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By Kanhaiya Mishra, Phanil. K. Mandal, S. K. Behera, P. S. Paul, Prashant Singh, C. N. Ghosh

The techno-economic and social benefits of cemented paste backfill (CPB) resulted in its wide acceptance by the mining industry. The Ordinary Portland Cement (OPC) remains the key binder but to diminish its economical constraints, suitability of alternate binders has been examined worldwide. The present study aimed to investigate the effect of partial replacement of OPC with fly ash on the CPB’s strength and to determine the most optimal mix to achieve the required strength (1 MPa at 28 days of curing) at the most cost-effective way using the Bayesian network (BN). The CPB mixes were prepared at 72 wt.% solid concentration with mill tailings (87–91%), OPC (6–13%), and fly ash (0–4%), and instantly after mixing, fresh (slump, bleeding, density) CPB properties were measured. The strength was tested at 7, 14, 28, and 56 days of curing and initially analysed through traditional model. The traditional models follow the aleatory principle and are considered not appropriate for geotechnical engineering. Hence, the BN model was developed and tested. The reliability of two classifiers in learning model structure was compared which gives Naïve Bayes as the highest reliable tool. The CPB’s strength is most sensitive to the OPC content. The most consistent mix(s) is mill tailings: 87–88%, OPC: 9–11%, fly ash: 1–4%. Adding fly ash at 89–91wt% mill tailings possesses high failure probability of the CPB. The collinearity test indicates that the fines percentage and chemical composition of CPB’s ingredients are highly correlated with its slump, bleeding, and strength development.

Jul 14, 2022

By Harrison H. Roberts

A. We are aware that many who are in the audience have perhaps heard before some of the material which will be presented. Since our firm is more closely associated with the heavy construction industry our experience is more oriented in that direction. Notwithstanding this, the subject your program committee has asked us to present centers mainly in the earth-moving field. We find a common denominator between say, the stripping of a site to uncover an ore-body which will be developed by open-pit methods, and that of excavating & transporting materials for an embankment dam, airport or other project. Both are earth-moving problems and we offer for your consideration a means of determining the most favorable method, equipment selection and resultant cost. We do considerable studies involving rock excavation for tunnels, underground powerhouses, inclined and vertical shafts for penstocks, muck-removal, electrical cable & other related underground work. Hence, we believe we speak the same language.

Jan 1, 1972

By Yongheng Jiang, Wentong Wang, Haoming Luo, Chuanju Liu, Qianjun Zhang, Sha Guo

Rock burst has always been a major problem in deep underground engineering with high stress, and rock burst strength evaluation has become an important research topic. To effectively predict the rock burst hazard in underground rock mass engineering, a cloud model (CM) rock burst intensity evaluation method based on the CRITIC method and order relation analysis method (G1) was proposed in this paper. First, a rock’s uniaxial compressive strength σc, tangential stress σθ, uniaxial tensile strength σt, ratio of uniaxial compressive strength to tensile strength σc/σt (brittleness coefficient), ratio of tangential stress to uniaxial compressive strength σθ/σc (stress coefficient), elastic deformation energy index Wet, and depth of cover H were selected as evaluation indices of rock burst intensity. Ninety-five groups of rock burst measured data at home and abroad were selected, and the objective weight and subjective weight of each index were calculated by using the CRITIC method and G1 method, respectively. The comprehensive weight was determined according to the combined weighting method of game theory, and the sensitivity of each evaluation index was analyzed. By utilizing a forward cloud generator, the membership degrees of different rock burst grades were calculated, and then the rock burst intensity grades of the samples were evaluated and compared with the evaluation results of the CRITIC-CM method and G1-CM method and the actual grades. Finally, the rock burst classification ability of the model was analyzed. To better verify the accuracy and reliability of this model, the rock burst case of the W39 line in the Chengchao Iron Mine was analyzed by using this model. The research results show that the rock burst evaluation results based on CRITIC-G1-CM are basically consistent with the actual rock burst grade, and the rock burst intensity grade evaluation model has good practicability and reliability.

Sep 1, 2023

By Omid Asghari, Amin Mousavi, Arshad Ranjbar

Geometallurgical modeling of the production benches is an attempt to estimate the geometallurgical variables of the different ore domains, which leads to a better understanding of the ore and its properties. Having geometallurgical variables results in a more accurate prediction of ore characteristics, an improved drilling and blasting operation, and better efficiency of the processing plant. In this research, the geometallurgical variables required for the geometallurgical modeling of the extraction benches are discussed. Then, the relations between Bond work index (BWi), as one of the most important geometallurgical variables and the primary grindability index, and rock geomechanical properties are investigated based on the previously published studies. The BWi is the main parameter for measuring the resistance to the grinding of ore minerals. It represents the energy required for processing (e.g., crushing, grinding) ore rocks in the beneficiation plant. As a real case study, BWi of a production bench in Sungun Copper Mine, located in East Azarbaijan province, Iran, was estimated. The rock’s geomechanical properties were measured using laboratory tests, including uniaxial compressive strength, Brazilian tensile strength, point load strength, and hardness. Then, BWi was estimated using the proposed formulas in the literature and the results of the rock’s geomechanical properties. The selected bench consists of three ore zones and two dyke domains. The laboratory tests revealed that the first ore zone has a slightly higher compressive strength than the other two zones, while the compressive strength of the waste rocks is larger than the ore domains. Using the proposed equations in the literature, the predicted values of the BWi for the samples in ore zones are in the range of 6.36 – 14.44 (kWh/t), and therefore this wide range must be considered when the short-term production schedule is planned. In addition, variations are observed in the samples within a specific zone and between the ore zones, demonstrating heterogeneity in the selected bench. Finally, wide-open results obtained by different equations show a necessity to perform a geometallurgical program specifically for the Sungun mine.

Oct 28, 2021

By W. J. Spat

Political risk is an integral part of the mining business in Northern Andean countries. Peru, Ecuador, Colombia, and Venezuela all have a higher than average political risk compared with other South American countries. Successful operations in such contexts require: 1. Good political risk information; 2. A thoroughgoing political risk management plan; and 3. A strategy to deal with political risk perception on the part of the investing public. Obtaining quality political risk information, developing a political risk management plan, and addressing political risk perception are the foci of this work.

Jan 1, 1999

By H. Gerry Stephenson, Devin Castendyk

"One of the most important environmental issues associated with contemporary openpit mining is the closure of mine pit lakes, and the perpetual legacy these lakes can potentially generate. Ideally, successful pit lake closure includes the following:• The water quality within the pit lake, plus surface water and ground water discharging from the pit lake, meets premining or other acceptable water quality conditions of the receiving environment. • The termination of all active treatment processes.• The return of the pit lake to the government for long-term care and maintenance.• The release of the mining company from all future liabilities associated with the pit lake.• The return of the environmental bond to the mining company.• The reuse of the pit lake for some post-closure, beneficial purpose.The achievement of these goals is known as walk away pit lake closure.Peer-reviewed publications of successful walk away, pit lake closure provide mining companies with the ability to address public concerns regarding the safety of pit lakes which commonly occur during the permitting, operations, and closure phases of mining. To date, most published work on walk away, pit lake closure work has occurred in the coal mining sector in Germany and Australia (McCullough et al., 2009; Jones and McCullough, 2011; Kumar et al., 2013; Schultz et al., 2013). In North America, examples of walk away, pit lake closure are not widely discussed in the literature despite there being excellent examples from the coal mining sector in Alberta, Canada (e.g. Pleasure Island, Black Diamond, East Pit, Sphynx, Robb, Lovette, Siltstone and Sterling), and from the iron mining sector in Minnesota in the United States (e.g. Portsmouth Lake, see MNDNR, 2018). Although seldom included in discussions of pit lakes from the metal and coal mining sectors, the aggregate and fabricated-stone mining sectors also produce pit lakes, and there are numerous examples throughout North America where these pit lakes have been successfully closed and transformed into post-mining resources (Vandenberg, 2018; Crossman, 2019). The difficulty of finding these good examples in the literature makes it challenging for companies to respond to public and regulatory questions regarding pit lake closure and reuse. As such, there is a pressing need to document the motivations and approaches used in examples of successful, walk away, pit lake closure in North America so that the mining industry, at large, can learn from these examples and can better address public concerns."

Aug 1, 2019

By Walter B. Hester

All persons and communities that have experienced strong-motion earthquakes are convinced of the importance and complexity of earthquake problems thatmust be solved in order to reduce the personal hazards and property losses to a reasonable minimum. It is also clear that absolute elimination of all risks is impossible. Reduction of existing hazards and precautionary measures which will minimize chances for disaster can be accomplished by realistic appraisal of the effects of recent earth- quakes on modern structures and installations. Localities that have reason to expect so-called strong- motion earthquakes can anticipate these effects by taking appropriate steps. Valid earthquake information can only be obtained from earthquakes. Each earthquake contributes to the body of knowledge by additional facts and by clarification of previous observations. Rational interpretation of the data followed by practical application of the conclusions can contribute greatly to the safety of persons and property. The general public expects the architectural and engineering profession to accept this obligation and render this service. Most earthquake hazards are man-made and arise from the imperfections of the works of man and his failure to anticipate the consequences when the natural characteristics of his environment are ignored. If it is not given to man to prevent such natural phenomena as earthquakes, it is sometimes within his power to control their destructive effects and to reduce to a minimum the toll of life and human suffering.

Jan 1, 1958

By L. O’Connor, E. Tarshizi

The objective of this work is to provide a detailed review and a list of references in chronological order, comprising 80 recent technical papers, on the use of discrete-event simulation (DES) modeling in mining engineering. In this article, the review papers of published mine simulation projects through 2007 are summarized, and then a comprehensive review of individual articles published from 2008 to 2015 is presented. This survey work also includes analyses of the simulation tools used in the published projects, mining types and applications in order to assess these key features and evaluate the recent state of research in mine DES simulation. In addition, an interactive map visualization for the locations of the simulated projects is made available on a website to benefit current and prospective scholars in the field. The results of this investigation revealed that the most common application of DES in mining had been mining equipment selection and analysis, while ore processing and risk management projects were less frequently reported. The results also showed that modeling surface mines were in the majority, but the trend of publications for underground mine simulations had also increased. According to the results, ARENA was the most popular simulation software package, but several simulation tools that were only used once or twice in the mining projects are also included in this review.

Jan 1, 2018

By L. O’Connor, E. Tarshizi

The objective of this work is to provide a detailed review and a list of references in chronological order, comprising 80 recent technical papers, on the use of discrete-event simulation (DES) modeling in mining engineering. In this article, the review papers of published mine simulation projects through 2007 are summarized, and then a comprehensive review of individual articles published from 2008 to 2015 is presented. This survey work also includes analyses of the simulation tools used in the published projects, mining types and applications in order to assess these key features and evaluate the recent state of research in mine DES simulation. In addition, an interactive map visualization for the locations of the simulated projects is made available on a website to benefit current and prospective scholars in the field. The results of this investigation revealed that the most common application of DES in mining had been mining equipment selection and analysis, while ore processing and risk management projects were less frequently reported. The results also showed that modeling surface mines were in the majority, but the trend of publications for underground mine simulations had also increased. According to the results, ARENA was the most popular simulation software package, but several simulation tools that were only used once or twice in the mining projects are also included in this review.

Jan 1, 2017

By T. J. Batchler, K. M. Mohamed, D. F. Gearhart, R. K. Zipf

Seals are explosion-resistant structures built in underground coal mines to isolate abandoned mining areas from the active workings. An equivalent single degree of freedom (SDOF) method such as the single-degree-of-freedom blast effects design spreadsheet (SBEDS) developed by the U.S. Army Corps of Engineers can be used to design seals to resist mine explosions. The critical input for the SDOF code is the seal resistance function. The objective for this study is to develop engineering data for design of plain concrete (PC) and reinforced concrete (RC) seals using finite element (FE) models. The FE models can then be used to generate resistance functions for different PC and RC seal designs, which can be used in the SDOF codes. The U.S. National Institute for Occupational Safety and Health (NIOSH) researchers designed and built a test fixture for use in conjunction with NIOSH’s Mine Roof Simulator to apply a four-point bending load on the face of the tested seal. Eight large-scale experiments for each PC and RC seal were conducted. The experimental design considered the effects of the foundation strength, hitching and roof-to-floor convergence. Calibrated FE models for PC and RC seals were developed using ANSYS Ver. 13. With a very limited number of engineering-based assumptions and a single set of data—including Young’s modulus, compressive strength, stress-strain relationships, etc.—the PC and RC seal models successfully calculated the recorded resistance functions and failure patterns for a wide range of boundary conditions. Plug and RC seals were assumed for a 1.83-m- (6-ft-) high entry to demonstrate the application of the calibrated finite element models for calculating the resistance functions of these seals. The resistance function of a particular plug seal case was found to be a bilinear relationship. The resistance function of a particular RC seal without shear reinforcement was found to be a nonlinear relationship.

Jan 1, 2013

At long last, mining is on the rebound in Minnesota?s Iron Range and the excitement is starting to show. The SME Minnesota Section?s annual meeting was once again held in the heart of Iron Range country, at the Duluth Entertainment and Conference Center on the Duluth waterfront. The conference boasted a record attendance of 475 people and its largest-ever trade show. Appearances by Governor Mark Dayton?s new Iron Range Resources & Rehabilitation Board (IRRRB) appointee, Tony Sertich, as well as a local Fox news crew (see clip on SME website [link: http://fox21online.com/news/duluth-mining-conference-breeds-optimism-tech-innovation]) made clear that a lot of eyes [ ] are on the industry as it dusts itself off from the 2008-2009 recession. While the early years of the 21st century were very good to the Iron Range, the global drop in commodities prices and production left many companies reeling and brought back bad memories of the collapse of the industry in the 1980s. However, two years of solid growth and a rebound to above pre-2008 production levels have let the Minnesota mining industry to relax a little and talk seriously about long-term growth and stability.

Jan 1, 2011

By Richard J. Stoehr

Man has mined in all his time on earth about 3 billion ounces of gold. About one-half of this has been mined in the past 35 years. This gold is roughly in 3 large holdings: one-third held as reserves in Central Banks; one-third held as personal reserves; and one-third is in jewelry or other fabricated products. The world per capita availability of mined gold is increasing and there are many factors and forces shaping gold's future. Currently, gold has a favorable exchange ratio and this is encouraging many new gold-mining developments. Production is increasing and new techniques are surfacing. The use of gold in the financial markets is increasing in some unique ways and gold is again fulfilling its role as a universal money, making gold's future predictable. Currently, man is mining gold at the rate of approximately 44 million ounces annually and is therefore adding to the total supply of gold approximately 1.5% of newly mined gold each year. This current production plays a small role in the pricing mechanisms since a very large part of the 3 billion ounces mined in all of history is available to the market in one form or another.

Jan 1, 1984

By P. Samanta, Mohammed N. Azad, Gustad F. Taraporewalla, A. K. Mukherjee, Abhay S. Patra, D. Sachinraj

Beneficiation of coal is a water intensive process, and the water is recovered in downstream operations in the high rate thickener (HRT) and vacuum belt filtration (VBF). Clean coal particles entering the HRT have an inherent tendency to enter the overflow because they are extremely fine and hydrophobic. Hence, flocculants (polymers) are used to floc the ultrafine particles so that they settle and enter the underflow. Ultrafine coal particles (−37 μ), which are highly hydrophobic, if present in the stream, will not be efficiently captured by using flocculants alone. This is observed in the normal plant operation at one of the beneficiation plants in the Jharia region, Jharkhand, India. Approximately 6–7% of the feed to the HRT enters the over flow (supernatant water). Hence, this amount of clean coal particles is not recovered and account for production losses. A comprehensive settling and dewatering test work was conducted with clean coal slurry using several commercially available reagents. Studies were also done on different combinations of reagents, including coagulants and surfactants along with flocculants, to improve the settling behavior of the coal particles. The reagents were assessed based on their performance with respect to settling rates, overflow water clarity, and compaction of the underflow solids. Emphasis was given to the ability of the reagents in compacting thickener underflow to higher densities so that maximum water could be recovered from the thickener. Pretreatment of highly hydrophobic coal slurry with a combination of coagulant and surfactant followed by flocculation showed very good settling characteristics with clear overflow.

Sep 30, 2021

By Nick Rose, Mathieu Veillette, Matthew King

"The Teck Highland Valley copper (THVC) mine is located approximately 55 km (34 miles) southwest of Kamloops and approximately 20 km (12 miles) west of Logan Lake, BC, Canada (Fig. 1). Mining at THVC is conducted at three openpit operations comprised of Valley, Lornex and Highmont with a total annual output on the order of 300 kt (330,000 st) copper concentrate and 5 kt (5,500 st) of molybdenum concentrate. The Phase 8 pushback in the Valley Pit (Fig. 2) was mined from 2011 to 2016. Successful slope steepening occurred in the later stage of the pushback with the implementation of presplit blasting in 2015 and 2016.This article summarizes the investigation and design approach including: structural analysis, kinematic assessments of bench breakback potential, development of discrete fracture networks (DFNs) to characterize discontinuity fabric, rockfall modelling, 2D anisotropic limit equilibrium and 2D distinct element modelling, assessment of potential kinematic failure modes affecting double benches with 3D distinct element modelling and improved blasting techniques using e-dets. THVC is currently undertaking a mine life expansion involving the pushback of the west wall of the Valley Pit above Phase 8 to extend the mine life to 2029. Engineering geologyThe east wall slope in the Valley Pit is comprised of a 350-m (1,148-ft) thick sequence of glacial valley sediments that occur along the Highland Valley (Fig. 2), exposing an overburden slope up to about 225-m (740-ft) high below the crest of the ultimate east wall. The glacial overburden units consist of pro-glacial outwash and glaciofluvial deposits, glacial outwash sands and gravels interbedded with till and alluvial fans consisting of cross-bedded sands and sandy-gravels. Lacustrine sediments occur within the mid to lower portion of the glacial sequence and contain intervals of low-shear-strength clays and silts. Two large (1.3 and 7 Mt or 1.4 and 7.7 million st) waste rock buttresses were required to maintain slope stability using slot-cut and fill mining methods, as described in Fortin et al. (2011).The Valley porphyry deposit occurs in the central portion of the late Upper Triassic Guichon Creek Batholith, which intrudes assemblages of the Permian Cache Creek and Upper Triassic Nicola groups. The Valley deposit occurs in an area of intense fracturing near the intersection of the northerly trending Lornex Fault and the northwest to westerly trending Highland Valley Fault."

Apr 1, 2019

By C. Mark, D. M. Pappas

From 1999 through 2008, groundfall events resulted in 75 fatalities, 5,941 injuries and 13,774 noninjury roof falls in U.S. underground coal mines, according to the U.S. Mine Safety and Health Administration (MSHA). A comprehensive analysis of these events was conducted to better understand where and why these incidents occurred. The first segment of the study used the MSHA database to evaluate groundfall injury rate trends related to mining method, year, locality, seam thickness, mine size, coalbeds and seasonal effects. In the past decade, roof fall injury rates have dropped 50%, but rib fall injury rates have remained constant. Room-and-pillar mines had a roof fall injury rate that was nearly 2.5 times the longwall rate. High groundfall rates occurred in the Illinois Basin, a finding that correlates with other studies that have shown that roof rock in the Illinois Basin is weaker than that in the central Appalachian coalfields. Finally, noninjury roof fall rates in the eastern and central United States were found to be 50% higher from July through September, possibly because of the changes in humidity levels that may cause shale mine roofs to deteriorate. The second segment of the study evaluated the root causes of failure by reviewing all MSHA groundfall fatality reports for 1999-2008. Pillar recovery was the leading cause of groundfall fatalities (19%), followed by rib falls, roof skin falls and traveling under unsupported roof (16% each). Defining prominent ground control incident trends and hazards will identify areas where additional study is needed and where innovative solutions need to be developed to reduce these severe occupational hazards.

Jan 1, 2011

By AMIR EHSAN KIANFAR, Moritz Ziegler, TOBIAS HARTMANN, ELISABETH CLAUSEN

Accurate positioning information is a central step in the process of increasing automation and digitalization in the mining industry. Underground mine environments are prime examples for GNSS-denied environments that pose several additional challenges for the employed indoor positioning system (IPS). This work presents an ultra-wideband (UWB)–based system specifically tailored for underground mine environments. Initially, the UWB technology is reviewed and basic concepts of IPS are explained. Both software and hardware are described in detail, including positioning algorithms, electrical circuitry, and the mining-compatible enclosure. Finally, the results from field tests in an underground mine are presented and positioning performance and the influence of dilution of precision (DOP) on positioning results are empirically evaluated. The results show that the localization errors are mostly below 1 m. Individual zones of high localization errors are suspected to be caused by noise interference. Significant DOP influence due to the mining drift geometry can be confirmed. The system shows promising localization results for different mining applications, while influences negatively impacting the accuracy are presented as items for future research.

Jul 7, 2023

By J. H. Adkins

The goal of the project reported in this paper was to make recommendations for changes in roof bolting procedures and bolter design that would reduce roof bolter accident rates. To that end the project identified the major hazards associated with each task a roof bolter operator per-forms, normalized task accident frequencies. by the time spent on each task, reviewed equipment design features and operating procedures related to the identified hazards and developed recommendations for equipment and procedural changes that would reduce, if not eliminate, the hazards. The research steps completed during the project were: a. A review of related literature and re-search including roof bolting time studies b. The collection and analysis of 1975 accident data pertaining to roof bolter activities c. The normalization of the accident frequency data on the basis of time/task data d. A review of roof bolting equipment e. The development of a field data collection instrument f. The selection of mines for bolter observations g. The collection of field data h. Data analysis and problem specification i. The development of recommendations for corrective measures

Jan 1, 1978

By James Corcoran, Richard McLane, Joseph DeMello, Eric Carlson, Hans van de Vrugt

The Los Angeles County Transportation Authority’s Purple Line Extension Phase 1 is a $3.12 billion (USD) design-build, underground heavy rail project, connecting an existing station at Wilshire Boulevard and Western Avenue and extending west 3.92 miles under Wilshire Boulevard and terminating approximately 550 feet west of Wilshire/La Cienega Station. The project alignment runs through the heart of the world famous La Brea Tar Pits and one of the world’s largest urban oil elds. This paper presents a case history of the planning, design, and construction efforts to achieve successful construction of the bored tunnels through Reach 3 of the alignment. Further, this paper outlines the proactive partnership between the owner, Los Angeles County Metro (Metro), the Design Builder, Skanska-Traylor-Shea oint enture (STS), and Southwest Geophysics who provided the geophysical services. Specically, the project included background review of historic site data (e.g., oil eld maps, building foundation plans, historic aerial photographs, etc.), geophysical demonstration testing to ascertain the capability of borehole magnetics to detect oil wells, directional drilling of thousands of feet of horizontal and vertical boreholes, collection of high resolution magnetic gradiometer data along vertically and horizontally cased boreholes as well as the collection of surface magnetometer data, discovery (“ground truthing”) of detected geophysical anomalies, and abatement of potential obstructions within the tunnel alignment.

Jun 23, 2024

By Robert Stefanko

13.1-SUBSIDENCE AND GROUND MOVEMENT ROBERT STEFANKO 13.1.1-SUBSIDENCE AND FAILURE This treatment of subsidence and ground movement will be confined to subsidence control for limiting surface damage by assessing the significant parameters affecting ground movements during mining to optimize mining techniques. The material will be equally applicable to evaporite mining as well as coal but will not deal with block caving or similar systems where failure is deliberately induced and surface protection is not necessary or provided. When an underground opening is established, the original equilibrium is disturbed with resultant stress concentrations. While many factors are involved in opening stability, the span (W) undoubtedly is one of the most important factors in failure. Assuming it is relatively small, the overlying rock strata can bridge across the opening and little if any movement or convergence of top and bottom will occur. However, as the span increases, a point is reached where the stress in the overlying rock strata exceeds some strength value of the rock, and the top breaks. If the opening span is limited to some subcritical value (-We) and/or is at great depth (D), a pseudo-arch will form, achielring stability before rupture occurs to the surface. The boundary of this arch is thought to approximate an ellipse in form with the major axis vertical and equal to four times W, although there has been little field research to substantiate this theory. However, if the width of this opening is increased at this horizon to some critical value (W,) or the same span is created in a shallower seam, the overlying strata ill progressively rupture to the surface and the characteristic subsidence trough is formed (Fig. 13-1) The area of the surface affected is much greater than the area of the seam extracted, depending on the "angle of draw" (a), which is the angle between a vertical line from the edge of the opening and another line extended to a point at which subsidence tails out to zero. This angle has been found to be about 35° in Europe but is rather academic, being a function of instrument precision in detecting subsidence. Since the subsidence effect is so small at any point beyond n 25° angle, this latter may be considered the practical limit of subsidence. Further- more, indications are that the angle of draw varies with depth and nature of the strata.' In a field study over a 1,000-ft-deep potash mine in New Mexico, the maximum angle of draw was found to be 51.5°.2 So far, only a single opening has been considered. However, the width of the excavation applies to any complex mining system of entries, rooms and longwalls as long as the seam has been fully extracted and the width represents the distance from one solid rib to another. It will be noted that the amount of vertical displacement varies from point to point on the surface (s), but the maximum subsidence for a given trough occurs at the center (S). This latter value may not he equal to the maximum possible subsidence (Sm) which occurs only if a critical or super- critical (+W,) width has been exceeded (Fig. 13-1). Substantial surface damage can result when subsidence occurs. Factors affecting the amount and type of ground movement are: thickness and properties of the seam, angle of draw, width of excavation, depth and type of overburden, inclinations of strata and surface, and the amount of support left in the gob. In Europe,

Jan 1, 1973

By T. Faulkner, S. A. Richards

"The Scale-Distance formula is one of the primary means of determining the maximum amount of explosives that can be safely detonated at one time by a single delay. This paper describes a method of applying the Scale-Distance formula to the entire mining area using gridded surfaces. Using this technique, the operator can better determine the economic impact of nearby structures on the mine plan. INTRODUCTION As the surface mining of coal and stone encroaches near populated areas, precautions must be taken to minimize blast vibration damage to protected structures. The common method employed to minimize vibration damage is not to reduce the total amount of explosive in the hole (which would negatively affect fragmentation), but rather to introduce delays to reduce the amount of explosive detonated at any point in time. The Scale-Distance formula, an industry-accepted standard, may be used to calculate the maximum weight of explosive that can be detonated at one time without damaging the structure. This information may then be used to determine the number of delays required for each hole. Detonators make up a large part of the cost of blasting. At roughly $15 per detonator an additional detonator in the hole can be significant. It is normal to set off hundreds of holes at in one shot. An additional detonator in each hole can cost additional thousands of dollars per shot. The number of detonators is also a function of the depth of the holes and the hole spacing. Being able to accurately forecast the economic impact of blasting near structures improves a company’s ability to make informed decisions on how to approach property owners. Operators basically have three options when dealing with property owners: 1. Buy the property and blast without restriction 2. Negotiate with property owner for a waiver to allow unrestricted blasting 3. Comply with the legal blasting restrictions This paper proposes a method for the engineer to forecast for all points in the proposed mining area the impact of nearby structures upon the blast design. Being able to create a contour map and ultimately estimate the number of delays required for the entire forecasted mining area, the engineer can create accurate economic forecasts of the cost of blasting. The objective is to reduce the level of uncertainty in the forecast of the blast component portion of the forecast."

Jan 1, 2016