals . The heats of fusion of InAs and GaAs were determined as, respectively, 8790 ± 200 and 12,590 ± 300 cal per g-atom at the respective melting points of 1210º ± and 1513º ± 1°K, yielding entropies of fusion of 7.26 * 0.16 and 8.32 ± 0.20 cal perºK per g-atom, respectively. A general discussion of the thermal properties of III-V com-pounds is given. THE low-temperature heat capacities of InAs and GaAs have been determined by Piesbergen.1Using a dynamic temperature modulation technique, Miller2 has determined the heat capacities of the compounds as well as GaSb and Ge between room temperature and 650°K; however, it has been observed that values determined by drop calorimetry for GaSb3 and for germanium4 are consistently about 5 pct lower than Miller's results. Cox and Pool10 report values for the heat content of InAs and GaAs and the heat of fusion of InAs. No value for the heat of fusion of GaAs appears to have been previously reported. This paper reports results of high-temperature heat content investigations of InAs and GaAs measured in the range 400" to above 1500°K employing a diphenyl ether drop calorimeter. These results, together with our previous results on III-Sb compounds3 as well as heat-content measurements5 of solid InP and Gap, are used in a general discussion of these compounds. EXPERIMENTAL PROCEDURES High-purity samples of the compounds, stoichio-metric to ±0.1 at. pct, were supplied in the form of crushed crystal fragments by Dr. Carl Thurmond of the Bell Telephone Laboratories. The sample preparation, description of the calorimeter, and details of the heat content measurement have been previously described.3 Samples were sealed in evacuated silica capsules and suspended by a Pt-Rh wire in a Pt-wound vertical tube furnace, heated to temperature

Jan 1, 1970

By M Norbert, D O’Connor

The mainline running tunnels for Legacy Way comprise two tunnel boring machine (TBM) driven tunnels. Both TBM drives commenced at the Launch Portal adjacent the Mt Coot-tha Road. Excessive surface settlement arising from tunnelling would have had a significant impact to the road infrastructure. The geological structure above the tunnel springline is a mixture of fill, residual soil and weak rock. Given the combination of low ground cover and weak ground materials, along with the use of an open face TBM, an oversize pipe umbrella system has been installed above the tunnels. This pipe umbrella system is similar to that commonly adopted in conventional mined excavation support in soft ground except that the steel pipes are substantially larger in geometry and filled with concrete. It is acknowledged that similar systems with oversize pipe umbrella have been adopted elsewhere in the world in other projects. These systems often comprise of a full arch formed by conjoining oversize steel pipes (in contact only). By aligning the pipes in contact, the arching behaviour of the steel pipe would have been enhanced. However, this poses a degree of construction difficulty due to excavation and installation method of the pipes. The Legacy Way pipe umbrella system only consists of a partial arch at the tunnel crown and each pipe is spaced approximately 1200 mm apart with 900 mm diameter pipe, leaving a gap of approximately 300 mm between pipes. A reinforced concrete portal block was used to support the exposed ends of the pipes.This paper reviews the design analysis, the recorded deflections from the pipe umbrellas and surface monitoring during TBM launch and revisits the analysis using the newly available RS3 program, from Rocscience for 3D analysis of geotechnical structures.CITATION:Norbert, M and O’Connor, D, 2014. Starting the journey – launching of the Legacy Way open face tunnel boring machines in mixed face ground conditions, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 307–314 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By T. J. Batchler, K. M. Mohamed, D. F. Gearhart, R. K. Zipf

Seals are explosion-resistant structures built in underground coal mines to isolate abandoned mining areas from the active workings. An equivalent single degree of freedom (SDOF) method such as the single-degree-of-freedom blast effects design spreadsheet (SBEDS) developed by the U.S. Army Corps of Engineers can be used to design seals to resist mine explosions. The critical input for the SDOF code is the seal resistance function. The objective for this study is to develop engineering data for design of plain concrete (PC) and reinforced concrete (RC) seals using finite element (FE) models. The FE models can then be used to generate resistance functions for different PC and RC seal designs, which can be used in the SDOF codes. The U.S. National Institute for Occupational Safety and Health (NIOSH) researchers designed and built a test fixture for use in conjunction with NIOSH’s Mine Roof Simulator to apply a four-point bending load on the face of the tested seal. Eight large-scale experiments for each PC and RC seal were conducted. The experimental design considered the effects of the foundation strength, hitching and roof-to-floor convergence. Calibrated FE models for PC and RC seals were developed using ANSYS Ver. 13. With a very limited number of engineering-based assumptions and a single set of data—including Young’s modulus, compressive strength, stress-strain relationships, etc.—the PC and RC seal models successfully calculated the recorded resistance functions and failure patterns for a wide range of boundary conditions. Plug and RC seals were assumed for a 1.83-m- (6-ft-) high entry to demonstrate the application of the calibrated finite element models for calculating the resistance functions of these seals. The resistance function of a particular plug seal case was found to be a bilinear relationship. The resistance function of a particular RC seal without shear reinforcement was found to be a nonlinear relationship.

Jan 1, 2013

Possibilities and Working of the Specific Agglomeration of Fibrous Materials and Residues Plant based fibrous materials are becoming of increasing interest in a multitude of industrial applications. Main advantages are the specific lower energy demand and virtually closed CO2 cycle, excellent mechanical properties based on low density as well as a high level of recyclables. In contrast, processing and handling of such materials is associated with a number of challenges. These challenges are mainly related to specific morphological characteristics in correlation to fibre length and structure (branching and splices). Specific problems in further processing steps including transport, dosage or storage for natural fibre compounding, result from form-locking bonds leading to burling, clusters or plaits. Technologies of fibre processing are well known, but other than textile based technologies they generally result in intermediate goods which do not allow direct industrial application. The investigation to be presented is based on results of recent research activities and shows two possible technical solutions of innovative fibre agglomeration procedures. These methods allow the conversion of middle to long fibres into a form, which eases further processing and dosage significantly and therefore allows free flowing too. The procedures are based on the working principles of rolling and winding technology. Within the work, both of the patented methods and their respected lab-scaled devices will be described. Further, results will be shown for an up-scaled rolling agglomeration unit applying the developed principle and consisting of multiple process zones. Possible variations of the resulting product characteristics and the impact of different process parameters will be discussed based on the trials with natural fibre (hemp and flax) agglomeration. As a main outcome of the research, product qualities can be supplied according to the requirements of the specific application in correlation to agglomerate strength, porosity or form. In conclusion, recent developments for specific methods of characterization will be depicted.

Sep 13, 2010

By Ting Lu, Gerard Laman

"This document compares the systems of coal classification described under ASTM standards used in Canada to GB standards used in China. A preliminary connection of metallurgical coal classes was set up between the two classifications. In GB classification system, there are nine metallurgical coal groups, namely PS, SM, JM, FM, ½ ZN, RN, 1/3 JM, and QM used in coal blending for coke production. PS coal is almost equivalent to the Low Volatile Bituminous coal; SM, JM, and FM coal groups fall into Low to Medium Volatile Bituminous range; ½ ZN, RN, 1/3 JM, and QM are equivalent to bituminous coal with medium to high volatile matters; QF contains higher volatile bituminous coal compared with High Volatile Bituminous coal. The caking properties commonly used in respective country are also compared in this document. These properties include free swelling index (FSI) and maximum fluidity used in Canada, as well as caking index (GR.I.), and the maximum plastic layer thickness (Y) mainly employed in China. It has been observed that the log of the maximum fluidity has a stronger correlation with the caking index than the Y values. Metallurgical coal processing strategy and typical coking coal product qualities are briefly discussed in the last section of this paper. Currently there is a trend to use heavy medium cyclone in both countries. In Canada the conventional two-product cyclone technology is the preferred practice; whereas in China the three-product heavy medium cyclone arrangement is widely used.INTRODUCTION Coal can be simply classified by applications into two categories: i) thermal coal used to provide heat energy in combustion, and ii) metallurgical coal which is converted to coke, in a carbonization process, and used mainly in the iron and steel industry. Metallurgical coal contains even higher heating values than thermal coal. In addition, it presents unique plastic properties during carbonization which in turn produces a porous solid, high in carbon referred to as coke. Coke is one of the most important raw materials in the iron and steel industry."

Jan 1, 2012

By Masaki Kitazume

"Abstract The wet type and dry type of deep mixing methods have been developed and widely applied for on-land and marine constructions in Japan. The quality assurance (QA) of the methods has been usually carried out by unconfined compression test on field stabilized soil sampled by core boring in Japan. In some other countries, stabilized soil excavated by the wet grab sampling instead of core sampling is often subjected to unconfined compression test for quality assurance. There are several merits and demerits in each method, but few studies have been carried out to compare the stabilized soil strength of these two types of specimens to discuss their applicability to practical construction. The author has conducted a series of field and laboratory tests to compare the stabilized soil strength and discuss the applicability of wet grab sampling to QA for wet and dry types of deep mixing method.In this study, the wet grab sampling was carried out at two road embankment construction sites where the wet type and dry type of deep mixing were applied. The cement stabilized soil was excavated at the three depths by a wet grab sampler soon after the DM column construction. The test result is compared with the other test data in the previous study to discuss the applicability of the web grab sampling method for QA of cement stabilized soil.IntroductionThe Deep Mixing Method (DMM), an in-situ soil stabilization technique using cement and/or lime as a binder, is often employed to improve soft soils (Kitazume and Terashi, 2013). A variety of factors and their interactions affect the eventual strength of a deep-mixed column, while some of which are controllable (e.g. binder type and dose) by engineers while the others are not (e.g. soil types, ground temperature, etc.; Babasaki et al., 1997). In addition to laboratory mix tests, which in essence are a parametric study to estimate the influence of these factors on a particular soil’s strength, the quality assurance (QA) practice in Japan usually involves unconfined compression test on sampling cores from the stabilized columns after a given curing period. It has been recognized, however, that the ‘field strength’, or the strength of the retrieved core, quf is on average lower than the ‘laboratory strength’, qul, evaluated by laboratory mix test. Also allowing for the inevitable variability, existing guidelines (for example, PWRC, 2004 and CDIT, 2008) recommend the design quf /qul values of, for example, 0.5-1.0 for the CDM (Cement Deep Mixing; a wet-type technique, in which binder is added as slurry) and 0.2-0.33 for the DJM (Dry Jet Mixing; a dry-type technique, in which binder is added as powder)."

Jan 1, 2014

At Copper Refineries Pty. Ltd., Townsville, two reverberatory furnaces of 420 tonnes capacity are used to melt 210000 tonnes/year of copper for subsequent anode casting. When the refinery commenced production in1959, these furnaces were of 300 tonnes capacity. The original furnaces featured a silica brick hearth, magnesite and chrome magnesite side 'walls, and a sprung silica brick roof, but were unsatisfactory because of thelow refractory life and high costs. With continuous expansion in production and the incentive to increase furnace life and capacity the design of these furnaces has changed greatly since that time.The present furnaces feature all basic brick, a flat suspended basic brick roof, very extensive use of watercooled copper sections, and are of substantially increased (420 tonnes) capacity. Particular attention has been concentrated on high wear areas such as the taphole, side walls, and charging door jambs. Each furnace in its 24 h cycle, is charged, the copper melted, impurities skimmed off, metal "poled" prior to casting, and cast.The service condition during each of these operations is important in considering furnace refractory life.The improvements in operating practices and furnace 'construction which enabled the capacity of the furnaces to be increased are discussed. The life between major repairs to side walls has increased from 90 charges to300 charges.The scope for future improvement is considered and areas for development are suggested.

Jan 1, 1977

By J. Gummer, M. Williams, S. J. Hawksworth

A common problem encountered in British coal mines is bearing failure on conveyor system idler rollers, which on occasions has led to fires. The UK Mines Inspectorate initiated a study of such failures to assess the potential for ignition of explosive atmospheres. As part of this study HSL have developed a system to measure the temperatures generated within the bearings during controlled failure. Temperatures are measured using both infrared thermal imaging and contact thermometry. The work to date has shown that temperatures well in excess of the auto-ignition temperature of methane can occur.

Jan 1, 2003

By Jeffrey M. Listak

This report describes a study, conducted jointly by BethEnergy Mines Inc. and the Bureau of Mines, to assess the effects of longwall front abutment loading on various supplemental support materials utilized in a predriven recovery room. The purpose of the predriven recovery room is to reduce longwall equipment transfer time by eliminating the premove preparation associated with conventional recovery methods. In addition, the room provides a large area in which face salvage equipment can maneuver. Results of four recovery-room study areas show the progression and influence of the front abutment on the longwall panel and supports and their subsequent behavior. The best performance (i. e. the support that most facilitated recovery) of support material was achieved through the use of a concrete mixture which had a sand content of 35 percent by volume. The longwall transfer time was reduced by 30 percent which translates to a production advantage of 37,000 raw tons of coal per panel.

Jan 1, 1989

By Mohab Sabry

Pile foundations are used extensively around the world to support both inland and offshore structures, including important structures such as nuclear plants and oil drilling platforms. The limit of the pile depth is currently predicted during the pile deriving process, given no chance for the designer to predict accurately the capacity of these piles prior installation. Furthermore, after pile installation, designer may not be able to modify the pile group design by increasing the number of piles and or changing the geometry of the pile group. This paper presents a numerical model for the case of single piles driven in homogenous sand using finite element technique and the theory of cavity expansion. The model is capable of simulating all the construction stages of concrete piles up to the maximum depth, which can be driven in sand and accordingly the capacity, which can be attained by these piles. The program "PLAXIS" is used to perform the proposed analysis. This model simulates the process of pile driving in terms of the changes in the earth pressure and the overconsolidation ratio acting along the pile's shaft. Based on the results of the present investigation, these depths can be predicted based on the pile geometry and the sand properties. Charts are given to provide these depths for given pile/soil conditions.

Jan 1, 2006

By R. M. Lamya

A considerable part of gold encapsulated in some refractory sulphides can be dissolved during sulphide matrix decomposition in non-complexing aqueous media. This has been concluded from laboratory results of gold extraction from pyritic and arsenopyritic concentrate containing 172.8ppm Au, into 10% hydrochloric, sulphuric and nitric acids. The degree of sulphides decomposition in the non-oxidative acids limits the gold extraction from this specific concentrate to about 10%. In the case of nitric acid, the gold dissolution follows the rapid decomposition of sulphides, reaching 32 to 42% of extraction at almost total decomposition of the sulphidic minerals. Accumulation of gold in this acidic and non-complexing solution to several ppm was not affected by the soluble products of the sulphides decomposition. An attempt to explain this gold behaviour is undertaken and some practical implications are discussed. In the investigated concentrate the "soluble gold" is mostly associated with arsenopyrite. This is consistent with the latest findings of other authors that gold disseminated in arsenopyrite can occur as cation Au3+. In a comparative test the gold extraction into highly concentrated chloride solution, in the same oxidative conditions, amounted to 92.34%.

Jan 1, 1995