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By M. T. Davisson

Pile compression load capacity prediction methods are divided into four categories for purposes of discussing their reliability compared to static load test results. The categories considered are: 1) static analysis, 2) driving formulas, 3) wave equation analysis, and 4) dynamic measurement and analysis. It is concluded that any method of static analysis that works for the geological deposit in question may be satisfactory. However, any given method can be quite wrong when applied to other deposits of soil that are different in terms of their engineering and geological characteristics. Dynamic formulas are found to be theoretically unjustifiable. The ready availability of the wave equation analysis for microcomputers eliminates the need to utilize dynamic formulas. The wave equation analysis is found to be the best analytical method for making predictions both for design and for construction control. Dynamic methods of measurement and analysis are found useful, but have limitations that have caused troubles on many projects. Two case histories are presented that show the limitations of dynamic measurement and analysis, and of the wave equation analysis. Soil deposits exist that defeat both the wave equation and dynamic measurement techniques; static load tests are currently the only method of proving the load capacity of piles in such soils.

Jan 1, 1991

By Arturo Ressi di Cervia

Construction of the drilled shafts for the Brightman Street Bridge Replacement Project were not only challenging due to working over the water but were also challenged by changed soil conditions, concurrent work being performed by an adjacent contractor on the same project, environmental restrictions and severe winter conditions. A total of 36 x 8 feet diameter drilled shafts with 7.5 feet rock sockets were installed for the East and West bascule piers. This project also included Osterberg Cell load testing on two production drilled shafts at each the East and West bascule piers. The results from the load test program were used to fine tune the design of the drilled shaft rock sockets. From a constructability standpoint the reverse circulation drilling method with a pile top drill rig proved to be an excellent choice for drilling the overburden and rock sockets of the large diameter deep drilled shafts.

Jan 1, 2003

By K. E. Manchester, C. B. Sibley

The feasibility of doping silicon to produce device structres by directly implanting impurity atoms has been demonstrated. Both phosphors and boron ions have been successfully implanted in silicon to produce electrical junctions. Junctions as deep as 1.2 p have been produced by phosphorus ions having energies the order of 80 kev. An electromagnetic separator has been used to controllably produce uniform, large-area implantations for evaluation experimentation. Correlations between junclion depths and ion energies huve been obtained. Orientation effects have been observed and it has been found that the (110) direction is the easy direction for implanting. Monitoring of thermal treatments oj implanted substrates by sheet-resistance measurement indicates a very mild thermal anneal removes most of the damage done during the implantation. These indications are further substantiated by reverse-current measurements of j,inctions Produced by implantation. Electrical characteristics of implanted junctions are compared with those of diffused junctions. We have been interi n the interaction of energetic ions in the III-V groups, in particular boron and phosphorus, with single-crystal silicon to produce type conversion for possible device use. A number of investigators, a few of whom are avies, Kornelson,3 and so forth, have reported on penetration of energetic ions into both amorphous and crystalline solids. While most work has been done with ions of the rare gas and alkali metal groups, some work has been reported by ing, erber,' and others6 in which ions of the 111-V groups have been implanted in single-crystal silicon. A large amount of this work has been done with ion energies in the 100-kev to 1.5-Mev range. An excellent review article has been written by caldin. We have concentrated on ion energies which are in the 10 to 80 kev range, with which over 1500 implanted junctions such as the one shown in Fig. 1 have been produced in silicon substrates with both phosphorus and boron ions. Fig. 1 is a 3-deg angle lap in which the n type area produced by 66 kev P is delineated and the junction is 9500A below the surface. EXPERIMENTAL Implantations reported in this paper were made with the ion source adjusted to produce ion currents in the range of 1 to 2 pa with accelerating voltages varied from 10 to 40 kv. When using doubly charged ions this produced 10 to 80 kev ions. This allowed substrate temperatures to remain below 100°C. Sam- ple movement resulted in beam impingement angle variation of 7 deg from the normal to the substrate surface. Substrate resistivities have been varied through the range of 0.001 to 500 ohm-cm and specimens oriented in three directions, (110), (Ill), and (loo), within 12 deg. RESULTS For the purpose of this paper, discussion of results will be limited to phosphorus implantations with mention of results for boron-implanted silicon. Similar results have been obtained for boron and will be reported at a later date. In Figs. 2, 3, and 4 depth penetration is shown

Jan 1, 1967

By H. S. Rathor

NTPC (National Thermal Power Corporation), a multi-unit organization, is generating 26% of India’s total power. This power is produced from its 14 coal based stations and 7 gas based stations. NTPC is entering into the business of power-distribution, power-trading, setting up of coal mines and diversification in non-conventional energy sector as well. For achieving the goal of the country “Power for All” NTPC has taken a giant stride by entering into Hydro Power generation which is also the cheapest and the cleanest renewable source of energy. In its pursuit for excellence, 800 MW Koldam Hydro Power Project is NTPC’s first venture in hydro sector. In Koldam, hydropower potential will be harnessed by constructing a 163m high earth and rock fill dam in a narrow gorge at upstream end of Bhakra reservoir. The river diversion is envisaged through two parallel, 14m finished diameter ‘horseshoe’ tunnels of length 901m and 934m at village Kian on the right bank, where the river forms a 180° loop. The diversion tunnels are designed to accommodate a flood of 6500m3/sec, taking into account the maximum probable discharge of 200 years return period. The tunnels pass through dolomite and limestone rock formations. The excavation of tunnels was done with drill and blast method. The excavation was attempted from both inlet and outlet faces. During geological investigation a rock fault was located at the outlet area. The location of the fault was such that it was passing through the edge of the Tunnel-1portal and around 30m away from the face of the Tunnel-2 portal. The quality of the rock at Inlet was also poor. To save the portals from slips, excavation of the tunnels was planned to start after the completion of the open excavation and its support system both at inlet and outlet. The tunnel excavation at inlet was envisaged by approaching the tunnels’ portal by constructing a road through 540EL bench and meeting the inlet portals on the upstream end, which would have been ready by mid2003, only after completion of the open excavation and its support system. To save time and cost, it was felt necessary to modify the planning by starting the tunnel excavation simultaneously along with open works both at inlet and outlet. The excavation at the inlet face of the tunnels started in December 2002 after rerouting the approach road to inlet portals through haulage road on the downstream and similarly Tunnel-1 at the outlet was started in the low cover area before completion of open area works. Thus the tunnel—heading excavation was started nearly 06 months early with the change of methodology.

Jan 1, 2005

By L. Archambeault

This paper describes preliminary research on the application of Markov Decision Processes (MDP) to Real Option Valuation (ROV) and the optimisation of mine scheduling. The MDP framework is a novel approach to option valuation and scheduling in mining operations. A learning agent is introduced into the valuation process of an open pit, where prices and block ore grades have probabilistic values. The prices are modelled using a mean reverting diffusion process and the block grades using sequential Gaussian simulation. The agent is asked to learn which production parameters should be used in order to maximise the overall value of the project. The introduction of the agent permits a real option approach to mine valuation, such that the value associated with the robustness of a design to uncertainty can be measured. A simulated example is used in which there are ten blocks to be extracted under conditions of grade and price uncertainty. Using policy iteration, an optimal policy is generated and the value of production options is found. The potential financial gains from applying MDPs to mine valuation and optimisation are substantial and warrant further investigation.

Jan 1, 2007

By S. Cossio, J. L. Noyola, R. Espinosa

"Minera Penmont’s La Herradura is a joint venture between Industrias Peñoles, S.A. de C.V. and Newmont Mining Corporation. The mine is located in the northern Mexican state of Sonora. La Herradura consists of an open pit mine with a two-stage crushing plant and heap leaching facility. Gold is recovered from the pregnant solution using the Merrill-Crowe process; production began in July 1998. La Herradura produces about 130 000 oz gold per year and its treatment capacity is approximately 22 000 t/d. Ore mineralization occurs in a shear zone with quartz and native gold. Gold distribution is quite heterogeneous due to coarse visible gold, which in some cases ranges from 100 to 600 microns.Sampling and assaying protocols were established during exploration and prior to start-up of operations, based on nomographs developed from early heterogeneity tests. However, as the coarse gold problem became noticeable, it was necessary to develop new sampling protocols to have an acceptable relative standard deviation to control the fundamental error within ± 15%.An experimental program was developed and conducted on a selected ore block consisting of 195 blastholes; regular ore grade control procedures were applied to both sets of data to evaluate the difference in results between the protocol established prior to start-up of operations (existing) and the new protocol (leaching). In the existing protocol, sub-sampling is done through riffle splitters, and coning and quartering. Fire assaying was used to estimate the gold content on a 50 g sample. In the leaching protocol, a 12 000 g sample of bottle-rolled cyanide was leached, and the leach residue was assayed on a 50 g sample using fire assaying, and a weighted average total gold content was calculated. Currently, a new alternative method is being evaluated, where sub-sampling is done using rotary splitters, and fire assay on a 50 g sample; in this rotary sampling protocol and for comparison purposes, gold assays were also repeated using the leaching protocol.Test results were compared in three groups: < 0.3 g/t (below cut-off), 0.3 to 0.8 g/t, and >0.8 g/t. Overall, results show that the protocol established prior to start-up of operations underestimates the gold assays. Detailed technical results, alternative options, and their implications are discussed in the paper."

Jan 1, 2004

By S. Banisi, M. Poorkani

The Sarcheshmeh copper deposit contains 1 billion tones of ore averaging 0.7% copper and 0.025% molybdenum. It is located southeast of Iran and currently processes 41,000t/d. Molybdenite as a by-product is recovered in two separate stages. First, a bulk coppermolybdenum concentrate is produced and in the second stage these two are separated. The recovery of molybdenite in the first and second stages is 65% and 85-90%, respectively. The yearly production of molybdenite concentrate varies between 3500 and 4000 t. Sodium sulphide is used as the depressant of the copper and iron bearing minerals which due to a rather high consumption (17.7 kg/t) constitutes one of the major cost items of the plant (i.e., 58% of total reagents cost). A detailed laboratory scale study showed that replacing air with nitrogen could reduce the consumption of sodium sulphide (i.e., H2S or mineral origin). Nitrogen for the plant was supplied from an oxygen plant used for the smelter through a 1400 m long pipeline. The existence of the oxygen plant at the Sarcheshmeh complex was a key factor in the implementation and success of this project. After using nitrogen in the plant for a period of twenty one months, the consumption of sodium sulphide was reduced from 17.7 to 14.2 kg/t at constant metallurgy. The reduction was lower than expected which was mainly due to the type of sodium sulphide used and the lack of any automatic instrument to control the depressant (sodium sulphide) dosage. The latter in turn caused the operators to overuse sodium sulphide in order to reach and maintain the target metallurgy (i.e., higher molybdenite recovery along with lower copper content of the concentrate).

Jan 1, 2005

Methods for Improving the Flotation Recovery of the Coarse Fraction of a Nickel Ore

Sep 13, 2010

By Peter Mitschke, Friedrich Rosenstock, Heinrich Meiler

"The development of the Centrifugal Mill jointly by Chamber of Mines (Johannesburg) and LURGI GMBH (Frankfurt) had been described by L. Kitschen e.al. during the 14th IMPC at Toronto in October 1982. Further investigations, using a 55 kW semi-industrial mill, installed at LURGI's Research Laboratories, were concentrated on efficiency and wear in grinding.The test results showed, that efficiency increases when increasing the ball load between 60 and 80 % by volume. Furthermore, the efficiency is increased by speeding up the mill, thus increasing the centrifugal force to up to 14 times the force of gravity. Applying these findings to grinding of a Canadian iron ore spiral concentrate, a saving in grinding power of 30 % was experienced, when comparing with ordinary wet ball milling.Investigations of several shapes of the grinding chamber cross section and linings and several types of materials showed, that no increase of liner or ball wear will occur compared to conventional ball mills when choosing suitable lining patterns. 1. DEVELOPMENT OF THE CENTRIPUGAL MILLThe centrifugal mill was developed with the aim of finding a grinding unit that can operate at a higher power concentration than the conventional tumbling mills.LURGI felt the necessity for such a mill in connection with a hydrometallurgical process developed at the beginning of the seventies, which incorporated an activating grinding step as one of the essential process features. At that time, the Chamber of Mines in Johannesburg was investigating possibilities of underground wet grinding and preconcentration of gold ores aiming at a decrease of mining costs by reducing the quantities, especially for mines operating at depths up to 3600 m, by changing over from rope hoisting to hydraulic transportation systems. After the Chamber of Mines had initiated the development work on its own, in 1974 a cooperation between the two organisations was started."

Jan 1, 1985

By D. N. Dietz

Jan 1, 1969

By Lex L. Udy

Properties of an explosive which itiuence its performance on rock breakage are analyzed in relation to the rock: hardness and a discussion on the interaction of an explosive with the rock during the blasting process is given. Theoretical concepts regarding ideal and non-ideal detonation are reviewed to explain how the physical and chemical factors of an explosive influence the rate of energy release and its consequence on blasting performance. While a lower velocity of detonation indicates a slowed chemical reaction it does not necessarily mean a loss in energy from the explosive. High density ammonium nitrate (HDAN) can be used effectively in the formulation of modern industrial explosives to slow the energy release rate with its attendant decrease in detonation velocity. Examples of blasting performance using custom formulated explosives with HDAN are presented.

Jan 1, 1995

By Alec C. Bloem

A 55&apos; deep excavation encompassing almost a city block in London, Ontario required a lateral earth retention system to provide both temporary excavation support and a permanent groundwater cut-off wall for a proposed office complex. The system selected was an interlocking Drilled Shaft wall with 3-4 levels of tiebacks. The specifications required the system to be designed for movements or settlements around the excavation of ¼" max. Design to be by the Contractor with design parameters and a comprehensive soils report provided. An extensive system of instrumentation in the form of inclinometers and survey targets were used to monitor vertical and horizontal movements of the shoring system and adjacent properties. Introduction The project, One London Place, is a two phase office tower development in downtown London, Ontario. Phase one consists of a 24 storey office tower on the northwest part of the site, with five levels of below ground parking over the entire site "Figure 1". A second office tower will be constructed at a future date.

Jan 1, 1991

By Aloke Verma, R. Singh, S. Jana, C. Sawmliana, P. Pal Roy

On July 21, 2004, a trial blast using electronic detonators was conducted in India for the first time in an opencast mine at Pundi-E Quarry of TISCO, West Bokaro. Orica-IEL conducted the test using electronic detonators. To provide necessary technical feedback on wider applicability, CMRI scientists also participated in the trial blast.

Jan 1, 2006

By A. A. Steel

(Spokane Meeting, September, 1909.) DURING. the summer of 1905 I was employed by the U. S. Geological Survey to investigate the geology, Mining, and preparation of barite in most. of the fields of the United States. The Eastern districts have been more or less completely described ; the Virginia field in detail by Thomas L. Watson, in his paper, Geology of the Virginia Barite-Deposits,&apos; and other fields in abstract., including statistics of production and references to current literature, by various authors .2 There have also been published a few details of the occurrence of barite in the lead-mines of Washington county, Mo.3 The other accounts of this district are erroneous and meager, and since this field is the most important one in the United States at the present time, a detailed description of the local geology seems doubly desirable. Barite-deposits are scattered over nearly the whole of Washington and adjoining counties, but. the product, is all mined from the areas indicated upon the sketch-map, Fig. 1, and is shipped from the stations of the St. Louis, Iron Mountain &. Southern railway, between Blackwell and Potosi, from 45 to 60 miles SW. of St.. Louis. The topography is for the most part gently rolling, with slightly graded streams, usually less than 200 ft. below the higher hill-tops. Along Mineral fork and Indian creek are :some steep bluffs and cliffs, affording good exposures of the

Feb 1, 1910

By J. J. Sammarco

Illumination is essential for mine safety because miners depend most heavily on visual cues to detect hazards associated with slips/trips/falls and powered haulage. The National Institute for Occupational Safety and Health (NIOSH) is conducting mine illumination research to improve miner safety by enhancing a miner?s ability to see mine hazards. Thus far, 16 papers have been published covering diverse topics such as cap lamps, machine-mounted lighting, glare, lighting maintenance, and light-emitting diode (LED) technology issues. NIOSH has also developed an LED cap lamp, LED area lighting, and a Visual Warning System (VWS). This paper provides an overview of the improvements from NIOSH-developed lighting that include: 94% faster trip hazard detection with the NIOSH LED cap lamp; 79% faster peripheral motion detection to detect pinning/striking hazards; no increase in glare; 71% faster machine movement hazard detection with the VWS. Current research is described concerning an LED cap lamp for metal/nonmetal miners, illumination for refuge alternative deployment and inspection, and whether lighting could be used to improve miner escape and rescue in smoke. Lastly, future possibilities of using lighting to improve miner safety are described.

Feb 27, 2013

By G J. Corbett, T M. Leach

A continued exploration programme has further defined the geology of the Tolukuma vein system, verified the resource indicated by Newmont, and identified potential for additional mineralisation. The resource at Tolukuma Hill, designated as zone C, is a mine recoverable 432,000 t at 18.1 g/t Au &amp; 46 g/t Ag. Mining will be by a combination of open pit and underground at a rate of 100,000 t per annum. Processing will be by SAG mill, gravity circuit and CIL plant. A diatreme breccia, localised at an intersection of structures and a relationship of gold to base metal sulphides, are indicative of a strong porphyry association. Typical epithermal features such as crustiform banded quartz and quartz pseudomorphing platy calcite are also present and locally contain lesser gold mineralisation. Pre-existing dilatant structures have acted as a host to the ore fluids, resulting in the formation of the semi-continuous Tolukuma-Gulbadi veins over a 1100 m strike. A fluid flow model suggests that mineralizing fluids were sourced from a diatreme margin and migrated laterally along dilatant structures. Bonanza gold grades are interpreted to be derived through fluid quenching in the flexure between a hanging wall split, which hosts much of the Tolukuma Hill resource, and the feeder graben structure. Thus, the relationship between the pre-mineral structural geometry and fluid upflow at the margins of a diatreme breccia, controls the ore setting.

Jan 1, 1995

By Xiang-yang Zhou

Keywords: Low-Grade Dolomite, Low CaO Content, High Specific Surface Area, MgO. A low energy consumption preparation technology of magnesium oxide with low calcium oxide content and high specific surface area from low-grade dolomite has been investigated. The optimum technical conditions for the preparation of magnesium oxide are the followings: dolomite is partially calcined at 750-800° for 2 h; the optimum solid-liquid ratio range in calcined dolomite slurry is 20-30 g?l?1; carbonation temperature, carbon dioxide pressure and end point pH value of carbonation are less than 40°, 0.4-0.6 MPa and 7 respectively during carbonation process; decomposition temperature of Mg(HCO3)2 solution is near 100°; calcination temperature of the precursor (i.e. precipitated basic magnesium carbonate) is less than 850°. More than 90% of magnesium can be extracted by the technology. The MgO product (CaO < 0.38%) with a specific surface area of near 50 m2?g?1 also can be obtained by the technology.

Jan 1, 2005

By Ma. X.

Passive seismic imaging is applied in underground mining to analyze the stress redistribution after the occurrence of a major seismic event. The velocity model is established to be utilized in velocity inversion. By comparing the images from velocity tomography on two different time scales, the average velocity of a mining area decreases significantly after the major event. It is highly likely that the stored energy level drops due to the occurrence of a major event. Also, total energy stored in micro-seismic events for each day is summed up and the energy change trend is plotted to illustrate the correlation of energy with a major event.

Feb 27, 2013

Investigation of the Classification Operation in a Coal Pulverising Vertical Spindle Mill Coal pulverisation in power plants is a major electrical energy consumer. In 2006 more than 41 per cent of world electricity generation was from coal where pulverisers use 0.5 to 1 per cent of gross generation. Therefore, pulverisers are an important target for optimisation not only for reducing costs of power generation but also for reduction of greenhouse gas emissions. A better understanding of the operation of pulverisers is an essential requirement for their optimisation. However, little information is available, other than operating experience, on the performance of pulverisers and how these react to changes in operational variables. This study investigates the effect of changes in coal and airflow feed rates on the classification performance that occurs in an industrial scale ball-and-race vertical spindle mill in which the pulverisation and classification processes are linked together due to the separator classifier being an integral component within the pulveriser. In order to decouple the breakage and classification processes, samples were cut from upward flowing streams through sampling ports drilled on the pulveriser body at different locations. Specific sampling tools were developed. Samples collected from the pulveriser were size and density fractioned to distinguish the differences in behaviour of the components, namely coal and mineral matter. The coal flow rates on dry basis within the mill and around the separator classifier were calculated by mass balancing the multi-component data. The difference in classification behaviour of components during pneumatic transport was confirmed. The response of the circulating load in the mill (~600 to ~1100 per cent) as well as the dependency of fineness of the streams to the operating variables was demonstrated. The approach taken in this study has proved that development of a classification model for a vertical spindle mill pulverising non-homogeneous materials, eg coal, requires treating these materials as multi-component/composite substances.

Sep 13, 2010

By H. G. Oltmann

The equilibrium nitrogen solubility in the CaO-SiO2system was studied by a slag-gas equilibration technique, in graphite crucibles at 1823K under a CO-N2 atmosphere. The nitrogen content of the slags was determined by the Kjeldahl method. A reliable technique was used to obtain an initial nitrogen content in the master slags, from the addition and pre-melting of silicon nitride. Reduction of silica by graphite was found to occur during the equilibration experiments, resulting in compositional changes of the slags. The results were extrapolated to equilibrium by kinetic evaluation of the data. The nitrogen solubility showed good agreement with the result of Suito and Sano, while Fruehan?s results were lower. However, the results of the present study do not support the maximum nitrogen solubility values found by Sano.

Jan 1, 1999