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By Francis S. Kendorski

Rock reinforcement has been in widespread use and generally has been accepted in underground mining and tunneling since the 1950s. The first rock reinforcement technologies employed were mechanical anchors such as split wedges or expansion shells with 5/8-inch-diameter steel bolts. Failures occurred in weak strata which provided poor anchorage or in ground with corrosive waters. Friction rock fixtures consisting of relatively thin-walled tubes have been in use for about 15 to 20 years. While generally performing adequately, longevity problems have developed from corrosion in water bearing ground Longevity of rock reinforcement is much enhanced with grouted bolts. Portland-cement-grouted rock reinforcement has been in use since the mid-1950s, primarily in funneling and other civil engineering underground construction. Tests of decades-old installations have revealed few problems except in ground with aggressive waters. Polyester-resin-grouted rock reinforcement was introduced in the United states to musing in the late 1960s and to tunneling in the early 1970s. Experience from 30 years of resin-grouted bolt installations and field tests have identified longevity problems associated with degradation of steel reinforcing bars, but in generally unusual situations. Improvements continue in resin chemistries, packaging, corrosion protection, grout quantities, and mixing and distribution in the drilled hole to achieve long-term performance. Specific case histories cited with resin- or Portland-cement-grouted rock reinforcement longevity or performance problems, upon close examination, reveal that the causes of the problems were qualify control procedures being inadequate and not in accordance with good practice. Manufacturers' recommendations and engineering specifications, if followed in the field, and with competent inspection and supervision, would have prevented must, if not all, reported longevity or performance difficulties.

Jan 1, 2000

By Daniel W. H. Su

Underground roof geology reconnaissance is being conducted by CONSOL Inc. to enhance mine productivity. Often, roof instability within mine entries is the consequence of highly variable geology that cannot always be detected from information provided by widely-spaced surface core holes. Utilizing a combination of roof drilling data, geophysical logs, and borehole camera and fiberscope observations, roof geology mapping is conducted within longwall development entries in areas of specific concern prior to commencement of longwall mining, Depending on the uniformity of the site-specific roof geology, data point spacing along the longwall development generally ranges from one to five crosscuts. Surface core hole data are correlated with the roof geology mapped underground to validate the underground observations. Detailed roof geology maps can then be produced to enable ground control engineers and mine management to select cost-effective ground control techniques. However, this procedure is not necessary or useful in all situations and it is employed only when there is strong geologic evidence to justify a closer inspection.

Jan 1, 1999

By X. L. Yao

This paper analyses the effects of mining extraction geometry (width/depth ratio) and dip of seam on subsidence parameters based on a large Database, containing 120 longwall mining cases all within the UK coalfields. The subsidence parameters evaluated in this paper include the following: the maximum subsidence value with different goaf-treatments, the position of maximum subsidence, the position of half-subsidence, subsidence value over the rib-side, positions of maximum tensile strains, positions of inflection points and the magnitude of maximum tensile strains on both rise and dip sides. Additionally, the maximum compressive strain and two limit angles are also studied in this paper. Based on a comprehensive Database analysis, several equations are derived relating these parameters to the width/depth ratio and the dip of seam. The results should assist engineers to design new structures, or take measures to protect existing structures from strain effects. The findings of the research assist in extension of the SEH to inclined seams with greater certainty.

Jan 1, 1990

By D. W. Evans

Mine subsidence problems due to coal extraction have occurred in a number of areas throughout the United States. Depending on the local geology, the depth of the mined seam, the type of mining method employed for extraction, and other related factors, subsidence can result in anywhere from slight displacements to a total loss of ground. These conditions can have serious consequences on the health and safety of the people living above the mined areas. A number of methods exist to provide support for the ground overlying mines. All of these methods employ some mechanism for providing additional support to either the roof of the mine or the sides of the pillars. Since failure usually occurs due to overburden stresses which are transmitted to the roof and pillars, these methods employ techniques to counteract stresses induced due to the coal extraction. The applicability of any particular method will depend on the availability of backfill material, the areal extent of the affected area, and of course, the cost. The primary use of coal ash for subsidence control has been as a backfill material for the stabilization of large areas. Large scale backfilling projects for subsidence control have been performed in Rock Springs, Wyoming, Wilkes-Barre and Scranton, Pennsylvania, and in Fairmont, West Virginia. Some of these projects have utilized sand, as well as, coal ash as backfill material. Much of the backfilling work performed in the United States has been done in an effort to control mine subsidence in abandoned mines. South Africa, on the other hand, has used backfilling extensively both for ash disposal and to increase extraction in active mines. The utilization of repetitive fill and mine techniques has resulted in extraction increases of as much as eight percent in shallow mines and as much as twelve percent in deep mines.(1) The coal ash injection system which can be used for backfilling depends largely upon whether the mine voids are dry or submerged. For dry mines, hydraulic or pneumatic conveyance systems can be used, while submerged mines are limited to backfilling by hydraulic methods. The use of coal ash as a backfill material has a number of advantages, such as: 1. Coal ash is available in areas throughout the United States and in many instances is conveniently located near areas requiring backfilling. 2. Coal ash is available in significant quantities since many coals when burned will result in about 15 to 30 percent ash by weight. 3. Coal ash as backfill is, in many instances, the most economical alternative fill material. Due to the costs associated with above ground disposal, power companies will often times give the material away to lower their overall operating expenses. 4. Coal ash is usually pozzolanic in nature, that is, this material results in cementitious bonding within the backfilled matrix of material.

Jan 1, 1982

By Kot F. Unrug

Since the introduction of longwall systems, the prediction of roof behavior and support requirements have become the major issue referring directly to safety as well as productivity. In more recent times, and especially in the USA where longwalls are exclusively equipped with costly hydraulic self- propelled support systems, a decision whether a longwall is applicable in a given condition, and when so, what kind of equipment should be selected, is of primary importance. There are numerous examples where lack of experience, and subsequently wrong selection of supports or winning machines, resulted in considerable losses. It should be emphasized that careful studies of prevailing geological and mining conditions, especially in a new area, are required to assure a successful operation. An evaluation of the conditions can be carried out in different ways utilizing such methods as: - Theoretical approach. applicable when geological conditions comply with the theoretical assumptions. - Empirical relationship which gives satisfactory results where the coefficients could be adequately determined. - Structural geological studies which must be undertaken in all cases, since the frequency of fractures and their orientation have a prevailing influence on roof behavior. - Scale model study on equivalent material for determination of failure conditions in the roof and mechanism of movement (flow) of broken rock matter. Coefficients for empirical formulas can be determined by these types of studies, as can boundary limits for mathematical modeling. - Mathematical modeling, e.g., finite element analysis. - Measurements and observations taken underground during the development period end utilization of experience for previous longwall panels in the area. Usually it is the most practical method where mining and geological conditions are comparable. An application of me or more of the above approaches remains to be a matter of judgement for particular conditions, however, the utilization of a practical experience, when available, is usually the safest way for planning a successful longwall operation.

Jan 1, 1982

By P. A. Gray

Artificial ground support has developed into a relined science over the past 20 years. From reactive support systems such as timber props and steel supports, to active systems such as roof bolts and cable anchors, ground support technology has now developed efficient systems that work well in many instances. However this paper demonstrates that there is still a long way to go to develop optimum ground support systems. Some conventional rock bolts and cable anchors emphasise their tensile capacity only, without considering other factors such as their shear strength or shear modulus, or if the support member can transfer all of its support capacity to the surrounding rock. Examples are given of the use of ground anchors with high tensile and shear capacity in underground coal mining as well as examples of slope failures in open pits where the cable bolts have remained intact because they have been unable to transfer their full capacity to the surrounding weak rock mass. For underground coal mines, speed of installation is also of primary concern, but it must also have high tensile and shear capacity both in terms of strength and stiffness. Ground support systems of the future must therefore address these problems. An innovative new rock bait is discussed which goes some way towards solving these problems. This new rock bolt is screwed into the rock and thus has a direct mechanical interlock with the rock. Initial field results show that it has an extremely high anchor capacity and can be fully installed in approximately 30 seconds. It has considerable capacity to improve the productivity of the coal mining industry.

Jan 1, 1992

By Ximeng Li

The entries that are subjected to dynamic pressure are much more difficult to maintain due to repeated disturbance. A case study of an entry stress distribution was performed using the FLAC3D program. By analyzing the distribution of stress field around the entries, this paper provides guidelines for entry support design in the lower (#16) seam subjected to the repeated disturbance from longwall mining in the immediate overlying (#17) seam, 72ft (22 m) above. The results showed that there was stress superposition inside the barrier pillar in the lower seam, 15ft (5m) to 45ft (15m) deep, during development. The influence zone of the front abutment pressure in the upper (#16) seam was about 100ft (30m) outby the faceline. The stress-relieved zone was from 0 to 100ft (30m) inby the face. The area further inby the face (i.e., 230 ft (70 m) inby the face) was within the gob compaction zone. Along the face advancing direction, the affected zones of the entries in the lower (#17) seam that were subjected to the dynamic pressure from longwall mining of the immediate overlying seam could be divided into four stages: pillar development stress stage, front abutment pressure stage, unstable gob stage, and stable gob stage. Those entries within an area from 100ft (30m) outby to 100ft (30m) to 230ft (70m) inby the faceline should be reinforced with special supports. The numerical modelling matched the monitoring results well.

Jan 1, 2013

By David F. Gearhart, Mark Van Dyke, Heather Dougherty, Ted Klemetti, Gabriel S. Esterhuizen

"Coal mine longwall gateroads are subject to changing loading conditions induced by the advancing longwall face. The ground response and support requirements are closely related to the magnitude and orientation of the stress changes, as well as the local geology. This paper presents the monitoring results of gateroad response and support performance at two longwall mines at a 600-ft and 2,000-ft depth of cover. At the first mine, a three-entry gateroad layout was used. The second mine used a four-entry, yield-abutment-yield gateroad pillar system. Local ground deformation and support response were monitored at both sites. The monitoring period started during the development stage and continued during first panel retreat and up to second panel retreat. The two data sets were used to compare the response of the entries in two very different geotechnical settings and different gateroad layouts. The monitoring results were used to validate numerical models that simulate the loading conditions and entry response for these widely differing conditions. The validated models were used to compare the load path and ground response at the two mines. This paper demonstrates the potential for numerical models to assist mine engineers in optimizing longwall layouts and gateroad support systems.INTRODUCTIONThe need for roof stability in coal mine longwall gateroads places significant demands on the gateroad ground support system. The variable loading conditions associated with the approaching longwall face can cause excessive ground deformations that need to be accommodated by the support system. In coal mines in the United States several different types of supports are used to maintain the stability of gateroads. The supports may include grouted roof bolts, cable bolts, and roof trusses as intrinsic support. Standing supports include timber cribs, engineered timber props, and various types of cement-based cribs. The intensity of support is governed by the expected geologic conditions and the expected stress changes that will occur during longwall mining. At present, the design of ground support for gateroads is largely based on local experience. In-mine trials are usually conducted when new support technologies become available or ground conditions dictate a change in the support system. The research reported in this paper has the objective to assist mining engineers in evaluating alternative gateroad supports and to design suitable support systems for the local ground conditions."

Jan 1, 2018

By Andy L. Shaffer

A novel liquid settlement system (LSS) was installed in advance of mining at a western United States (U.S.) longwall mine to measure total roof sag from the time of cutting to days after mining during gate road development. The system was used to compare differences in roof sag between conventional place-change mining using a Joy continuous miner and a Fletcher roof bolter and mining using a miner-bolter. The LSS was installed with an intrinsically safe, miniature data acquisition system (MIDAS) to record roof response at four locations in the same gate road. The system utilized pressure transducers to measure roof sag by the principle of falling head (fluid pressure) in fluid-filletubes installed in the immediate roof. Details of the LSS design, installation, data collection, post-processing, and future applications are discussed.

Jan 1, 2014

By Xicai Gao

With the intensification and expansion of deep coal mining, the surrounding rock stress environment becomes further deteriorated because of the complicated geological environment and powerful mining effect, so the major deformation of roadway appeared frequently. The proportions of floor heave are increasing and , the most serious problem is the floor heave of preparatory workings. The coal seam of Binchang coal area in Shaanxi province is at a depth of 621.6 ~ 817.0 m, the average thickness of the coal seam is 25 m, and the overburden and coal measure strata are the main regional aquifers and are highly permeable. The properties of water-weakening are obvious in the floor strata. The main preparatory workings or chambers were driven in the coal seam. The severe floor heave of the water chamber appeared during early mining and the amount was 180 ~ 910mm, and seriously affected the normal installation and use of the water chamber. Theoretical study and numerical simulation as well as the in-situ measurements were carried out to investigate the deformation and failure characteristic of the surrounding rock with non-support in the floor and the main reasons which caused the floor heave were determined. A new combined support technology was proposed which consists of overcutting, grouting, backfilling and invertedarch and bolt-grouting. The field monitoring showed that the cumulative convergence of the water chamber was 20mm, the maximum convergence speed is 1.2 ~ 2mm/d, the accumulative convergence of two ribs was 36mm and the maximum convergence speed is 2mm/d. The combined support technology will enhance the support intensity between the roof and floor, the two sides of the entry and improve the loading capacity of the floor effectively and the floor heave can be controlled effectively.

Jan 1, 2013

By Khaled M. Mohamed, Michael M. Murphy, Ted M. Klemetti, Heather E. Lawson

"The design of rib support systems in U.S. coal mines is based primarily on local practices and experience. A better understanding of current rib support practices in U.S. coal mines is crucial for developing a sound engineering rib support design tool.The objective of this paper is to analyze the current practices of rib control in US coal mines. Twenty (20) underground coal mines were studied representing various coal basins, coal seams, geology, loading conditions, and rib control strategies.The key findings are: (1) any rib design guideline or tool should take into account external rib support as well as internal bolting; (2) rib bolts on their own cannot contain rib spall, especially in soft ribs subjected to significant load—external rib control devices such as mesh are required in such cases to contain rib sloughing; (3) the majority of the studied mines follow the overburden depth and entry height thresholds recommended by the Program Information Bulletin (PIB) 11-29; (4) potential rib instability occurred when certain geological features prevailed—these include draw slate and/or bone coal near the rib/roof line, claystone partings, and soft coal bench overlain by rock strata; (5) 47% of the studied rib spall was classified as blocky—this could indicate a high potential of rib hazards; and (6) rib injury rates of the studied mines for the last three years emphasize the need for more rib control management for mines operating at overburden depths between 500 ft and 1,000 ft.IntroductionEfforts to improve the stability of underground mine ribs have continued for decades. These efforts by mining professionals around the world persisted throughout the 1990s and 2000s as well, though much of this work focused on rib support methodology and selection of proper support for a specific location. Despite these efforts, it is unfortunate that there has been a continual occurrence of rib-related fatalities in underground coal mines. While overall improvements in rib safety have been achieved, the average fatality rate is still about 1.3 fatalities per year over the last 18 years (Jones, 2014).To manage and control the rib hazard, rib support is used in U.S. coal mines. The current rib support methods for U.S. mines fall into two main categories: rib control based on intrinsic support systems and those based on external support systems. Intrinsic or rib-bolt support requires a roof bolting machine that can install a bolt fixture into the rib. Furthermore, the appropriate level of support needed to control the ribs with an intrinsic-based support system as well as the design parameters for those support systems for various mine conditions have not been established in U.S. coal mines. Furthermore, surface control systems are often an integral part of these support systems and must be considered in the system design."

Jan 1, 2015

By Rafal Misa

In order to prevent the formation of mining damage or to reduce its reach, it is advisable to look for technical solutions which would enable effective protection of construction sites from the impacts of underground mining. So far, other authors have mainly focused on developing methods of securing construction sites in order to minimize the damage resulting from underground mining; the issue of geotechnical methods for protecting buildings against mining damage has not been thoroughly covered in those articles. It should be noted that there are relatively few publications directly related to this issue, nor are there practical examples of geotechnical protection. In this paper, a geotechnical solution available for securing building structures is discussed. Trenches presented in this research reduce the size and range of mining deformation. The results of numerical modelling for sample protective solutions, aimed at reducing the impact of mining activity on the terrain surface under various conditions, are presented. The calculations were performed with the aid of the Abaqus 6.10-2 software, based on the Finite Element Method.

Jan 1, 2014

By Yang Li

For the study of overburden movement in longwall mining of shallow coal seams, most scholars merely consider the thickness of bedrock and top soils. In this paper, the overburden movement in longwall mining of shallow coal seams with thin top soils and key strata group was studied. By using numerical simulation, the development of fractures in the overburden was analyzed for different ratios of panel width to depth (W/D) and depth to mining height. The results show that the overburden movement changed with the variation of mining height, panel width and depth under the specific geological conditions. It also explain how different overburden disturbance structures, such as ?three zones? (caved, fractured, and continuous deformation zones), ?two zones?(caved and fractured zones) or ?steps-like collapse? are formed under different mining conditions. The results broaden the vision for research on overburden movement in longwall mining of shallow coal seams.

Jan 1, 2014

By James D. Pile

Following a methane ignition in the active panel of a longwall coal mine, the affected panel was successfully isolated from the rest of the mine. This allowed for the remainder of the mine to return to regular operation, and the conventional practice of having to seal the portals for a defined period of time was avoided. After the affected panel had remained isolated for a regulatorily mandated period of time, it was reopened in preparation for longwall face recovery. As it was not possible to move the shields from their existing positions to facilitate the installation of recovery mesh prior to shield recovery, alternative methods had to be considered to stabilise the gob and minimise flushing, thereby improving operator safety. The objective of the paper is to show how stabilisation of the gob was achieved during shield recovery, thereby minimising flushing, and improving operator safety. Phenolic foam was chosen and injected from between the shields into the gob behind them. This is a technique that has been used to great effect in Germany, to a lesser extent in Australia, but not knowingly to date in the United States. To ensure nothing was left to chance and thereby guarantee the project?s success, the procedure used in Germany was employed, down to the application of equivalent hardware, which was sourced through the North American supplier.

Jan 1, 2013

By Stephen C. Tadolini, Anthony T. Iannacchione

"Coal burst represented a major hazard for some U.S. mining operations. This paper provides an historical review of the coal burst hazards, identifies the fundamental geological factors associated with these events, and discusses mechanisms that can be used to avoid their occurrences. Coal burst are not common in most underground mines. Their occurrence almost always has such dramatic consequences to a mining operation that changes in practice are required. Fundamental factors influencing coal burst events include strong strata, abnormal strata caving, elevated stresses, critical size pillars and the lack of sufficiently sized barrier pillars during extraction. These factors interact to produce excessive stress, seismic shock and loss of confinement mechanisms. Over the 90 years of dealing with these hazards, many novel prevention controls have been developed including novel mine designs and extraction sequences, most of which are site specific in their application. Without an accurate assessment of the fundamental factors that influence coal burst and knowledge of their mechanisms of occurrence, control techniques may be misapplied and risk inadequately mitigated. INTRODUCTIONCoal burst1are violent failures of ribs, roof or floor in underground mines. They are known to occur in complex ways and often under unique sets of conditions. This has made them extremely difficult to anticipate and control. Assessing coal burst risk requires engineers, managers, and safety professionals to recognize the fundamental factors responsible for these events. This helps practitioners recognize the hazard potential and understand the context in which various controls and barriers should be used. Only then can coal burst events be anticipated andappropriate mitigation techniques deployed.Over the last 90 years, a few coal burst events have been anticipated but most have eluded prediction. The authors examined the historical record (Appendix A) and determined that an inadequate understanding of the initiating geologic factors and their associated mechanisms of occurrence have contributed to the poor predictive capability. The historic record also indicates that control techniques have typically been site specific in their application."

Jan 1, 2015

By Meng Xiao, Peng Huang, Lizin Lan, Feng Ju, Shuai Guo

"Through changing the axial load on backfilling material compaction test to reflect different overlying strata pressure on backfilling material, the stress-strain relations in the compaction process of backfilling material under the geological condition can be obtained. Based on the characteristic of overlying strata movement in backfill mining, a model of roof thin plate is established. By introducing the stress-strain relation in compaction process into the model and using RIZT method to analyze the bending deformation of roof, the bending deflection and stress distribution can be obtained. The results show that the maximum roof subsidence and maximum tensile stress occurring at the center are 255mm and 5 MPa, respectively. Tensile fracture of roof under the geological condition of Dongping mine did not occur. The dynamic measurement results of roof in Dongping mine verify the theoretical result from the aforementioned model, thereby suggesting the roof mechanical model is reliable. The roof thin plate model based on the compaction characteristic of backfilling material in this study is of importance to research on backfill mining theories and application of backfilling material characteristics.INTRODUCTIONSolid backfilling mining (SBM) is a green mining technology in which the solid waste materials is placed into the gob to support the overlying strata and to control roof's subsidence and movement (Miao, 2012; Miao et al., 2010, 2015). SBM has been successfully used in several mines to solve many problems, including coal extraction under buildings, water bodies and railways, surface subsidence, and environmental problems. Good results have been obtained in many mines (Zhang et al., 2009). The key in the application of SBM technology is controlling strata movement. However, the critical factor influencing the controlling effect of strata movement is compaction characteristics of backfilling materials. Thus, a roof model of SBM is built based on the filling materials' compaction characteristics. A subsidence equation and the critical failure condition of roof was given and field verification was performed at Panel 15061 of Donping Mine."

Jan 1, 2016

By Pengfei Wang, Guorui Feng

With increase of cover depth, dynamic incidents, such as large gateroad convergences and coal bursts, are frequently encountered when mining deep longwall panels. It would be more adverse due to large inclination of the coal bed. Because of the shearer and armored face conveyor (AFC) sliding downhill, toppling of shields, disconnection of AFC to the stage loader are related to it. Tangshan coal mine is a typical deep, inclined coal mine situated in the east of China. The split-level longwall panel layout is being adopted for mitigating problems above, where tailgate entries of longwall panels are driven below gob edge and along the floor, while headgate entries are driven along the roof. Wire mesh and steel sets have been used empirically for support for tailgates for about a decade, which reduces the tunneling speed. In view of this fact, the paper serves to investigate the proper adjustment of the tailgate locations and to analyze the resulting stress and yield conditions according to support strategy. First, field measurements and observations were carried out. Stress data distributed within surrounding rock mass were obtained, especially within the roof since the roof consists of only a coal sheet with a thickness of 2–4 m. Roof pressure of the tailgate represents the pressure at the gob edge since it is below the gob edge. The convergence data were also collected. Numerical modelling using FLAC3D™ was conducted and validated by side abutment stress data. The double-yield constitutive model was used to simulate the gob. The finalized tailgate layout and design were determined through comparison of three scenarios. The research in this paper can help engineers choose the proper tailgate layout and support strategies for coal mines that are going to adopt a split-level longwall panel layout for mining deep, inclined longwall panels.

Jan 1, 2018

By Chengguo Zhang, Bruce Hebblewhite, Faham Tahmasebinia, lsmet Canbulat

"Coal burst is a dynamic release of energy within the rock (or coal) mass leading to high velocity expulsion of the broken/ failed material into mine openings. This phenomenon has been recognised as one of the most catastrophic failures associated with the coal mining industry, which can often lead to injuries and fatalities of miners as well as significant production losses. This paper aims to examine the mechanisms contributing to coal burst occurrence, with an emphasis on the energy release concept. In this study, a numerical modelling study has been conducted to evaluate the roles and contributions of difference energy components. The energy analysis presented in this paper can help to improve the understanding of energy release mechanisms especially under Australian conditions.INTRODUCTIONCoal burst is one of the most hazardous problems encountered in underground coal mines, which occurs at different locations in a variety of mining systems and operations. This phenomenon always involves a violent and dynamic energy release with large rock mass/coal deformation and ejection that can cause severe damage to openings, equipments and may result in fatalities and injuries.The first coal burst occurrence was reported in Britain in 1738 (Dou 2001). Since then, international experiences are available in Canada, South Africa, USA, former Soviet Union, China, India, France, Germany, Poland and Czechoslovakia. Rice (1935) classified coal bursts as two general types, namely excessive pressure bumps and shock bumps and he further mentioned that pressure bumps are caused when pillar stress exceeds bearing strength. Shock bumps are induced by the breaking of thick, massive strata at a considerable distance above the coal-bed, causing the immediate roof to transmit a shock wave to the coal."

Jan 1, 2016

By Donovan J. Benton

Photogrammetric methods are advancing rapidly and show considerable promise as a ground control research tool. The ability to quickly capture three-dimensional geometry, especially changes in geometry, in underground and laboratory settings is a significant advance from point distance measurements. Photogrammetry is being applied in both of these settings as part of the NIOSH ground control research. This paper describes these applications and the equipment and software being employed. It also describes tests conducted to quantify the accuracy of these systems. Accuracy varied with system specifics and procedures. A factory-calibrated camera produced results within 1/32 of an inch, plus 0.04%. A user-calibrated camera was found to be less accurate, at 1/20 of an inch, plus 0.24%. These calibrations demonstrate that photo grammetry can produce research quality measurements in laboratory and mine settings.

Jan 1, 2014

By Zbigniew Lubosik, Andrzej Walentek, Stanislaw Prusek, Sylwester Rajwa, Aleksander Wrana

"Underground coal gasification (UCG) provides a solution to supply electricity from high ash coal or deep deposited seams. The coal is consumed in situ, and, accordingly, the ash is left underground. UCG could play a major role in the future of coal, which is expected to fuel 44% of the world’s energy in 2030, in a more environmentally friendly and commercially viable manner. Nevertheless, it is known that the UCG can impact the environment. One of the most important factors in safe UCG process should be the evaluation of rock mass quality and the monitoring of its behaviour. The changes of rock mass parameters and quality have an influence on numerous aspects, such as subsidence and the stability of underground workings in georeactor vicinity, however, they also increase the possibility of pollutant migration through fractures and pores. These issues are especially important in cases of gasification conducted in an operating mine or on areas of high ecological vulnerability. This paper details observations made in two underground trials of UCG performed in Poland recently. The first of which is the Experimental Mine Barbara (under the project entitled HUGE-2 Hydrogen oriented underground coal gasification for Europe – Environmental and Safety aspects, (Wiatowski et al., 2015). The other trial has been conducted at an operating mine, Wieczorek, which is in the framework of a research project on the development of coal gasification technology for highly efficient fuel and electricity production (Czaplicka-Kolarz et al., 2013). During these trials, investigations were carried out aimed at assessing geomechanical parameters of rock mass and support behaviour in surroundings of UCG geaoreactors. Investigation comprises assessment of geomechanical parameters of coal, floor and roof strata, roof displacements, and concrete support strength parameters variation, as well as standing steel support load. Hydraulic penetrometer, endoscopic camera, Schmidt hammer, pull-out method, telltale, and ground penetration radar (GPR) were used in the investigation. Research conducted at both EM Barbara and Wieczorek Collieries revealed that the UCG process did not adversely affected the competency of rock mass (expressed by number of fissures and strength parameters of rocks), the stability of roadways and the support performance in the areas located in the vicinity of the georeactors."

Jan 1, 2017