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By B. T. Stanley

The basic geological data, derived from boreholes, exploratory test pits, drivages, and mine development, include information on parameters such as ore thicknesses, grades, depths below surface, structural attitudes of beds, rock types, and lithology of beds overlying and underlying the deposit. These data are usually supplemented by analytical information obtained from more detailed chemical, physical, and structural investigations of the various horizons. Even then, the relatively small number of sample points in the ore body and the sparsity of the sample volume make it necessary that the available information be interpolated between sample points and extrapolated into areas beyond the limits of the sample points. Such interpolation and extrapolation are usually done by making suitable assumptions about the parameter's continuity in the ore body and by building a suitable mathematical model. The mathematical model provides the values for chosen parameters at the nodes of superimposed conceptual grids of any desired dimensions such as a grid cell equal to the size of a mining block or any other criterion. This network of values, for any parameter, can then be used for mine planning, designing, and controlling functions. Additionally, these data can also be used to calculate ore reserve and quality in total and/or for any required block. Figs. 1 and 2 broadly illustrate the scope of work that may be involved in a geological ore-body modeling study for a coal deposit. Figs. 3 through 6 describe the scope of a commercially avail- able computerized system (MEDSYSTEM of MINTEC, Inc.) for creating drill-hole data base, mineral inventories, and for planning coal and uranium projects. The application of MEDSYSTEM to calculate reserves and to long-range planning in steeply pitching coal deposits is described in subsection 3.4, Chapter 4.

Jan 1, 1979

By Peter Kolitsch, Galyn Rippentrop

INTRODUCTION On April 14, 1994, the joint venture of Kiewit Construction Company and Kenny Construction Company was awarded a 76 million dollar contract for the construction of the New Hampshire Avenue Tunnels in Washington D.C. The Notice to Proceed was given on May16, 1994 and scheduled completion is September 1997. This project is one of five contracts for the Mid-City E Line as part of the Washington Metropolitan Area Transit Authority (WMATA)Greenbelt Route. Once completed, the Mid-City E Line subway tunnels will connect service between the U Street-Cardozo and Fort Totten stations (See Figure 1). The New Hampshire Avenue Tunnels project consists of approximately 6800 feet of twin single track subway tunnels, three vertical shafts, associated utility work and comprehensive restoration work. Section E4b involved two methods of tunneling along the project alignment. The first method consisted of the well known soft ground open face shield driven tunnel and the second method consisted of tunnels driven using the New Austrian Tunneling Method (NATM) . The NATM section of twin tunnels begins at the Buchanan Vent Shaft and proceeds approximately 2630 feet under Rock Creek Cemetery, including the Farragut Emergency Access Shaft and connects approximately 390 feet beyond to the existing Fort Totten running tunnels (See Figure 2). Special considerations had to be given to the portion of the tunnel alignment which passed beneath Rock Creek Cemetery. The analyses and subsequent selection of the tunnel support system were based on anticipated geological conditions and the sensitive tunnel alignment. The New Hampshire Avenue Tunnels project was the second soft ground NATM project in Washington D.C. The first, by no coincidence, was completed at the adjacent Fort Totten Station and Running Tunnels Project by Mergentime/Hochtief, AJV. Currently, on a nearby WMATA jobsite, the J.F. Shea Construction Company has started a third NATM soft ground tunnel. Tunnel support systems were studied with respect to three tunneling methods: •A one-pass system consisting of a bolted precast concrete segmental lining •A two-pass system consisting of an unbolted precast concrete segmen

Jan 1, 1997

By Robert T. McKnight

Introduction The minerals exploration business, like many businesses, is faced with the problem of valuing future, risky cashflows. These cashflows are derived from those mineral deposits which have been successfully commercialized. Many deposits, however, do not have the quantities or grade of ore to be considered economic at the projected metal prices using the traditional tools of the Capital Asset Pricing Model and discounted cashflow analyses. If one calculates the future revenues, costs and cashflows of one these marginal properties, and discounted it at the appropriate risk-adjusted discount rate, it may have a negative present value. Yet such a property may still have real, positive value in the marketplace. Why would a firm pay money for a property with an (apparent) minus present value? Mining properties such as these are bought and sold in arms- length transactions on a regular basis. Why is this so? Part of the reason relates to the nature of ore reserve information. To generate cashflows, the analyst must t assume that the reserve information is known with certainty when, in fact, reserves are not known with certainty. Mineral reserves are a function of commodity price, extraction costs and the level of (usually drilling) information about the reserves. Stated, or currently known, mineral inventories may vastly understate the true state of nature. Some firms may therefore be buying a property based on a completely

Jan 1, 1988

By J. F. T. Agapito, C. E. Brechtel, C. J. Gilbert, T. R. Kelly, R. C. Karlson

A multi-lift benching cut-and-fill mining method was adopted at Asamera Minerals (U. S.), Inc.'s Cannon Mine to balance the goals of high productivity and near 100 percent recovery with the need to minimize subsidence. High strength backfill was required to provide effective long-term overburden support and safe working conditions during the pillar recovery operations. Operational designs were evaluated using numerical modeling to predict global mine stability and backfill strength requirements. These models incorporated sequential mining of primary stopes, backfilling of primary stopes and recovery of pillars, and have been transferred to the mine operations group for use in evaluating different production sequences. The modeling has provided a better understanding of the structural response of the mine to excavation of the primary stopes and removal of the pillars. Predictions about the transfer of overburden weight to the abutments, pillars and cemented fill pillars have provided a criterion to evaluate mining plans and production sequence. Comparison of these predictions with actual mine structural performance has developed confidence in the design of the mining method and in the geomechanical design methods being employed. Primary mining of the B-North zone is nearly complete, and the stopes have been generally stable, as projected in the original design. Some exceptions have occurred where locally stope pillars have failed due to the presence of adversely oriented sheared beds. Recovery of the pillars between the

Jan 1, 1987

By G. S. Grainger, R. A. Cummings, F. S. Kendorski, R. L. Butts

Georgia Power Company's Rocky Mountain Project, located approximately ten miles northwest of Rome, Georgia, in the Valley and Ridge Physiographic Province, is a pumped-storage facility rated at approximately 800 megawatts of peaking energy. Geological field explorations and borings enabled the division of the rocks along the tunnel and shaft alignment into distinct lithologic units and defined the ground--water regime. Field explorations included a detailed analysis of the rock mass discontinuities at available rock unit exposures. Testing of rock strengths was performed in several phases in both the field and the laboratory. The field testing consisted of point-load testing, geophysical testing, in situ load testing, and hydro-fracture testing. Laboratory testing determined the Brazilian split-tensile strength, the unconfined compressive strength, the triaxial compressive strength, the joint-direct shear strength, and the pulse velocity. The rock mass along the tunnel and shaft was also characterized by empirical classification systems. The classification systems included the Rock Mass Rating (B1IR) and the Rock Mass Strength Determination (RHSD). The results of the field explorations, field testing, laboratory testing, and rock classifications were used to divide the rocks into two structural groups. These rock groups were defined as volumes of rock wherein the rock mass behaves similarly in response to the excavation. Each group, therefore, required separate rock engineering consideration.

Jan 1, 1986

By L. Alan Weakly

The purpose of this paper is to present a viable method of reinforcing rock pillars by utilizing fully grouted reinforcing steel and a cement - fly ash mortar. Although the fully bonded bolt concept is not new, as exemplified by the present widespread use of resin bolts within United States mines and by the use of cement grouted reinforcing used as back pins in the Kiruna Iron Ore Mine in northern Sweden, (1) (2) the method of stabilizing mine pillars with fully bonded reinforcing is new. This method, called the "grout-rebar system", was first incorporated at St. Joe Minerals Corporation’s Fletcher Mine in December of 1972. The system was used on an emergency basis before extensive research on the mechanics of the system could be completed. Since December of 1972, however, approximately 206 pillars have been reinforced at Fletcher and the system is currently being used on a regular basis at two other St. Joe mines and at two competitor mines in the area. Basically, this paper is a case study of the efforts, research and results of utilizing the grout-rebar system, on a selective basis, at the Fletcher Mine. In addition to information about the system, this paper will explain in detail the three rock mechanics instruments developed by St. Joe and used to measure and monitor rock movement to validate the grout- rebar system.

Jan 1, 1977

By Edward J. Zeigler, John T. Miller

INTRODUCTION Construction of Phase I, Section A, of the Baltimore Region Rapid Transit System required that six underground stations be built using a cut and cover excavation technique. For five of these stations, soldier piles, used as support of excavation, were installed with tip elevations well below the bottom of the excavation. However, in the case of the sixth subway station, the Mondawmin Station, soldier piles were installed only through soil and decomposed rock, with the tips of the piles being stopped well above the bottom of the excavation in partially decomposed rock. Below the tips of the soldier piles, and below a cut slope where piles were not installed, the sides of the excavation consisted of partially weathered and fresh rock and were supported by a combination of rock bolts, wire mesh and shotcrete. An extensive installation of geotechnical instrumentation permitted detailed monitoring of horizontal and vertical movements of the soldier piles and the walls of the excavation. Preliminary studies indicated that the excavation support system selected for the Mondawmin Station would have several advantages over a conventional system consisting of soldier piles extending to the bottom of the excavation, braced with prestressed struts. These advantages included lower cost of installation, a decreased time required for installation, and a more open excavation for the contractor during construction of the station. The Mondawmin Station is situated in the northwestern quadrant of Baltimore City, approximately 6.4 km (4 miles) from the center of the City. The station lies midway in a project 12.9 km (8 miles) long identified as Phase I, Section A, of the Baltimore Region Rapid Transit

Jan 1, 1981

By Garland R. Dever

Extensive deposits of high-calcium limestone occur in the Upper Mississippian Warsaw and Ste. Genevieve Limestones in the region of the lower Cumberland, Tennessee, and Ohio Rivers in western Kentucky. Analyses of foot-by-foot samples from 20 quarries and cores in 8 counties show variations between the chemical composition of high-calcium deposits in the 2 formations. Knowledge of probable variations in composition should aid in prospecting for high-calcium stone for a specific use and in evaluating potential deposits. High-calcium strata in the Warsaw consist of bryozoan- and crinoid-rich bioclastic limestones, and in the Ste. Genevieve, predominantly oolitic limestones. Values used for comparison were obtained by averaging the foot-by-foot analyses of each high-calcium deposit, 10 in the Warsaw and 15 in the Ste. Genevieve. Average MgCO3 and Fe2O3 contents are generally lower in the Warsaw than in the Ste. Genevieve. Average SO2, S, and P contents are- generally higher in the Warsaw. No characteristic differences are apparent between the average CaCO3 and A1203 contents of the two formations. The higher S and P contents of the Warsaw are believed attributable to the predominance of biogenic material in these limestones. Within the Warsaw Limestone, higher average S and A1203 contents and lower average Fe2O3 contents were found in deposits in the northern half of the region. In the Ste. Genevieve, vertical variations in composition occur within individual high-calcium deposits containing oolitic and nonoolitic limestones. Lower average CaCO3 contents and higher average contents for the other constituents were found in the nonoolitic intervals.

Jan 1, 1972

By Charles L. Kimbell

In 1989, worldwide total mineral industry activity registered advances from 1988. The advances may not have been as noteworthy as in 1988, but they can be regarded as a worthy theme for this article. The momentous political events throughout the centrally planned economy world had only a modest impact on actual 1989 industry performance. But these events have such potential for worldwide changes in economic activity in future years that they dwarf the actual happenings of 1989 in the minerals industry. Perhaps most significant factor here is the rapidity with which these changes have occurred. The end of World War II saw the almost immediate division of the world into major economic blocs. Since then, mineral industry activities and other industrial operations have been governed, to a considerable extent, by this partitioning. The developed market economy nations have operated as a group, the centrally planned economy states as another group. And these two groups essentially have vied for recognition in mineral industry operations in the developing economy states of Asia, Africa, and Latin America. The boundaries of these country blocs were fixed in the late 1940s and early 1950s. They were not markedly altered in the ensuing 40 years. We have seen the establishment of the Organization of Petroleum Exporting Countries, the continued Arab-Israeli confrontations in the Near East, the upheavals surrounding the rise of Moslem Fundamentalism in Iran, and the establishment of Soviet-oriented governments in Cuba and Nicaragua. These events have had notable effects on the world economy. But they have done little to change the pattern of market economy states functioning as a competitive bloc with the centrally-planned economy countries.

Jan 1, 1990

By James E. Friant

The technology applied to shaft sinking has lagged far behind other construction activities. While surface oriented construction and mining have made great strides with new processes and equipment, the majority of shafts sunk currently still follow a drill, blast and muck-out cycle developed in the 16th century. Today, in 1979, the shaft sinking industry is in the midst of its own private industrial revolution. Millions of dollars are being spent annually by industry and government alike to spring the art of shaft sinking into the 20th century. The objective of this paper is to review a few of the newest mechanized schemes for shaft sinking. This is not a theoretical review, however, but a practical one, and deals only with hardware and projects which are currently on jobsites. Figure 1 shows the equipment. On the left is the 241SB 184, a 24 foot diameter blind shaft borer. This machine is currently at about 200 feet, constructing a coal mine shaft in Alabama. It is built and utilized in a manner similar to a tunnel borer. In the upper center is the 1211SR, a 12 foot diameter blind shaft reamer. This machine follows a 6 foot pre-drilled blind pilot hole, and is at work in Chicago. On the upper right is the 121BR, a powerful new blind drill. Just below it is the conical drill head for the 121BR which can utilize either carbide or standard disc cutters. At the center bottom is an expandable back reaming head which can be used to enlarge a drilled shaft up to a maximum of 16 feet diameter, or can be used to produce a shaft having several diameter changes. This equipment is also in use in Chicago.

Jan 1, 1979

By S. K. Kawatra, K. A. O, DeLa&apos

On-line sensors and process controls are important for efficient operation of coal preparation plants. The objective of this paper is to describe the current practice in on-line measurement of composition, density, moisture, level, flow and weight. This paper also discusses how on-line sensors can be implemented in process control, and how sensors which are currently being developed can be utilized.

Jan 1, 1988

By Murray D. Lester

The relationship between bauxite and energy has two distinct aspects. On the one hand, since virtually all of the bauxite that is mined winds up as aluminum metal, the economic health and future of the bauxite industry and of the bauxite-producing countries depend on the continuing vigour and competitiveness of aluminum against alternative metals and materials. The price of aluminum is, in turn, particularly dependent on the price of energy. Hence, the need for bauxite is ultimately affected by the price of energy. The second aspect relates to location of the bauxite industry. There is no shortage of bauxite resources in the world. For various reasons, as we shall see, there is a growing tendency toward the integration of bauxite mining, bauxite refining and aluminum smelting in those countries that have the resources both of bauxite and of energy necessary to support the entire production chain. Thus, the availability of attractive energy supplies will increasingly favour development of bauxite mining: the traditional export of bauxite as a simple raw material is likely to diminish in relative terms. In short, both the amount of bauxite mined and where this mining will take place are related to energy considerations. Let us first have a brief look at the four basic activities that are involved in our integrated operations: A. The bauxite is mined and moved to an ore plant. This step does not require more than relatively modest amounts of energy normally associated with excavation, loading and shipping of any bulk material. We need about four or five tonnes of bauxite for every tonne of metal produced.

Jan 1, 1984

By Ian McFeat-Smith, Robert J. Fowell

Roadheader machines have a specific place in modern tunnelling, not simply as a compromise between drill and blast techniques and full face machines, but as an economic and versatile form of mechanised tunnelling where the method of excavation is easily integrated with tunnelling operations. In the past, roadheaders have been subjected to misuses by engineers who failed to realise that, as in all mechanised tunnelling, a planned and systematic approach is essential if the full potential of these machines is to be gained. An increasing awareness of this, together with the introduction of the more powerful roadheader carrying their cutting potential into the hard range of rock is changing this situation and now makes the prospect of using roadheaders particularly attractive (1). The advantages gained by employing these machines can be considerable and Table 1 lists some of them. This table illustrates that from both cost, and installation points of view, the roadheader has considerable benefits over the full face machine. However, the principal advantage gained is in broken ground where heavy supports can be installed immediately at the tunnel face. In addition, access for planned maintenance and repairs to most working parts of the machine is at a premium and average machine utilisations of 40 - 60% can be expected. In comparison to drill and blast methods, up to 40% better progress can be regularly achieved, and the subsequent savings in overbreak costs alone would more than pay for the cost of a roadheader used to drive a 3km long tunnel. As with full face machines, ground disturbance is minimal and for short tunnels in urban areas a road-

Jan 1, 1979

By P. D. Roa, O. Noirot, H. Owens, D. E. Walsh, J. R. Mokka

Over a period of eight years (1989 through 1997) the Mineral Industry Research Laboratory (MIRL) at the University of Alaska, Fairbanks, AK, has investigated the effects of temperature, residence time and particle size on the degree of low-rank coal (LRC) upgrading for a nonevaporative, hydrothermal drying process, also known as hot water drying (HWD). The following three Alaskan LRCs were used in this study: Usibelli coal (Seam No. 4) from the Nenana Coal Field, Little Tonzona coal from near McGrath, and Beluga coal from the Beluga-Yentna field on the west side of Cook Inlet. Replicated factorial tests were conducted. Experimental results indicate that most of the low-rank coal upgrading via HWD occurs rapidly within the first 10 to 20 min of residence time. Thereafter, the upgrading process slows down, and more than 100 min of additional residence time is required to produce percentage increases equivalent to what was achieved in the first 10 to 20 min. The properties of the hot water dried products were very sensitive to process temperature. Calorific value, carbon and oxygen contents, equilibrium moisture levels and Hardgrove gindabilities all appear to change linearly with temperature within the 275°C to 325°C (525°F to 61 5 OF) range.

Jan 1, 2000

By Ajay Mahajan, Manoj Mohanty, Vishal Gupta

Modern coal processing plants utilize multiple cleaning circuits to efficiently beneficiate different size coal fractions of run-of-mine coal. An older plant optimization approach is to maintain average product quality from individual cleaning circuits at the same level as the given product specifications for the overall plant. However, many past studies indicate that the equalization of product quality approach fails to produce the maximum plant-yield. A newer approach, known as equalization of incremental product quality, requires that the incremental product quality obtained from each circuit be maintained at the same level to satisfy the overall plant product quality. This approach ensures the maximization of plant yield while satisfying a single product quality constraint. However, while dealing with multiple product quality constraints, this approach by itself may not be sufficient to obtain the desired maximum yield. For the simple reason that the dirtiest particle (or group of particles) with respect to one quality constraint may not be the same particle (or group of particles) with respect to another quality constraint, the mass yield versus product quality relationship generated by equalizing different incremental product quality may not be exactly the same. Therefore, an additional search technique has to be utilized to determine the global-maximum value of plant yield. Thus, the main objective of this study was to utilize an emerging optimization technique, known as genetic algorithms (GA) to maximize plant yield while satisfying multiple product quality constraints. The maximum plant yield obtained from this approach was nearly same as the maximum yield obtained by the incremental product quality approach while satisfying one specific product quality constraint. The GA was applied on a coal preparation plant that utilizes four circuit operations - heavy medium bath, heavy medium cyclone, spiral and froth flotation. The results showed that using GA as an optimization process gives 2.56% higher yield that will result in additional revenue generation of $5,120,000 per annum than average product quality approach.

Jan 1, 2005

Stratabound uranium deposits consist generally of two comingled geologic and statistical populations. Barren zones, usually having radiometric assays too low for recording on digitized logs, comprise a large portion of a mineralized stratum. In between are mineralized zones; where the grades are distributed essentially lognormally. Estimation of open-pit ore reserves requires the prediction of the tonnages of selective mining units (the smallest mined volume which may be segregated as ore or waste) and their grades within panels of convenient size for open pit planning and economic analysis. The proportionate tonnage of mineralized selective mining units within each panel can be predicted by kriging an an indicator function assigned to each composite (1 if mineralized, 0 if barren). Next, using logarithms of mineralized assays, the conditional lognormal distribution of grades of mineralized selective mining units can be found. Using this distribution and the krigedestimate of the probability a selective mining unit is mineralized, the grade and tonnage of selective- mining units above any cutoff can be predicted. A case study illustrating this two- step procedure is presented for the Imouraren uranium deposit located in the Republic of Niger. Using cross validation, the estimation procedures were checked and were shown to be adequately accurate for mine planning purposes.

Jan 1, 1979

By Roger D. Sharpe

The United States Gypsum Company operation at Plaster City, in Imperial County, California, consists of the largest gypsum quarry in the United States, a company-owned, narrow-gauge railroad and wallboard and plaster manufacturing facilities. A variety of gypsum products, including many types of wallboard, construction plasters, portland cement setting agent, and agricultural gypsum are manufactured. Gypsum is quarried from the Miocene age Fish Creek Gypsum. Evaporite minerals were deposited in a clastic-rich sabkha environment along the margin of a small embayment in the Salton Trough. The Salton Trough is a major regional structure that formed by rifting and transform faulting along the Elsinore, San Jacinto, and San Andreas fault zones. Sedimentary basins were formed between tilted fault blocks. The basins were filled by prograding alluvial fans, basin margin sabkha and marine sediments, and deltaic deposits from the Colorado River. Gypsum is exposed in the quarry on rounded hills with 250-300 feet of relief. The evaporites are up to 200 feet thick and average 125 feet in thickness. Anhydrite commonly occurs in the lower part of the evaporites under the crests of hills and beneath thick alluvial cover.

Jan 1, 1995

By D. R. Schricker

Mine managers rely on their experience, section foreman's daily reports and occasional time studies to make important production, maintenance and forecasting decisions. This information is often subjective and imprecise, consumes expensive engineers time, is often biased and is restricted to short time periods. Managers need better information. Furthermore, if a recently purchased machine is being evaluated, a large increase (>10%) in productivity may be obvious, but small increases are usually masked by other variables. In today's highly competitive markets, cumulative small changes are important, especially since managers have already exhausted most available, obvious avenues of improvement. A technique to separate these charges from effects of other variables and to quantify the target effect is necessary. CSM researchers are addressing this need by developing an intelligent decision support system (IDSS). It provides key production and maintenance information to support management decisions by recognizing patterns in mining machine sensor data and representing knowledge about mine management, operations, layout and equipment. A continuous miner section at Western Fuels-Utah Inc.'s Deserado Mine in Rangely, CO is the test facility for the research. Power transducers located in the sections load center provide kilowatt versus time data from continuous section equipment. The IDSS pattern recognition algorithms classify the kilowatt versus time patterns into individual machine operating modes. It produces an output similar to a typical industrial engineering time study but continuously, automatically and without an engineer in the section. It is relatively easy for a time-study engineer to identify the stop and end points of a cycle element and classify it by looking at the machine and glancing at a stop watch. The problem is that monitoring system hardware and software do not have these unique capabilities. Consequently, IDSS algorithms must automatically define the begin and end points of machine tasks and identify the task by recognizing patterns in kilowatt versus time data. However, many mines have file drawers of time-study type data that are not very useful. So, IDSS contains the knowledge representation subsystem (IDSS/KRS) to produce short reports containing only key information. This is difficult because mine environments continually change and information requirements differ for each management level. Consequently, IDSS/KRS must learn and adapt to new conditions in a dynamic mining environment.

Jan 1, 1990

By L. J. Nicks

The current U.S. Bureau of Mines research program is addressing the recovery of flake graphite from kish, a steelmaking waste product, and the use of zeolites from abundant domestic natural deposits for efficiently cleaning up mining industry wastewater. The United States is almost totally dependent on imports for its graphite needs, but this may change depending upon the results from a pilot plant being constructed by industry using Bureau technology. Standard mineral processing techniques were applied by the Bureau to recover high-quality flake graphite from kish. It was considered innovative enough to receive an R&D 100 Award in 1992, and its commercialization has the potential to supply the total U.S. demands for graphite many times over. Zeolites have ion exchange properties similar to ion exchange resins, but are less expensive and available in large quantities. Samples of naturally occurring zeolites were tested for their efficiency in removing metal ions from synthetic and industrial waste solutions. The tests focused on defining their selecting, loading, eluting, and regenerating characteristics, and on developing a method for recovering the metal ions as added value products. The results showed that the removal of metal ions with zeolites from acid rock drainage (ARD) solutions is technically feasible and that this technique has the potential for being used in an integrated chemical treatment systems approach either as a primary or secondary cleaning step.

Jan 1, 1995

By Finn Ouchterlony

INTRODUCTION Much of present fracture toughness testing con¬cerns chevron notched specimens (Newman Jr., 1984) since these, in principle, require neither fatigue precracking nor more registration than failure load to determine fracture toughness. Two such specimens which can be made from diamond drilled rock cores with minimal machining are the Short Rod (Barker, 1977) and the Chevron Edge Notch Round Bar in Bend¬ing or CENRBB Specimen (Ouchterlony, 1980). Even if the precracking property is especially valuable for a material like rock, practice has made the relative advantages of these chevron notched specimens much less apparent (Ouchterlony, 1982; Ouchterlony and Sun, 1983). Enough remains, however, to have the Commission on Testing Methods of the International Society for Rock Mechanics (ISRM) focus on them as standard configurations in a "Suggested Method for Determining Fracture Tough¬ness of Rock Material", which is in preparation. This paper presents material which supports the ISRM effort: 1. An experimental compliance calibration of the Chevron Bend (CENRBB or CB for short) and re¬sulting formulas. 2. Specimen tolerances, evaluation formulas, and loading rate requirements relating to both Short Rod and Chevron Bend Specimens of suggest¬ed standard proportions. 3. Some fracture toughness values obtained with the Chevron Bend Specimen. This material is mainly based on two reports (Ouchterlony, 1984 and 1985). CALIBRATION OF THE CHEVRON BEND SPECIMEN Preliminaries The specimen and basic notation is shown in Figure 1 together with a straight notched variety (SECRBB). Subscripts c and s are sometimes used below to distinguish between them. Assuming linearly elastic conditions the load point compliance [ ]

Jan 1, 1986