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By J. J. K. Daemen, C. Fairhurst

Two aspects of tunnel support design are considered, and for both particular attention is paid to the influence of rock failure around the tunnel on the loads developed on the supports. 1) In general it has not been possible to extend analytical methods for the study of rock failure around tunnels to three dimensions. As a consequence it was not possible to calculate either the influence of the face or the actual sequence of support loading as the face advanced. The finite element method made this extension possible. A simplified analysis of the influence of the face and of the sequence of support installation has been made. The influence of the original stress field and of the rock behaviour on the length of tunnel which can be left unsupported (related to the stand-up time) is shown. The degree to which a 2-dimensional analysis can be used to approximate the final support load is shown to be dependent upon the post-failure behaviour of the rock. 2) Tunnel support design requires a knowledge of the forces and of the -rock displacements which cause stressing and deformation of the support system. A 2-dimensional model incorporating a detailed representation of several support systems, of the rock behaviour in the broken zone and of the interaction between rock and support is given. The model allows the calculation of the stress distribution in the support. The significance of the relative stiffness of support and rock on the stresses developed in the support is shown.

Jan 1, 1997

By Neil J. Duncan, Edward R. Langfield

A hydraulic rock breaker was developed in Germany by Helmut Darda and uses a wedge-plug and feathers mechanism powered by a 10,000 p.s.i. power pack. During the past four years these tools have been increasingly used all over North America for secondary breaking of boulders and rock. More recently, techniques have been developed to break rock off the solid in trenches and rock emplacements where blasting is pro¬hibited or very limited. Underground operations are commencing to adopt the splitter for scaling plus including systems which can be efficiently applied to chambers and mines. Mr. Neil Duncan, who was originally scheduled to give the main part of this presentation has, during this past month accepted a position with the Alberta Energy Resources Conservation Board in Calgary. The board encourages its members to take part in seminars such as this but, unfortunately, due to the heavy pressure of work, it was impossible for him to attend this conference. Mr. Duncan has, however, forwarded me his notes and suggest¬ions, and using these, combined with a slide presentation, we feel that we can quickly and clearly define the operations and application of the hydraulic splitting technique as it applies to your profession and tunnelling work. The first question that most of you are asking is, "Why use a hydraulic splitter if you can blast?" Our answer to this is that we are not advocating the use of hydraulic splitting where blasting is feasible - but, during the past decade many applica¬tions have arisen where blasting is not allowed, or restricted

Jan 1, 1997

By K. Vaxevanidou

A combined chemical and biological treatment for the removal of heavy metals and arsenic from a contaminated soil was studied as a potential method for soil remediation. Small scale and column tests were conducted in order to ex-amine the effect of plant-compost and Na2CaEDTA addition on a calcareous soil highly contaminated with heavy metals and arsenic. EDTA is known to be an efficient leaching agent of heavy metals from contaminated soils but has no effect on arsenic. Compost tea on the other hand contains humics that can leach several iron compounds including Fe(III)-oxides and thus can extract arsenic bound to these oxides. The action of Fe(III)-respiring bacteria D.palmitatis was also evaluated for the reduction of iron oxides and compared to simple chemical treatment in the presence of compost in small scale tests. Results indicated that the addition of compost and EDTA into soil pulp lead to the predominance of reductive conditions and the simultaneous dissolution of both heavy metals and arsenic at high percentages. The presence of D.palmitatis did not further enhance the reductive dissolution of Fe(III)-oxides by compost and EDTA as it was observed in the inoculated samples. Column tests using soil as received revealed that, although the extraction of metals seems to be a slow process, compost is an effective oxygen barrier that promotes the reductive dissolution of iron oxides and the subsequent arsenic release together with the dissolution of heavy metals by EDTA.

Jan 1, 2005

By William P. Barnett

In 1988, the US Department of Energy's (DOE) Pittsburgh Energy Technology Center identified three coal cleaning options for achieving flexible environmental control strategies aimed at reducing energy-related SO2 emissions. These are selective agglomeration, advanced froth flotation and advanced cycloning. Each relies on maximum liberation of pyrite and other mineral matter through feed coal comminution to fine and ultrafine sizes. The National Energy Strategy (NES) and the Clean Air Act Amendments (CAA) of 1990 are examples of the nation's commitment to a clean environment. The need to use the nation's energy resources in an environmentally sound manner presents critical challenges and opportunities for coal preparation during the next decade, particularly regarding the control of SO2 emissions. The principal challenge is the development of cost-effective coal preparation approaches for sulfur removal beyond currently achievable levels. Opportunities are provided in the form of incentives associated with a novel system of SO, allowances and a policy environment based on the proper functioning of familiar market forces. An allowance, as defined in Section 402(3) of the Amendments, is "an authorization ... to emit ... one ton of sulfur dioxide." To achieve the objective of the Clean Air Act Amendments, SO, emissions will be eventually capped at 8.12 Mt (8.95 million st) annually by controlling the number of allowances issued nationally. By permitting allowances to be bought and sold once issued, the law encourages "overcompliance" as a source of profit for owners of excess allowances. Many details concerning the administration of allowance trading are not yet written.

Jan 1, 1992

By Robert J. Wise

The mine plan for an underground longwall mine plan usually requires a longwall panel conveyor that begins operation at its maximum length and gradually shortens over the life of the panel. Current mine plans around the United States require initial panel conveyor lengths of up to 4500 m (15,000 ft) and capacities of up to 3.2 kt/h (3500 stph). Because these conveyors are constantly being moved from panel to panel, their components must be as compact and light as possible, and the design must be flexible enough to be modified as new terrain and conditions are met. In the past, when drive horsepowers or belt tensions were exceeded due to conveyor length, a new flight would be added, including additional belt storage units. In some cases, this led to as many as three flights installed in a single longwall panel. As the longwall retreated through each flight, mining was required to stop during removal of the drives and storage units. This sometimes meant several days of lost production. Intermediate drive technology was developed to eliminate this excessive downtime and still keep conveyor belts, motors, pulleys and other components as small as possible. With intermediate drives placed along the carrying side of the conveyor, belt and motor sizes are kept as small as possible, and only one storage unit is needed. Most importantly, as the longwall retreats through a booster drive station, it can generally be removed in a regular downtime slot and no additional production time is lost.

Jan 1, 1993

By G. Norman Owen, Roger E. Scholl, Tor L. Brekke

INTRODUCTION Underground structures are generally regarded to be safer than surface structures during strong seismic motion, except when crossing a causative fault. Recent studies of observed earthquake damage to tunnels generally support this view, although instances of severe damage and, occasionally, collapse are reported. For proposed underground construction of sensitive structures such as nuclear power plants, liquefied natural gas facilities, and nuclear waste repositories, a verification of the seismic response of underground structures will be required.. This paper discusses the stabilization recommendations used in a study of additional costs required to protect tunnels against ground motion caused by earthquakes and underground nuclear explosions (1). The study is a part of the site investigations for possible construction of a nuclear waste repository. The additional costs estimated in the study are not presented here; only the stabilization measures are presented in the present paper. The tunnels, which would constitute the underground facilities of a possible repository, are assumed to be 5.5 m (18 ft) in diameter and to be located at a depth of 600 m (2,000 ft). Three candidate geological materials are considered: argillite (shale), granite, and tuff. Several peak ground accelerations are used: 0.3g, 0.5g, and 0.7g for earthquakes, and 0.5g, 0.7g, and 1.0g for underground nuclear explosions. Potential damage due only to shaking is considered here. This paper does not discuss problems that result from creep or sudden rupture of intersected faults or from ground failures at portals.

Jan 1, 1979

By Charles E. Joachim

Current Army tunnel destruction criteria (1) are based on limited nuclear-explosive (NE) and high-explosive (HE) test data. The PILE DRIVER (2) and HARDHAT (3) events investigated tunnel and support system response where yields were relatively large and tunnel diameter small compared to typical underground openings and localized stress fields of low yield weapons. Some limited tunnel destruction information was obtained from underground events of the PLUMBBOB and HARDTACK II Series (4). These events used access drifts which were designed to be self closing at the weapon point. The limited NE data are augmented by HE results from the Underground Explosion Test (UET) Program, a series of model and prototype-scale experiments in granite and sandstone (5). Weapon standoff distances (charge c.g. to tunnel wall) were at or near the maximum for major damage. Limited tunnel destruction was produced by a series of hasty and deliberate tests (6) on abandoned railroad tunnels in basalt. Additional HE data were obtained from model tests at the Waterways Experiment Station (WES) (7) using 2.1 MJ (2 lb) TNT charges and tunnel diameters varying from 3 to 17 cm (1.2 to 6.6 in). Recent laboratory scale HE experiments (8) conducted at the WES under the ESSEX program investigated the effects of tunnel diameter, standoff distance, charge confinement, material strength and to a limited extent, tunnel spacing and liner strength variations on tunnel damage. This paper summarizes the analysis conducted to develop predictions for the effects of low-yield nuclear weapons against tunnels and underground openings in rock.

Jan 1, 1979

In 1991, environmental issues related to coal mining continued to be an integral part of managing a cost-effective operation. Environmental regulations and their implementation can create considerable cost burdens on operating mines. Environmental responsibilities require management decisions to be made on a whole systems approach that is comprehensive in costs and consequences. Most of the regulatory activity in 1991 that affected coal was related to reauthorization or revision of several pieces of legislation. Issues related to the reauthorization of the Clean Water Act, the Resource Recovery and Conservation Act (RCRA) and Abandoned Mine Land. Clear Water Act considerations will encompass discharge standards, wetlands issues and proposals to regulate ground water quality at the federal level. Discussion regarding RCRA includes efforts to expand regulatory authority into the area of coal mine waste. That is currently regulated by the Office of Surface Mining (OSM). Another RCRA consideration will be the disposal of coal combustion byproducts. Abandoned Mine Land reauthorization continues the Abandoned Mine Land tax on coal operators. This tax has been in effect since 1977. Regulatory revisions were also proposed by the Department of Interior on valid existing rights, subsidence, federal coal leasing programs and OSM's troubled Applicant Violator System. Industry officials have been critical of the revisions. A federal appeals court found that evidence supported claims by Whitney Benefits, Inc. that the passage of the Surface Mining Control and Reclamation Act (SMCRA) deprived the owner of full economic use of its property. Before SMCRA's passage, Whitney established an operating agreement with Peter Kiewit Sons Co. to mine coal.

Jan 1, 1992

By James W. Martin, Robert R. Faddick

INTRODUCTION Virtually every sector of society in our country feels the impact of tunnels, either through the transportation of water, commodities, or people. The economic implications are staggering. The Committee on Rapid Excavation (1) reported that during the near future, 1968-1975, underground excavation activity will comprise 946 miles of tunnels (subways: 85 miles; underground urban highways: 123 miles; intercity highway tunnels: 210 miles; water supply tunnels: 528 miles) and 5,119 million tons of crude ore; metals: 874 million tons; nonmetals: 899 million tons; and coal: 3,346 million tons. It is estimated that the cumulative demand for underground excavation in the decade 1970-1979 will be 13 billion dollars for construction-oriented demand and 16 billion dollars for mining-oriented demand. The respective figures for the decade 1980-1989 are estimated at 22 billion dollars and 18 billion dollars. Of the many advantages claimed for tunnels (2, 3, 4, 5) the environmental considerations are becoming increasingly important. Transportation tunnels particularly for rapid transit systems, offer reductions in noise pollution and air pollution while improving aesthetics and optimizing land use (fewer problems of right-of-way and disruption of utilities). Considerable interest has been shown recently in sub-surface construction and mining (6, 7, 8). Recognizing the future demands for tunnels has led to considerable study of methods to improve rates of tunnel advance per day, safety, and the overall economics. The search for higher rates of advance has Led away from what has heap termed conventional methods (drilling

Jan 1, 1974

By John W. Rushton

THE PLANNED MAINTENANCE PROGRAM All concentrators should start with a planned maintenance program from day one. Every- body thinks they have a program in place before start-up, but in reality, most have only a fraction of what is needed to avoid the "Post Start-up Disaster" (PSD) - two years for start-up is not that uncommon. An effective program has all of the following: (1) Good people. (2) Area Maintenance. (3) Good PM Checklists. (4) Daily Work Schedules. (5) Written Work Orders. (6) Equipment Histories. (7) Backlog Control. The installation of a workable program takes hard work, talent, and commitment. You have to know what you are doing (hard work will not replace talent). Good People Good people are available in any location if you make the effort. Always check references carefully (both superiors, peers and subordinates). Was the last concentrator they worked at successful? Was it clean? Find out! Success or failure follows people around. I know people who are experts on PSD because they have lived through it three or four times. You need some college trained people with hands-on experience. There are no secrets, you have to make the effort. If you make a mistake in hiring (and you probably will), make the tough decision necessary to rectify it quickly. Area Maintenance Area maintenance refers to organization of supervision such that one person is uniquely accountable for every inch of ground and piece of equipment. Avoid overlapping authority if at all possible. You must have a planner as a staff position. A foreman cannot effectively plan and

Jan 1, 1986

Traditionally, production volume has been considered the major determinant of cost. As volume increases, total cost increases but unit cost decreases. This concept has been so widespread in industry that many of the tools used to analyze costs are based on production volume as the sole measure of activity and driver of unit cost-fixed and variable costs, cost-volume-price and breakeven analysis, contribution margin, flexible budgets, and others. Clearly, volume is a driver of cost. It is important in both a tactical sense (to the manager at an operating mine) and a strategic sense (as one determinant to the firm's overall cost position). However, many other factors influence costs as well, even though they have not been studied to the same extent. For example, production managers know that their costs will be reduced if the workforce does not have accidents. Safety costs are to a large extent independent of volume. Other cost components increase as volume increases, such as some environmental charges. Some costs may or may not reflect volume changes. Maintenance, for example, may appear as either a fixed or variable cost, as can operating labor in facilities that are highly automated. In the strategic sense, where the firm is selecting a strategy to pursue competitive advantage and increased profitability, all costs are variable. This reflects both the strategic intent and the long-term time frame associated with strategic positioning. Tactically, on a month-by-month basis, some costs are essentially fixed. Cost driver analysis must therefore consider the relevant time frame.

Jan 1, 1999

By J. F. T. Agapito, R. R. Goodrich

Yield pillars have been used for many years to help reduce stresses near mine openings and improve roof and floor stability. A yield pillar is often defined as a pillar that fails but retains residual strength. Stress transfer occurs through the roof and floor after the peak strength of the pillar is reached. High stresses are transferred from around the openings onto abutments that can be barrier pillars or unmined ground. This mechanism, often referred to as pressure arching, is possible as long as the width of yield pillar mining (panel width) is less than the critical width above which stresses cannot be carried by the overburden. Significant stress transfer also can occur due to small amounts of pillar and/or floor yielding before the peak strength is reached. This is accomplished in a quasi-elastic manner with little or no visible roof and pillar fracturing or floor heave. Long-term stability may be achieved when stresses and mechanical properties are favorable to prefailure yielding. This paper gives practical examples where improvements in stability and resource recovery were achieved with this mechanism. Yielding was assessed by comparing measured and calculated vertical pillar stresses. Results indicated that calculated stresses in the pillars were 25% to 40% higher than the measured stresses, demonstrating significant arching load transfer to the abutments. Prefailure yielding is probably often present but unintentional in both development and production areas. Better recognition and use of this mechanism should lead to design improvements, as mines become deeper.

Jan 1, 2003

By D. E. Ranta, Stephen W. Thomas, Clancy J. Wendt

One of the most difficult tasks associated with placer mining is the sampling of the deposit. More placer projects have failed due to inaccurate assessment of the reserves than to any other reason. Within the realm of placers, those containing valuable minerals with a high unit value are more difficult to sample than those with larger bulk, lower unit value minerals. Some items to consider when sampling a placer deposit are as follows: A. A relatively large sample is needed for accurate valuation of the ground being tested. Placers are composed of many sizes of gravel which makes a representative sample difficult to obtain. B. When sampling placers for high unit value minerals such as gold, any error in mineral content of the sample will be magnified in the calculation of reserves. C. Values are usually erratically distributed within the gravel mass. Therefore, some placers with a more uniform value distribution may be adequately assessed with a minimum number of samples whereas a deposit with a highly erratic distribution of values may not be adequately sampled regardless of how many samples are taken. D. The investigation of a placer deposit should be made by, or be under the direction of, a person experienced in the art of placer sampling. F) During a sampling program, items that must be observed and noted in addition to the sample size and valuable mineral content should include boulder size and number, clay content, bedrock conditions, water, frozen ground, false bedrock, and any other physical characteristics that would affect mining of the deposit.

Jan 1, 1992

By C. B. Manula

This paper presents the results of an application of the PSU/USBM Open Pit Materials Handling Simulator (1) to a large stripping mine in the Southwestern Coalfield. The specific objective of the study was to demonstrate the application of the simulator to a complex multi-pit operation, with emphasis on simulating short term and long term production plans recommended for the mine by Theodore Barry Associates (2). Mine Description The mine is located in the Southwestern Coalfield, which encompasses parts of the states of Utah, Arizona and New Mexico. The lease area presently covers 121500 x 103 m2 (30000 acres) in a strip 37.007 x 103 m (23 miles) from north to south and up to 1609 m (1 mile) in width, located at an elevation above 1525 m (5000 ft). Three gently dipping coal seams are present, of which the upper seam (#3) averages 0-5.5 m (0-18 ft); the intermediate seam (#2) averages 0-1.2 m (0-4 ft); and the lower seam (#1) averages 0-2.4 m (0-8 ft). Overburden is mixed sand, gravel, calcareous clay, caliche and sandstone, with calcareous shale and sandstone burden between seams. Where the seams are covered by less than 6.1 m (20 ft) of overburden, they are generally weathered and oxidized and are not extracted. Stripping ratios have ranged from 3.5 to 6.0 with an average of 5.4. All future plans were based on a stripping ratio of 5.3.

Jan 1, 1979

By C. P. Siess, S. L. Paul, E. H. Gaylord

Several types of tunnel supports are being investigated experimentally and analytically at the University of Illinois at Urbana-Champaign under the sponsorship of the Federal Railroad Administration, Department of Transportation. The results of work on two types will be discussed here. These are steel sets and continuous, monolithic steel-fiber-reinforced concrete liners. The latter is a model of a short length of liner that might result from a continuous slip-forming operation in a tunnel excavated with a boring machine. Tests have been performed on both types of support and analyses are being developed which will greatly broaden the scope of the test program. The objective of these studies is to improve the understanding of basic behavior of these supports, and to develop techniques for their analysis. The analyses will then be used to perform parameter studies that will lead to more rational procedures for structural design. The tests provide a check on the accuracy of the analysis and demonstrate the overall behavior and modes of failure. Another part of the project is concerned with the interaction of support and medium, and thus prediction of loads for the supports. These studies are presented in greater detail in a recent report (1). A brief outline of results obtained to date are presented in this paper. STUDIES OF STEEL SETS Description of Set Tests The sets tested were of the horseshoe type with a 5-ft radius arch section and 7-ft straight legs. They had bolted joints at the crown

Jan 1, 1974

By K. Wangerud, B. S. Caruso

A water-balance model with deterministic and stochastic components was developed and used for the Gilt Edge Mine Superfund Site in South Dakota. The model was developed to evaluate the risks of contaminated runoff discharging to surface waters based on assumed water treatment plant (WTP) rates, for different remedial alternatives. The objectives of the modeling were to use a stochastic approach for the analysis of precipitation based on historic records and to make a probabilistic estimation of annual and monthly runoff from disturbed/mining activity areas that now require, or will need, treatment at the WTP, water storage and changes in a major pit, and risk of contaminated water bypass of the WTP to a downstream drainage. Subareas/source areas generating contaminated runoff requiring treatment were delineated. A simple water-balance model was used based on precipitation inputs and evapotranspiration and groundwater losses. Annual and monthly precipitation records for Lead, South Dakota, were used to estimate precipitation at the mine site. A lognormal distribution was estimated for monthly precipitation. The stochastic software package/ Excel add-in "@Risk" was used to generate random monthly precipitation values using a Monte Carlo method based on the distributions. The average annual and monthly distribution of pan and lake evaporation and of groundwater losses were also estimated for the site. Stochastic outputs from the model for the end of each month and year included contaminated runoff requiring treatment, water storage in mine pits and the risk of WTP bypass given different assumed WTP rates. The probability of the time required to dewater the pits was also modeled.

Jan 1, 2003

By S. K. Kawatra, K. J. Shoop

An analysis of an iron-ore processing plant showed that its performance was affected by seasonal temperature variations, resulting in reduced grinding efficiency during the winter months. Laboratory and pilot plant studies were conducted to determine the cause of the observed loss of efficiency at lower temperatures. Two types of experiments were performed: drop tests and wet grinding tests. Drop testing was performed to determine the effect of brittleness and frozen pore water on the breakage characteristics of the ore. The wet grinding tests were divided into laboratory tumble tests and pilot-plant tests. The combined results of drop testing and wet grinding were used to make predictions on the performance of plant-scale autogenous grinding. From the drop tests, it was determined that dry iron ore, basalt and sandstone did not change in brittleness over the temperature range studied (-25º to 25ºC). However, when the rocks were water-saturated, the highly porous sandstone became considerably more fracture-resistant upon freezing, due to "grouting" of the pores and preexisting cracks by ice. This effect was not seen for either the iron ore or the basalt, because they were considerably less porous than the sandstone. Tumble tests on both laboratory and pilot scales showed that both the addition of fines to the test charge and a reduction in temperature caused a decrease in the amount of new fines produced. This reduced fines production was the result of increased slurry viscosity when either the fines content increased or the temperature decreased.

Jan 1, 1998

The transfer of Langmuir-Blodgett (LB) monolayers of collector molecules to the surface of mineral crystals is an excellent method for the study of collector adsorption phenomena and is of particular significance in the understanding and development of improved flotation separations. The fatty acid/fluorite and amine/sylvite potation systems were investigated by the Fourier transform infrared/internal reflection spectroscopy (FT-IR/IRS) examination of transferred LB monolayers of collector molecules at the surfaces of the mineral crystals. The [ir]-A isotherm study of fatty acid and amine, typical anionic and cationic collectors, showed the different packing trends dependent upon the pH and/or type of subphase. This result clearly reflects the effect of pH on compound formation and dissociation of the collector molecules. Identification of the collector adsorption state and confirmation of the validity of the FT-IR/IRS adsorption density equation were included in this research effort. This allowed for a detailed discussion of collector adsorption phenomena. As a result of these experiments, it is possible to relate the hydrophobic character of a surface to the nature of the adsorbed collector structure and thus describe flotation behavior in greater detail. For example, it appears that in the case of oleate/ fluorite the equivalent of an LB monolayer can form spontaneously during adsorption from solution, and this structure is known as a self-assembled monolayer (SAM). Such a state is significantly more hydrophobic than the oleate structure which forms on the calcite surface at an equivalent adsorption density.

Jan 1, 1996

By Ricardo D. Presnell, Erich U. Petersen, William J. Tafuri, Donald M. Hausen, Russell C. Babcock, William L. Gunter, Thomas R. Gibson, Douglas N. Halbe, Jay W. Hammitt

The Barneys Canyon orebody is a sediment-hosted disseminated gold deposit located 8 km (5 miles) north of the Bingham Canyon porphyry copper mine. Mineable oxide reserves are 8.6 million tonnes (9.5 million short tons) grading 1.64 g/tonne (0.048 oz/ton) gold. Host lithologies are carbonates and siliciclastics of the Park City and Kirkman-Diamond Creek Formations of Lower Permian age. Gold distributions are controlled by favorable stratigraphic units and associated alteration, and structures. Dominant alteration is decalcification and bleaching of carbonates, and argillization and bleaching of sandstones. Gold to silver ratios are greater than 1:1. Anomalous trace metals include arsenic, antimony, mercury and thallium. The Melco deposit lies 2.4 km (1.5 miles) southwest of the Barneys Canyon deposit. It is spatially associated with a steeply northwest-dipping siliciclastic breccia in the Kirkman-Diamond Creek Formation at the contact with underlying orthoquartzites of the Freeman Peak Formation. Both gold-bearing oxidized and sulfide lithologies are present, often in sharp contact. Mineable oxide reserves are 2.8 million tonnes (3.1 million short tons) grading 2.40 g/tonne (0.07 oz/ton) gold. Anomolous trace metals include arsenic, antimony, mercury and thallium, which are generally present in concentrations greater than those at Barneys Canyon, particularly in sulfide-bearing material. A spatial, temporal and genetic relationship is proposed between the Melco deposit and late-stage gold mineralization at Bingham Canyon, although both the Melco and Barneys Canyon deposits have many similarities to Carlin-type gold deposits.

Jan 1, 1990

By Steve Tadolini

Underground roof falls can have devastating effects on the safety of operations personnel, and equipment, and seriously impact production. Immediate steps are usually taken to danger off and secure the area while clean-up efforts are designed and implemented. A critical step, often overlooked due to production demand, is the determination of - why the roof fall occurred so that additional occurrences can be avoided in future developments or what measures can be taken to identify areas that have similar ?symptoms?? Forensic engineering includes the investigation of materials, products, structures or components that fail or do not operate/function as intended. The authors define forensics in ground control engineering as the study of evidence discovered while examining underground roof falls by applying expert observational techniques and established mining engineering principles to determine the probable cause, hypothesize solutions, and design engineering safeguards to prevent reoccurrences. Simply stated, the primary steps in the forensics of underground roof fall techniques are: ?Assess regional and local conditions prior to the event. ? Assess post-event conditions. ? Hypothesize plausible ways in which the pre-event conditions became the post-event conditions. ?Search for evidence that either denies or supports the various hypotheses. ?Apply engineering skill to relate the various facts and evidence into a cohesive scenario of how the event may have occurred. This paper details the proposed technique by utilizing a roof fall case study that required the examination of five primary factors: mine design parameters, excavation geology, method of excavation, method of support, and mining cycle times.

Jan 1, 2009