Longwall Mining Subsidence Research Articles

Investigations on longwall mining subsidence impacts on Pennsylvania highway alignments

Abstract Over 600 longwall panels have been mined in Pennsylvania in the last 50 years. Of those 600 panels, 25 panels undermined interstates highways. Despite this quantity of panels, much is still unknown regarded the detailed effects of undermining highways. The Gateway Mine, the Emerald Mine, and the Cumberland Mine undermined I-79 with 17 panels in 1982–1989 and in 2003–2008, respectively; Mine 84 undermined I-70 with 4 panels in 1987–2000. Through the examination of the panels that undermined I-70 and I-79, it is possible to determine which factors have most impacted the highway alignments. In some locations, the highway intersects with panels at angles ranging from 45° to 80°; and at the others, it runs between two panels, which simulates the effect of gateroads on the subsidence. The panel width to overburden ratio varies between 0.64 and 1.7, meaning that the interstates were influenced by both subcritical and supercritical subsidence basins. The face advance rates and overburden depths also vary between the panels. Unfortunately, specific information detailing highway impacts associated with unique characteristics of the subsidence basins are limited. In this paper, using the profile function model and influence function model within the surface deformation prediction system (SDPS), the effects of overburden, panel size, and orientation of the road on the highway can be indirectly assessed.

A Quantitative Approach to Evaluate Changes in Hydrologic Conditions of Headwater Streams: A Case Study of Restoration and Recovery Following Longwall Mine Subsidence

Mine subsidence can induce streambed ruptures that pirate surface water from a stream. Current understanding of the effects of longwall mining on streams lacks rigorous analytical approaches to detect hydrologic effects and does not consider the efficacy of streambed restoration techniques to address flow disruption. CONSOL Pennsylvania Coal Company, LLC (CPCC) collected and analyzed pre-mining, post-mining, and post-restoration stream discharge and flow duration data from 51.9 km of streams overlying its Bailey Mine to define pre-mining flow variability, detect post-mining changes, and evaluate post-intervention flow recovery. The primary intervention method for restoring stream flow was bedrock permeation grouting. Pre-mine and post-mine baseflow data were compared using both parametric and non-parametric hypothesis testing, which yielded similar results. An environmental flow assessment method for headwater streams using probabilistic risk assessment and correlation analysis of change threshold criteria was developed to differentiate hydrologic change as induced by mine subsidence or explained by natural variability. The method is objective, pragmatic, and statistically delimited.

Use of Time Series Analysis to Evaluate the Impacts of Underground Mining on the Hydraulic Properties of Groundwater of Dysart Woods, Ohio

Dysart Woods is the largest (≈ 23 ha) old-growth forest in southeastern Ohio. It was donated to Ohio University for research purpose and public use by the Nature Conservancy. The mineral rights beneath Dysart Woods are held by the Ohio Valley Coal Company, who conducted underground coal mining in the area. We performed correlation analyses of time series data of precipitation, hydraulic head, barometric pressure, and Earth tide data from before and after mining to characterize the hydrogeologic processes and changes in the aquifers in the mined areas. Results of transient data analyses revealed higher permeability and hydraulic conductivity after mining and decreased storage capacity in the upper groundwater system. Analysis of the Earth tide data also suggested that the groundwater flow regime responded better to Earth tides prior to mining than after mining, which was probably due to the draining of water through mining-induced fractures in the system. Changes in hydrogeologic parameters suggest that the capacity of aquifers to hold water against gravity has declined, due to increased fracturing and faster vertical movement of water. At Dysart Woods, old trees obtain water from springs that discharge groundwater. If the groundwater levels drop, the Dysart Woods ecosystem can be adversely affected. Increased understanding of the potential hydrogeologic impacts of longwall mining subsidence is necessary, especially for mine operators and regulators, to preserve the ecosystems that rely on the groundwater flow system. In addition, it is very important that mine operator and regulators cooperate, as it is not enough to protect the soil surface from subsidence; the surface and groundwater systems should also be preserved.

Satellite radar interferometry for monitoring subsidence induced by longwall mining activity using Radarsat-2, Sentinel-1 and ALOS-2 data

Abstract This paper describes the simulation and real data analysis results from the recently launched SAR satellites, ALOS-2, Sentinel-1 and Radarsat-2 for the purpose of monitoring subsidence induced by longwall mining activity using satellite synthetic aperture radar interferometry (InSAR). Because of the enhancement of orbit control (pairs with shorter perpendicular baseline) from the new satellite SAR systems, the mine subsidence detection is now mainly constrained by the phase discontinuities due to large deformation and temporal decorrelation noise. This paper investigates the performance of the three satellite missions with different imaging modes for mapping longwall mine subsidence. The results show that the three satellites perform better than their predecessors. The simulation results show that the Sentinel-1A/B constellation is capable of mapping rapid mine subsidence, especially the Sentinel-1A/B constellation with stripmap (SM) mode. Unfortunately, the Sentinel-1A/B SM data are not available in most cases and hence real data analysis cannot be conducted in this study. Despite the Sentinel-1A/B SM data, the simulation and real data analysis suggest that ALOS-2 is best suited for mapping mine subsidence amongst the three missions. Although not investigated in this study, the X-band satellites TerraSAR-X and COSMO-SkyMed with short temporal baseline and high spatial resolution can be comparable with the performance of the Radarsat-2 and Sentinel-1 C-band data over the dry surface with sparse vegetation. The potential of the recently launched satellites (e.g. ALOS-2 and Sentinel-1A/B) for mapping longwall mine subsidence is expected to be better than the results of this study, if the data acquired from the ideal acquisition modes are available.

Comparison of L-band and X-band differential interferometric synthetic aperture radar for mine subsidence monitoring in central Utah

Abstract Differential interferometric synthetic aperture radar (DInSAR), a satellite-based remote sensing technique, has potential application for measuring mine subsidence on a regional scale with high spatial and temporal resolutions. However, the characteristics of synthetic aperture radar (SAR) data and the effectiveness of DInSAR for subsidence monitoring depend on the radar band (wavelength). This study evaluates the effectiveness of DInSAR for monitoring subsidence due to longwall mining in central Utah using L-band (24 cm wavelength) SAR data from the advanced land observing satellite (ALOS) and X-band (3 cm wavelength) SAR data from the TerraSAR-X mission. In the Wasatch Plateau region of central Utah, which is characterized by steep terrain and variable ground cover conditions, areas affected by longwall mine subsidence are identifiable using both L-band and X-band DInSAR. Generally, using L-band data, subsidence magnitudes are measurable. Compared to X-band, L-band data are less affected by signal saturation due to large deformation gradients and by temporal decorrelation due to changes in the surface conditions over time. The L-band data tend to be stable over relatively long periods (months). Short wavelength X-band data are strongly affected by signal saturation and temporal decorrelation, but regions of subsidence are typically identifiable over short periods (days). Additionally, though subsidence magnitudes are difficult to precisely measure in the central Utah region using X-band data, they can often be reasonably estimated.

Agricultural impacts of longwall mine subsidence: the experience in Illinois, USA and Queensland, Australia

Unlike conventional room and pillar underground coal mining, where subsidence is designed to be prevented, subsidence is a planned outcome of other methodologies. These include high extraction retreat, where the roof supporting pillars are systematically removed, and longwall mining, which employs a machine that mines a continuous strip of coal, thus leaving no roof supports. Both types result in the surface dropping ~70 % of the mined-out thickness. In Illinois there was a concern that farm land thus subsided would be lost to productive agriculture. Consequently, the possibility that planned mine subsidence would be banned in Illinois lead to the creation of the Illinois Mine Subsidence Research Program in 1985 to investigate agricultural impacts of planned mine subsidence and the possibility of mitigating its impact. Its findings established that subsidence was not as detrimental as feared and that the impacts could be mitigated. The project was a successful collaboration of state and federal governments and local Universities. Similarly, in Queensland, longwall mining is opposed by some in the farming community. In response, Bandanna Energy, the company planning the mining, organized the Agricultural Coexistence Research Committee to oversee research into the mitigation of longwall mining impacts. Although the soils, climate, and regulatory regimes are different, concerns of the local communities are similar.

Vegetation, fauna and groundwater interrelations in low nutrient temperate montane peat swamps in the upper Blue Mountains, New South Wales.

Newnes Plateau Shrub Swamps are a series of low nutrient temperate montane peat swamps around 1100 m elevation in the upper Blue Mountains, west of Sydney (lat 33° 23' S; long 150° 13'E). Transect-based vegetation studies show a closely related group of swamps with expanses of permanently moist, gently sloping peatlands. Vegetation patterns are related to surface hydrology and subsurface topography, which determine local peat depth. While there is evidence that a group of the highest elevation swamps on the western side of the Plateau are more dependent on rainwater, the majority of swamps, particularly those in the Carne Creek catchment, and east and south of it, may be considered primarily groundwater dependent with a permanently high watertable maintained by groundwater aquifers. An integral part of the swamps are a number of threatened groundwater dependent biota (plants-Boronia deanei subsp. deanei, Dillwynia stipulifera, dragonfly- Petalura gigantea, lizard- Eulamprus leuraensis), which are obligate swamp dwellers. This association of dependence leaves the entire swamp ecosystem highly susceptible to threats from any loss of groundwater, the current major one being the impact of damage to the confining aquicludes, aquitards, aquifers and peat substrates as a result of subsidence associated with longwall mining. Impacts on the swamps may also result from changes to hydrology through damming of creeks, mine waste water discharge, increased moisture competition from pine plantations, recreational motorbike and off-road vehicle tracks and climate change. If these groundwater dependent ecosystems do not receive protection from activities such as longwall mining subsidence, significant ecological damage is unlikely to be avoided or able to be mitigated even where provisions of the Commonwealth Environment Protection and Biodiversity Conservation and NSW Threatened Species Conservation Acts apply to groundwater dependent swamps and biota. The importance of the highest elevation part of the Plateau for a number of restricted (some endemic) plant species is also discussed.

English

Dr. Zhenqi Hu of the China University of Mining and Technology, Beijing, organized the 2010 International Symposium on Low-Carbon Development and Land Reclamation Policy. The meeting was from November 20-21 in Beijing, and I was invited to present a paper at the symposium by Professor Hu. In addition, he invited me to give lectures on reclamation at his university. I also gave a lecture at Shandong Agricultural University at Tai'An, which is south of Beijing about 260 miles. I stayed in China long enough to visit mine sites near Jining and cultural venues in Beijing and near Jining, including Confucius' compound. This presentation recounts my experience visiting China and includes my observations on the similarities and differences in the American (Illinois) and Chinese approach, attitudes, and techniques in regard to mine reclamation. My presentations in China included a recap of the impact of longwall mine subsidence in Illinois. This is a still-controversial mining technique despite a near decade of research into its agricultural impacts. I also spoke on surface mine reclamation in Illinois, where many of the mines are on Prime Farmland and reclamation is held to a high crop productivity standard. The coal industry is very active in China, and their need for good reclamation is acute given their vast population and high density.

Isaac river cumulative impact assessment of mining developments

Longwall mining and related subsidence, and watercourse diversion for surface mining operations have the potential to impact on fluvial geomorphic processes and the health of river systems. This is evident in the Isaac River in central Queensland. The scale and likelihood of these impacts are a function of the extent of existing and proposed mining developments and of the ongoing geomorphic, hydrologic and ecological processes within the Isaac River. Understanding the objectives for the river, the past and ongoing processes at work, the cumulative impacts of longwall mining development and the options for managing those impacts is essential for the development of an effective strategy to manage the health of the river system. An assessment has been undertaken to identify and understand the cumulative impacts of mining subsidence and other mining influences on geomorphic processes and waterway health in the Isaac River over a river length of approximately 100 km near Moranbah in central Queensland. The assessment included the development of a vision and objectives for waterway health. The assessment has identified mining and landuse changes that have impacted on the hydrology, geomorphology, ecology and hence the health of the Isaac River. The assessment has then sought to identify the cumulative impact of longwall mining and related subsidence on current stream condition and the proposed vision for the system. The primary impact of longwall mining on the river was found to be associated with sediment transport. The investigation included assessment of total sand available for transport, the volume of sand transported annually and the fluvial process response to subsidence. Recommendations have been developed for the management of the system and for longwall mining to increase system robustness and achieve the river health objectives.

Anomalous Increases in Piezometric Levels in Advance of Longwall Mining Subsidence

The typical initial piezometric response to long-wall undermining is a decline in head due to the opening of fractures and bedding planes during early subsidence. However, in studies over two active longwall mines in southern Illinois, temporary rises in head just before subsidence were observed in piezometers constructed in low-permeability units. Although the initial phase of subsidence is considered dilational, these head increases indicate com-pressional effects that raise pore-water pressures. Possible mechanisms are shear stresses at the leading edge of subsidence or transmission of stress related to dewatering of underlying permeable units.

Positive and negative impacts of longwall mine subsidence on a sandstone aquifer

Subsidence due to longwall underground coal mining changes the hydraulic properties, heads, yields, and in some cases the groundwater chemistry of overlying bedrock aquifers. A 7-year study of a sandstone aquifer overlying an active longwall mine in Illinois has supported a comprehensive model of these impacts. Subsidence caused increases in permeability and storativity over the longwall panel. These changes initially caused a major decline in water levels in the sandstone, but the aquifer recovered slightly within a few months and fully within several years after mining. The enhanced hydraulic properties combined with potentiometric recovery resulted in a zone of greater well yield. However, at sites with very poor transmissivity and inadequate recharge pathways, recovery may not occur. Also, at the study site, the physical enhancement was accompanied by a deterioration in groundwater quality from slightly brackish, sodium bicarbonate water to more brackish water with increased sulfate levels.

Possible Applications of OTDR in the Mining Industry

Mineral Resources EngineeringVol. 07, No. 01, pp. 5-14 (1998) No AccessPossible Applications of OTDR in the Mining IndustryV. Kumar and Dinesh ChandraV. KumarDepartment of Electronics and Instrumentation, Indian School of Mines, Dhanbad-826004, India Search for more papers by this author and Dinesh ChandraDepartment of Electronics and Instrumentation, Indian School of Mines, Dhanbad-826004, India Search for more papers by this author https://doi.org/10.1142/S0950609898000031Cited by:1 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail AbstractThis paper has described two important applications of Optical Time Domain Reflectormetery (OTDR) for mining industry. One, for the measurement of temperature and two, for the measurement of displacement of rock mass which may be useful for the remote monitoring of strata movement above a longwall coal mine, collapse of a longwall panel, opencast mine, mine subsidence and underground nuclear tests. Optical fiber, being a dielectric, non-metallic, non-sparking, free from electromagnetic and radio frequency interferences is an intrinsically safe media and is ideally suited to the hazardous environment present in mines. FiguresReferencesRelatedDetailsCited By 1Fiber optic methane and strain sensors for minesV. Kumar1 Jul 2010 Recommended Vol. 07, No. 01 Metrics History PDF download

Modeling agricultural impacts of longwall mine subsidence: A GIS approach

ABSTRACT Coal mining and agriculture are both land-intensive industries that often operate in the same area. Illinois, for example, is both a major agricultural state and one of the leading coal-producing states in the U.S. The future of coal mining in Illinois and in other similar areas is longwall mining. One of the advantages of longwall mining, and the most noticeable consequence, is immediate lowering, or subsidence, of the land above the active mine. Having immediate subsidence is advantageous because it can be dealt with or mitigated soon after it happens. With conventional mining, subsidence is unexpected and therefore if it occurs, it is unpredictable. Mitigation of subsidence effects, including the impact on agriculture, is the responsibility of the mining company. Research has shown that mitigation of agricultural impacts is usually effective, but may not be fully successful in some cases. Minimizing subsidence impact by avoiding sensitive soils in the mine plan is a possibility that should be ...

Effects of Longwall Mining Subsidence on Ground Water Levels Within a Watershed Hydraulically Isolated from Mine Drainage

Effects of Longwall Mining Subsidence on Ground Water Levels Within a Watershed Hydraulically Isolated from Mine Drainage

Modeling Agricultural Impacts of Longwall Mine Subsidence: A GIS Approach

Modeling Agricultural Impacts of Longwall Mine Subsidence: A GIS Approach

A numerical approach to subsidence prediction and stress analysis in coal mining using a laminated model

Subsidence due to underground mining may cause damage to surface structures and farmland and change surface and subsurface drainage patterns. During the past few decades, a number of subsidence prediction techniques have been proposed. Currently, the influence function method is the most widely used method for prediction of longwall coal mining subsidence. The influence function method may provide accurate results if a suitable function can be established for a specific site or region based on field observations. The method, however, suffers from generality, and cannot be used in virgin areas. Furthermore, there is a need to develop a model which can simultaneously analyze in-mine stability of mine workings including roof-pillar-floor interaction and associated surface and subsurface subsidence. Since the rock mass surrounding coal seams usually consists of distinct layers/beds and field observations suggest relative movements along bed interfaces, a homogeneous isotropie continuum model cannot effectively describe ground movements due to coal mining. Therefore, in finite element modeling some investigators reduce the values of the Young's modulus to very small, say one percent of the original laboratory value, to obtain acceptable subsidence results, e.g. Bowders et al [1]. Valuable attempts have also been made to model the sliding between beds in finite element modeling [2], but results have been presented only for two-dimensional problems due to large memory and computation time requirements for three-dimensional problems. A three-dimensional numerical model based on a laminated medium used in conjunction with boundary element technique was developed to simulate the ground movements due to coal mining, and results obtained were reasonable [3]. Recently, this model has been further modified to simultaneously analyze both subsidence and in-mine stability of mine workings including roof-pillar-

Overburden deformation and hydrologic changes due to longwall coal mine subsidence on the Illinois basin : Kelleher, J T; Van Roosendaal, D J; Mehnert, B B; Brutcher, D F; Bauer, R A Proc 4th International Conference on Land Subsidence, Houston, 12–17 May 1991P195–204. Publ IAHS Press: Wallingford, 1991

Overburden deformation and hydrologic changes due to longwall coal mine subsidence on the Illinois basin : Kelleher, J T; Van Roosendaal, D J; Mehnert, B B; Brutcher, D F; Bauer, R A Proc 4th International Conference on Land Subsidence, Houston, 12–17 May 1991P195–204. Publ IAHS Press: Wallingford, 1991

Methods for assessing effects of longwall mining on surface subsidence : Hazen, G A; Sargand, S M Min EngngV40, N6, June 1988, P451–454

This study monitored longwall mining subsidence profiles over three panels that were mined beneath state highways in southeastern Ohio. The average maximum subsidence was 1.07 m (3.5 ft). The average maximum compressive strain recorded was 0.008 mm/mm. Three predictive methods for the determination of displacements and strains were compared: The National Coal Board (NCB) graphical method, the profile method with empirical constants determined for southeastern Ohio, and a finite element excavation program. Excellent subsidence agreement was found with the profile method, and reasonable strain agreement was determined with the finite element program.

Undersea longwall mining subsidence with special reference to geological and water occurrence criteria in the north-east of England coalfield : Aston T.R.C.; Whittaker B.N Min Sci TechnolV2, N2, April 1985, P105–130

Undersea longwall mining subsidence with special reference to geological and water occurrence criteria in the north-east of England coalfield : Aston T.R.C.; Whittaker B.N Min Sci TechnolV2, N2, April 1985, P105–130

Influence of lithology on longwall mining subsidence : Tandanand, S; Powell, L R Min EngngV36, N12, Dec 1984, P1666–1671

The US Bureau of Mines assessed the geological effects on the ratio of maximum subsidence and extraction thickness, known as the subsidence factor, to develop a simple method for predicting the maximum subsidence. This study is restricted to the Northern Appalachian Coal Basin where data were collected from 13 coal mines. A model previously developed to relate the subsidence factor with the lithology and with the width and depth of working panels was used in the assessment. The result shows the possibility of determining maximum subsidence without resorting to a rigorous method.