Search Documents

By David R. Hanson

Seismic tomographic imaging, based on the same principles as a medical CAT Scan (Computer-Aided-Tomography). has been used for many years in the oil industry for large-scale subsurface stratigraphic characterization. and has most recently been applied to various structure- and stress-related problems in the coal industry. New developments in signal processing have greatly enhanced the speed, resolution, and range of applications of topographic imaging in underground settings, and recent innovations in data acquisition hardware have further increased data reliability and repeatability. Whereas past structure mapping applications relied on Seismic velocity and/or attenuation tomopraphy within an enclosed seismic source gram receiver array, recent developments in "True Reflective Tomography- (TRT TM) have expanded the application of this technology considerably. For example, in-seam TRT TM seismic reflection tray now he used to image structure, and/or old workings from one general location in the mine face areas of mains and panel developments) well ahead of planned developments largely eliminating the need to probe-hole drill on regular intervals. This new reflective technology bas also been combined with traditional cross-hole seismic tomography-providing a comprehensive, powerful tool for velocity attenuation. and reflective imagine utilizing the same source/receiver array data sets (borehole-to-borehole. borehole-to-entry and entry-to-entry). These new developments in data acquisition and image processing have greatly expanded the variety of applications for tomographic site characterization allowing the mine operator considerable flexibility to cost-effectively characterize previously inaccessible areas of the property. This paper presents examples of 2-D and 3-D .seismic topographic imaging applied to (1) the location of old works in Appalachian room-and-pillar operations and (2) the identification of anomalous zones ahead of mining/tunneling developments these applications demonstrate the state-of-the-art in seismic ground imaging using velocity, attenuation. aril reflection techniques land combinations thereon, and further illustrate the flexibility of data acquisition from a variety of tinning arid tunneling settings. Recent examples are presented from projects in the United States and Europe.

Jan 1, 2000

By Anthony T. Iannacchione

Underground bituminous coal mining is a large and significant industry within the Commonwealth of Pennsylvania, and it has a legacy of environmental consequence. For example, in 2008, 13.5 acres (5.5 hectares) of land were undermined by longwall mining every day. Laws and regulations have been promulgated requiring companies involved in this industry to remedy mining damage caused to homes, businesses, and land; replace impaired water supplies; and repair impacts to streams and wetlands. The regulations and technical standards set by the Pennsylvania Department of Environmental Protection (PA DEP) have been put in place to assure that coal operations comply with ACT 54 of the Bituminous Mine Subsidence & Land Conservation Act and other related legislation. These regulations and standards require operations to address impacts when a mining permit is submitted and as permits are modified and extended. One of the special provisions of ACT 54 is the requirement by the PA DEP to produce an assessment of the surface impacts of mining every five years. The University of Pittsburgh was contracted by the PA DEP to perform the 3rd assessment, which spanned from August 21, 2003, to August 20, 2008. This paper details the findings related to surface structure undermined during this period. A total of 3,735 structures were tracked. Four-hundred-fiftysix reported effects were found, and each required additional information and analysis. The majority of the reported effects were associated with eight longwall mines. Characteristics of the structures were analyzed and discussed, with special attention to those with reported effects. The number of undamaged and reportedly damaged structures (i.e., dwelling, barn, commercial building, etc.) undermined during the assessment period were listed. Lastly, the resolution status and type of resolution were analyzed for all structure reported effects.

Jan 1, 2011

By Chris T. Franke

The Waste Isolation Pilot Plant is a deep underground facility mined in bedded salt interspersed with persistent clay inter- beds. The clay seams delineate beams of salt above and below the excavations which strongly influence excavation performance. This paper reviews available rock mechanics information relevant to improving drift stability by removing the roof beam. Conceptual deformation mechanisms, relevant field data, and numerical analyses were used to investigate the effects of mining the roof of the excavations along a clay seam. Finally, a case study that applies the results of this investigation is presented.

Jan 1, 1997

Design and selection of support systems for longwall faces call for in-depth knowledge of strata mechanics and in particular of strata-support interactions. The paper presents the results of field investigations and analysis of a difficult-to-cave roof using powered supports under a massive dolerite sill in Central India using a state-of-the-art datalogger system. The mechanised longwall face was equipped with 4/680 tons chockshields operated on the IFS mode using a 300 K W DERD shearer. The datalogger system was capable of storing data simultaneously in 32 channels. The paper describes the monitoring system and the monitoring programme. The system provided useful information on support behaviour, build-up of leg pressures and face convergence during an intense dynamic periodic weighting phenomenon which destroyed the integrity of almost half of the face supports. At this point, the face had advanced by about 197 metres from the barrier. The paper outlines a post-mortem analysis of this dynamic event and provides a critical evaluation of the data collected for understanding strata support interaction and the behaviour of the massive sill in the overburden.

Jan 1, 1992

By Gregory Hendon

Jim Walter Resources, Inc. (JWR), has successfully longwall mined for many years at depths ranging from 1200'-2500'. However, full pillar extraction has proven difficult and generally economically unfeasible. Overburden and redistributed stresses at these depths require relatively large pillars, which become unmanageable with most pillar extraction practices. The economic benefits of taking gateroad pillars as part of a longwall face have been recognized for some time, including increased life of mine recovery, elimination of belt moves, reduced overcast requirements, and improved longwall to continuous miner ratios. Until recently, the associated risks of pulling pillars prevented any extensive use of this concept at JWR. Due to geological, economic, and longwall repeatability problems, JWR accepted the risks, and undertook pillar extractions with longwall faces in several different applications. The applications included taking a stable pillar (250' wide) as a longwall panel, taking yield pillars on the headgate and tailgate of panels, taking yield pillars and stable pillars in the middle of a panel, mining through chain pillars in the middle of a panel, and taking a support pillar on the tailgate end of a panel. This paper describes the background and experience of pillar extraction with longwalls at JWR.

Jan 1, 1998

By P. Forrest

Based on the results of mathematical analysis, photoelastic modelling, and case studies, the mechanisms of longwall under- mining interaction has been thoroughly investigated. The effects of using yield pillars in combination with rigid pillars in lower seam mine design have been found to provide significant improvement in ground conditions during undermining. Off- setting of solemnized longwall panel entries relative to upper-seam remnant structures has proven to be effective in alleviating adverse stress conditions.

Jan 1, 1988

By C. P. Mangelsdorf

The success of the Birmingham roof truss (Figure 1) in supporting some difficult roof conditions, particularly in the Illinois coal basin, has given impetus to the development of a number of alternate schemes. These schemes attempt to alleviate two major problems with the Birming-ham truss, namely, the time required for installation and the cost of material. Because of the difficulty of drilling angled holes and the number of different pieces of hardware which must be handled manually, most operators have been unable to install Birmingham trusses in the cycle and have had to schedule truss crews during the maintenance shift or whenever they would not impede production. Due to this delay the truss has traditionally been viewed as a supplemental form of roof support. In fact, the truss might qualify as primary support and replace at least two bolts if it could he installed in the cycle (and MSHA would accept it as an alternate in the roof plan.) [ ] Figure 1. The Birmingham truss. Two attempts to deal with the first difficulty have sought to streamline the truss hardware while preserving the essential character of the Birmingham truss. One of these, by Peabody Coal, is reported elsewhere in these proceedings by C. Bollier. Another is a contract issued by the Bureau of Mines to Bendix Corporation for the development of a machine, particularly suited for use in low coal, which will automate many of the operations currently executed manually. This machine is expected to be ready for field testing by fall of 1982. Once in place, a truss installed by either of these schemes will interact with the roof in the same way as a conventional Birmingham truss. An alternate approach has been proposed by several different manufacturers independently. Although the hardware details differ. the essential idea consists of two angle bolts, the heads of which are connected by a horizontal chord tightened to some pre-determined tension. Figure 2 shows the generalized concept and does not depict any one of the four systems proposed. The advantage of this scheme is that the angle bolts can be installed and tightened in the cycle, and as bolts, immediately satisfy the roof control plan. The horizontal chord can be added later to achieve almost any initial desired roof loading, the limits of which are defined below this scheme is referred to here as the angle-bolt truss. Because of a fundamental difference in the way in which load is transferred between chords, this design does not interact with the roof under subsequent loading in the same manner as a Birmingham truss. The purpose of this paper is to examine this fundamental difference and its consequences. [ ]

Jan 1, 1982

By D. Newman

An underground limestone quarry, developed in the 1940's, transitioned from a surface quarry to an underground room-and-pillar operation. The quarry expanded to a second underground level when the reserves on the first level reached the property boundaries. The historical basis for the sill pillar thickness between the first and second level, pillar dimensions, and mining height was lost during the course of several changes in ownership. When reserves on the second level reached a five-year life, and plans were initiated for a third level, quarry management embarked upon a thorough evaluation of i. current ground control practices for the support of the immediate roof, ii. roof support in the declines between the surface, Level 1, and Level II, iii. pillar centers and pillar safety factors, iv. pillar alignment between levels, v. mining height within a level, and vi. the locations of declines to access future reserves on level three. The evaluation began with detailed mapping of the location and orientation of calcite veins, joints, fractures, and ground conditions in the immediate roof of Level II. The orientation and location of calcite veins, joints, and fractures on Level II were compared with similar mapping on Level 1, completed in the 1970's to establish whether these features were continuous and would be expected to affect conditions on Level III. Rock strength, physical properties, and fracture spacing were obtained from two (2) diamond core holes drilled from Level I to Level II and two (2) holes drilled from Level II to define the vertical extent of future reserves on Level III. The effort to characterize geological conditions was expanded to a rock mechanics investigation of the: i. performance of the current roof support, ii. optimization of roof and rib scaling, iii. calculation of safety factors for 416 pillars on Level II, iv. evaluation of future pillar centers and mining height within a level based upon pillar strength and pillar geometry, v. development of beam safety factors for the immediate roof on Level II, vi. identification of the most suitable strata for the roof in the future level three, and vii. use of LAMODEL to develop a large numerical model of overburden, inter-level, and total stress on the pillars in levels one and Level II with a stress "footprint" on the proposed level three. The characterization of engineering parameters and geological conditions resulted in changes to the: ? active operations in Level II regarding scaling ? equipment and scaling practices, ? pillar centers, ? mining height, ? raising the immediate roof horizon to avoid ? laminated strata in the current roof, and ? a change in rock bolts from a friction based system ? to active tensioned rebar. The planning and design of level three is ongoing and relies heavily upon the geological and engineering investigations conducted during the past year and one-half.

Jan 1, 2001

By Ismet Canbulat

The cut out distance in the continuous miner sections in South African collieries is limited to 12 m. However, this distance can be extended to 24 m by the permission of the Department of Mineral and Energy (DME). This paper investigates the risk of roof Calls associated with the extended cut out distances permitted by the DME. Extensive underground experiments have been conducted using sonic probe extensometer under various geological conditions to identify the effect of cutting distance and tinge on the stability of the workings and the performance of the support. The results showed that that the most critical parameter with respect to ground control aspects of extended cut out distance is the bord width, which determines the amount of deformation that will take place in the roof. This was confirmed by the numerical modelling. The results also showed that a significant portion of the maximum deformation in the roof takes place before the ratio of cut out distance to bord width exceeds two. This indicates that once the face is extended more than twice the bord width, the roof will stabilise, assuming that no geological discontinuity is present and that there will be no further geometrical changes in the area as a result of for example the development of an intersection.

Jan 1, 2000

By Edward McHugh

While less than 1% of reported accidents are associated with slope stability problems. slope failures were responsible for about 15% of all U.S. surface mine fatalities between 1995 and 2001. Small rockfalls, which may involve hand-sized rocks weighing only a few kilograms, can cause fatal injuries to workers away from the protection of large machinery. Massive highwall failures containing a million cubic meters of material or more can be fatal even for heavy equipment operators. As part of an ongoing study at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health, several remote-sensing technol¬ogies are being evaluated as tools to monitor slopes for hazards and to assess slope stability. Field tests of a hyperspectral imager were conducted to assess its value for improving geologic maps of poten¬tially unstable alteration zones on mine slopes. An interferometric radar device capable of detecting very small displacements on slopes awaits final assembly and field testing. Computerized moni¬toring methods using images from digital and video cameras are being assessed for application to mine slope surveillance. These and other techniques will eventually provide new tools to augment current methods for monitoring ground control hazards in mines.

Jan 1, 2002

By Francis Kendorski

One of the most dangerous events in underground coal mining is unexpectedly encountering water inrushes from undetected abandoned mines in the same seam. The surest and most confident method is probe drilling either from the mine or from the surface. However, drilling is expensive and may even miss the suspected mine voids entirely by drilling through pillars. Many operators rely upon one or more of several remote sensing techniques for detecting mine voids. However, mine "voids" often are not air- or water-filled open cavities, but are collapsed, rubble-filled chimneyed columns in the strata. Geophysical techniques, such as seismic reflection and refraction, electrical resistivity, magnetics, ground-penetrating radar, and others, often assume a continuous or fractured rock mass that has varying properties which provide the signatures that allow discrimination of one strata from another, or of strata from voids. However, a rubble-filled cavity has rock block-to-rock block contact throughout its volume and can still respond as a continuous rock mass with the rock blocks allowing signal transmission or mass detection, rather than a void space. Hydraulically, a rubble-filled cavity is essentially as transmissive to water as an open mine void. Thus, the problem of detecting a mine void with confidence is significantly compounded.

Jan 1, 2004

By Jeffrey K. Whyatt

Estimation of the initial vertical stress carried in a coal seam is an important first step in virtually all methods of evaluating the required size of pillars in coal mines. Such estimates are a trivial exercise in coal fields overlain by gently undulating topography. The LaModel program is easily and routinely applied in such cases to efficiently estimate mining-induced stresses throughout the coal seam. However, application of LaModel to coal mines operating under rugged topography and/or in tectonically disturbed regions is more difficult. LaModel estimates stresses in a twostep process. Topographic and multi-seam mining effects on insitu stresses are estimated in an initial step, and then mininginduced stresses are estimated in an independent second step. A LaModel program function has recently been introduced that decouples these two steps, allowing in-situ stresses to be directly entered from a file rather than calculated. One application of this function is to streamline sensitivity studies by avoiding repeated recalculation of in-situ stress. The function also allows importation of in-situ stress estimates developed by other means. There are no constraints on the imported stress field, which may include significant stress perturbations due to topography, faults, etc. Hence, the range of geologic environments that can be examined by LaModel is significantly increased. This study uses the new decoupling function in an exploration of in-situ stress estimation in mountainous terrain. One option is to use the topographic stress estimation feature included within the LaModel program, and the influence of important parameters in this routine is explored. Another option explored is importation of results from a detailed volume element model. Results of this study suggest that the method used to estimate in-situ stress, and the details of its execution, can have a significant impact for mines in mountainous terrain with strong overburden. More generally, decoupling is an efficient and flexible function that should be considered for most design studies.

Jan 1, 2011

By Joe Zelanko

In order to prevent roof fall accidents and injuries, U.S. underground coal mine operators must develop and implement effective roof control strategies. Various tools are available to assist engineers in developing designs. For example, criteria to address global stability issues (e.g., pillar stability) are well established in the U.S.; effective tools (e.g., empirical and numerical) are available to diagnose potential problems and avoid catastrophic failures. However, most miner injuries occur as a result of local instability (e.g., a roof fall in a single heading or a rib roll from a pillar corner). Hazard recognition and the availability of support plans suitable to those conditions are key to maintaining stability and safety on the working section.

Jan 1, 2011

By John L. Edwards

The underground coal mines in the Lake Macquarie area of the Newcastle Coalfield, New South Wales, Australia are constrained by surface subsidence restrictions as low as 150 mm. The mining environment is shallow, generally between 100 m and 200 m, often multi-seam and commonly overlain by residential development or tidal waters. Most mines use partial or panel and pillar extraction techniques to meet the subsidence restrictions and allow maximum resource recovery. This paper gives an overview of the results of a recent two year government funded research project aimed at developing a mechanistic, geomechanically based mine design criteria for subsidence control. Three extraction layouts were monitored in detail to assess the relationship between mining geometry, pillar behaviour and surface subsidence. Pillars at each site were instrumented with stress cells, convergence monitors and extensometers. Field data was used to initially calibrate, and subsequently, verify stress and displacement predictions made by the three-dimensional displacement discontinuity code, SUBSOL. Back-analysis of the modelling results indicate SUBSOL's capability as a tool to satisfactorily predict surface subsidence magnitudes and pillar loads for alternative pillar and panel layouts.

Jan 1, 1993

By T. N. Singh

Board and pillar system of mining has beer, practised in India in view of abundant availability of cheap labour force, low investment and quick return. Subsequently, selective mining from thick seems and partial mining under surface features boosted the trend. As s result over 2000 million tonnes of coal is locked up in form of developed pillars inclusive of about 1000 million tonnes of high grade coking coal in Jharia field alone. The trend of pillar formation is still uninterrupted as the estimated pillar reserve in this field in 1974 was only 700 million tonnes which increased to 961 million tonnes in 1983. The trend is not much different in other coalfields end as a rough estimate 100 million tonnes of virgin coal reserve is being transferred to pillar every year. The method of board and pillar mining is likely to remain moat preferred technology for decade9 to come in view of several inherent advantage in Indian mining conditions.

Jan 1, 1984

By M. Karmis

mining factors and representative ground movement parameters. Based on this analysis, the previously developed prediction methods were modified and tested for their applicability in the Appalachian coalfield. Finally, in order to facilitate the implementation of the prediction methods, as well as the data processing of the monitoring program, a number of computer software were developed and will be discussed in the paper. Surface deformations above underground mines and their prediction and control have been the topics of an extensive research effort by Virginia Polytechnic Institute and State University over the past few years. During the initial stages of this research, a number of case studies were collected from the literature, the mining industry and various government and state agencies and, based on the analysis of this information, appropriate prediction methods were proposed (Goodman, 1980; Webb, 1982; Hasenfus, 1984; Karmis et al., 1984). Although the prediction methods were based on sound concepts, it became evident that their accuracy and implementation were a reflection of the size and quality of the collected case studies. In this respect, the data bank was rather insufficient and posed certain questions regarding the development of subsidence information due to inappropriate length and spacing of monuments used in subsidence surveys, density and accuracy of such surveys, lack of monitoring horizontal movements, etc. In an effort to alleviate these problems, a comprehensive monitoring program was initiated in the coal mines of southwest Virginia, which included: - Two longwall and five room and pillar mines. - In total, seven longwall and sixteen room and pillar panels. - Monitoring lines in excess of 35,000 feet. - Vertical as well as horizontal measurements. A high accuracy digital computer tacheometer was used in all surveys and the type and spacing of all monuments were in accordance with well accepted guidelines. The data from this monitoring program completed the initially collected data bank and, thus, enabled a much needed statistical analysis between

Jan 1, 1987

By Karl Jr. Zipf

The famous Homestake gold mine in Lead, SD. closed recently alter 125 years of operation. However, the mine may receive a new lease on life as a National Underground Science Laboratory (NUSL) supported by the National Science Foundation (NSF) and dedicated to high-energy physics experiments involving neutrinos. These experiments require the construction of many large underground chambers tells of meters wide at depths of over 21 18 m. Construction of such large openings at such extreme depths has few precedents m civil-engineering-type construction. The Spokane Research Laboratory has a long history of ground control research at the Homestake Mine and has supported NSF and the physics community in their efforts to develop a NUSL at I Homestake or other suitable location. This paper will summarize underground science and describe proposed underground science laboratories ill the United States, in particular tile proposed NUSL at Homestake. Next, the paper describes an empirical design approach using the Q system of rock mass classification for these large Openings. .M initial site investigation that produced three good case histories is described. The actual support system used at the three sites agrees well with support recommendations from current support design charts, giving credibility to estimates of the classification parameters and Q. Feasibility of, and support requirements for, 25-, 50-, and 100-m spans arc estimated in the anticipated rock mass. This analysis indicates that 25- and 50-m spans are probably feasible, but a stable 100-nn span may be unachievable. The empirical predictions are then compared to detailed numerical analyses. The paper concludes with preliminary support recommendations and necessary site investigations needed to make a proposed NUSL a successful reality. These studies have been important input to NSF for their decisions on the technical feasibility of developing the proposed NUSL. If NUSL is developed, it could enable scientific experiments in areas beyond high-energy physics. 'the laboratory could also enable research in rock mechanics. ground water hydrology. mining engineering, nine safety and health, and ground control.

Jan 1, 2002

By Dennis Dolinar

In general, the direction of the maximum horizontal stress in the eastern United States is fairly well defined. However, the variation of the magnitudes of the horizontal stresses is not very well understood. Because the horizontal stresses cause severe ground control problems in underground coal and limestone mines throughout the eastern United States a more complete understanding of how the magnitudes vary would be useful for developing mine design strategies to combat horizontal stress related ground control problems. Therefore, in this National Institute for Occupational Safety and Health (NIOSH) study, the variation of the magnitude of the horizon stresses in sedimentary deposits in the eastern and Midwestern United States are examined with respect to two factors, the elastic modulus of the rock and the site depth. Stress measurements from thirty-seven sites are used in the evaluation. Examining the applied excess strains indicates that the eastern United States can be, separated into high and low strain zones. For most of the eastern United States the maximum applied excess or tectonic strain ranges from only 300 to 550 micro strains. However, there is one area, a portion of the Beckley seam in the central Appalachian region where the strains are significantly higher than the other regions. In this higher strain zone, the maximum applied tectonic strains range from 700 to 1,000 micro strains. Regression models for each zone based on the elastic modulus can explain between 83 to 85% of the variation of the maximum horizontal stress. Because one region, the northern Appalachian district, has strains that are about 20% higher than the other regions in the low strain zone, multiple strain models based on geographic regions were developed for the low strain zone that can explain 87 to 91% of the maximum horizontal stress variation with the elastic modulus. Depth was found not to be a significant causal factor in any increase in the horizontal stress even though the site depths ranged from 275 to 2,500 ft. Beyond a theoretical increase, based on Poisson's effect and gravity, no other increase in the horizontal stress with depth can be justified with this data. The most significant factor controlling the variation of the maximum horizontal stress is the elastic modulus of the rock, not the overburden depth.

Jan 1, 2003

By Y. P. Chugh

The use of wooden supports, supplementary to the primary method of roof control using roof bolts in mines, consumes over 3 million cubic meters of hardwood in the U.S. annually. These supports arc primarily used in the form of cribs and posts. Along with a rapid depletion of high quality timber resources, supplies fluctuate seasonally, costs are escalating rapidly, and product quality is highly variable. Environmental considerations of global climate change put additional pressure on deforestation for utilization of timber for artificial supports. On the other hand, management of coal combustion byproducts (GCBs) from power plants has become a major issue to maintaining a healthy coal industry. The USA currently produces over 100 million tons of CCBs annually and the average cost for their management in the US is about $20/ton. This cost is expected to escalate rapidly with tougher environmental regulations. The principal author has been directing research, development, and demonstration studies for CCBs-based artificial supports and lightweight structural materials in mines for the past seven years and has made significant progress toward commercially viable products. More specifically, first and second generation crib elements and post elements have been developed, characterized analytically, and demonstrated in the field. It is estimated that about 2.5 x 10" tons of fly ash could be utilized for artificial supports in U.S coal mines and this would double if these materials were utilized in non-coal mines as well. The author believes that CCBs-based artificial supports have the potential to replace wooden supports and blocks with better performance and cost competitiveness while managing CCBs in an environmentally sound manner. This paper focuses on the development and field demonstration of CCBs-based artificial supports for use in underground mines, and its pilot scale fabrication facility. Recent analysis results on engineering performance evaluation of the developed crib under various loading conditions using finite element method are presented. The following comments highlight the developments: I ). Engineered artificial supports, crib and post elements, using CCBs as a major constituent, have significant potential for application in mines because their structural performance is significantly better than wooden cribs counterparts. 21. Engineered crib elements provide about 50% larger area for air-flow than a conventional wooden crib. 3). Engineered crib elements are not flammable. 4). Each engineered crib element utilizes about 10 kg of fly ash, about 40 % of the weight of crib element- Therefore, a typical crib 2.0 m high utilizes about 200 kg of fly ash. 5). Each 16.5 cm diameter engineered post utilizes 50 kg of fly ash. 6). Assuming 3.0 million cu. meter of wood consumed for post and crib support systems, it is estimated that about 4 - 5 million tons of fly ash may be utilized for supports fabrication in the USA. 7). An engineered post has excellent post-failure characteristics similar to wood. In addition, the engineered post also has excellent loading and unloading characteristics close to the yield point of about 75% of the ultimate load carrying capacity.

Jan 1, 2004

By David J. Reddish

Longwall systems are inflexible in layout, intolerant of disruption and represent a substantial investment. It is therefore essential drat all understanding of the likely strata behaviour and support requirements is obtained prior to panel development. For many tears rock mechanics engineers have applied numerical modelling based kill finite element techniques to the design of the support and layout of underground excavations. Whilst such design methodology has worked well in civil engineering and hard rock situations, it has been less reliable when applied to excavation design in the soft rocks of the coal measures. This lack of reliability has been identified largely as being the result of the utilisation of unsatisfactory input data, This paper describes the results of an ongoing research programme at the University of Nottingham in which a novel rock mass rating system known as the UK Coal Mine Classification system was developed to enable the prediction of the strata properties that are required as input parameters for use in numerical modelling of the deformation of soft rocks around excavations such as roadways and longwall faces in coal mines. The paper describes the development of the system. the way in which classifications are applied to derive input data for numerical models and gives two case studies ill which deformations and stress re-distributions around coal mine excavations have been simulated by numerical modelling using the FLAC finite difference code.

Jan 1, 2000