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By S. McAlister

This paper outlines the development of the Falcon enhanced gravity separator. Design objectives included continuous operation with sharp separations, mechanical simplicity, minimization of process water demand, the ability to apply a centrifugal field up to 300G's, unit capacity in excess of 100 t/h within a footprint of 10 square meters, a capital cost below $US 4,000 per t/h capacity, and total operating costs of less than $US 0.40 per tonne. A parallel development has been inexpensive, effective, semi-continuous equipment for recovery of precious metals in the free metallic state. These objectives have been largely met. There are significant opportunities for the technology in many mineral processing applications.

Jan 1, 1998

By Alden B. Carpenter

Oil-field brines have been collected and analyzed from Jurassic and Cretaceous rocks in the Mississippi Salt Dome Basin, from Jurassic and Lower Cretaceous rocks, southwestern Arkansas, and from Ordovician and Silurian rocks, southern Michigan. All of these brines are genetically related to evaporites and appear to be brines expelled from halite-bearing rocks, presumably during compaction. The brines in rocks closest to the halite-bearing rocks are uniformly low in lead and zinc suggesting that the metals in metal-rich brines are not acquired within evaporite sequences. The metals in metal- rich brines in Mississippi and in Russia appear to be derived from red beds and may have been originally associated with ferric iron oxyhydroxides. Reduction of these compounds by migrating hydrocarbons appears to release lead and zinc to the associated brines accompanied by the fomation of authigenic ankerite.

Jan 1, 1979

By Daniel de la Rosa, Juan Manuel Mayoral, Damián Vital

"This paper presents a numerical study regarding the loads, and the corresponding damage, taken by the primary and secondary lining of a tunnel built in cemented fine-grained stiff soils. This study aims at establishing more rational design criteria that take into account explicity the lining performance. A 3.5 km long tunnel to be built in a densely populated northwest area of Mexico City, was considered as case study. Series of three-dimensional finite difference models, developed with FLAC3D, were used to simulate the tunnel construction, and to compute the ground settlements, internal forces, bending moments, and displacements acting both on the primary and secondary tunnel linings. Interaction diagrams were used to study the lining performance. Several advancement lengths, and tunnel covers were considered to establish their impact on the loads transferred to the tunnel lining. A practice-oriented damage criterion for tunnels was proposed based on the interaction diagram analysis. INTRODUCTION Lining performance during conventional tunnelling, CT, as defined by the International Tunnel Association, ITA (ITA 2009) is strongly affected by the construction procedure. Special attention must be taken in cemented fine-grained materials, such as those found in the northeast portion of Mexico City, due to the potential of fragile failure (i.e. the soil fails suddenly without important deformation) that these soils may exhibit. During CT, it is assumed that the ground strength contributes to the stability of the excavation, as long as the lining is built correctly. It is common practice to consider two structures, which together form the tunnel support: 1) A primary lining, which is a flexible support, which allows excavation walls to deform to mobilize part of its shear strength, and thus contributes to the tunnel self-stability, and 2) A secondary lining. Commonly, the primary lining consists of several layers of shotcrete. In this case the installation method guarantees perfect contact between the lining and the excavation perimeter. The secondary lining, if required, is used to withstand the load conditions in the long term and also has an esthetic function. This paper presents a numerical study aimed at establishing a performance damage criterion for the primary and secondary lining design in cemented fine-grained stiff soils. Due to the lack of data, the strength and deformation parameters were established through empirically-derived relationships. Three-dimensional finite difference models were developed to simulate the tunnel construction, and compute ground settlements, internal forces, bending moments and displacements acting both on the primary and secondary tunnel linings. Interaction diagrams, along with a damage criterion were used to study the lining performance. From the results gathered insight was gained regarding tunnel lining performance during CT."

Jan 1, 2016

By A. Toulet

Mining in Mexico has an immensely long tradition. In his first letter reporting to his sovereigns from Mexico in July 1519, Hernan Cortes wrote, "To our mind it is probable that this land contains as many riches as that from which Solomon is said to have obtained the gold for the temple ... " 1 But not only precious metals drew his attention; in 1524, short of tin needed for casting guns, he found it in Taxco. As an added bonus, those who went to find it "came upon a vein of iron which according to experts is of exceeding richness." 2 Since then, the mines of Mexico have yielded up enormous amounts of mineral and continue to do so. Mexico is one of the ten principal producers of minerals world-wide both in production volume and diversity. 3 Tens of thousands of tons of iron, sulphur, and coal come from its earth annually; it is the world's second largest producer of barite; third of antimony, fluorite, and graphite. 4 Copper, zinc, silver, molybdenum, arsenic and cadmium and others are wrested from its mines. The wealth is there; but maximizing its potential requires investment, technology, and markets that the government cannot itself provide. Thus mining, since the Mexican Revolution severely restricted by both law and policy, today looks to private investment to develop its potential. Beginning in 1989, Mexico's government cautiously moved to liberalize private sector involvement in mining; 5 using the experience gained from these initial regulatory changes, the current new Mining Law was adopted in 1992 6 and new Regulations were promulgated in 1993. 7

Jan 1, 1994

By G. H. Harris

The flotation behavior of two high sulfur coals using a non-ionic surfactant as collector from two series of compounds containing oxygenated functional groups was studied in detail using a 2-liter Denver flotation cell. The performance of these reagents was compared with that of an oily collector, namely dodecane. The results showed that at the same coal recovery, a much lower dosage of these non-ionic surfactants was required as compared with that of dodecane. More import was the performance of these compounds as promoters for oxidized as well as un oxidized coal. Mechanisms of interaction of these compounds with the coal are suggested.

Jan 1, 1993

By Frank C. Stevens

Many changes have taken place in the "World Cement Market" since Joseph Aspdin discovered portland cement in the early 1800's. At the turn of the century, production of cement world wide was a few million tons; today, it is over one billion tons. By 1995, world production is estimated to reach 1.2 billion tons. Cement processing has changed from inefficient, small vertical kilns to large efficient, precalcining kilns, and large automated crushing, blending and grinding systems. Consequently the cost of production has declined in real terms, resulting in significant economic benefits to the general public. In addition, quality and uniformity of cement have increased, strengths have increased, and at least 25% fewer pounds of cement are needed for each cubic yard of concrete. Today, cement moves thousands of miles on the inland rivers and great lakes of the U. S., across Siberia and across the oceans of the world. The volume of cement moving more than a few hundred miles is almost 100 million tons, or 10% of world production. Today, on a per ton basis, it costs no more to move 40,000 tons of cement to the United States from the Western Pacific rim or from Europe than it does to truck cement 200 miles. For example, cement shipped by water from Spain costs $5.00 to $7.00 per ton compared to cement shipped by truck 200 miles at $16.00 per ton. This low cost water transportation has been a major factor for the increased movement of cement between countries. Table 1, Cement Production Summary-World, gives a global picture of production, export and import tonnages in recent years. Figure 1 is a graph showing CEMENT PRODUCTION SUMMARY WORLD WIDE.

Jan 1, 1987

By S. J. Lefond

Most people, when Borates are mentioned, mentally visualize the famous twenty mule team (really eighteen mules and two horses), trudging across the Mojave Desert or "she burns green Rosie, we are rich." Actually, however, the first use of borax was prior to Babylonian times. Their emissaries had orders to bring borax Iron the Gobi desert for use as a flux by the Babylonian goldsmiths. The borate mineral imported for this is not known but probably was borax. The ancient Persians and Arabians knew about borax and the Arabic word "Baurach" appears in a two thousand year old manuscript. The Sanscrit word for borax was tincana which has been corrupted to tincal. The Chinese were using borax as a glaze in three-hundred B.C. Marco Polo brought the first borax, along with gunpowder and spaghetti, from Mongolia to Europe in the late 1300's. Borax from Tibet was imported to Europe for nearly 500 years. In 1772 boric acid (sassolite) was discovered around Tuscany, Italy as a precipitant from volcanic steam vents. Production of boric acid started there about 1815 and provided the sole competition to the borax from Tibet. Borate deposits in Turkey have been known and exploited on a small scale since the 13th century. It is only recently that the operations are being modernized and production increased. About 1836, borax minerals were found in Chile and Argentina with borax production starting in 1852 in Chile and in Argentina in 1886. During the latter half of the 19th Century, Chile was the principle world producer of borax.

Jan 1, 1980

By M. A. Qianjie

The problems of coalmine safety in china remain unsolved for decades. Starting with the description on safety status quo of coalmine in china, different existing analysis and measures discussed for the safety problem solution of coalmine china. With the consideration of system thought in mind, the author present with a unique systematic reason analysis method on such actuality--individual analysis and general analysis--each for its particular purpose. Upon such cause analysis, construction of the safety system is made clear and, solutions for such problems provided.

Jan 1, 2006

By M. Vesely

Abrasive grinding, leading to ultrafine product and "critical size" material build-up inside the mill, is proposed as the cause of high power consumption and low capacity in many fully autogenous grinding processes. Addition of steel balls (hence, semiautogenous grinding) or pebble removal and separate crushing have been used, with different efficiencies, to overcome the problem. Information and data for the conceptual analysis, basic design and operation of a pebble crusher at the Los Bronces semiautogenous grinding plant is presented along with data showing a production increase of 1000 mtpd and significant operating costs savings.

Jan 1, 1985

By Andrew C. Katen

The mining industry faces increasing geopolitical risk in the coming decades. Constraints such as resource nationalism, corruption and social license could grow to outweigh fundamental limitations like geology or supply and demand (Ernst & Young, 2013; Verrastro et al. 2010). Lurking beneath these more immediate and palpable concerns, however, may be more significant risks entrenched in geography and history. Deep-rooted cultural and strategic forces that emerge slowly ? or erupt suddenly and unexpectedly ? can generate momentous and far-reaching political, social and economic changes. While multinational enterprises routinely assess for political risk, the nature of minerals extraction means long-term and systemic geopolitical conditions are especially important for mining companies to identify and understand. Mine development is a decades-long process that binds companies to the land and makes changing course to avert emerging threats a difficult and costly option. Consequently, geopolitical assessment is a pertinent and valuable tool that mining companies can use to more comprehensively evaluate strategic threats and opportunities. Geopolitics is the study of society, politics and strategy through the lens of geography (Gray, 1996). Its emphasis on relatively permanent physical features of the earth makes geopolitics a uniquely valuable tool for assessing political risk. Topography, climate and natural resources have shaped, constrained and motivated peoples and governments throughout history. These influences transcend regimes, policies and borders ? and even states themselves ? which, by contrast, change often and dramatically. Framing politics against mountains, deserts and rivers supports identification of historical patterns and forecasts of emerging trends. In other words, the physical map provides an objective and consistent model for studying a subjective and dynamic subject such as politics (Sloan and Gray, 1999). Consequently, geopolitical assessment can highlight threats and opportunities that go unaddressed by other risk methodologies that emphasize current conditions (Glancy, 2012). Taken together, the permanence of geography, hindsight afforded by centuries of political history, and interconnectedness of world events makes geopolitical assessment a valuable approach for conceptualizing strategic risk.

Mar 1, 2014

By G. Włoch, E. Rudnik

The oxide fraction of industrial zinc ash was characterized in terms of chemical and phase composition, leaching behavior in sulfuric acid solutions, and leaching thermal effect. The waste product contained about 68 percent zinc (Zn), 7 percent chlorine (Cl), 2 percent aluminum (Al) and less than 1 percent other metals, such as iron (Fe), manganese (Mn), calcium (Ca) and silicon (Si). It consisted mainly of zinc oxide contaminated with metallic zinc and zinc hydroxide chloride. The dissolution of metals from the zinc ash was determined for solid-to-liquid ratios ranging from 100 to 500 kg/m3, acid concentrations of 10 and 20 percent, and temperatures of 20 and 40 °C. The best result — 130 g/dm3 Zn(II) at 95 percent zinc recovery — was obtained at a solid-to-liquid ratio of 200 kg/m3, sulfuric acid concentration RI SHUFHQWDQGLQLWLDOWHPSHUDWXUHRI ƒ& 7KH¿QDOVROXWLRQVZHUHFRQWDPLQDWHGPDLQO\E\0Q ,, DQG)H ,,, ions, but the presence of cadmium (Cd(II)) and lead (Pb(II)) ions enabled electrowinning of zinc of about 99 percent SXULW\DWKLJKFXUUHQWHI¿FLHQF\RI WR SHUFHQW /HDFKLQJRIWKHPDWHULDOZDVDQH[RWKHUPLFSURFHVVZLWKUHDFWLRQ heat of about 520 kJ/kg

By Thomas S. Nye

Mineral exploration in the United States relies heavily on theoretical geologic concepts and indirect methods such as geophysics and geochemical prospecting, as there are few exposed areas of mineralization which have not already been explored at least once. In Mexico ore-grade samples can be cut at the surface on vein, replacement, and disseminated types of deposits in many areas. Here the problem is not in finding a mineralized area but in deciding which mineralized area can be explored and developed at the least risk and cost, and have the greatest profit potential, within the framework of Mexican mineral economics and government policies. Mexico's min¬eral industry is regulated through a system of permits for various phases of mineral exploitation, and by taxes. This regulation and its effects are not unlike those which may be expected in the United States if present legislative and administrative trends continue.

Jan 1, 1972

By James P. Odendahl

Missouri is a state rich in mineral commodities. There is a variety of types of mining as well as minerals in the state. Different phases of mining are controlled by a variety of state and federal laws. What I hope to do today is to present briefly some of the interaction and interplay that has occurred in the recent years between the mineral industry and the Missouri regulatory agencies, as well as some of the interactions by federal agencies. First a little history which dates back to the late 1600's. For many years Missouri has been a leader in the production of lead and zinc. In fact, recent studies have indicated that Missouri produces better than three-fourths of the nation's present lead supply. Less well known but important resource is iron mining. Some of these operations were the source of confrontation during the Civil War. Major battles were fought in and around Ironton, Missouri where iron mining has occurred for many years. One of the largest pelletizing operations in the state is currently located within the city of Ironton. Joplin, Missouri, the home of Thomas Hart Benton, the famous Missouri painter, has a history of lead and zinc mining, going back to the later 1800's. Many of the paintings by Benton contain reference to the early days of mining in Missouri. There is a Benton mural in the City Hall at Carthage depicting the early days of lead mining in that area. Later, the center of lead mining moved to southeast Missouri near Bonne Terre and Flat River. The names of the towns in this area reflect the history of mining, examples - Leadington, Old Mines, Rivermines, etc. The history of lead mining in Missouri has been referred to in some detail in various publications(l).

Jan 1, 1977

By P. Zhang, S. Al-Thyabat

"Phosphate rock contains traces of rare earth elements (REEs) and can be a secondary source of these critical materials as large tonnages of phosphate rock are mined annually. Attention has mostly focused on the extraction of REEs from phosphogypsum, which contains more than 70 percent of the REEs reporting to phosphate concentrate, with only limited work conducted on REE extraction from sand tailings and slime even though they account for 16 percent and 15 percent, respectively, of REEs mined with phosphate matrix.In this work, phosphate flotation tailings were upgraded by gravity separation and froth flotation. Gravity separation was conducted using a laboratory shaking table, while flotation was conducted in a Denver D-12 flotation cell. The concentrated tailings were then leached by nitric acid followed by REE extraction with solvent and ion-exchange resin.The sand tailings were assayed as having 2.6 percent phosphate (P2O5 ) and 198.1 µg/g REEs. It was found that the shaking table could produce tailing concentrate assayed as having 8.6 percent P2O5 and 616 µg/g REEs but with only 20 percent REE recovery, while the froth flotation produced froth concentrate assayed as having 8.1 percent P2O5 and 368.2 µg/g REEs with 63.5 percent REE recovery. Leaching the flotation concentrate with 5.2 M (25 percent) nitric acid followed by extraction with solvent and ion-exchange resin yielded precipitates with REE contents of 0.926 and 0.314 percent, respectively, compared with 0.716 and 0.213 percent when table concentrate was used.IntroductionRare earth elements (REEs) consist of a group of 17 elements: the 15 lanthanides along with yttrium (Y) and scandium (Sc). They are rare not because of their scarcity in the Earth’s crust but because they are rarely found in economic and mineable deposits. REEs are called “seeds of technology” because of their importance to some critical technological industries such as renewable energy, hybrid cars, electronics and batteries. On average, an electric car or a hybrid car contains about 10 kg of REEs (Grasso, 2012; Radhika et al., 2011).REEs are usually categorized into light (LREE) and heavy (HREE). LREEs consist of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pr), samarium (Sm), europium (Eu), gadolinium (Gd) and scandium (Sc), while HREEs consist of terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) and yttrium (Y). About 200 minerals contain traces of REEs, but only three are considered economically significant: bastnasite, with the formula La,Ce(CO3)F; monazite, with the formula(Ce,La,Nd,Th)PO4; and xenotime, with the formulaYPO4 (Jordens, Cheng and Waters, 2013)."

Jan 1, 2016

By K. Galos

The paper presents increasing importance of mineral secondary and waste raw materials in the minerals management in Poland. Definition of mineral secondary and waste raw materials is proposed, according to current Polish law. On this basis, sources of various types of mineral waste raw materials are analysed. The special attention is paid to the wastes from mining and processing, wastes from power plants, and wastes from steelworks and other smelters. Other types of waste and secondary materials, such as metallic containers, glass containers, batteries, metallic wastes and scraps, are also taken into account. Analysis of sources of such materials is shown together with the main directions of their economic use. Available sources of information on manufacture and use of the mentioned secondary and waste raw materials are also analysed. Finally, for a wide range of waste materials, their current and expected significance as substitutes for some industrial and construction minerals in Poland is given.

Jan 1, 2011

By David B. Brooks, Roger L. Williams

Control of the environment is as old as mining. Engineers have always had to consider how best to deal with the surface, and the character of the surface environment always affects mining method in some way. However, if the relationship of the mine to the environment is old, today's approach is new. For one thing, land, air and water formerly could be viewed simply as obstacles to be overcome or resources to be utilized to win ore at the lowest possible cost. Now we have come to realize that these nonmineral components of the environment also are highly valuable. For another thing, environ- mental protection has become a public policy issue. Again, a special public interest in land and land use is old. From the firs(, the crown claimed extra rights in valuable minerals, and to this day a multitude of laws and regulations control-and tax-land use in every country. What is new is the detailed public attention bring given to waste management practices, whether these wastes be in the form of solids, liquids or gases, and regardless of where in the environment they appear. (It is convenient to lump all mining environmental problems, including hank fires and subsidence, together under the term "waste management," for in effect that is what they are.) As a result of these changes, the mining engineer must consider that lie is dealing with two productive resources the minerals and the remainder of the environment-and he must expect that lie will be judged not only on his efficiency in recovering the one but also on his effectiveness in protecting the other. Further, in seeking to protect the environment, the modern mining-environmental engineer has a dual role. First, there is the obvious task of finding better ways for industry to cope with waste-management problems in actual operations. Second, there is the less obvious but equally important task of helping formulate appropriate public policy objectives for the environment. Throughout; the section it is assumed that mining is an acceptable land use for the tracts under consideration. The question of whether mining will be permitted at all on these tracts is a further public-policy issue, ultimately to be resolved politically and thus, since it is beyond the scope of engineering, is not a subject that can be usefully discussed in a mining handbook. Finally, none of the statements in the section are predicated on the assumption that required waste-management measures will be privately profitable in the conventional sense. Indeed, the reverse is more likely to be the case-at least if accounts are kept so as to include all appreciable costs and a normal rate of return on investment in waste-disposal and reclamation equipment.',',' However, it is clear that improved waste management will be required of mining firms and that, to a considerable although undetermined degree, this expenditure is in the best long-run interest of both public and industry. The several studies that have attempted to quantify the impact of mining on the environment are admittedly rough but still provide enough information to indicate that there is a big job to be done. For example, something approaching 7,000 mi of stream in Appalachia alone are continuously or significantly affected

Jan 1, 1973

By E. Steel

The asbestifom habit is most commonly developed in certain amphiboles and chrysotile, but other minerals may also crystallize with this unususual habit, The habit may be characterized by 1) a fibril structure, single or twinned crystals of very small widths (generally less than 0.5 inn) which have gram with a common fiber axis direction but which are disoriented in the other crystallographic directions, 2) anomalous optical properties, primarily parallel extinction, 3) unusual tensile strength, 4) high aspect ratio, and 5) flexibility. In addition, there is evidence to indicate that some amphibole asbestos may have unusual surface properties.

Jan 1, 1979

By Christopher R. Winter

Mining companies have sharpened their refocus on their tailings management strategies in recent years. Mining companies with tailings storage facilities that use the upstream construction method have been challenged to track the evolution of industry standards, assess risks, revise design, and communicate design revisions with regulators. While many aspects of best practices and industry standards have evolved in recent years as an attribute of continual improvement, the controlling standard in the design of many upstream dams is understanding the foundational strengths of hydraulically deposited tailings. Following best practices and industry standards, Hibbing Taconite Company managed by Cleveland-Cliffs, began the re-evaluation of foundation strengths underlying a system of upstream dams at the company’s iron ore mine tailings storage facility in northern Minnesota. Initial steps in the re-evaluation require reanalysis of design parameters and recommendations by the Engineer of Record to the Owner, which was followed by a series of meetings with the Technical Review Board to determine an initial path forward. Once a path forward and preliminary design parameters were determined, the Owner engaged with the State Dam Safety Engineer to discuss and seek approval of the plan. With continuous regulatory engagement throughout the process, further refinement of the design parameters for the hydraulically-placed tailings foundations underlying upstream dams began with field and lab geotechnical investigations. Following a review of risk assessments and trigger actions response plans, Hibbing Taconite revised its tailings storage facility operating plans and budget for the coming years. Based on the findings of the re-evaluation, reanalysis, and refinement of parameters, a paradigm shift was realized with the hydraulically placed tailings foundation strengths underlying the upstream system of dams. This paper explores the path that the Hibbing Taconite Company followed to understand the paradigm shift and construct downstream improvements. The plan involved tailings re-characterization, dam design revisions, operating plan reconciliation, budget revisions, wetland permitting, dam safety permit amendments, storm water prevention plans, borrow materials studies, new concrete decant structures and the pursuit to recognize and be consistent with industry standards.

Feb 1, 2024

By Tim Neil, O&apos

Introduction On the banks of the Columbia River, about halfway between Seattle and Spokane, sits Wenatchee, WA. It calls itself "the apple capital of the world." And it has a gold mining history that dates back to the 1880s. It was just outside Wenatchee - three blocks outside, to be exact-that Asamera recently dedicated its $60 million Cannon underground gold mine. At full production, it is estimated the Cannon mine will yield between 5 and 5.6 t/a (160,000 and 180,000 oz per year) of gold. That would make Cannon the largest North American underground gold mine to be brought into production this year. Cannon should also be among the top 10 of all North American gold producers. Asamera officials project Cannon's operating costs at about $4.8019 ($150 per oz). At that rate, the mine should also be one of the lower cost and most profitable gold mining operations in North America. One reason for low operating costs is low electric power costs. The Cannon operation will be paying about 2.5 cents per kWh for hydroelectric power supplied by the Bonneville Power Authority. Proven and probable ore reserves at Cannon are in excess of 4.7 Mt (5.2 million st). Reserve grades average 7.29 g/t (0.21 oz per st) of gold in three ore zones, in order of discovery - B, B West, and B North. The ore bodies could have been mined by open-pit methods. But underground mining was chosen for environmental reasons. In addition, the rich B North ore body extends beneath a nearby horse stable and arena. The Cannon mine area comprises some 20 km2 (5000 acres) in Chelan County. The mine site is located at the 305 m (1000 ft) elevation in Dry Gulch at the base of the Cascade Mountains. The initial estimate of mine life for the Cannon operation is eight years, depending on gold prices. But Asamera officials believe the Wenatchee area has excellent potential for future gold discoveries. Asamera, Inc. of Calgary, Alberta, owns 51% of the Cannon property, through its wholly-owned Asamera Minerals (US). Breakwater Resources Ltd. of Vancouver, British Columbia owns 49% of the operation. The Cannon mine is named in honor of longtime Asamera, Inc. executive and current company director, geologist Donald G. Can¬non. It was he who first brought the Wenatchee property to Asamera's attention and urged the company to pursue it. Asamera is a major explorer and producer of oil and gas. Its Cannon operation is the largest and most significant to date in its mining division, according to Rob¬ert G. Welty. He is Asamera's chairman and chief executive officer. It should be noted there was an element of serendipity involved in Cannon's development. The development program be¬gan when geologist Cannon visited the Wenatchee area. He was visit¬ing old mining districts. He liked what he saw. The Cannon property was eventually optioned for ex¬ploration, including a modest drilling program.

Jan 12, 1985

By P. H. S. W. Kulatilake

The presence of discontinuities strongly affects the mechanical and hydraulic behavior of rock masses. Joint geometry networks play a vital role in civil, mining, and petroleum engineering projects associated with jointed rock. The need for a realistic representation of joint geometry in rock masses has been recognized. The first part of the paper shows how to build three-dimensional stochastic joint network schemes and also shows how to perform validation studies for these schemes using joint data from the Stripa mine, Sweden. Due to the existence of complex joint patterns, mechanical behavior of jointed rock masses usually exhibit scale effects and an-isotropic properties. A correct understanding of the mechanical properties (strength and deformability) of jointed rock masses is important for designing and performance estimation of structures build in and on rock masses. Beyond a certain volume, the mass proper-ties of the rock may remain essentially constant with respect to the effect of joints. This minimum volume may be used as the element size to represent the equivalent properties of a statistically homogeneous rock mass volume which contains a significant number of joints. This volume may be termed as a "Representative Elementary Volume" (REV) and may be of great importance for engineering purposes. Investigations are underway at both the 2D and 3D levels to look into the possibility of establishing relationships between REV mechanical properties and joint geometry parameters. Recently developed joint geometry modeling schemes are linked with existing distinct element codes (both 2D and 3D) to create a stochastic/deterministic stress analysis approach in achieving the goal. Results obtained so far in this direction are presented in the second part of the paper.

Jan 1, 1992