Opencast Coal Sites Research Articles

Wavelet-based models for air pollution modelling around coal mining sites in Jharkhand for 1, 3 and 5 day lead time

Coal dust is a major cause of air pollution in areas around opencast coal mining sites. Prediction of ambient concentration of pollutant should be known to implement any control techniques or to install any control equipment. Combining adaptive network based fuzzy inference system (ANFIS) and linear regression (LR) with discrete wavelet transform (DWT), two types of hybrid models were developed to forecast concentration of suspended particulate matter (SPM) for 1, 3 and 5-day-ahead around open cast coal mining sites in Jharkhand, India using DWT-obtained sub-time series of SPM and other relevant parameters, i.e., distance of point of forecast from core zone (x), ambient temperature (T), wind speed (w) and relative humidity (h). For the purpose of comparison ANFIS and LR models were also derived for the same lead time using original antecedent time series of SPM, T, w and h and distance of point of forecasting from the core zone. When compared, wavelet-based hybrid models predicted SPM with greater accuracy than ANFIS and LR models. Between the two types of hybrid models, the WANFIS type models gave slightly better results than the WR type.

Assessing public preferences: The use of stated-preference experiments to assess the impact of varying planning conditions

Planning takes public preferences into account in determining planning applications. This paper shows how public preferences and utility for planning conditions attached to planning permission can be evaluated and estimated using stated choice experiments; and the marginal rate of substitution between different planning conditions determined. It illustrates how changing planning conditions can increase or decrease public acceptability, and utility, of a development. The study of an opencast coal site in Northumberland reveals the differential utility of different planning conditions, and heterogeneity in preferences. Stricter planning conditions created majority acceptance of the development, compared to current planning conditions, except for those living in close proximity to the development. The welfare effects of changing planning conditions, in terms of planning gain, are also calculated.

The use of X-ray computer tomography to investigate particulate interactions within opencast coal mine backfills

Restoration of opencast coal sites frequently involves the controlled compaction of heterogeneous arisings, and accurate prediction of the settlements associated with such backfill is difficult. Attention has previously focussed on improving the specifications used to control backfilling as a way of both reducing the magnitude of the settlements and improving their predictability. However, there still exists a large degree of uncertainty about the fundamental particulate interactions that occur within a fill. The range of mechanisms previously considered to be influential on creep behaviour is described. A current research programme is investigating the use of X-ray computer tomography (CT) as a means of nondestructively observing particle interactions during settlement, in conjunction with both long-term creep tests and short-term compressibility tests. The principles of this radiographic technique, which is relatively new to geotechnical engineering, are described, and findings are presented that illustrate the potential of the method. Interim findings indicate that large particles are distributed on an apparently random basis within a fill, and the nonuniform distribution of voids is clearly demonstrated. Moreover, the results presented conflict to some degree with the general consensus of opinion that particle crushing is a major mechanism in the settlement process. Rather, local collapse into small voids left by compaction, and relative sliding and rotation of particles, seem to be the dominant factors for a range of compaction efforts. Particle splitting is discernible on some sections, but this mechanism appears to be less significant than others. Research is continuing into the time dependency of the observed mechanisms, the effects of moisture content changes and the effects of heterogeneous initial particle strengths.

The River Aire slope failure at the St. Aidans Extension Opencast Coal Site, West Yorkshire, United Kingdom

The St. Aidans Extension Opencast Coal Site is located in the flood plain of the River Aire 10 km southeast of Leeds, United Kingdom. In March 1988, a massive (600 000 m3) slope failure caused a breach of the riverbanks and flood-protection levee, and so connected the river to the opencast void, resulting in flooding of the site. A lake of about 100 ha and up to 70 m depth was created, and coal winning operations had to be suspended for 10 years. The causes of this slope failure included the effects of previous underground coal mining beneath those seams which were being surface mined, resulting in large tensile strains (up to 10 mm/m) in a heavily faulted zone that lay beneath the river bed and an adjacent navigation canal. The fracturing and opening of existing faults and joints greatly increased the permeability beneath the river, which then acted as a source of continuous recharge as the failed mass moved towards the opencast void. Subsequent remedial and recovery works (costing £20 million) have included the rerouting of the River Aire together with the canal, and pumping the flood water from the void and restarting opencast mining operations (tender sum £36 million) with a new box cut. This paper details the ground conditions and the history of events and discusses the probable mode of failure.Key words: opencast mining, slope failure, flooding, mining subsidence, ground strains, faulting.

The Fourth Glossop Lecture

Professor John Hutchinson is the Emeritus Professor of Engineering Geomorphology and a Senior Research Fellow at the Imperial College of Science, Technology and Medicine, University of London. He is a Fellow of the Institution of Civil Engineers and a Chartered Geologist and is eminently qualified to be the Fourth Glossop Lecturer.⇓ Fig. 1. John was born in Coventry in 1926 and (like Professor Fred Shotton before him) was educated at Bablake School. In 1944 he went up to the University of Birmingham to read civil engineering. He was enthused by the excellent geology courses provided under Professor L. J. Wills, which leavened a programme that was otherwise heavily structures-orientated, and nearly switched to geology at the end of the first year. He graduated in civil engineering in 1947 with first class honours and was invited to continue in doctoral research into the strength of bolted aluminium joints. This he declined, preferring to work with the contractor, R. M. Douglas, mostly on open-cast coal sites and heavy industrial foundations. In 1950, inspired by Sir Martin Conway's example, he made, with a friend, a three-month …

The River Aire slope failure at the St. Aidans E×tension Opencast Coal Site, West Yorkshire, United Kingdom

The River Aire slope failure at the St. Aidans E×tension Opencast Coal Site, West Yorkshire, United Kingdom

Opportunities, not threats: how today's coal-mining industry can resolve problems created by past mining

Viewed simply, the legacies of coal mining may appear to present insurmountable problems for the environment, local communities and developers. From a different perspective, however, these 'problems' can be transformed into challenges and opportunities. The impact of previous coal-mining activity on today's society can be subdivided into hazards for health and safety (e.g. the production and release of harmful mine gases into the atmosphere), landscape despoliation (e.g. unsightly and unrestored spoil tips), environmental and agricultural impacts (e.g. inadequate soil restoration on early opencast sites) and ground instability (e.g. arising from the presence of shallow mine workings). Careful planning, design and implementation, coupled with a partnership approach between mining companies, the local community and statutory authorities, can allow many of these problems to be minimized, managed and, possibly, eradicated while allowing the exploitation of valuable reserves of coal.Three opencast coal sites where past mining has had a particular impact are used to illustrate how problems created in the past can be rectified and highlight some of the design and operational difficulties that can be encountered on such projects.

Translocation of Herb‐Rich Grassland from a Site in Wales Prior to Opencast Coal Extraction

AbstractReinstatement of vegetation to a similar condition to that prior to disturbance is often required in industrial restoration schemes. Seeding with specially prepared seed mixes containing species suited to local soils is often the preferred option on grounds of practicality and cost. Turf translocation is more difficult and costly but, if successful, meets the reinstatement requirement more precisely. In a pilot study at a proposed opencast coal site in Wales, we compared the effectiveness of whole‐turf translocation of herb‐rich mesic grassland communities, with a less technically demanding and more cost‐effective technique involving spreading turf over twice the area at the receiver site and rotovating it into the underlying soil. The translocated whole turf and rotovated turf plots were cut annually and the vegetation removed to simulate grazing that had occurred prior to translocation. Both the whole‐turf and rotovated turf transplant techniques gave successful re‐establishment of 50% or more of the species originally present. After three years, the cover and species composition were similar in “whole‐turf” and “spread and rotovated” plots. This suggests that the “spread and rotovate” technique provides a satisfactory ecological alternative to whole‐turf translocation. However, plant communities changed, in some cases substantially, after translocation using either technique. Altered soil hydrology and nutrition combined with the substitution of cutting for grazing are probably the main causes of these changes.

The impact of tectonic deformation upon coal seams in the South Wales coalfield, UK

Observations on the nature and appearance of coal seams, which were deformed during the late Carboniferous Variscan orogeny, have been made over several years within a number of opencast coal sites located across the South Wales coalfield. The deformation of coal seams was dominated by brittle failure and subsequent movement along fracture planes. Examination of hand specimens and smaller-scale samples using a scanning electron microscope reveals the presence of two distinct types of small-scale, tectonic fracture markings within deformed coals. Striated fracture surfaces with prominent ridges and grooves can bear a superficial resemblance to shatter cones in appearance but are unique to coal in their tectonic setting and appear to have formed by static shear failure, whereas strongly polished fracture surfaces result from movement across fracture planes. Deformed coal seams are also affected by distinctive, large-scale, tectonic fracture sets. The extent of fracturing within coal seams can be assessed using different techniques including measuring fracture frequency directly, performing various strength and hardness tests, making relatively simple subjective assessments on the appearance of the coal or monitoring the size distribution of the coal product. By applying some of these methods within working opencast sites, it can be shown that large amounts of abnormally fractured coal were formed along coal-based thrust flats or detachments but that the distribution of fractured coal along detached seams is rarely homogeneous. Enhanced fracturing often occurred in association with the localised thickening of seams along small-scale thrusts or within coal duplexes. Variable seam thicknesses and pockets of structurally thickened coal are seen as the most efficient means by which the presence and location of significant amounts of fractured coal can be predicted from borehole evidence during prospecting.

Soil development on restored opencast coal sites with particular reference to organic matter and aggregate stability

Abstract. Organic indices and aggregate stability were measured in soils of similar texture on two restored opencast coal sites and on adjacent, undisturbed land in South Wales, UK. The aim was to assess rates of soil change over time, to relate these changes to conditions in undisturbed land and to evaluate organic‐aggregation relationships across these range of soils. Several management factors were included in the comparisons.Organic matter accumulated at the surface (0–7.5 cm) of restored soils, contents being greater than undisturbed soils after 21 years. However, this increase in total organic matter did not result in proportionate increases in carbohydrates and microbial biomass, nor did aggregate stability increase to the degree expected. Between 7.5 and 15 cm depth, rates of change were slower. Microbial metabolic quotient and respiration relative to total soil C were highest in recently (9 years) restored soils, intermediate in 21 year old restored soils and least for undisturbed soils.Sewage (100t/ha) applied at reinstatement improved clay stability but had little effect on other parameters when measured 9 years later. Drainage of soils restored in 1972 reduced total organic content but its influence on other organic indices was more complex. Carbohydrate contents had the closest association with aggregate stability and microbial biomass.Although the productivity of restored land may recover more quickly, findings suggest that rehabilitation of normal soil processes following surface mining may take much longer than the normal five year aftercare period.

Arbuscular mycorrhizal associations of plants colonizing coal mine spoil in India

A survey of soil and root samples collected beneath some pioneering plants colonizing reclaimed mine spoil at an opencast coal mine site at Chandrapur, Maharashtra State, India, was conducted in October 1994 to examine the possible host and edaphic influence on the occurrence of arbuscular mycorrhizal (AM) fungi. Thirteen plant species were sampled to determine the mycorrhizal root colonization and the number of spores of individual AM fungal species in the rhizosphere.Typical AM fungal infection was observed in roots of all the plant species examined. Mycorrhizal infection ranged from 20 to 95%. Sampled soils contained six spore-forming species of AM fungi (Acaulospora scrobiculata, Entrophospora colombiana, Glomus aggregatum, Glomus ambisporum, Scutellospora calospora and a previously undescribed species of Glomus). Fungal spore densities were not related to the mycorrhizal infection levels. E. colombiana and G. ambisporum were the leading species in terms of spore densities and frequencies. Phenotypic variations in spores of AM fungi were possibly related to the physical and chemical properties of the mine spoil.It is concluded that the pioneering plant species on mine spoils can cause the development of different populations of AM fungi. The study also indicates that certain species of AM fungi have broad environmental requirements.

Variscan compressional structures within the main productive coal-bearing strata of South Wales

The structure of the main productive Coal Measures within the anthracite zone in the western part of the South Wales coalfield is re-examined using data from recently operational opencast coal sites. Variscan thrusts and/or folds and bed-parallel shear structures are present within all of the sites studied. At East Pit, unaffected by any large-scale zone of disturbance, bed-parallel shear structures are developed along many of the gently dipping coal seams, which form a series of simultaneously active detachments, representing a process of easy-slip thrusting. A NE-SW-striking, fold dominated disturbance at Gilfach Iago is interpreted to overlie a reactivated basement fault. A more complex disturbance zone at Ffos Las combines both E-W-trending folds and more variably oriented thrusts which together shorten the coal bearing strata by up to 2 km and this is interpreted to be the major Variscan frontal thrust ramp in the extreme west of the coalfield. The Variscan compressional structures within South Wales are not consistent with a simple thin-skinned thrust system. The strain induced by deep-seated Variscan thrusts was distributed throughout much of the coal bearing sequence by easy-slip deformation rather than being localized along a single regional detachment, and additional thrusts present around the northern margin of the coalbasin appear to have formed as isolated autochthonous structures. The inherent weakness of coal seams across South Wales is attributed to the presence of greatly increased fluid pressures, which would have been generated both by the maturing coal and by the influx of fluids along deep-seated disturbance zones.

Health dust monitoring at derlwyn opencast coal site

Health dust monitoring at derlwyn opencast coal site

Restoration of the Ackton opencast coal site, West Yorkshire: ANON, Coal International, 244(2), 1996, pp 73–74

Restoration of the Ackton opencast coal site, West Yorkshire: ANON, Coal International, 244(2), 1996, pp 73–74

Plenmeller opencast coal site: a geotechnical and planning case study

Abstract Plenmeller is a remote upland opencast site in Northumberland designed to produce just over 2 million tonnes of coal during eight years of production. The complex ground conditions comprise thick peat and glacial deposits, overlying much faulted and steeply dipping Coal Measures strata. Previous under- ground workings, high groundwater levels and associated sub- surface reservoirs of water are also present. In order to mine and export the coal off-site, extensive infrastructure works were necessary including impounding embankments for lagoons, public road diversions, an overland conveyor with a tunnel and major river crossing, coal screening and crushing plant and a rapid loading bunker with associated railway sidings. A lengthy planning history included a public inquiry and a high court heating before coal production commenced in August 1991. Imposed planning constraints required modifica- tions to the development, additional construction works and restoration measures. The combination of the site location, infrastructure requirements and planning constraints gave rise to the need for a wide range of ancillary civil engineering works; this was one of the most extensive programmes in connection with an opencast project in the UK. These engineering works in turn required a substantial geotechnical input. This paper presents a general account of the extensive ground investiga- tions and construction works carried out at Plenmeller, and briefly discusses some geotechnical aspects of the site operations and the construction works.

Soil factors affecting tree growth on former opencast coal land

AbstractThe growth of three tree species (Alnus glutinosa, Betula spp. and Quercus spp.) was related to soil factors on two restored opencast coal sites in South Wales, UK. The main factors favouring tree growth were greater soil depth and organic content. Factors limiting growth included poor site drainage and high magnesium levels. Whilst all species were related to most of the above factors, soil depth was of particular importance for Alnus glutinosa and Betula spp., whilst site drainage had the greatest influence for Betula spp. Soil‐tree associations tended to be closer on the older of the two sites. Combinations of soil depth, percentage clay and percentage organic content in a multiple regression predicted around 40 per cent of the growth variation in Alnus glutinosa, between 6.9 and 32 per cent of that for Betula spp. and between 14.5 and 32.6 per cent of that for Quercus spp. Growth prediction for Betula spp. improved to 40.9 and 34.8 per cent when a site drainage factor was included in the regression. The development of such predictive relationships might contribute to the planning of site reinstatement for tree planting after opencast mining, and to a better ‘matching’ of tree species to site characteristics.

Regulating rural change: Property rights, economy and environment — a case study from Cumbria, U.K.

A new set of priorities increasingly determines the development of the British countryside. It is encouraging a more economically and socially differentiated countryside in which spatial patterns of development will be less predictable and environmental concerns more evident. New means of examining these complex processes of change are urgently required. In particular, they must engage with and adequately reflect the significance of local circumstances. Drawing upon Clark's notion of ‘real’ regulation, with its focus upon administrative processes, a framework is presented which re-directs our understanding of regulation as a focus for examining the relations between the market, the state and civil society. The framework is operationalized through an examination of the redefinition and redistribution of real property rights. Changes to property rights provide a means of establishing altered priorities. These priorities are reflected in the nature and outcomes of the rural land development process which, it is argued, continues to afford a particularly powerful ‘window’ on the nature of rural change. The field enquiries are based upon a detailed, case study approach using an ‘actor-in-context’ methodology. A case study drawn from Allerdale in Cumbria, England, which examines the debates and outcomes surrounding the Lostrigg open-cast coal site, is used to illustrate the methodology, to indicate the growing political substance of environmental as opposed to employment concerns in the countryside, and to demonstrate the effectiveness of local resistance to established norms of land development.

The Establishment and Maintenance of a Species‐Rich Grassland on a Reclaimed Opencast Coal Site

AbstractWe conducted an experiment with the dual aims of (1) examining the feasibility of establishing a species‐rich grassland using a commercially available grass and wild‐flower seed mixture and (2) examining the effects of different defoliation and fertilizer managements on the productivity, species richness, diversity, and composition of a species‐rich grassland established on a site reclaimed after opencast coal mining. The use of the seed mixture successfully established a sward of some 18–25 species per square meter. The species composition was enriched to some extent by recruitment of unsown species, principally from the soil seed bank. Hay‐type defoliation management produced greater dry matter yield and species richness than grazing defoliation, but grazing defoliation produced greater species diversity. Fertilizer application had no significant effect on dry matter production but reduced species diversity. Ordination analysis revealed that both defoliation and fertilizer management significantly affected species composition. The response obtained by individual species was explicable largely by their comparative biology.

95/01982 Emergency lighting

A study of physical and biological soil parameters was undertaken on reinstated opencast coal sites of varying ages from final topsoil replacement. Earthworm population levels were determined at the same time as sampling of pH, particle size analysis and bulk density. The results indicated that the pH of a site was not limiting to earthworm activity, but that all the reinstated sites had zones of compaction which were remnants of the restoration practice and may be limiting to earthworm activity. Total earthworm populations reached levels similar to undisturbed adjacent controls within 10–20 years after topsoil replacement, although there were differences in species composition.

Newly developed techniques to determine proportions of undersized (friable) coal during prospective site investigations

Abstract Site investigations to date have been unable to determine the presence of friable (undersized) coal within areas of extreme tectonic deformation. This is especially important in the northwest of the South Wales coalfield, where most of the coal extracted is for the smokeless fuel domestic market, which requires a consistent grade size. Coal in the proximity of the deformation zone is unlikely to be suitable for its intended market due to its small grain size. The deformation process and fracture styles which contribute to the development of friable coal are discussed and a remote method utilizing the drilling parameters of speed of advance, thrust and torque is investigated to ascertain its suitability in determining the amount and position of friable coal within a prospective coal site. If areas and volumes of friable coal can be determined before the extraction stage of an opencast coal site, site boundaries can be amended so that they do not contain large volumes of the friable product.