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By Weijia Guo

With the exploitation of coal resources, a large area of land had been affected by surface subsidence, causing conflicts between man and land to become more conspicuous by the day, affecting the life of general public, and constraining further development of the land. This paper predicts the subsidence areas according to the 10-year mining plan of the Jibei mining district as an example. A plan of environmental management was developed based on sciences and practical economics.

Jan 1, 2006

By Bowler Jonathan, Lorraine Kent, Tereza Crisu, Stuart Walker, Nicholas Lightfoot

"It has been the practice in Europe to extract the most economic seams first: taking the seams sequentially, top down, to avoid operating within the fractured strata formed by the subsidence trough above previously mined coal seams. In the 1990s, the UK coal industry found itself at a number of sites having to operate over one or more previously mined seams. This led to specific geotechnical challenges with respect to maintaining economic, safe and stable rectangular roadways with rock-bolted support.Within this paper, the current challenges and mitigation strategies of overmining in the UK are described following the completion of a -three-year European Commission-funded project in 2015. The challenges and mitigation strategies are related to:• A case study with overmining of older workings of variable geometry;• Numerical modeling for overmining layout and support design; and• A case study site planning mine layout when considering future overmining.INTRODUCTIONAt the first case study site, case histories were examined for a mine operating at a depth of approximately 700 meters where five longwall panels were extracted above workings 35-40 m below. The overmining of various extraction geometries below led to challenging conditions in areas of high vertical stress concentration. It was found that results from one longwall panel could be suitably used to predict behaviour in a subsequent panel. The experience was used to update previously existing guidelines on the positioning of roadways in relation to subsidence troughs. Existing guidelines recommended that only as a last resort should longwalls be planned to retreat over narrow pillars, or from solid ground into a subsidence trough. Existing guidelines regarding the layout of overmining panels are conservative, and new work indicates that such multi-seam geometries are possible with appropriate support management strategies."

Jan 1, 2016

By R. F. Valene

This paper is not available for inclusion in the Proceedings at the time of printing. but it will be included as an insert

Jan 1, 1984

Large-scale shear apparatus is designed to investigate the shear hehaviour of simulated soft rock joints under constant normal stifmess condition. Regular saw-teeth profiles having inclinations between 9.5" and 26.5" have been tested. The strength envelope based on these test results indicates that predictions made by Panon (1966) are accurate for the lower asperity angles. However, for higher asperity angles, Patton's model overestimates the shear strength especially in the low to medium normal stress range. In contrast, while Barton's model (1973) is realistic for Constant Normal Load (CNL) condition, it seems to be inappropriate for modelling the shear behaviour of soft joints under Constant Normal Stiffness (CNS) condition. An empirical strength envelope for the prediction of peak shear strength of joints is proposed in this study to account for the change in normal stress and surface degradation during CNS shearing.

Jan 1, 1997

By Christopher Mark

"Many problems in rock mechanics are limited by our imperfect knowledge of the material properties and failure mechanics of rock masses. Mining problems are somewhat unique, however, in that plenty of real world experience is generally available and can be turned into valuable experimental data. Every pillar that is developed, or stope that is mined, represents a full-scale test of a rock mechanics design. By harvesting these data, and then using the appropriate statistical techniques to interpret them, mining engineers have developed powerful design techniques that are widely used around the world. Successful empirical methods are readily accepted because they are simple, transparent, practical, and firmly tethered to reality.The author has been intimately associated with empirical design for his entire career. But where his past papers have described the application of individual techniques to specific problems, the focus of this paper is the process used to develop a successful empirical method. A six-stage process is described:1. Identification of the problem, and of the end users of the final product2. Development of a conceptual rock mechanics model, and identification of the key parameters in that model3. Identification of measures for each of the key parameters, and the development of new measures (such as rating scales) where necessary4. Data sources and data collection5. Statistical analysis6. Packaging of the final productEach of these stages has its own potential rewards and pitfalls, which will be illustrated by incidents from the author’s own experience. The ultimate goal of this paper is to provide a new and deeper appreciation for empirical techniques, as well as some guidelines and opportunities for future developers."

Jan 1, 2015

By Peter Fischer, Heinz-Jiirgen Kateloe, Anton Sroka, Axel Preusse

"Since mining in Germany has a long history, there are still many locations where the surface fracture problem has to be solved. Shallow mine workings from an earlier era can affect the surface in a discontinuous way. In many cases, due to light overburden load, those mine rooms did not collapse and a downfall can suddenly happen for many reasons, e.g., in connection with a changed load entry into the subsurface or by additional influence of water. This results in ground movements, which in extreme cases, appear as surface fractures.Depending on the use of the surface, ground movements caused in such a way constitute an endangerment by law. Particularly, within the southern Ruhr district, surface fracture and subsidence endangered ranges are determined on the basis of an empirical method that resulted from a systematic evaluation of surface fractures and rock disclosures. This method indicates maximum ranges within which impacts from abandoned shallow mine workings must be assumed.With a special emphasis on a risk management approach, RWTH Aachen University adapted the model of stochastic media to the conditions of abandoned shallow mining to compute and illustrate potential ground movements due to the collapse of shallow mine workings. Further investigations were concerned with the analysis of characteristic parameters which can serve for the assessment of the surface fracture probability in a comparative view of different cases. In recent years, more than 50 surface fractures in the southern Ruhr district were analyzed in order to develop a risk assessment of surface fracture endangered ranges over shallow mine workings. The results that have been obtained so far are described in this paper.INTRODUCTIONAbandoned underground mine workings of shallow depth can pose a threat to the surface. Due to small overburden rock loads, shallow excavations often remain intact for decades after the operations have ceased and may collapse abruptly (Braemer et al., 2005; Hollmann and Nuerenberg, 1972; Preusse et al., 2007). Several approaches for prognosis of surface fracture resulting from 97 subsurface collapse deal with this topic (Loebel and Sroka, 2001; Tajdus and Sroka, 2009)."

Jan 1, 2010

By Brian E. Perrine

Underground mining requires a variety of specialized equipment. With ever-changing mining conditions and methods, some mines have had to resort to purchasing existing industrial equipment and adapting it for underground use. Since this equipment is not made for underground mining or their specific task, the result is often lost time, money, and sometimes an unsafe working condition. One such application is the setting of a CAN. A CAN is a type of cylindrical secondary roof support made from a cement composite and encased in steel. The CAN has become popular because of its simple one-piece design that can handle heaving and sagging better than other available designs. ?Because of this exceptional ability to sustain load through extended convergence and displacement, the CAN is one of the most robust and stable standing supports in use today.?It also promotes better air flow due to the size and shape of the CAN. CAN size and weight have increased over time to handle more difficult mining conditions. Significant down time and inefficiencies with existing CAN setting machines at Twentymile Coal were directly due to the item in use not being designed to be task-specific. They were undersized with very limited movement. The miners had to take extra steps and precautions when setting CANs. Maintenance delays were significant. Twentymile Coal Company realized that they required a safer, more reliable and more efficient machine to handle and set CANs, and looked for a partner to develop a new design-specific machine. They worked jointly with J.H. Fletcher® engineering and sales to design and manufacture a machine specifically made for setting CANs. The objective was to produce a machine that would handle the conditions and methods that the mine required for setting CANs during longwall retreat. The resulting design had to be safe, stable, have a wide range of motion, be ergonomic, simple to use, and easy to maintain. The machine also had to improve efficiency. The resulting machine has been operating for approximately one year at Twentymile Coal and has been proven to improve safety, reliability, and efficiency. In conclusion, with the task-specific CAN Manipulator, the mine is able to better plan daily tasks with the knowledge that the machine will be available throughout a shift, and the employees will be safer because of the machine?s ergonomics, stability and safety. This has resulted in better productivity and a safer environment.

Jan 1, 2013

By Rob Thomas

"In Australia, a wide roadway is commonly defined as any roadway that is driven to a width greater than 5.5 m (18 ft). These roadways are typically required to enable the installation of longwall equipment (termed installation roads); however, other applications include the need to house conveyor driveheads and pre-driven recovery roads.As a result of the increasing size of longwall equipment and mine infrastructure, in some mines, roadway widths of between 9 and 12 m (30 and 39 ft) and are being developed.Accepting that these almost always constitute strategically important and often long-term roadways, this paper considers the use of: (i) an empirical roof support design model, which is based on over one hundred case histories, (ii) various roof support design principles, and (iii) commonly accepted strata management techniques.The paper demonstrates that wide roadways can be driven and supported to an acceptable standard providing due consideration is given to the prevailing ground conditions (including the quality of the immediate and upper roof strata, the Depth of Cover and the horizontal stressfield), the final width of the roadway and the required use of the roadway.INTRODUCTIONRoof behaviour and the associated roof support requirements in wide roadways, which are roadways typically driven to a width that is greater than 5.5 m (18 ft), are controlled by a number of key geotechnical and operational factors. The recognition of these factors is an important first step in the design process and it is imperative that each is considered in conjunction with local mine site information.The main points of note in this regard can be summarised as follows:• The greater the final width of the roadway, the greater the resulting surge in roof displacement on widening - note: a) see Figure 1 for a schematic illustration of the roof displacement trends typically measured during the development of the first pass and roadway widening, b) since displacement increases with roadway width, it is always recommended that the roadway width is kept to the minimum required and c) general buckling beam theory indicates that the capacity of any beams present in the roof will reduce in inverse proportion to any increase in roadway width squared (i.e., [final width2 -first pass width2] I final width2)."

Jan 1, 2010

By Sahendra Ram, Arnn Kr Singh, Dheeraj Kumar, Rajendra Singh

"Inherent existence of different rooms (openings) along the extraction line in a depillaring panel provides an easy path for the goaf to encroach the working area. Each of these openings in a mechanized depillaring (MD) operation along the extraction line is supported by the roof bolt-based breaker line support (RBBLS) to restrict the goaf encroachment. Different field studies by Council for Scientific and Industrial Research - Central Institute of Mining and Fuel Research (CSIR-CIMFR) found that the RBBLS works effectively during the depillaring under the shadow of stable surrounding ribs/fenders only. It is observed that, generally, these natural supports experience high value of induced stresses after a large amount of void creation inside the goaf. The induced stress creates spalling/loosening of the sides of the natural supports. Field studies also found that the positions of the RBBLS at the goaf edge need to be adjusted according to the depth of this spalling/ loosening. However, a systematic study in field for the correct positioning of the breaker line as per the spalling/loosening under different site conditions is difficult. Therefore, on the basis of the data and guidance provided by these field investigations, a detailed parametric investigation was conducted in the laboratory on simulated models for an effective design of RBBLS in a MD panel. FLAC3D is used for the simulation of the depillaring, and the available empirical formulations for Indian coalfields are used for subsequent calibration. An analysis of stress redistribution for different stages of the MD in simulated models showed the significance of the nature of overlying strata/induced stress for the RBBLS design. Discussing some results of field studies, this paper presents results of the laboratory investigations for an effective design of the RBBLS.INTRODUCTIONContinuous Miner (CM)-based mechanized depillaring (MD) is an important issue for Indian coalfields, where huge amounts of coal are locked up in standing pillars (Dixit and Mishra, 2010). Considerable variations in site conditions of these developed pillars bring a number of technical challenges into consideration during their final extraction. One of these challenges is goaf encroachment/overriding during caving of the competent roof strata. Goaf encroachment/overriding can effectively be controlled, mainly, by suitable design of natural supports (rib/snook/fender). However, there is a requirement of applied supports against the immediate roof as a considerable portion of this roof is exposed due to the presence of different openings along the line of extraction. These applied supports act as a fulcrum at the goaf edge between the working area and the goaf to facilitate the break out of the hanging roof inside the goaf. This is called breaker line support. An effective breaker line support is important for the efficiency of a depillaring operation. Generally, MD adopts roof bolt-based breaker line support (RBBLS) at the goaf edge (Singh, et al., 2014). For the first time in India, roof bolts were applied at the goaf edge as RBBLS in a CM-based MD (Leeming, 2003). In the beginning, three rows of roof bolts were installed as primary and secondary breaker lines support. On the basis of the observations of instrumented bolts, only two rows of roof bolts were used as secondary RBBLS (Ram, et al., 2014). Now, most of the MD operations in India are using only two rows of bolts as RBBLS (Table 1). However, the strata mechanics studies at different MD operations showed interesting characteristics resulting from this support (Ram, et al., 2015)."

Jan 1, 2016

One of the most important parameters in rock/resin/bolt load transfer mechanism is the surface property of the bolt. Although there are various bolt surface configurations available in the market, very little work is reported on the bolt/resin interface failure mechanism. This paper examines the behaviour of bolt surface roughness under constant normal stiffness conditions which is considered as being a realistic way of evaluating bolt surface roughness. A series of shear tests have been conducted on the flattened bolt surface to study the shear behaviour of bolt/resin interface. Based on the experimental results, a mathematical model has been developed to predict the shear resistance of the bolt/resin interface at various normal stress levels for the bolt types used in the study.

Jan 1, 1999

By G. R. Corbett

Between 1977 and 1984, No. 26 Colliery, at Glace Bay in the Sydney Coalfield, suffered from a series of 37 rock/gas outbursts. These events were characterized by the complete pulverization of a sandstone which was propelled into the mine roadway and an associated release of methane gas. The events began to appear at a depth of 700 m and increased in intensity and damage to the excavation as the mining depth increased. At the time of the closure of No. 26 Colliery (as a result of an unrelated fire), these outbursts were the subject of intensive investigation. Although No. 26 is now closed, there is concern that similar events could appear at Phalen Colliery where current development work is proceeding at a depth close to the 700 m threshold. Past investigations into rock/gas outbursts included studies of in situ stresses, the simulation of outburst events in the laboratory, investigations into the potential for destressing an& degassing of problem sandstone and the development of numerical models to assist in the design of openings in outburst prone ground. However, despite this work, methods of predicting outburst conditions are presently limited to examination of probe hole cores for core discing, and methods of working under such conditions are limited to boring and firing and using volley firing techniques to initiate any outbursts while workers are safely out of the heading. During this investigation of worldwide occurrences of this phenomena, literature obtained suggested that outbursts might generate microseismic precursors. An intrinsically safe (IS) microseismic monitoring system was designed and developed based on CANMET's rockburst monitoring system currently in use in hardrock mines, and installed in a development roadway at the deepest extent of the Phalen Colliery. The system will record microseismic activity associated with development work to try to identify characteristic precursors of outburst-prone conditions. This paper describes the steps taken to identify a microseismic system suitable for use at Phalen colliery, of which part of the requirement was that it be IS and approved for use in the Sydney Coalfield. The modifications to the selected system are described, along with its capabilities and the preliminary results of its performance over the first few months of use.

Jan 1, 1994

By Essie Esterhuizen, Michael M. Murphy, Chris Mark

"The response of the surrounding rock mass to the creation of mining excavations determines the ultimate load on a pillar support system. In conditions where the ground is relatively soft and weak, the full overburden weight can be transferred to the pillar system. However, in stiffer and stronger rocks, a greater portion of the overburden load is transferred to the unmined coal barriers or abutments, and the pillar stress is reduced. This paper makes use of numerical models to examine the interaction between typical pillar systems and the surrounding rock mass for weak and strong geological conditions at various spans and depths of cover. The concepts of structural failure and functional failure of pillars are used to assess pillar performance when pillars are deformed beyond their peak resistance. The results show that the span-to-depth ratio is an important factor in determining the pillar stress and the ultimate deformation of pillars. The ultimate pillar strain appears to be closely related to the functional success of pillar systems.INTRODUCTIONThe National Institute for Occupational Safety and Health (NIOSH) was requested by Congress to study the safety of retreat pillar mining following the Crandall Canyon Mine disaster that took place near Price, Utah in August, 2007. As a part of this study, an investigation was made to better understand how the rock mass responds to the creation of mining excavations and how the loads are distributed among the pillars and the surrounding abutments or barriers. The outcome of these investigations contributed to the development of a modified loading model for the ARMPS-2010 (Mark, 2010) method ofretreat mining pillar design.Structural and Functional Failure of PillarsPillar design is typically conducted by estimating the pillar strength and stress, and then sizing the pillars so that an adequate margin of safety exists between the expected strength and stress. The pillar strength can be defined as the maximum resistance of a pillar to axial compression (Brady and Brown, 1985). If a pillar is loaded beyond its peak strength, load shedding or yielding can occur, and the pillar is considered to have failed as a structure. Structural failure generally refers to a loss of loadcarrying capacity."

Jan 1, 2010

By Zhikai Wang, Wensheng Lyu, Peng Yang

"To better understand the mechanical behavior of the compression deformation of backfill under high stresses corresponding to large depths, consolidation compression tests were performed for cemented tailings backfill with a cement-sand ration of 1:10 and 30% water under confined conditions. After applying different loading stress functions from 0.5 MPa to 32 MPa, the final axial deformation of the test specimen of backfill was obtained, and the micromorphology of backfill was studied before and after consolidation by scanning electron microscopy. Additionally, fitting analysis was performed for backfill confined compression deformation data and device model constitutive equations by the minimum square law. The constitutive model was revised according to the analysis results. The research results indicate that, as the load increases, the void ratio e obeys the functional relationship e=alnt + b (where a and b are fitting constants and t is compression time). Under the high-stress conditions of confinement, the constitutive model of backfill consolidation and creep can be used to describe the creep behavior of the backfill. Under high-stress conditions, after the consolidation of the confined backfill, the space between the tailing particles diminishes, the particles becomes more compact, and particle slippage occurs. INTRODUCTION With the depletion of shallow mineral resources, the mining industry has gradually shifted to deep mining (Zhang, Li, An, and Huang, 2010). Furthermore, with the continuous introduction of sustainable development policies regarding development and utilization of mineral resources, the mining industry must protect the limited available land and make full use of mineral resources as much as possible (Sijing, 1994; Zhihua, 2009). Backfill mining technology offers an unparalleled advantage in fully recovering mineral resources, controlling pressures, and improving environmental protection. As a result, this method has been widely used in various countries in the world (Burd, 2002; Benzaazoua, et al., 2008). Of the underground mines in the world, 45% of the large and medium-sized non-ferrous-metal mines and 37% of the gold mines use backfilling (Fuhrman, et al., 2014; Khaldoun, Ouadif, Baba, and Bahi, 2016). In addition, 45% of underground non-ferrous-metal mines and 37% of the gold mines use the filling method (Mchaina, Januszewski, and Hallam, 2001). According to incomplete statistics, more than 80 metal mines operate at a depth of more than 1 km; the depths of several typical deep mines are shown in Figure 1 (Burd, 2002; Fall, et al., 2009)."

Jan 1, 2017

By Frank E. Chase

Geologic structures have been responsible for numerous underground accidents and fatalities, and are a constant-source of down time. During - longwall mining, ground control problems associated with geologic anomalies are aggravated by the abutment pressures which develop as the panel is retreated. Therefore, it is imperative that these structures be recognized and properly supported in head- and tailgates. Fractures, faults, clay veins, igneous dikes, and ancient stream channels (paleochannels) disrupt the lateral continuity of the mine roof and can cause falls in gateroads. Horsebacks and kettle bottoms are also hazardous because abutment pressures tend to "pop out' these structures into the gateroads. This Bureau of Mines investigation describes the physical characteristics associated with hazardous geologic structures, identifies the coal fields where-they have been observed, and, where possible, suggests support strategies and other mine plan modifications to help minimize their effect.

Jan 1, 1990

By Freddie Hunter

An underground mining method for extracting an eight metre (26') coal horizon, containing a sandstone layer. A decrease in the thickness of the rock strata between the number two and number three seams of the Sasolburg Coal Field, has resulted in a total mining horizon approximately eight metres (26') thick. This parting varies in thickness and competency and in some areas is impractical to cut with a continuous miner. In addition, the general mining area is highly jointed. The top seam is first mined to a normal bord and pillar plan with a continuous miner. The bottom seam is then mined by selectively undercutting the stone parting constituting the floor of the top seam. In areas where this parting is between 0.75 - 2.50 metres (29.5" - 98") thick, it is suspended from the primary roof support installed when mining the top seam. Secondary, high extraction retreat mining is then undertaken in the coal pillars adjacent to the suspension supported headings in the bottom seam. Left in-situ, the parting provides lateral support to the pillar sidewalls in both the top and bottom seams, enabling high percentage extraction rates in what was previously thought an uneconomically mineable area. The paper proposed, presents the challenges and practical implications of executing the mining method, including the primary roof control of the top seam and the stone parting between scams.

Jan 1, 2003

By Peng-Fei He

CT scanning tests were used to detect the pre-existing fracture systems of 36 cubical coal blocks. Systematic procedures were developed to construct the pre-existing fracture geometry of the cubical coal blocks from the CT images. Based on the constructed fracture systems, the fracture tensor components were calculated to capture the directional effects of the fracture system of the cubical coal blocks. The effect of the pre-existing fracture system and different combinations of confining stresses on the strength and deformability of coal masses was investigated at a preliminary level using some true triaxial test results and the computed fracture tensor components. The strength of the cubical coal blocks in the loading direction was found to be closely related to the summation of the fracture tensor components in the two perpendicular directions to the loading direction and the level of the confining stress system. The deformability of cubic coal blocks in the loading direction was found to be correlated to the fracture tensor component in the same direction.

Jan 1, 2014

By Kazem Oraee, Mehran Gholincjad, Navid Hosseini

"Chain coal pillars are pans of the structure of longwall mining system that play a significant role in the stability of the entries. With mechanization and developments in the various aspects of the method, higher efficiency in optimization of the design of chain coal pillars seems appropriate. In this paper the three main methods of chain pillar design, namely the empirical analytical and numerical methods arc compared. Real data from the Tabaslran coal mines have been used in order to make the comparison process reliable. It is concluded that the most apparent advantage of the empirical method is the reliability of the results while the use of numerical methods enjoys the advantage of flexibility. On the other hand the analytical methods are complex unless simplifying assumptions arc made that can substantially decrease the accuracy of result which is thought to be the main advantage of the design method. A new method is therefore introduced here that combines all of the three presently used methods and by doing so the new method has the advantages of the three while minimizing complexities and inaccuracies associated with the use of the individual methods.INTRODUCTIONLongwall mining is a high production method that can use mechanization to its full extent. Its initial development can be traced to 17th century European collieries but it was not until the second half of the 20th century with the development of self advancing support systems that the method gained popularity in the USA (Oraec. 2001). During the last decade, the production of longwall faces has increased significantly (Peng. 2006). The ability for mechanization along with good safety condition is the main reasons for such development. In the longwall mining method a good design for panel and entries on both sides, are two essential parameters. In this method, the thickness of overburden (depth of mine) nom1ally ranges from 60 to 20 m (197 to 2.7 9 ft) (Hartman, 2000) and with increasing mine depth designing for stabilizing the entries on both sides of the panel become more difficult. Thus, for safety and stability the size of chain pillar must increase. This causes the overall coal recovery to decrease and increase mining costs per ton. As such wide pillars hinder the air flow and hence ventilation costs increases too. Therefore with accurate identification of loading conditions and stress analysis. pillar that are a minimum size and sufficient safety factor are carefully designed."

Jan 1, 2010

By Michael Gauna, Christopher Mark

"For decades, pillar recovery accounted for a quarter of all roof fall fatalities in underground coal mines. Studies showed that a miner on a pillar recovery section was at least three times more likely to be killed by a roof fall than other coal miners. Since 2007, however, there has been just one fatal roof fall on a pillar line. This paper describes the process that resulted in this historic achievement. It covers both the key research findings and the ways in which those insights, beginning in the early 2000s, were implemented in mining practice.One key finding was that safe pillar recovery requires both global and local stability. Global stability is addressed primarily through proper pillar design, and became a major focus after the 2007 Crandall Canyon mine disaster. But the most significant improvements resulted from detailed studies that showed that local stability, defined as roof control in the immediate work area, could be achieved with three interventions:• Leaving an engineered final stump, rather than extracting the entire pillar;• Enhancing roof bolt support, particularly in intersections, and• Increasing the use of Mobile Roof Supports (MRS)A final component was an emphasis on better management of pillar recovery operations. This included a focus on worker positioning, as well as on the pillar and lift sequences, MRS operations, and hazard identification. As retreat mines have incorporated these elements into their Roof Control Plans, it has become clear that pillar recovery is not ""inherently unsafe.""The paper concludes with a discussion of the challenges that remain, including the problems of rib falls and coal bursts.INTRODUCTIONPillar recovery has always been an integral part of underground coal mining in the US. When room-and-pillar methods are employed, large blocks of coal in the form of pillars are initially left in place to support the weight of the overburden. Unless these pillars are subsequently recovered, the coal they contain will never be mined."

Jan 1, 2016

By Nathaniel Schaefer, Christopher Newman, Zach Agioutantis

"As mining reserves continue to be developed in deeper and more complex geological and geometric conditions, there has been an increased demand for underground mine designs to better reflect site-specific conditions, measurements, and observations with respect to ground control safety and stability. Current ground control design software are limited to a given device and data files generated can only contain a single design. However, with the growth of cloud computing and increases in internet access, even underground where permissible, web-based software applications allow for in-the-field calculations, as well as collaborations, from multiple users. webGroundControl (webGC) utilizes a multiple-tier architecture, building upon existing NIOSH ground control design software, more specifically ARBS, ALPS, and ARMPS. By providing operators the ability to access ground control design programs from any device, given an internet connection, webGC allows for on demand calculations to ensure underground pillar and roof stabilities with respect to current site-specific parameters, geometries, and geology. Through the development of new features, which aid in design analyses, as well as project collaborations, webGC provides the modern engineer with a more versatile ground control design tool for the improvement of underground health and safety. With the completion of the ARBS, ALPS, and ARMPS modules, this paper introduces potential users within the mining industry to the navigation and operation of the webGC application, as well as its ability to facilitate collaborations between operational personnel and planning engineers. The purpose of this paper is to raise interest in the web-based application before its official launch in Summer 2018."

Jan 1, 2017

By John A. Rusnak

"This paper discusses the variation of coal strength based on the megascopic coal lithotypes for Central Appalachian high-volatile A coal beds. The composition of coal beds is complex and variable, depending on the depositional environment associated with original plant material, inflow of clastic material, and water level fluctuations in the original swamp/mire environment. Thus, different types of coal and sediment are formed within each coal bed. These differences in coal composition were first classified by Marie Stopes, a paleobotanist, in 1919. The classic coal megascopic lithotypes are vitrain, clarain, and durain, which correspond to bright, bright banded, and dull coal, respectively. Stopes also identified that the lithotype fusain, which is mineral charcoal, has no inherent strength and can act as a plane of discontinuity. In this study, two other coal-bed lithologies are also considered—bone and carbonaceous shale. This makes for a comprehensive suite of coal-bed stratigraphic components apart from rock partings. A total of 1,000 uniaxial compressive strength (UCS) and 440 indirect tensile strength (ITS) tests were conducted on cores from southern West Virginia that were specifically logged and described using the megascopic coal lithotype nomenclature. Statistical analysis is presented showing the results for each lithotype group with mechanical properties correlated to the lithotype. Previous studies have analyzed the mechanical breakage properties associated with coal lithotypes, which correlate well with these results. However, coal rank does appear to be a contributing factor, and this study is confined to only high-volatile A bituminous rank. Application of these results would be well suited to a rock mass classification system to address coal pillar rib stability. This would allow for rib support design and implementation to consider relative coal strength by visual observation of the seam stratigraphy through ongoing observations within a mine. Changes in seam composition can be readily identified, allowing the adjustment in rib support design. Another application would be for the determination of numerical modeling inputs based on detailed seam stratigraphy. However, these results, even with the standard strength reduction criteria, may not be applicable to currently accepted empirical coal pillar design procedures."

Jan 1, 2017