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By Ambarish Ghosh, Chitralekha Ghatak, Tanumaya Mitra, Tarun Sengupta, Sajib Das, Sankar Kumar Nath

"Currently construction of important structures like bridges, flyovers and high rise buildings in and around Kolkata are in full swing. These structures have mostly pile or well foundations. The design methodology and construction techniques are being employed keeping in view both the safety and economy of the project. The data presented in this investigation have been taken from Geotechnical Investigation report of Component B in connection with construction of Extradosed Cable Stayed Bridge over River Hooghly in Hooghly and Nadia district of West Bengal, India. The investigation site is located within close proximity of Eocene Hinge Zone which is being taken as the principal contributor of Earthquakes in and around Kolkata. Considering the importance of the project detailed and exhaustive geotechnical investigation has been carried out and site specific response spectra have been generated for analysis and design of the bridge. This paper presents site specific response spectra, liquefaction analysis and comparison of lateral load carrying capacity of pile using Winkler approach and IS 2911 guidelines.INTRODUCTIONPile foundations are used to transfer the load of the super structure through soft soil deposit to deeper bearing stratum by means of skin friction or end bearing or both. Pile foundations are regarded as a safe alternative for supporting structures in seismic areas and have been used for this purpose in non-liquefying as well as liquefying soils. But their design in case of potentially liquefiable soil is quite different from that of non liquefiable soil. In liquefiable soil the progressive buildup of excess pore water pressure will cause stiffness degradation and loss of strength which in turn will induce additional shear force and bending moment in the pile. The mechanism of pile behavior in liquefying soil has been investigated by several investigators in the recent years based on observations of pile performance during earthquakes and studies in the centrifuge and Shake Table tests. Exhaustive geotechnical investigation has been carried out along the proposed alignment of the Extradosed Cable Stayed Bridge i.e., along Baropara, Bansberia ROB, Ishwar Gupta Bridge, Saraswati River to collect disturbed as well as undisturbed soil sample, to develop average soil profile and to determine the design parameters. The proposed project site is very close to Eocene Hinge Zone, which is basically a strike slip fault, capable of generating an earthquake of Mw 6.7. Thus it is evident that the proposed Bridge needs to be designed considering the adverse geo-hydrological condition as well as the earthquake aspects needing special attention following the state-of-the-art technology as guided by relevant codes and published literatures. Considering the soil profile of these locations ground response analysis has been carried out using equivalent linear method to determine the site amplification. Site specific response spectra have been developed for the four zones and zone factors have been determined. The computed zone factors are 0.198g, 0.195g, 0.195g and 0.20g for the four zones respectively, much higher than the zone factor 0.16g, which is for zone III, as stipulated in IS 1893:2002."

Jan 1, 2015

By Donald W. Mitchell, John Nagy, Edwin M. Murphy

"Investigations in the Federal Bureau of Mines Experimental coal mine near Pittsburgh, Pa., have shown that high-expansion foam containing at least 0.2 ounce of water per cubic foot of volume is effective in controlling exper-imental underground coal, oil, or wood fires. Some of the fires were extinguished, but more of the coal and wood fires were brought under enough control to permit direct attack with water or other extinguishing agent or loading the hot material into cars. The largest controlled experimental fire, which burned about 5 hours before attack, was in a coalbed 5 feet wide, 10 inches thick, and 100 feet long. The greatest distance foam was transported to control a fire was 1,010 feet.An incipient fire should be attacked promptly with water, rock dust, or other approved and readily available extinguishing agents. Where heat, roof falls, and smoke prevent direct approach, the more involved procedure of using foam may be advantageous. The effectiveness of the foam in controlling a deep coated fire of considerable extent H,vet to be proved by actual trials in aSome hydrogen, carbon monoxide, and methane gases are generated when a fire is attacked with foam. Calculations showed that in experimental fire tests an explosive mixture could form; however, this would occur only within a narrow range of combustible gas-air mixtures not likely to be found in practice. The principal explosion hazards are due to generation of gases by the foam, localized build-up of normally liberated methane, and volatiles liberated by the coal during heating. The quantity of combustible gases generated by the action of the foam on the fire is about the same as that when an equivalent amount of water is applied."

Mar 1, 1960

By José Fernández Dávila Borja

El presente texto señala la eficacia del uso de la fluorita como reactivo de concentración por flotación desarrollado en la mina Canaria de Ayacucho, Pozos ricos, Mansita y San Agustin, donde el fluor como elemento más electro negativo del grupo de los halógenos, ataca a todos los metales excepto al oro y al platino, posilbilitando la limpieza de superficie de los minerales, así como el uso del bario, metal alcalino-térreo, que en su forma de Baritina o sulfato de Bario ha sido utilizado en la "prueba de descarte", concluyendo que la frecuencia del comportamiento de la fluorita, prueba la influencia positiva de esta en la flotación de los valores metálicos.

Nov 20, 1978

By P. J. Nicholson

The methods of reinforcement to be discussed in this paper are all insitu methods, ones that can be used on the soil structure as it exists in the ground, and do not rely on excavation and replacement of the soil. Current practice in the United States, as well as new ideas and methods, will be discussed as they relate to slope stability, retaining walls, and to other uses such as control of mine or cavity related subsidence and to liquefaction control under existing structures. The method is based on the concept of "nailing" or reinforcing the soil in place, and thereby causing a mass of soil to act as a coherent unit. When performed properly, a true gravity structure can be constructed, one that will remain intact under both horizontal and vertical loadings and that will also resist vibrational and seismic loadings.

Jan 1, 2010

By R. L. Nyirenda

An investigation of the reducibility of a cassiterite concentrate with charcoal was made in the temperature range of 1123-1373 K. The course of the reaction was monitored by a combination of sample weight loss measurements, product gas analysis, and chemical analysis of the reaction product. It was found that the cassiterite could be best reduced by a combination? of high temperature, reasonably high charcoal proportions, high charge poroslty, and the addition of a small percentage of lime. Analysis of kinetic data obtained from isothermal experiments using theory from the oxidation of carbon by carbon dioxide gave an activation energy value of 255 lci/mole for the consumption of carbon by reaction with cassiterite.

Jan 1, 1990

By William Bergeson

"BACKGROUND As of December 2015, there are roughly 475 road tunnels within the United States according to the most recent national tunnel inventory data compiled by the Federal Highway Administration (FHWA); whereas, there are more than 615,000 highway bridges on public roads. The FHWA estimates that tunnels represent nearly 100 miles of Interstates, State routes, and local routes. Tunnels are part of the national transportation infrastructure and represent a significant financial investment for the owner and, hence, the tax payers. Tunnels, that are not properly maintained, usually require more extensive repairs and consume more resources. Tunnels must provide safe, reliable, and effective transportation even as these structures age and deteriorate. Furthermore, tunnels generally remain in service for extended periods of time due to their very high construction costs. For example, many tunnels were constructed decades ago during two historic periods of highway system expansion; the first period correlated with the era of public works programs linked to the Great Depression of the 1930-40s; and the second period of expansion occurred with the building of the interstate highway system in the 1950-60s. As such, these tunnels are fast approaching 60 to 80 years old. Congress enacted the Moving Ahead for Progress in the 21st Century Act (MAP-21), which was signed by the President on July 6, 2012. This legislation followed a fatal tunnel incident on July 10, 2006 and a National Transportation Safety Board (NTSB) report1 that noted the importance of conducting regular tunnel inspections. MAP-21 authorized the Federal Highway Administration (FHWA) to develop a mandatory inspection program for all tunnels on all public roadways (Bergeson and Ernst 2015): To help safeguard tunnel users and to ensure reliable levels of service, the FHWA developed the National Tunnel Inspection Program (NTIP), which is comprised of the National Tunnel Inspection Standards (NTIS), the Tunnel Operations Maintenance Inspection and Evaluation (TOMIE) Manual, the Specifications for National Tunnel Inventory (SNTI), and the Manual for Bridge Evaluation (MBE). The data collected from the program will be stored in a National Tunnel Inventory (NTI) database. A comprehensive and refresher training program was also developed to help qualify and certify key tunnel inspection personnel to include the program manager and team leader."

Jan 1, 2016

By R. J. Durrheim, Y. Yabe, M. S. D. Manzi, DSeis team, N. Z. Nkosi, S. B. Mngadi, Jr. H. Ogasawara

On 5 August 2014, the Orkney M5.5 earthquake, the largest in South African gold mining districts, occurred with an unusual strike-slip mechanism at great depth of 4.78 km below the surface. In a rare case, the ML 5.5 earthquake occurred within the area covered by the legacy 2D and 3D reflection seismic data acquired in the 1990s and 2000s for gold exploration and mine development. In addition, the earthquake ML 5.5 rupture plane was recorded and accurately delineated by the underground in-mine seismic network near the source region. The integration of the legacy 2D reflection seismic data and mine seismicity data allowed us to identify a near-vertical structure, striking northnorthwest-south southeast (NNW-SSE). The ICDP-DSeis team drilled three holes (Hole A, Hole B, and Hole C), and two holes (Hole B and Hole C), intersected the upper edges of the ML 5.5 rupture. These holes recovered metasediments, metabasalts, intrusive rocks including dolerite sills and lamprophyre dykes adjacent to the fault zone, and the fault gouge. Late Prof. Tullis Onstott and geomicrobiologists installed a packer in Hole A and successfully recovered saline water and detected gas (~10 MPa). Slip weakening and rupture propagation are significantly influenced by the existence of fault gouges and the production of wear material between two sliding rock surfaces. Using the fault gouge material recovered from Hole C, we conducted friction experiments under dry and room temperature conditions at high slip velocity of ~100 mm/s and normal stress of 2 MPa. The resulting steady-state frictional strength was ~0.66 over a slip weakening distance of ~9.1 m. The steady-state frictional strength was high, which may be caused by large gouge thickness, and the rate of wear generation. As a result, it is proposed that the Moab Khotsong ML 5.5 seismogenic zone is complex and could be controlled by three main processes: a) the complex structural architecture of the seismogenic zone (e.g., intersection of fault, lamprophyre dykes, and dolerite sills); b) the mechanical process induced by tectonic and/or mining related stresses; and c) the mechanical and chemical processes caused by the water and rock interaction.

Jan 12, 2025

By T. P. Weldum, W. Conger

"These studies address the relationship between mill media sizing and its grinding efficiency. Starting with the results from a review of the literature, the issues of initial media sizing for a new ball milling circuit, and then optimal media sizing for an existing milling operation, were studied. The Functional Performance parameters “Mill Grinding Efficiency” and cumulative “Mill Grinding Rates” from both plant and test-scale equipment were used, and provide valuable new insight into this topic. A plant media sizing diagnostic tool is presented, as are newly developed testing equipment and evaluation methods, and recent case studies. REVIEW OF MEDIA SIZING LITERATURE For a plant metallurgist to answer the question “How can I maximize plant profit by manipulating this grinding circuit variable?” she must know what effect the variable has on grinding circuit efficiency. Despite the significant cost of grinding media and its potential effect on production capacity, the ‘best’ media sizing remains ill-defined for any given ball mill circuit in the industry today. The underlying reasons for this will be discussed. But the importance of this issue drove Metcom and its industrial partners to take on the challenge of how to engineer the ball charge for an existing grinding circuit. In the absence of any proven method, the first step was a review of the literature. Sponsored by Cleveland-Cliffs, Inc., a broad review of the literature was undertaken, producing “The Effect of Media Sizing on Ball Milling Efficiency” (McIvor, 1997). Among hundreds of publications that were reviewed that discuss the topics of media sizing or wear, forty-five were studied in detail. These were grouped into: plant experiences; laboratory and pilot plant investigations; media wear studies; population balance modeling studies; and general papers on ball milling which included the topic of media sizing. The reader is encouraged to refer to that review. The findings remain unchanged, although some relevant papers have been written since (e.g. Staples et al, 1997; Banasi et al, 1999; Orford et al, 2006; LaMarsh, 2015). The main findings of the review were as follows."

Jan 1, 2018

By A. R. Sheik, A. A. Baba, M. K. Ghosh, K. Sanjay, R. B. Bale, A. G. F. Alabi, F. A. Adekola, L. Ibrahim

"This paper studies the characterization and dissolution of a Nigerian pyrolusite ore, reporting the results of ore physicochemical analyses and detailed ore characterization before and after leaching at optimal conditions. Ore dissolution rate increased proportional to acid concentration and temperature, but decreased with ore particle size. In a 4 M H2SO4 solution at 80°C with a particle size of –90+75 µm and moderate agitation, ore dissolution rate reached 78.7%. Unleached residue produced under optimal leaching conditions consisted of silica with admixtures of cristobalite and stishovite. The calculated activation energy supported the proposed diffusion control mechanism for the process.RÉSUMÉ Le présent article étudie la caractérisation et la dissolution d’un minerai de pyrolusite du Nigeria, il donne les résultats des analyses physicochimiques du minerai et de la caractérisation détaillée du minerai avant et après la lixiviation sous des conditions optimales. Le taux de dissolution du minerai augmentait proportionnellement à la concentration de l’acide mais décroissait avec la taille des particules. Dans une solution 4 M H2SO4 à 80 °C, avec une granulométrie de –90+75 µm et une agitation modérée, le taux de dissolution du minerai a atteint 78,7 %. Les résidus produits sous des conditions optimales de lixiviation étaient constitués de silice avec un mélange de cristobalite et de stishovite. L’énergie calculée d’activation supportait le mécanisme de contrôle de la diffusion proposé pour le procédé."

Jan 1, 2016

By Richard Rothwell

At the last meeting of the Institute, Mr. Per Larsson read a very interesting paper on the Chapin mine of Michigan, in which he described the systems of mining that had, at different times, been tried in that great ore-body, and especially the system now in use, which consists in working the ore out from the bottom upward in lifts. Shortly after that paper was written, but before it had been published, or that I had had an opportunity of reading it, I bad the pleasure of visiting the mine. At that time I was making a profes sional examination of a nnmber of the mines on theGogebic Range, and others in the Menominee region, Michigan and Wisconsin, and had occasion then, as during several previous visits, to study closely the methods and cost of mining in these districts. As the outcome of these investigations, it appeared evident to me that the system of working on the chamber-and-pillar plan, which up to that time had been the only method of underground work adopted in the Gogebic

Jan 1, 1888

By W. Rostoker

Packing Experiments The porosity and most of the other physical properties of a coherent mass of any material built up by the packing together of discrete particles will obviously vary with, and be governed by, the manner of association of the particles. The relation of packing to powder metallurgy has been discussed in some detail by at least two authors. Packing Theory Theories of particle packing have been put forward by C. C. Furnas and A. E. R. Westman. Although their approach to the problem is not the same, their conclusions are similar. In the process of packing, they visualize the voids of a uniformly sized material becoming filled with particles of a smaller size, and the voids between these being filled in turn with still finer particles. Obviously, if this process is carried ad infinitum, the resultant mass will have the same density as the constituent particles. In practice, of course, such a density of packing is never attained. In addition, the premise is made that successive particle sizes must fit into the voids left by the immediately larger particles- an assumption requiring definite size gradations and also particle shapes. It remained, then, for theory to correlate relative diameter ratios, and proportions and numbers of sizes of particles, for requisite packed densities. Briefly, the following principles were postulated: (a) For an infinite diameter ratio between largest and smallest sizes, an infinite number of particle sizes in proper proportion is required to give natural density. (b) For a given diameter ratio, there is a maximum number of permissible particle sizes for maximum packed density (Furnas). (c) Provided the particle shape is spherical, or approximately so, the proportions o particle sizes can be calculated. (d) The ratios of successive diameters of particles are in geometric progression.

Jan 1, 1947

Bernard MacDonald, Guanajuato, Mexico (communication to the Secretary*):—Mr. Iceyes's paper is very interesting to me because of my personal experience with the development of the ore-deposits of Lake Valley.

Jan 1, 1909

By S. Mohanta

In composite washeries optimization of operating parameters to achieve maximum clean coal yield at the desired clean coal ash level is a major problem. This problem is more acute in countries like India, which have predominant reserves of difficult-to-wash coals. The constrained operational parameters of washing for some equipments make it more severe. In addition to this, the dependence of separating performance of different equipments upon various variables aggravates the situation. Here an attempt is made to find a numerical solution to get maximum yield and minimize the difference between the actual and the theoretical yield. The solution is arrived through constrained non-linear optimization of a multivariable objective function that utilizes spreadsheet tools; the method accommodates any number of source coals or washing size fractions. By using a designed Ep value the predicted yield of composite clean coal has been calculated and the yield is optimized subject to constraints on both the ash and specific gravity. It is shown that operational constraints of different washeries in the composite plant that utilizes gravity separation methods can also be over-come. The technique offers the coal preparation engineer an effective and straightforward method for determining the optimum cut-points of separation for different coals or blended coals to obtain maximum product yield at a specified level of ash content.

Jan 1, 2014

By M. E. Wilson

"The property of McWatters Gold Mines, Limited, is in the east-central part of Rouyn township and about 6 miles east-southeast of the town of Rouyn. It includes 35 claims, the group of 5, staked originally, and 30 claims acquired in later years. The Rouyn-Val d'Or road and the Noranda Senneterre branch of the Canadian National railway both pass within a few hundred feet of the mine.The group of claims in which the mine occurs was first staked in 1922, but gold was not discovered until August 1932 when a schistose zone including veins of quartz carrying considerable free gold was laid bare in a stripped area in the northeastern part of claim R.11604. Diamond drilling undertaken in 1932, and continued into 1933, shouwd that the gold extended for at least 1,000 feet along the strike. A 3-compartment shaft was sunk to 418 feet in 1933. A mill having a capacity of 50 tons a day was constructed in 1934, and enlarged to 150 tons in 1935. Production began in 1934 and continued without interruption to June 1944. Except for a few diamond drill holes, there have been no operations on the property since that time. The maximum depth of the mine workings is 1,50) feet. A total of 368,013 tons of ore having a value of $3,946,752 and an average grade of $11.04 was mined during the years of operation.GEOLOGYThe ore mined from the property occurred within the south limb of an eastward plunging syncline of volcanics and sediments cut off on the north by the Cadillac-Bouzan Lake fault. Because the rock formations within the syncline have been severed from those outside with which they were originally continuous, their correlation is based almost wholly on lithological similarity. They include an irregular middle zone of conglomerate and greywacke underlain by north and south bands of andesite agglomerate and andesite tuff, in which lenticular bands of pillowed andesite are included."

Jan 1, 1954

The development of short- and medium-term mine production schedules in isolation from each other has meant that only a local optimum can be achieved when each scheduling phase is carried out. The globally optimal solution, however, can be achieved when integrating scheduling phases and accounting for the interaction between short-term and medium-term activities simultaneously. This paper addresses the task of integrating short- and medium-term production plans by combining the short-term objective of minimizing deviation from targeted mill feed grade with the medium-term objective of maximizing net present value (NPV) into a single mathematical optimization model. A conceptual sublevel stoping operation comprising 30 stopes is used for trialling segregated and integrated scheduling approaches. Segregated medium- and short-term scheduling using separate models achieved an NPV of $42 654 456. The final scheduling approach involved integrating the two scheduling horizons using the newly-developed globally optimal integrated production scheduling model to achieve an NPV of $42 823 657 with smoother mill feed grade. The larger the stope data set, the larger the difference between the two scheduling approaches is likely to be. At the very least, an integrated approach ensures feasibility across the two scheduling horizons, which cannot always be assumed when using a segregated approach.

Jan 1, 2012

By Chao Zhang, Wenhao Xia, Jianxin Fu, Ling Yu, Weidong Song, Yang Li

Sanshandao Gold Mine is the only undersea metal mine in China. To deal with the collapse and pumping of stopes and roadways caused by complex ore-rock occurrence conditions, the mine conducts filling and sealing of some areas, and the remaining ore reserves will be mined after treatment. Therefore, it is urgent to evaluate the stability of rock masses, fault fracture zones, and aquicludes during the secondary mining process. In this study, displacement and microseismic methods are employed to monitor rock deformation and fractures. Additionally, FLAC3D was used to simulate the process of secondary mining, reproducing the evolution of stress fields, displacement fields, seepage fields, and plastic zones at different mining stages. The combination of numerical simulation and on-site monitoring verification demonstrates that the deformation of surrounding rock presents a rapid growth at the initial stage of mining, followed by a gradual decrease in the growth rate, and finally tends to stabilize; the fracture zone area at the 151–159 exploration line on the − 320 m level (near the 7# and 8# stopes) exhibits poor stability, and monitoring measures should be strengthened; the deformation value of the aquiclude is less than the deformation value of I protection level in the Code for Design, the impact of secondary mining on the aquiclude is limited; fault and fracture zone deteriorate rock mass stability, and their impact is related to their spatial locations. Hanging wall fault has a more significant impact on the settlement of the aquiclude, while the footwall fracture zone has a greater impact on the development of the plastic zone.

Feb 21, 2024

By James M. Link

The transportation of solids by slurry pipeline is a rapidly growing field. Although early patents date from the latter part of the nineteenth century, it has only been within the last twenty years that successful long distance slurry transport lines have come into their own. The pioneering efforts in this country include the gilsonite slurry pipeline from Bonanza, Utah, to Grand Junction, Colorado, and the coal slurry pipeline from Cadiz to Cleveland, Ohio. Both of these lines were constructed in 1957 and had a combined annual capacity of about 360 million ton miles. Although the Cadiz pipeline was mothballed in the early 1960's, the interest in slurry transport systems continues to increase and one engineering and construction company is predicting that by 1980 an annual slurry system rate of more than eight billion ton miles will be achieved. The design and construction of cross-country pipelines for fluids such as crude oil appears relatively simple when contrasted against the complex problems encountered in slurry systems. Considerable effort has been expended in hydraulic research laboratories in an attempt to improve our understanding of slurry behavior. This effort has been rewarded with considerable success and is best illustrated by the large number of slurry systems now planned or under construction. However, slurry transport in pipelines is still, in many instance more of an art than a science. In order to minimize the risk factors in the construction and operation of large scale slurry systems, studies are frequently conducted in pilot scale test

Jan 1, 1972

By G Harbort

Traditional engineering design for flotation circuits use the “Rule of Thumb” approach. Typically this uses a nominated maximum head grade for design. A scale-up factor is applied to laboratory flotation tests for residence time. This scale-up factor is usually based on a designers experience at other flotation sites and may or may not be relevant to the circuit being designed, or the flotation equipment being used. A small number of locked cycle tests are assumed to represent the ore body and the results of these are often used for financial analysis, independent of changes in mine plan throughput and mineralogy.The engineering “Rule of Thumb” approach is only strictly accurate where there is very little variability in throughput, head grade and mineralogy. It may provide accurate design for mature established operations where a brownfield expansion is being considered but is unlikely to provide accurate design for a new, greenfield site.The use of geometallurgical modeling with floatability component simulation provides a design methodology with significantly less associated risk. The use of geological data for optimisation of operating plants has become a significant part of the modern process mindset. The underlying principle is to use spatial metallurgical information to drive production planning, mine planning, blast design, blending strategies and plant set-up. At a design stage the process designer can use geometallurgical information to evaluate bottle necks and potential design flaws and propose the best investment strategy for the project benefit.This paper details the geometallurgical characterisation of the Andash deposit and methodology used to review the project’s detail design and projected production.

Aug 8, 2011

By XUEWEN WANG, Changda Zhang, Huaguang Wang, Mingyu Wang, Bin Hu

The copper smelting process produces plenty of copper slag every year, which is a hazardous solid waste, but a secondary resource. In the present study, the extraction of copper, nickel, and cobalt from copper slag was investigated through the process of sulfation roasting–water leaching and the process of sulfation roasting–sulfate decomposition roasting–water leaching respectively. Compared with the process of sulfation roasting–water leaching, the process of sulfation roasting–sulfate decomposition roasting–water leaching is a better choice, which could not only get almost the same leaching of copper, nickel, and cobalt as the former process, but has a lower leaching of iron and aluminum. For the process of sulfation roasting–sulfate decomposition roasting–water leaching, the leaching of Cu, Ni, and Co reached up to 74.2%, 71.1%, and 69.6% respectively, under the optimal conditions including sulfation roasted with 80 wt% sulfuric acid addition at 200 °C for 60 min and sulfate decomposition roasted at 650 °C for 60 min, followed by water leached at 90 °C for 30min with a liquid–solid ratio of 2 ml/g. The leaching of Fe and Al was only 4.9% and 17.6%.

May 4, 2020

By D. Saramak

The proposal of the nip zone angle determination in HPGR crushing process is presented in the paper. Knowledge of the nip zone angle value, in turn, makes it possible to determine the real maximum pressing force in the high-pressure comminution. Two methods of determination of this maximum pressure were proposed and verified. The first method is based on the roll?s geometry, and the change of the HPGR chamber?s volume together with the roll rotation, while the second one considers the outlet gap width impact. Results of the nip zone angle calculations according to both methods are similar and show convergence with the real operating conditions. The verification was carried out in a piston-die press, and experimental results show that methodology of the nip zone angle determination presented in the paper has its practical confirmation. A proper determination of the nip zone border makes it possible to calculate the comminution probability of given type of material and is a basis for the HPGR crushing process modeling and optimization. Keywords: HPGR, comminution, nip zone, ore processing

Sep 1, 2012