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By M. S. Raseroka

An experimental rig has been constructed to produce chloride stress corrosion cracks in Type 304L stainless steel tube samples. The samples are to be used to test possible in situ repair methods in future work. The factor which influences the time to failure most strongly is the sample temperature; the distribution of cracks within the sample is affected by local temperature variations and by the position of the water line. Low-frequency oscillations in stress, caused by the on-off temperature controller, did not appear to influence cracking in these tests.

Jan 1, 2009

By G. Vijaya Kumar, B. Srinivasa Rao, G. V. Krishna Rao

The paper outlines the ventilation practices prevailing in coal mines of Singareni Collieries Company (South India). The high annual average surface temperature and relatively steep geothermic gradient results in virgin strata temperatures in the region of 38- 42°C creating environmental problems in the working places. Expensive methods of air cooling can not be employed as the mines are small, and production and productivity do not justify the costs of artificial cooling of mine air. Controlled recirculation of mine air -- the unconventional technique being tried with success in some coal mines in U.K. has been analysed for improving the environmental conditions. The analysis shows that the method is safe, cost effective and can be applied with very little extra equipment.

Jan 1, 1991

By Kwang-Tae Kim, Yong-Kun Choi, Jeong-Soo Chong, Yun-Jae Lee

An annex building at the former Agency for National Security Planning(NSP) complex located in downtown Seoul was demolished by progressive collapse method. This work was done as a part of efforts to restore the landscape of Namsan Mountain which lies in the Center of Seoul. The five-story reinforced concrete structure was razed in 5.5 seconds by the 29kg of high powered explosives which were placed in some 320 holes in the building with floor area of 2,577 m². The asbetos and all the other finishing materials in the building were removed before the demolition and the specially coated wrap minimized the spread of blasting dust. Seismic and air overpressure waves were monitored at 8 points, which were below safety limits and the continuous communication with neighborhood prevented any complaint.

Jan 1, 1998

By Douglas M. Deason

Swelling clays, such as montmorillonite, contribute significantly to the poor dewatering and consolidation behavior of the Florida phosphate clay wastes. Understanding and to a degree, control of the forces which cause the swelling behavior may aid in supplying a solution to this problem. The technical feasibility of utilizing control- led dispersion for aiding dewatering of phosphatic slimes was investigated. This technique is based upon inhibition of swelling and self-dispersing tendencies of the montmorillonite clays by dispersing the solids in electrolyte solutions. Through this process, significant improvements in settling rates and sediment solids content were achieved in both pure clay systems and on simulated phosphate slimes.

Jan 1, 1983

By D. M. Deason, G. Y. Onoda

Phosphate clay wastes, as currently produced, leave montmorillonite clay in a highly dispersed and disintegrated form. Alternative processing, where the extent of swelling and self-disintegration of such clays is controlled or limited, may result in improved settling and consolidation behavior. In this study, a method to control montmorillonite dispersion, through preservation of clay tactoids, was examined. Through this process, significant improvements in settling rates and sediment solids concentrations were achieved in both pure clay systems and on simulated phosphate clay wastes.

Jan 1, 1985

By Edward Fitch

The DOE is evaluating Yucca Mountain, Nevada as a potential site for disposal of high level nuclear waste. Yucca Mountain is located approximately 160 km northwest of Las Vegas on the western edge of the Nevada Test Site and the Nellis Air Force Range. An exploratory tunnel has been constructed through Yucca Mountain for site characterization. A controlled drilling and blasting technique, smooth wall blasting, was used to excavate the TBM starter tunnel and alcoves off the main tunnel to provide areas for scientific investigation. Fundamental to the blasting program has been the use of two blast design equations used in concert to minimize blast damage to the surrounding rock mass. The first of these equations was developed by Roger Holmberg and estimates near-field peak particle velocity that is the basis for minimizing blast damage to the host rock. The second of these equations was developed by B. H. Sanden and provides bore hole pressure estimation which allows controls to minimize crushing of the rock mass along the perimeter yet allowing enough force to create tensile failure between perimeter bore holes. This is key to the smooth wall blasting technique. To date, essentially the same controlled drilling and blasting program has been in place for all excavation requiring controlled drilling and blasting at the ESF. The controlled drilling and blasting program uses an iterative process to achieve continuous improvement in the blast rounds. This involves interaction between Architect and Engineer (A/E), Constructor, and Testing Coordination O&e (TCO) to ensure each blast round successfully meets the expectations of affected participants. The A/E requested that the TCO provide validation of the near-field peak particle velocity estimation under the Construction Monitoring Program. Data gathered under this program were reduced by statistical analysis and used to verify blast design parameters and provide a site specific blast damage relationship.

Jan 1, 2000

By Scott L. Burrill

In the past 100 years in the mining industry, many references are made to the "Widow Makers", 'Miners Con" and many other derogatory names related to physical hazards. They reflect the lack of understanding of the problem facing the early day miner. Workers were enticed, in some cases, to take a chance against a medical question mark that could not be explained by the doctors of those early days. The optimism of the mining man and the challenge of work led him to believe that the physical results could not apply to himself and only applied to some of his fellow workers. Much of the time, to his dismay, he found that he had lost to the game of chance. As medical knowledge improved and mining management began to understand the effects of conditions in the mines and beneficiation plants, steps were taken to alleviate or eliminate the health hazards that were present, The organizations engaged in mining that did not take an active interest in employee health found themselves to eventually be placed in the position of being forced to take action by Federal and State legislation. We find ourselves in the 1970's on the threshold of a new era where the general public is concerned vociferously about "their" environment and the industry feels the governmental controls more strongly than ever before. It can be said that in the past 100 years we have advanced from the "Widow Makers" of the 1870's to the "Retirement Makers" of today. The difficulties of the early days in underground mining were of times compounded in the beneficiation plants above ground. As late as the 1950's some crushing and milling installations in the United States were operating under environmental conditions that complied to the then existing legislation but were below the health level sought by conscientious management. The Mission Concentrator Crushing Plant was designed in 1959 and placed in operation in July, 1961. In the past ten years the crushing plant has been continuously complimented by technical people, government inspectors and casual

Jan 1, 1971

By Ken Fiorentino, Gordon F. Revey

H3 Tunnelers recently excavated two conventional 48 foot diameter highway tunnels through the Halawa side of the Tran-Koolau Mountains on Oahu. The primary blast design challenge on this Job was minimizing overbreak In the alternating layers of pahoehoe and aa lava, clinker, end tuff. Two different excavation techniques were evaluated in the Halawa tunnels. The first method used drilling and blasting to excavate the tunnels to within one foot of their final perimeter. A roadheader, mounted on a backhoe, was then used to excavate the remaining foot of ground. The second method used conventional smoothwall blasting techniques, without any mechanical excavation. This paper describes the details and relative success of the two excavation methods tried in the Halawa tunnels.

Jan 1, 1993

By Ulrich Leiste

If the iron ore loss is 15% in the process of mining, the total iron ore loss in the world will be about 461 million tons, this is equal to the total production of 230 iron ore mines each of which produces 2 million-tons of iron ore per year. Based on a series of blast tests in the Malmberget mine, this paper shows that ore recovery can be markedly increased by improving blasting technology such as choosing a correct primer position and making use of shock wave collision. The paper further suggests that a high ore recovery can not only reduce natural resource loss and mining cost but also prolong the life of a mine. In addition, the paper shows an example of reducing blast-caused rock damage in the roofs and walls of underground drifts (tunnels) by using new blasting methods in the Malmberget mine. Finally, the paper shows how the Malmberget mine has successfully reduced the ground vibrations, without adversely affecting fragmentation and ore recovery in sublevel caving mining.

Jan 1, 2014

By N Elith

The explosives demolition of a post-stressed, steel reinforced, concrete road bridge in Australia’s capital city, Canberra. The bridge was 50 m from the new replacement bridge, 320 m from community structures and within five kilometres of the national parliament buildings. The job required multiple overlays of risk assessment, public relations, safe work procedures, specialised blast design, environmental predictions and flyrock controls. Project stakeholders included Worksafe, Roads ACT, bridge owners, consulting structural engineers, community groups and road users. The bridge precincts, including a major road underneath, had to remain operational to peak traffic in the days leading up to the demolition. The break-up and removal of debris had to be executed in just two days from Friday to have the road beneath re-opened for Monday morning city-bound traffic.In Canberra, all explosives demolitions are now viewed with particular caution after a demolition in 1997, during which a young girl was killed. Any approval requires that Explosives Regulations, AS2187 2006 and Worksafe processes are satisfied, and a convincing case presented for blasting as a safe and viable option.Our design used specialised shaped cutting and blasting charges to sever in situ concrete beams and tendons and to shatter components of the stressed concrete bridge assembly. We include comments on structural engineering reports dealing with pre-weakening mechanisms. The benefit of pre-weakening is that it reduces the amount of explosives needed to safely complete the job and facilitates quick removal of debris after the shot. The complementary skills of the team, each one an expert in his field, resulted in a highly successful demolition, praised by authorities as an outstanding example of controlled use of explosives.

Nov 8, 2011

The processes by which particles and bubbles interact capture many of the central concepts of colloid science and hydrodynamics. This area of research embraces hydrodynamics, interfacial(including capillary) forces, particle and bubble behaviour and solution chemistry. In this review, we discuss collision, attachment and stability efficiencies. We deal with the identification of a flotation ?domain?, the deformation of a bubble surface upon interaction with a solid surface, the kinetics of three phase contact line expansion and the determination of attachment efficiencies through to the direct measurement of bubble-particle interaction forces. We have recently carried out a test of collision theory where the latter embraces both inertial and centrifugal forces. The real challenge is now to quantitatively describe the behaviour of real systems and to incorporate a reliable description of the behaviour of particles in flotation froths. The approach described is very robust when applied to flotation, both from qualitative and quantitative points of view, providing an intellectual foundation for understanding this complex process in separation science and technology.

Jan 1, 1999

By John A. Shuster

INTRODUCTION Controlled ground freezing for mining and construction applications has been in use for over a century. Despite the great technological evolution which has occurred during this period, ground freezing is still used on projects today with much the same basic technology as that used originally over 100 years ago. Major developments have occurred in the separate fields of frozen soil mechanics, refrigeration, and heat transfer analysis. However, except for a few projects in Europe and Asia, these developments have not been combined to upgrade ground freezing techniques to their potential level. In view of this situation, it is believed desirable to examine the art of ground freezing in light of recent technical developments, together with highlights on some of the apparent advantages, disadvantages and economics of the various alternative approaches. The purpose of this paper is to attempt such an examination, with particular emphasis on the practical application of presently available technology. GENERAL ADVANTAGES AND DISADVANTAGES Ground freezing may be used in any soil or rock formation, regardless of structure, grain size or permeability; however, it is best suited to soft ground rather than rock conditions. Freezing may be used for any size, shape or depth of excavation and the same physical plant can be used from job to job despite wide variation in these factors.

Jan 1, 1997

By R. A. Matuszak

Throughout the history of power excavating machines, engineers have continuously tried to shape the main drive speed-torque characteristics to provide an optimum performance from each main motion. Selection of prime mover for the various motions has been the subject of many engineering studies and most forms of energy conversion have been tried. A new form of electrical power conversion looms on the horizon' as the most optimum yet. Controlled frequency operation of a squirrel cage induction motor increases the reliability of the most reliable form of energy conversion (electrical) found thus far and at the same time improves the performance characteristics.

Jan 1, 1977

By R. A. Matuszak

Abstract-Throughout the history of power excavating machines, engineers have continuously tried to shape the main drive speed-torque characteristics to provide an optimum performance from each main motion. Selection of prime mover for the various motions has been the subject of many engineering studies and most forms of energy conversion have been tried. A new form of electrical power conversion looms on the horizon as the most optimum yet. Controlled frequency operation of a squirrel cage induction motor increases the reliability of the most reliable form of energy conversion (electrical) found thus far, and improves the performance characteristics.

Jan 2, 1978

By R. A. Matuszak

Throughout the history of power excavating machines, engineers have continuously tried to shape the main drive speed- torque characteristics to provide an optimum from each main motion. Selection of prime mover for the various motions has been the subject of many engineering studies and most forms of energy conversion have been tried. A new form of electrical power conversion looms on the horizon as the most optimum yet. Controlled frequency operation of a squirrel cage induction motor increases the reliability of the most reliable form of energy conversion (electrical) found thus far, and improves the performance characteristics.

Jan 1, 1979

By M. Ganster

Austria’s biggest supplier of oil and gas, transports gas through the West Austria Gasline for domestic consumption. In addition, the OMV also works as gas carrier and ensures the transit into neighbouring countries.

Jan 1, 2010

By A. K. Isaac

The effectiveness of coalface powered support depends upon its structural nature and the manner of application of the hydraulic system. A critical and largely unresolved feature of the system is the optimum setting pressure level at which a support should operate in its geological environment. This paper provides an argument for a generalised approach to the issue of setting pressure level quoting case study data for a high output British longwall installation.

Jan 1, 1984

By N. Kuyucak

Uranium ores leached with sulphuric acid typically have poor dewatering properties. Applicability of controlled neutralization where gypsum precipitates as crystalline particles, improving dewatering properties of material was examined. Neutralized material was then dewatered using paste thickener to increase underflow density. The objectives are to maximize water recovery due to water scarcity and to produce suitable cemented paste fill material for optimizing underground ore recovery. Work was performed on acidic slurry samples collected after leaching but before the resin-in-pulp uranium recovery. Controlled neutralization greatly reduced volume of neutralization precipitates giving higher densities and improving the dewatering (filtration) properties. As a result it would be possible to increase the water recycled to the mill. Another benefit is that sulphate in the recycled water was reduced to saturation limit minimizing scaling of process equipment. Additional test work is needed; however, Unconfined Compressive Strength results imply that controlled neutralization increases the strength of paste fill and possibly offers opportunities towards a viable backfill option.

Jan 1, 2010

By Leszek Maldzinski

The present concept assumes carrying out the process of controlled nitriding with NH3 alone. This is a simpler process than that using two-component mixes of ammonia diluted with N2 or NH3diss. The regulation of the chemical composition of the atmosphere in the retort, and therefore the regulation of the nitriding potential KN, is obtained through the variation of the inflow rate of NH3 into the retort. What is a completely new things in a relevant process, the inflow of NH3 into the furnace is at times reduced to zero, which widens the range of the gas composition in the retort (and by the same token, of KN). The amount of NH3 introduced into the furnace is regulated (controlled) with the aid of a gas analyzer (for example an infrared analyzer). The gas analyzer opens and closes periodically the NH3 inlet valve with a frequency maintaining a desired gas composition (a desired KN) in the retort. The concept was based on experimental and theoretical investigations in term of thermodynamic and kinetic of gas nitriding. Investigations were carried out in a laboratory furnace with a quartz tube and also in an industrial furnace with a steel retort and a circulating fan. Nitriding was performed using NH3, NH3+H2, NH3+NH3diss. mixtures. In an industrial furnace the supply of NH3 into the retort was periodically closed, though with an operating circulation fan. The studies demonstrated that the growth rate of nitrided layer depends only on the composition of the atmosphere, (or KN), in the retort. It depends neither on a type of atmosphere introduced into furnace (NH3, NH3+NH3diss. or NH3+H2) nor a type of furnace (laboratory with a quartz tube or industrial with steel retort and fan). The results proved also that entirely closing of NH3 supply to the retort does not affect the growth rate of nitrided layer. A detailed analyses of the results was performed in a paper.

Aug 16, 2017

A brief review of the problems in ventilating and cooling deep and hot Australian mines is presented. An overview is given on the development of the controlled partial recirculation concept. The main part of this paper describes the first majo

Jan 1, 1994