Search Documents

By Elizabeth Varghese, Sanket Rawat, Prachuryya Kaushik, Ravi Kant Mittal

"Geo5 Software is gaining popularity worldwide due to its expediency in analysis and design of pile foundation. The analysis is based on various theoretical, empirical and semi-empirical methods available in existing literature and various country standards. Moreover, the ultimate resistance of pile in the software is based CSN 73 1002, Fellenius method, NAVFAC DM 7.2 and Tomlinson method. Due to the specificity in calculation of ultimate resistance, it becomes necessary to validate the results arrived using the software for better accuracy. Furthermore, the above-mentioned methods are not necessarily popular in every design offices. Therefore, an attempt has been made to predict the efficiency of Geo5-v15 software to analyze the pile foundation by comparing it with the results obtained using the analysis based on Indian Standard IS 2911:2010, performed with spreadsheet specifically designed for the same purpose. The accompanying outcome of the comparison and several shortcomings found in the design part associated with the software has been highlighted in the later part of the paper. Besides, the optimization tool present in the software is also described for the more efficient and economic design of pile foundation, hence contributing as practical aid to structural engineers.INTRODUCTIONThe analysis of individual pile foundation and pile in groups can be said to include the three main important parameters – Ultimate bearing capacity, Settlement and Structural Design. The first two parameters are to be evaluated to check the reliability of foundation against ultimate limit state and serviceability limit state. The third parameter includes the analysis of pile against both horizontal and vertical load. This parameter mainly intends to evaluate the size of foundation and the amount of reinforcement. Geo5 is a software which can expediently compute the above mentioned three parameters just by the mere input of the necessary factors. The ultimate bearing capacity analysis in Geo5 is based on various theoretical, empirical and semi-empirical methods available in existing literature and various country standards depending upon the drained and undrained condition of soil (Bowles, 1968; CSN 73 1002,1987; Felenius,1991; NAVFAC DM 7.2,1984; Tomlinson,1977). However, the method mentioned in IS 2911 (2010) is not the same and have slight variations in way of evaluating the parameters which affect ultimate bearing capacity. Therefore, it becomes necessary to evaluate the efficiency of Geo5 with respect to the value of ultimate bearing capacity and therefore, asserting the confidence in the software based method for the convenience of the designs in Indian Scenario. The present study aims to evaluate the efficiency of Geo5 v-15 software in predicting the ultimate bearing capacity of pile foundation. The results of the software are compared with the bearing capacity calculated using IS 2911 (2010) with the help of excel sheet. Moreover, as the software is frequently put under revision, therefore a comparison of this version has also been made with the latest version of Geo5 (2017) to check whether the latest revision has accounted for the discovered shortcomings. The design steps performed in the software is also shown. As Geo5 make use of IS 456 (2000) for the design purpose, hence it can be considered as reliable with respect to the estimate of the third parameter. Furthermore, the optimization process is also shown in the later part of the paper to emphasize the simplicity of the software in economizing the design cost."

Jan 1, 2017

By T. C. Woo

This report describes the program that studied the theoretical and practical aspects of the belt cleaning systems, investigated-the possibilities of a self-replacing and/or sell-adjusting belt cleaning device, and designed a horizonal pentagonal turret setup for the underground mine belt conveyors. This design resulted from comprehensive literature survey (both academic and commercial), actual mine visits, study of the mechanics of belt cleaning and bench-type experiments. It has complete working drawings and rough cost estimates.

Jan 1, 1977

The growth of "Unit Load-cargo handling technology in world cargo lin- er trades over the last decade has cre- ated a situation in which special pur- pose-vessels (cellular container ships, roll-on/roll-off vehicle deck ships and Lash type vessels) are rapidly replac- ing conventional cargo ships, the principal means previously available for transporting heavy lifts. Consequently heavy lift traffic has tended to accumulate awaiting ship- ment, especially where discharge is required in "off beat" locations. A partial solution to this problem will be provided by new and small but exceptionally versatile ocean going heavy lift carriers now finding their way into world trade routes. These new ships combine extremely high lifting capacity, high manoeuvreability and exceptionally shallow draft with bow and stern Ro/Ro capability. They can handle rolling loads of exceptional size and weighing up to 1,000 tons Each. But the problem is a far larger and more serious but essentially a domestic one. Major industrial pro- jects in Australia will require pro- gressively heavier and larger plant and construction sites are becoming much more inaccessible. Whereas these new ocean going heavy lift carriers have ample capacity to satisfy part of the total transport requirement, there is clear evidence to show that domestic transport resources have little if any potential for increase in capability at the same rate as demand or at the same rate as sea transport facilities. Resolution of the larger problem is within reach but only through a pro- perly co-ordinated approach to future planning for the overall needs of large scale projects on a national basis. This co-ordinated approach must involve Federal and State government transport administrators, railway and highway authorities, shipping and road haulage interests and finally the planners of the projects which require these improved heavy haulage services.

Jan 1, 1973

By B. D. Paphane

Since the commissioning of the Tati Hydrometallurgical Demonstration Plant (HDP), which produces Ni and Cu cathodes as well as Co salt from sulphide concentrate employing Activox® technology for leaching, no kinetic data has been generated from the plant under normal operating conditions, from start-up to steady state. Therefore, this study seeks to determine the rate of reactions in the leaching circuit with a view to obtaining kinetic data for the system under the current operating conditions. Within the five-compartment autoclave operating at temperatures of 105°C to 110°C and 1100 kPa pressure, the extraction of Ni, Cu, and Co ions into solution is achieved through the oxidation of the sulphide concentrate using approximately 50 kg H2SO4 per ton, 10 kg NaCl per ton, and 1.21 kg O2 per kilogram of S2-. The autoclave reactions showed complex kinetics, with the reactions proceeding via some intermediate(s) before the formation of products. The results suggest that the reactions were dependent on the size of the metal ion of interest and the concentrations of the metal ions in the Tati concentrate as well as in chloride leaching. The order of the leaching rate constants was Fe2+ > Cu2+ > Ni2+ > Co2+ in all the compartments studied. The rates of leaching were also found to decrease as the concentrate moves from compartment 1 to compartment 4. For compartments 1 to 3, leaching was observed to be preceded by dilution of the repulp liquor (copper raffinate). The leaching rate for compartment 5 was slightly lower than that of compartment 1 but higher than the rates of compartments 2, 3, and 4 for all the metals studied. Keywords kinetics, hydrometallurgical plant, Activox

Jun 1, 2013

By Grigori Abramov

Borehole Mining (BHM) is a remotely operated underground and underwater method of extracting (mining) mineral resources by high-pressure water jets. It can be carried-out from the land surface, open pit floor, underground mine and floating platform or vessel. The method is currently in use in mining and exploration of such natural resources and industrial materials as: uranium, iron ore, quartz sand, gravel, coal, poly-metallic ores, phosphate, gold, diamonds, rare earths, amber and several more. Yet another application of Borehole mining technology is construction of subsurface collectors, ground walls and storage for compressed or liquefied gases, oil and other products.

By Yvone Franco Crosato

The dense population of Hong Kong requires the construction of tall buildings in reclaimed areas or perched on the slopes of the many hills. The large loads to be supported are carried by deep foundations. Many of those are bored piles, to rock, of diameters up to the 3.0 m. of today.

Jan 1, 2000

By Jack Wright

The analysis of water produced with crude petroleum has interested oil producers since inception of the industry. Records of the first analysis of mineralized water produced from an oil-productive formation are obscure, and references to the first use of brine analyses to assist in solving problems of petroleum production are not available in the technical literature. However, many early reports of the Federal Bureau of Mines5-8 and Federal Geological Survey,9-11/ as well as articles in engineer and geological journals12-14/ placed special emphasis on the importance, interpretation, and application of water analyses. One of the earliest applications of water analyses, and still a major one today, is for identification of intrusive waters in oil wells. This may be done by comparing the chemical constituents of a sample of water indigenous to the oil-productive formation with those of samples from upper, water-bearing formations within the same general area. Some earlier investigators recognized the need for Analyzing samples of all waters encountered in drilling operations. Ambrose15/ stated, in part, "In wells being drilled, the engineer should grasp every opportunity to get a true sample of water from each sand. . .," and, "The waters of each oil field are chemically different from those of another field." The validity of the latter observation and the importance of the former one have been borne out by comparing the results of analyses of many samples and noting the differences in relative concentrations of like constituents of waters from the a geological formation in different localities or oil pools.

Jan 1, 1957

By N van Aarde, B A. Moore, S van der Merwe

Frequently materials handling operations are compromised by transfer chute problems ranging from high wear rates, blockages and ineffective loading of the downstream conveyor. This paper will present the design flow implemented to overcome problems in two case studies utilising discrete element modelling incorporating material characterisation.Material testing is relevant in achieving a valid discrete element method (DEM) simulation model and subsequently a valuable design tool for transfer chute assessment and design. It is well recognised that in the current growth and demand for mineral resources, leading to ever increasing conveyor capacities associated with export terminals and mineral processing facilities that transfer chutes are a key focus point. The successful performance of the transfer chute is also dependent on operating with a ærobust rangeÆ of material flowability and handling characteristics. This requirement is crucial in accommodating mineral ores from developing resources, which are often more friable and stickier than in past decades.This paper will include details of chute installations associated with iron ore and coking coal, from the DEM simulations through to the performance of the installed and commissioned plant.CITATION:Moore, B A, van der Merwe, S and van Aarde, N, 2013. Implementation of advanced transfer chute designs, in Proceedings Iron Ore 2013 , pp 445-450 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By J Law, S Jahanshahi, R Holmes

Iron ore is AustraliaÆs largest commodity export and is vitally important to AustraliaÆs current and future prosperity. However, while major expansions are currently in progress to satisfy demand, the industry is also undergoing major transformations. Reserves of traditional high-grade Brockman ores that have underpinned the Australian iron ore industry since its inception are slowly being depleted and alternative ore types such as Marra Mamba bedded iron deposits, Yandi and Pannawonica channel iron deposits and magnetite deposits are now being developed. However, the impurity levels in some of these alternative ores are higher and they require blending and/or upgrading as well as an advanced knowledge of their downstream processing characteristics to facilitate cost-effective utilisation by overseas customers. The research challenge is to use advanced techniques for mineral exploration, ore characterisation, mineral beneficiation, agglomeration and sustainable processing to identify and develop innovative and breakthrough options for locating, unlocking and enhancing the value of AustraliaÆs iron ore resources. Furthermore, to sustain the steel industry and hence secure the demand for iron ore, there is a growing need to enhance the environmental and business performance of the industry through reductions in wastes and emissions. Therefore, cost-effective breakthrough and enabling technologies that massively cut waste generation, CO2 emissions and water consumption are also being developed. These include the use of renewable fuels and reductants, waste heat recovery and conversion of by-product slag into a saleable substitute for Portland cement. A number of examples of recent developments in the above areas are provided in this paper.CITATION:Holmes, R, Jahanshahi, S and Law, J, 2013. Research and innovation for the iron ore to carbon steel value chain, in Proceedings Iron Ore 2013 , pp 3-6 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.Low-sulfidation epithermal gold mineralisation at Ridge Mountain occurs within the Oligocene to Miocene volcanic rocks comprising andesite, porphyritic dacite and diatreme breccia. A diatreme breccia complex with a NE–SW elongated orientation covers an area of 3.0 × 1.7 km. Four main stages of mineralisation were identified, comprising: E–W- to NW–SE-trending quartz-chalcedony veins with disseminated pyrite, chalcopyrite and gold. N–S- to NNE–SSW-trending breccia veins with quartz matrix and disseminated pyrite and accessory sphalerite, galena, chalcopyrite and gold. NE–SW-trending quartz and calcite veins with disseminated pyrite and accessory sphalerite, galena, chalcopyrite and gold. ESE–WNW- to ENE–WSW-trending quartz veins with disseminated pyrite. This stage is only mineralisation that is hosted by diatreme breccia and clearly postdates.Quartz veins of the first, third and fourth stage are less than 2 m wide. Only breccia veins of the second stage are up to 10 m wide. Gold is present in all stages as microscopic inclusions in quartz and sporadically in pyrite. Macroscopic gold can be seen in the first and second mineralisation stages. Gold commonly occurs in association with sphalerite, galena and chalcopyrite in the second and third mineralisation stages.CITATION:Kucera, J, 2015. Diatreme breccia-hosted epithermal gold deposit at Ridge Mountain, eastern Mindanao, Philippines, in Proceedings PACRIM 2015 Congress, pp 587–592 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By David C. Oyler

The Bureau of Mines conducted research at the 9-Right Section of the Olga Mine to determine the cause of bumps and aid in the development of appropriate control techniques. The purpose of this paper is to identify the factors which affect the occurrence of bumps at the Olga Mine. These factors have been broken down into two categories, in situ and mining related. The in situ factors include those conditions which exist prior to mining, such as variations in lithology and overburden, presence of jointing, the composition and the physical properties of the rock, and the original stress field existing in the coalbed and adjacent strata. The mining factors include the mining sequence, changes in stress in the coalbed and adjacent strata during mining, rates of convergence, and the pattern of failure of the coal and adjacent strata. The factors which appeared to have the greatest effect on bumping were the overburden, the lithology of the roof and floor rock and the physical properties of the rock. The roof rock is generally a massive, stiff sandstone which does not break until coal pillar extraction is complete. The immediate floor is a strong shale which generally grades into siltstone and then into sandstone. The overburden at 9-Right ranged from 990 to 1,600 ft. Secondary factors appeared to be the in situ (pre-mining) stress and the mining sequence. When barrier pillars were split., pressures measured in hydraulic cells (Borehole platen flatjacks) located in those barriers showed large pressure increases, and the incidence of bumps increased, especially when the barriers were near old gob areas. The pillar extraction system used at Olga, where three rows of pillars are mined concurrently, appears to reduce pillar loads at the face areas, thereby reducing the exposure of men and equipment to the risks of bumps during mining operations. The horizontal components of in situ stresses at Olga were found to be nearly the same as those at 5 other mines in southern WV, where humps were not common, so it appears that horizontal in situ stress alone is not a major influence on bumping at the Olga Mine.

Jan 1, 1987

By M Wimmer

LKAB operates two underground iron ore mines located in the northern part of Sweden, both using sublevel caving (SLC) as the mining method. Knowledge of the mechanisms of gravity flow is important since it affects both ore recovery and waste dilution. This paper describes results from a large-scale field test carried out at the Kiruna mine with a focus on gravity flow. It is part of Work Package 2 in the I2Mine project financed by the EU. A total of ten rings were blasted. Smart Markers based on radio frequency identification technology were used to monitor the gravity flow. An accurate delineation of the isolated extraction zone requires reliable detection of all recovered Smart Markers and precise knowledge of the 3D position of the markers within the burden. It was therefore necessary to carry out borehole deviation measurements (collar, alignment and trajectory). The blast performance was monitored by high-speed filming, near-field vibration monitoring and velocity of detonation measurements. Three-dimensional stereo images were taken from the drawpoint and the loaded bucket after each mucking cycle. Based upon that, fragmentation was assessed both in 2D and 3D. Furthermore, volumetric differences were determined at the drawpoint, which reflects the mobility of loaded material. For draw control, the Fe content is estimated by measuring weight and assuming a full bucket. The measured volume of rock in each bucket further improves this estimate. Possible flow disturbances occurring at the drawpoint were revealed by video recording. Two-dimensional laser scanning was carried out during mucking to track the position of the bucket and estimate the position and slope of the muck pile.The results from this test clearly show that the gravity flow in the large-scale sublevel cave in Kiruna mine is often of disturbed character. Standard draw occurred only in three rings and shallow draw in the remaining seven rings. In five cases, shallow draw developed towards standard draw, but occurred at rather late stages during extraction (70–125 per cent). The maximum width of the draw varied between 10 m and 13 m except for one ring (6 m). The draw reaches the cave rather early (5–25 per cent extraction) in shallow draw situations and much later (about 50 per cent) during standard draw. Waste originates from above in most cases, while more significant portions often occur at about 20–45 per cent extraction.All the results from this extensive field test are not yet fully analysed, and further field tests are planned. A more detailed insight into gravity flow in large-scale SLC and possible influence by drilling, blasting and the mucking procedure is expected in the future.CITATION:Nordqvist, A and Wimmer, M, 2016. Holistic approach to study gravity flow at the Kiruna sublevel caving mine, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 401–414 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By David Allen

Cable bolting is a relatively new strata reinforcement technique that has been used successfully in Australia and the United Kingdom. Jim Walter Resources, Inc. has examined the principles and can visualize its useful application in many areas, such as: a) Longwall pull-out areas, b) Roadway junctions, particularly those involving yield pillars, c) Rib reinforcement, and d) Possible replacement of cribbing in roadways, especially longwall tailgates. This paper describes the conditions which led to cable bolt testing, the results of tests conducted to date, and conclusions about the direction that Jim Walter Resources, Inc. is heading as far as testing and potential applications are concerned.

Jan 1, 1994

By Greg Hendon

Various methods have been used to evaluate the effectiveness of shields in place. The most common method used is static recording of leg pressures by visually examining pressure gauges. In an effort to more closely examine the shield cycle and therefore the shield effectiveness, Jim Walter Resources has implemented a program of monitoring utilizing a polycorder system which is capable of recording convergence and pressure measurements on a continuous basis. This paper will discuss two longwall panels at Jim Walter Resources which have been monitored.

Jan 1, 1990

By M. Rakoma

Following the blasting fatality on 17 December 2009, Landau Colliery was forced to change from the blasting practices that had been utilized since the start-up of the mine. Since then, attempts have been made to optimize blasting results. The challenge is rooted to the mining environment - during the early life of the mine, mining took place in virgin areas, whereas currently mining is taking place in areas overlying old underground bord and pillar workings. The underground bord and pillar workings aggravate phenomena such as spontaneous combustion, hot holes, and sinkholes. The 2009 fatality was attributed to hot holes causing premature detonation. Landau has been struggling with poor results from their overburden and coal blasts; leading to poor fragmentation of overburden and the PI parting that lies between the No.1 and No.2 coal seams. An extensive literature survey was completed in order to identify possible alternative solutions that could be evaluated for this unique mining environment, which demands a high degree of caution during mining to ensure factors such as dragline stability and personnel safety. The literature survey confirmed that the previous blasting technique, which was mainly characterized by air decking, was indeed the more efficient, although it was deemed unsafe because of the possibility of hot holes and the high sensitivity of detonators. Potential modifications to the blasting technique were modelled in a Microsoft Excel simulation that was available from the mine, and pit visits were conducted in order to determine whether implementation would be a problem. From the model it is evident that results can be improved by changing the current burden and spacing ratio. Visiting the pit revealed that the tie-in pattern and drilling inaccuracies are contributing to problem areas.

Jan 1, 2013

Introduction Research has shown that when an emergency occurs, work-ers often do not get the information they need to take appropriate action. Important information about incidents is either not com-municated effectively or not at all to those affected by the event. The "Emergency Communication Triangle" safety talk focuses on the content of emergency warning messages. It presents a procedure using mental cues that can be used by senders and receivers of emergency warnings. The talk includes graphics for use during the presentation, as well as references for more information. Background Interviews with 48 miners who had escaped one of three different underground mine fires revealed that warning information provided to them was inadequate. Either insufficient information was provided to miners inby the fire areas or they failed to ask the questions needed to let them plan and execute an effective escape. Most of the miners who evacuated from these three mines did not have information that would allow them to make decisions about efficient escapes. The communication breakdown came from two directions: (1) the individuals providing the warning did not offer details about the situations even though some were known and (2) the individuals who received the warnings did not ask for clarification of the situation. The lack of information allowed miners to continue attempting to place cues into normal frameworks after they should have evaluated the situation as abnormal and threatening. The uncertainty created by the lack of information influenced their decision-making and therefore their actions. Approach Researchers at the NIOSH Pittsburgh Research Laboratory have developed a training intervention that can be used by senders and receivers of warnings during a mine emergency. This material was developed for use in short safety training sessions such as start-of-shift safety talks. The information can be presented in about 15 minutes. Although the illustrations were taken from the underground coal mining industry, the training can be tailored to any work setting by substituting appropriate examples. How It Works During the safety talk, miners learn about the six categories of critical information that should be provided during emergency communications: Who, Where, What, Miners, Event, and Response. • Who: When reporting an emergency or receiving a warning, the first thing a miner must do is identify himself or herself. This is important because people react differently based on who gives them information. • Where: Giving or finding out the location of the problem is important. Of the 48 miners interviewed about their escape, only 2 knew where the fire was located. However, this information was known by either the dispatcher or the person who discovered the fire. • What: Miners must tell or ask exactly what is happening. At one mine fire, miners near the phone heard the message to evacuate and went to gather the others on their crew. One worker shouted to a machine operator: "Come on down to the mantrip. We're going out." Because it was close to quitting time, the machine operator thought they were just leaving the section a little early and went through his normal end-of-shift routine, wasting valuable time. After giving or obtaining the three initial pieces of critical information, miners can then give or obtain details about the response in progress. • Miners: Is anyone hurt? Has everyone been accounted for? When and where was a missing person last seen?

Sep 1, 2004

Norway, a country large in area but small in population, has put large effort in protect- ion of its inhabitants in case of war. The Civil Defence has provided shelters for more than 50% of the population. Some of these shelters are put into rock. Since rock installations give large resis- tance against weapon effects and also by advan- tage can be used for several purposes in peace- time, an interesting development has taken place the last decades. In towns and cities you will find sport halls, swimming pools, bowling and shooting ranges etc in rock, which easely can be conver- ted to civil defence shelters. Some typical installations are highlighted in the following.

Jan 1, 1987

By Dennis R. Dolinar

In general, the direction of the maximum horizontal stress in the eastern United States is fairly well defined. However, the variation of the magnitudes of the horizontal stresses is not very well understood. Because the horizontal stresses cause severe ground control problems in underground coal and limestone mines throughout the eastern United States a more complete understanding of how the magnitudes vary would be useful for developing mine design strategies to combat horizontal stress related ground control problems. Therefore, in this National Institute for Occupational Safety and Health (NIOSH) study, the variation of the magnitude of the horizon stresses in sedimentary deposits in the eastern and Midwestern United States are examined with respect to two factors, the elastic modulus of the rock and the site depth. Stress measurements from thirty-seven sites are used in the evaluation. Examining the applied excess strains indicates that the eastern United States can be, separated into high and low strain zones. For most of the eastern United States the maximum applied excess or tectonic strain ranges from only 300 to 550 micro strains. However, there is one area, a portion of the Beckley seam in the central Appalachian region where the strains are significantly higher than the other regions. In this higher strain zone, the maximum applied tectonic strains range from 700 to 1,000 micro strains. Regression models for each zone based on the elastic modulus can explain between 83 to 85% of the variation of the maximum horizontal stress. Because one region, the northern Appalachian district, has strains that are about 20% higher than the other regions in the low strain zone, multiple strain models based on geographic regions were developed for the low strain zone that can explain 87 to 91% of the maximum horizontal stress variation with the elastic modulus. Depth was found not to be a significant causal factor in any increase in the horizontal stress even though the site depths ranged from 275 to 2,500 ft. Beyond a theoretical increase, based on Poisson’s effect and gravity, no other increase in the horizontal stress with depth can be justified with this data. The most significant factor controlling the variation of the maximum horizontal stress is the elastic modulus of the rock, not the overburden depth.

By K. C. Ko, M. D. Bunnell

The studied coal mi1e is an underground coal mine located in the northern Wasatch Plateau of central Utah (Figure 1) . Since operation began in 1981, in situ stress conditions have been encountered which differ from the assumed conditions utilized during early mine design efforts. Geologic structures also varied somewhat from those projected during initial geologic interpretations of the area. The encountered geologic conditions combined with the unusual stress conditions prompted a combined study of in situ stress and stress-related geologic structures. The study was conducted in two phases, with phase 1 consisting of detailed underground mapping and analysis of stress-related geologic structures to determine stress orientations from which they originated; and phase 2, consisting of over- coring two sites within the mine to determine present in situ stress orientations and magnitudes. GEOLOGIC ANALYSIS Three types of geologic structures have been encountered in the mine that act as indicators of stress orientations of the geologic past. Two of these structures, faulting, and igneous dikes, are directly measurable in the mine. A third type of structure, photolineation, was detected through remote sensing methods and shoe god correlation to roof conditions in certain areas of the mine. Faults Two major orientations of faulting have been encountered in the studied coal mine, including a system of N 80 W striking normal faults and a system of N 55 to 70 W striking oblique-slip faults. Only data collected from the oblique-slip faults were used for this study due to the fact that these faults offset the N 80 W faults wherever the two systems intersect, indicating that the N 55 to 70 W system was created by a more recent stress field. Figure 2 shows locations within the mine where data were collected from seven locations along oblique-slip faults. Data collection consisted of measurement of fault plane strike and dip, fault slickenside trend and plunge, and slip direction. The data are tabulated in Table 1. The fault data were then plotted on stereo nets to determine the stress orientations present at the td of faulting (Figure 3). The determined stress orientations are 32~0 included in Table 1. The stereo net plots show average principal stress orientations of: 1) [ ] plunge 1 degree. These data suggest that the N 55 to 70 W oblique-slip faults were produced by a nearly

Jan 1, 1986

By Roberto Balarini Junior

Tribological behavior of Si3N4 balls sliding against Al2O3 discs in water was investigated by studying the influence of parameters such as initial surface roughness and circular axial run-out of the discs. The objective was to relate these parameters with the occurrence of the phenomenon known as ultra-low friction coefficient (ULFC), which is characterized by µ < 0.01, including the correlation with running-in duration. As a general trend, greater initial surface roughness and circular axial run-out resulted in greater running-in duration. In addition, it was verified that a mixed lubrication regime (hydrodynamic and boundary) is required to guarantee the occurrence of ULFC by comparing the calculated minimum film thickness with the composite roughness of the worn surfaces. Also, ICQ-OES analysis of the water after the tests indicated that a silicon concentration greater than 1.3 mg/l should be fundamental for the occurrence of µ < 0.01.

Jul 31, 2018