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By D. Marsh

The feasibility study for the Grasberg Block Cave mine, finalized in May 2008, indicated a production capacity of 160,000 tonnes per day. A rail haulage system was an integral part of the mine design. This paper describes the simulation process used in optimizing the design and discusses the key factors and variables that impact the capacity of the system. The final recommendations for the haulage level layout and associated equipment are also included.

Jan 1, 2010

By Klaus Rieker

"Since the mid-19th century the River Emscher in the German Ruhr District has been used for disposing of wastewater. In the early 1990s, it was decided to replace the existing open wastewater system with a sewer system and to restore the River Emscher to its natural state. The major Emscher conversion project is divided into a large number of individual schemes, with construction phase 30 being the largest. By applying the pipe jacking method, interlinking tunnels with section lengths in excess of 1,100 m are constructed. USAGE OF THE EMSCHER OVER TIME The 85-km long river Emscher flows right through the Ruhr District. It has its source to the east of Dortmund and flows into the river Rhine near Dinslaken (Figure 1).The Emscher has been used to dispose of wastewater since industrialization began about 200 years ago. Intensive coal mining over the years led to considerable subsidence causing stagnant sewer areas which in turn led to typhus and other deceases. Thus in 1899, the Emschergenossenschaft was founded to create an efficient interceptor system for a catchment area of 865 km² through lining, raising and Emschergenossenschaft decided to free the waterways of the Emscher system from sewage and to improve them in ecological terms by 2020. A budget of 4.5 billion euros was earmarked for this purpose.The construction of sewer conduits began in order to no longer transfer the wastewater into the Emscher. The currently ongoing construction of the “Emscher Interceptor” - the main sewer - represents the heart of the Emscher conversion project. The interceptor will run along the river over a length of 51 km. Three pumping stations are required to confine the sewer’s depth to elevations between 15 and a maximum of 40 m below the surface. Since early 2012, the Emscher has been free from wastewater east of the Dortmund-Deusen clarification plant. There are two further clarification plants situated along the Emscher, which treat the still contaminated river water down-stream. Once the Emscher Interceptor is in operation, they will receive wastewater solely from the tunnel system."

Jan 1, 2016

By John D. Morgan

The United States is the world's most productive nation and its citizens enjoy one of the highest material standards of living of any people in the world. Materials and energy are the lifeblood of any industrialized economy. Annually the United States uses over 4 billion tons of mineral materials and fuels, or 40,000 pounds per person as detailed in Figure 1. Domestic processed materials of mineral origin and energy are valued at more than $150 billion annually, and they are derived largely from domestic sources, supplemented by imports, as detailed in Figure 2. In recent years the superior productivity of the United States has also enabled it to give food and manufactured articles to many other less fortunate nations and peoples of the earth. What then is our concern with materials at this time? Seeing the burgeoning increases in our mineral demand: from 2 billion tons in 1950, to over 4 billion tons today, and projected to 11 billion tons by 2000 - we are getting questions concerning our ability to continue to increase production sufficiently for the future.

Jan 1, 1974

By E. L. Bohnet

The purpose of this paper is to translate a mining company's "Corporate Objectives" into usable and practical guidelines for long term mine design and production scheduling. These guidelines are required to ensure that both operating and development properties are designed and economically ranked on the same basis, and with the "current" Corporate Objectives in mind. Secondly, if both management and mining engineers have a better understanding of the cause and effect of corporate policies, then penalties and risks associated with various Corporate Objectives can be put into better perspective for management. Corporate Objectives, relative to usable guidelines for either short and/or long term mine planning, could be defined as one or more of the following four objectives: 1) Maximize the recovery of the economic portion of the defined geologic resources, and hence, maximize total non-discounted project cash flows and profits (most common approach in mine design), 2) Maximize the Net Present Value (NPV) of the after-tax cash flows from each existing or proposed project, either on an individual basis or in concert with other projects, including downstream processing facilities (primary method used to judge relative investment merit of a proposed development or operating concept), 3) Limit short and long term capital expenditures to a defined ceiling, 4) Maximize product output for the existing facilities in the short term, or conversely, keep commodity production at a constant level for a series of years.

Jan 1, 1994

By Sahendra Ram, Ashok Kumar, Rakesh Kumar, AMIT KUMAR SINGH, Dheeraj Kumar, Arun Kumar Singh, Rajendra Singh

This paper describes the successful mechanized extraction of coal pillars in 11 panels using the fish-tail method from 2010 to 2017 at Pinoura Mine in India. This method proved its potential of coal recovery with efficient strata control under weak roof due to faster rate of extraction in a single lift. Observations of strata and snook behavior during the field studies in different panels of the mine are included.

By L. Widdifield, R. Riggle

"In today’s challenging mining environment the “Big Picture” (Caterpillar, 2013) approach to mining is often neglected. With haulage costs approaching up to 45 % of the overall mining costs, all too often the load-haul-dump- return cycle is not investigated in its completeness. This paper will discuss the aspects of taking the time to observe an operation from the “Big Picture” approach. In today’s mining business miners, engineers, trainers, supervisors, and managers have ever increasing roles and responsibilities as never seen before in the past decade. The endless human resource, safety, environmental, cost control issues and performance initiatives, detracts from precious time that may have been dedicated to examining the day to day operation. Having examined numerous mining operations over the past several years, one common denominator is lack of time to properly observe operating practices in the field and recognize both positive and negative observations. The old fashioned vocation of observing the operation to assess the haulage, loading and maintenance processes to adjust, maximize or enhance operations have sometimes vanished. Four areas to be discussed in this paper: (1) Look at the “Big Picture”(Caterpillar, 2013), (2) Use common sense, (3) Areas identified for biggest improvements in the operations, (4) Observation of small details for big impacts to lower cost per ton and increased production. The objective of this paper is to provide low cost recommendations to lower cost per ton and increase production. INTRODUCTION Whether miners claim to have been around and experienced it all or the “rookie” on the mine site, miners are expected to execute the mine plan at the lowest cost possible. So why is it so difficult to execute this task? Shouldn’t supervisors just have to man the equipment, tell operators to have a safe day and tally up the numbers at the end of the shift? And let the technology system do the rest? So what could go wrong? Lots. Mining companies seek help from consultants, training departments, performance reporting systems and an arsenal of resources. Armed with all this information, the supervisors just hop in the pick-up and tell the shovel operator to speed up. Sounds simple enough. When the improvements don’t happen, what could have gone wrong? It comes down to people, the simple things that were not executed over the months previously and as a result today the mines performance is not where it should be. A mine is built by people. Managers who have the vision to develop the ore body in a manner that follows sound engineering practices. The infrastructure to mill the ore and support the equipment needed to move the material. Along the way equipment is procured and operators trained to run the gear. Engineers and geologists set up the design, the material movement, and haulage routes. Sounds easy to this point. So, why mine after mine is there this constant struggle to move more with less and get the costs down? Understanding how to make “Great Miners” out of these people is critical to lowering your cost per ton."

Jan 1, 2016

By K. E. Robinson, G. Re, L. Skoski

Introduction A new technology is evolving as a result of growing industry and government concerns over the potential impacts of possible airborne emissions from uranium tailings piles. A major component of the technology is the use of earth covers to stabilize the tailings after mill operations have ceased. While various analytical models have been used to predict the thickness of required covers, experimental validation of the models has been necessary. This paper presents the results of a field program to select and test cover material to determine its suitability for eventual reclamation of a currently active tailings pile. The two main criteria guiding the study were the U.S. Nuclear Regulatory Commission radon flux requirements (reduction to less than twice background pre-1979, and to 2 pCi/m2 -sec above background post-1979) and the desire to employ locally available material. The methodology chosen for this study consisted of three main elements: o Determination of the background radon flux. o Determination of the radon flux from the tailings pile. o Experimental determination of the cover material diffusion coefficient and and calculation of cover thickness. The first two elements of the study are relatively straightforward, the last phase is discussed in detail. Background Radon Flux Measurements of radon-222 emanation rates from the surface of the ground were taken at three sampling locations. Samples were collected by means of the accumulator can method described by Wilkening, 1977. Both morning and afternoon samples were collected at each site to obtain an average. The measured fluxes were fairly uniform and did not differ greatly among sites. The overall average flux for all sites was 0.63[+]0.28(o) pCi/m2 -sec. This value is equal to the average radium-226 concentration determined in the soil, thus yielding a one to one ratio of radon-222 emitted (in pCi/m2 -sec) to soil radium content (in pCi/g). Tailings Pile Radon Flux Two sites on the tailing pile

Jan 1, 1980

By Robert M. Stevens

INTRODUCTION Truck haulage of muck in underground mining operations has been in use around the world for many years. From the late 1.950s into the early 1970s, haulage by means of load-haul-dump (LHD) units challenged haulage by means of trucks, and, to a large degree, LHD units dominated the trackless concept of moving mate¬rial underground. However, beginning in 1975, the emphasis began to shift back to the use of trucks, with LHD units assuming the secondary role of loading the trucks. Over the years, several manufacturers have been offering trucks with capacities ranging from 4.5 to 45.4 t (5 to 50 st) and with features that specifically address the constraints of underground operation. TRUCK TYPES Three different types of trucks are available for use underground, namely the tip dumpers, telescoping dumpers, and push-plate dumpers. The following para¬graphs describe each of these three types. Tip Dumpers Tip dumpers are designed to lift the truck box, using gravity to dump the load out the rear of the box. The primary application of these trucks is in the haulage of muck to the surface. However, these trucks also may be utilized underground, if a chamber is provided to accommodate the raised truck box at the dumping point. Fig. 1 illustrates a four-wheel drive truck with a 10.0-t (11-st) capacity; this truck is only 1.9 m (6.25 ft) wide and is designed specifically to follow narrow and winding vein courses. Fig. 2 illustrates a two-wheel drive tip dumper with a 24.5-t (27-st) capacity; this truck operates on 12% grades with firm dry surfaces and in modes both loaded-up and loaded¬down. Telescoping Dumpers Telescoping dumpers specifically address the constraints imposed by low back heights, and they represent an optimization of compressed envelope size with maximum payload capacity. Figs. 3 and 4 illus¬trate a typical telescoping dumper with a capacity of 18.1 t (20 st). Fig. 3 shows the box in position for carrying the load, and Fig. 4 shows the same truck with the box in the full-dumping position. Fig. 5 illustrates the loading and dumping cycles. Fig. 6 illustrates an approximation of how an LHD unit with an eject-o-dump (EOD) bucket would be used to load over the rear of this type of truck. Fig. 6 shows a low-profile telescoping truck in the first stage of loading, with a 6.8-t (7.5-st) LHD unit equipped with an EOD bucket. A loader with a smaller capacity and a narrower bucket would allow the bucket to fit inside the truck box and would achieve an even lower loading height than that illustrated. Gen erally, an LHD unit equipped with an EOD bucket and teamed with a telescoping dump truck can be used with a lower back height than could any other front-end loader and truck team. Push-Plate Dumpers Push-plate dumpers are similar to telescoping Bump¬ers, except that they do not have the two-stage box. Instead, push-plate dumpers utilize a single push plate to discharge the load out the rear of the box. Gen erally, these units are limited to payload capacities of about 9 t (10 st). Fig. 7 illustrates a typical push-plate dumper.

Jan 1, 1982

By L. C. de Kooker, K. Esmaeili, I. Musonda, M. Ferentinou

This paper presents the results of an investigation into the effect of pore pressure regime on the factor of safety (FS) and the anticipated critical failure mechanism for a fly ash storage facility. In this study, pore pressure measurements from standpipe piezometers and pore pressure estimated from seepage analysis were used for a comparison of the estimated FS for a fly ash slope. This comparison was applied for static and seismic scenarios. To account for the uncertainties resulting from the limited data available and support a qualitative risk assessment evaluation, a probabilistic analysis was performed. The slope stability analysis was conducted in 2D and 3D, adopting the limit equilibrium analysis approach, and a finite element seepage analysis. The results suggest consistency of failure surfaces for 2D and 3D and an increase in FS values of 5 percent for the 3D approach, limitations of standpipe piezometers. The study demonstrated the sensitivity of the FS value, and the implication of adopting representative material properties, and water table levels, especially in cases where limited data are available, and assumptions need to be made to assess the long-term stability of a fly ash dam facility.

Aug 1, 2024

By David Beck, Eko Wibowo, Hendri Silaen, Andres Sugiyanto, Karl Llewelyn

PT Freeport Indonesia’s Deep Mill Level Zone mine is one of the deepest block cave mines in the world and is in mountainous terrain in West Papua, Indonesia. The mineralization is hosted in a skarn deposit in a structural setting that is complex at the footprint, mine and regional scale. Large seismic events and significant episodes of rapid rock mass deformation are potentially critical geotechnical risks during this ramp-up stage of mining. Understanding the interaction between stress, strain, rock mass strength and geological structures is essential to minimize the hazard and engineer control measures to help ensure the safety of the employees while achieving production targets. This paper discusses how the seismicity and excavation damage have been shaped by the interactions between the mine and geological features, and how this affects strategic mining decisions. Additionally, the paper presents a summary of the mitigation measures used for mining the DMLZ in the safest and most productive way. These include improvements to geotechnical characterization of rock mass and structure, dynamic ground support designs, production scheduling for desirable cave propagation and a seismic monitoring system with re-entry protocols.

Apr 26, 2022

By Brian McInnes, Joseph A. Sopko, Behzad Khorshidi

"The Port Mann Main Water Supply Tunnel involves a 1km long tunnel beneath the Fraser River from Surrey to Coquitlam, BC. At depths of up to 60 m below ground, the earth pressure reached 6 bar. The tunnel is constructed using an EPB TBM and gasketed precast concrete segmental liner. The tunnel and two shafts were constructed in a variety of soil conditions ranging from soft to stiff clays and silts, to compact to very dense sands and gravels. After approximately 800m of mining, a very dense and highly variable soil group consisting of cobbles and boulders halted the TBM. Several options were considered to stabilize the TBM face so an intervention could be conducted. Although de-watering was considered, there was risk of settlement to the Port Mann bridge piers, which was within 500m of the tunnel. Hyperbarics were also considered, however, the cost, schedule and uncertainty of the work that needed to be done, made it a risky option. Ground freezing by Liquid Nitrogen was chosen as the best solution, which would provide a frozen block around the face of the TBM. A temporary platform on the river was designed and constructed to enable drilling and installation of the freezing pipes and temperature monitoring equipment. The operation required close coordination among the tunnelling, marine and freezing sectors. Following the intervention, the TBM successfully broke through the reception shaft, and the remaining project was completed. This paper describes the design, construction and operational approaches used for the freezing and serves as a basis for future projects requiring expedited ground freezing."

Jan 1, 2016

By J. Pereyra, M. DeMarco

"INTRODUCTION It can be vital that bolted joints holding subassemblies together remain secure. Bolts should resist the loosening effects of vibrations and dynamic loads yet need to be easily removable during maintenance. When a threaded fastener is subjected to vibration, the rapid movement causes a lowering of friction against the threads and a subsequent loss of preload. The loss of preload allows the fastener to vibrate loose and possibly fall out. As the diameter of fasteners increase desired preload becomes increasingly more difficult to achieve. Input torque requirements for achieving proper bolt preload is exponentially related to any given fasteners diameter. This means that specialized tooling or bolting practices are usually required to attempt the tightening of fasteners to reach their required preload. Traditional methods can cause problems with joint integrity and do not provide consistent bolt load across the bolted surface. BOLTED CONNECTIONS A failed critical bolted joint can lead to high maintenance costs, machine downtime, and risk to worker safety. Control of the clamp load in a bolted joint is vital. However, when faced with a problem joint, it is not surprising that the design engineer will not have an answer if asked about the clamp load. Torque calculations must always be based on the existing conditions that often are vague. Unless all parameters are correct, the calculation will be unreliable. Examples of parameters are: • Thread condition of the fasteners • Hardness of contact surface • Material (steel, aluminium, copper, etc.) • Extra friction from a locking fastener • Extra friction from an adhesive • Lubricant on the thread • Type of bolt head (flanged, regular or serrated) • Surface coating of the bolt • New or reused fastener During tightening, bolts are subjected to both tensile and torsional stress. The total stress in a bolt can be calculated using the formula: Total stress = vsx2 + 3txy2 In order to maximize the desired tensile stress (sx) it is vital to minimize the torsional stress (txy). Tensile stress (clamp load) is achieved when the bolt is axially elongated. Unwanted torsional stress (twisting) in bolts arises during tightening due to thread friction. High thread friction increases torsional stress and causes yielding at lower clamp load levels than normal. A lubricant is necessary to minimize the malign torsional stress. However, many commonly used bolt-locking systems are based on increased thread friction (deformed nuts, adhesives, etc). To minimize thread friction and concurrently safely secure the joint has often incorrectly been considered impossible. The use of locking systems that increase thread friction is the single most common reason why the full capacity of bolted joints is not utilized. The following example illustrates the problem."

Jan 1, 2015

By B. Weaver

Every year Pit & Quarry Magazine surveys the industry to produce their annual review. Here's a sampling of some of the statistics the survey produced from the end of the year 1994 survey.

Jan 1, 1995

By C. S. Vender

Knife River Coal Mining Company's Beulah Mine is a multiple seam lignite operation located in western North Dakota. The mine began production in 1963 with annual production at 450,000 metric ton and now produces 2.2 mm ton. As development progresses, operations have advanced into more complex geologic areas. Various techniques have been analyzed to maximize coal recovery in a cost effective manner. Additional studies are on-going to determine what changes will be implemented as we encounter deep wet sands in the reserve area.

Jan 1, 1991

By J. Yao

Synthetic indium-bearing zinc ferrite (IBZF) was mechanically activated by a tumbling mill. Subsequently, the behavior and kinetics of leaching zinc and indium from the initial IBZF and activated IBZF in sulfuric acid solution were investigated. The results demonstrate that the tumbling ball milling enhances the leaching reactivity of IBZF and increases the zinc and indium extractions. The reaction temperature and H2SO4 concentration have an important effect on leaching zinc and indium from the initial IBZF and activated IBZF. The kinetic model -ln(1-x) = kt was used to describe the kinetics of leaching zinc and indium from the initial IBZF and activated IBZF and to calculate the kinetic parameters. The tumbling ball milling causes a decrease in activation energy and reaction order, which indicates that the dissolution of IBZF after mechanical activation by a tumbling mill becomes less sensitive to temperature and H2SO4 concentration. For the zinc leaching, the activation energy decreases from 73.9 to 70.3 kJ/mol and the reaction order decreases from 0.72 to 0.70. For indium leaching, the activation energy decreases from 78.1 to 73.5 kJ/mol and the reaction order decreases from 0.82 to 0.69. It is found that the dissolution rates of the initial IBZF and activated IBZF are controlled by surface chemical reactions.

By Hans Ehdwall

INTRODUCTION Investigations of radon and radon daughter concentrations in Swedish [non-uranium] mines started in the late 1960's. The first screening measurements showed that the average annual exposure to radon and radon daughter products was 4.7 WLM. The main reason for high radon and radon daughter concentrations was inefficient ventilation and radonrich water entering the mine. In the radon regulations worked out later it was stated that no miner should be exposed to more than 60 000 pCi h/1 equilibrium equivalent concentration of radon annual exposure, corresponding to 3.6 WLM. Now, 1981 the situation has changed considerably. From the average annual exposure of 4.7 WLM in 1970 it is now only 0.7 WLM. Sweden has up to now had only one [uranium] mine and the work there has only been investigative. However, there are plans for a commercial uranium mine in another part of Sweden. The radon problems in these mines are widely different depending on the mineralogy. NON-URANIUM MINES The radiation problems in Swedish mines were not recognised until the late 60's. The first radon and radon daughter measurements were made in some sulphide ore mines in 1967 (1). The radon and radon daughter concentrations were surprisingly high for non-uranium mines. In order to have a complete picture of the radon situation in Swedish mines the National Institute of Radiation Protection (NIRP) decided to make measurements in all, at that time about 60 mines (2). To get results as fast as possible measurements on radon gas seemed most appropriate to start with. Sampling was made by mailing a number of evacuated 4.8 litre conventional propane containers from NIRP to each mine. The containers were then opened at the place of interest. After sampling the containers were sealed and then mailed back to the institute for measurement. The measurements were made in ionization chambers. This method only gave the radon concentration and the radon daughter concentration was estimated by multiplying the radon concentration by an assumed equilibrium factor. The equilibrium factor is defined as the ratio of the total potential alpha energy for the given daughter concentration to the total potential alpha energy of the daughters if they are in equilibrium with the given radon concentration. The results of this first preliminary survey indicated that a great many of the Swedish miners probably had an annual radon daughter exposure of more than 3.6 WLM. As the radiation exposure in non-uranium mines was not regulated in either the Swedish Radiation Protection Act or the Swedish Labour Protection Act work was started on special radon regulations. A lung cancer mortality study was also started. To check the results of the first survey and to get experience and knowledge of radon problems in mines, it was decided that personnel from the NIRP should visit each mine for a detailed investigation of radon and radon daughter concentrations starting with the ones with the highest radon concentrations. The main reasons for these so-called "basic measurements" were: 1. To estimate the doses received by Swedish miners 2. To find the sources of the high radon and radon daughter concentrations 3. To find appropriate counter-measures 4. To determine the most typical equilibrium factor for each mine. Unlike most uranium mines the reason for high radon concentrations in non-uranium mines is seldom the occurrence of highly radioactive minerals. The main sources were found to be waste-rock and radon-rich water. In order to filter and warm up the inlet air, especially in winter time, it was very common at that time to suck the air through broken wasterock. By doing so the air was contaminated with radon from the waste-rock and radon-rich water in it. It is noteworthy that the radium and uranium concentration in the waste-rock is relatively low. The uranium concentration is only of the order of 15 - 20 ppm. The action to prevent this contamination of the inlet air was to change the direction of the ventilation and in the case of radon-rich water entering the mine the action was to prevent the air coming into contact with the water. The first calculation of the radon daughter exposure of Swedish miners was based on radon gas measurements. The radon daughter concentration was estimated by using an assumed equilibrium factor of 0.5. Later when the mines were visited by institute staff it was possible to compare the assumed equilibrium factor with the measured ones. It was found that the factor varied from 0.15 at the air inlet to 1.0 at the air outlet and the average equilibrium factor on workplaces for almost all mines was between 0.4 and 0.6. The result of the exposure calculation in 1970 showed that more than 40 % of the miners had an annual radon daughter exposure of more than 3.6 WLM. The overall average was 4.7 WLM and the maximum annual expo-

Jan 1, 1981

By James W. Guider

Of all the technology available to the iron blast furnace operator, raw materials preparation is by far the most important. Superior raw materials have been basic to the success of the Japanese steel industry, and they are just as essential to the American steel industry in winning its competitive battle against foreign government subsidized steel imports. Therefore, the mine operator and the ore beneficiation engineer must strive to produce the highest quality raw materials possible to meet the precise demands of the modern blast furnace and steel plant.

Jan 1, 1978

By Olivier Kraft, Olaf Kortz

"Project-specific optimized tunnel boring machines represent the spearhead of technological progress in tunneling because with their use, very long-lasting, high quality tunnel structures in almost any geology, depth and topography can be produced with a high degree of automation. The mechanized excavation of tunnel structures ensures the greatest possible environmental protection during tunneling itself. Professional, systematic and high quality rebuilds and reuse of already proven equipment also ensures maximum efficiency in the use of materials and energy resources. It offers an enormous potential for a highly optimized environmental balance. Here the manufacturers of tunnel boring machines and their users in particular have a duty to ensure transparent, high quality and binding standards in the entire rebuild cycle and in the refurbishment management of innovative tunneling technology. This paper deals with the comprehensive processes with rebuild levels of tunnel boring machines and highlights some exemplarily implemented projects. 1 INTRODUCTION All over the world, the number of tunnel boring machines (TBM) in which equipment rebuilds from previous projects are re-used has increased over the last few years. This text presents the technical and economical aspects of this market development. It also takes a look at the practical implementation of rebuild measures. The ""ITAtech Guidelines on Rebuilds of Machinery for Mechanized Tunnel Excavation"" from 2015 lay down the requirements that the machine manufacturers must meet. 2 ECONOMICAL AND ECOLOGICAL ASPECTS OF RE-USING COMPONENTS The globalization of the construction sector and the consideration of environmental aspects promote an increased re-use of machines and machine components. Nowadays, large-scale construction projects are often carried out by international joint ventures of several individual companies that are established specifically for this purpose. After the completion of the project, the joint ventures are dissolved and they liquidate their project-specific equipment, such as tunnel boring machines. Today, it is much more uncommon for such machines to remain permanently in the possession of construction companies. Joint ventures offer TBMs on the free market, or they exercise contractually agreed repurchase options with the manufacturer. On the whole, this increases the number of re-usable components or complete tunneling systems available on the market."

Jan 1, 2016

By Yuting Xue, Danqing Gao, Brijes Mishra

Heterogeneity and discontinuity significantly affect rockmass strength. Past studies have largely used arbitrary scaling approaches to produce rockmass strength from laboratory rock tests. This paper proposes a stochastic approach to produce rockmass strength from laboratory rock tests. Based on the laboratory data, MATLAB with an extreme value stochastic model generated a database for each physico-mechanical property of the rock. Then finite-difference software FLAC2D simulated laboratory-sized rock specimens. Random material properties in MATLAB were generated using the grids developed in the numerical model. The random properties were then applied to the final FLAC2D model. Model runs simulated the approach performed in the laboratory. The results from the model indicate that a stochastic approach produced compressive strengths that were lower than those from the deterministic approach. Failure modes for each specimen were different from those observed in the laboratory. In addition, random density also influenced the failure mode, highlighting the importance of stochastic analysis in rocks.

By S. Dempsey

Since its passage in 1872, the Mining Law has been modified on several occasions to meet the changing needs of America's society and economy. Despite its evolution, the Mining Law continues to be criticized as outdated. This paper briefly traces the major points in the history and evolution of western mining laws, and reflects on the current status of ongoing discussion to reform the 1872 Mining Law.

Jan 1, 1997