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During the last decades, natural hazards, such as earthquakes, volcanic eruptions, landslides, floods, storms, droughts, and cyclones, have increased in frequency and severity, influenced by climate change and population growth. These natural hazards can become sudden-onset disasters, causing human losses and property damages that affect economic stability and growth. Although there is a pressing need for risk decrease and adaptation strategies to these unexpected events, targeted natural hazard insurance would be a valuable tool to counteract governmental and individual consequences. This paper summarizes an overview of risk assessment and mitigation strategies based on geological, geomorphological, and meteorological factors. The study includes an examination of monitoring systems for movement and gas emissions, risk and emergency maps, and highlighting the vulnerability of different areas at national and regional levels. Furthermore, the paper addresses the importance of promoting comprehensive geological and geotechnical knowledge among citizens of every socio-economical group and proposing the tools to effectively deliver the message, aiming at increasing the willingness for natural hazard insurance at both individual and governmental scales for human and property protection. [ABSTRACT FROM AUTHOR]

Rainfall leads to the deterioration of slope stability conditions, while intense rainfall has been commonly associated with landslides on natural or engineered slopes. Deep excavations, typically related to geo-resources exploitation, e.g., in the case of surface mining, are often affected by rainfall events that jeopardize their stability. In this work, rainfall infiltration is directly incorporated in the slope stability analysis; this investigation is currently missing from the literature as mainly empirical methods are used regarding deep excavations. The very deep slopes from lignite mines are employed as typical examples, often reaching 200 m and presenting smooth inclinations and fine-grained soils. A general numerical framework was used; the safety factor's deterministic analysis was supplemented by a Monte Carlo investigation to determine the probability of failure. The importance of the involved parameters—slope geometry, rainfall intensity, and soil properties—was studied through a parametric analysis. Initially, a typical slip surface is presented, relatively deep and reaching from toe to crest. The critical mechanism was the development—after the rainfall—of a smaller and more local than the initial (before rainfall) slip surface. Although the final surface is smaller than the initial one, it can be more than 50 m high denoting a significant hazard. The most influential parameters are rainfall intensity, soil permeability, and slope height. This study can serve as a basis for similar preliminary analysis in practice. Stability and reliability analysis reveals the need to supplement conventional safety factors with the probability of failure for a broader and improved overview. [ABSTRACT FROM AUTHOR]

Mining operations can drastically affect the stability of nearby areas. A representative case for this has been the Mavropigi mine, a part of an open-pit lignite mining complex in northwestern Greece. Mavropigi is a vast excavation that has reached 150 m depth and has posed severe challenges and stability issues that caused problems in the area. In 2010, noteworthy surface tension cracks appeared near the excavation, leading to extensive monitoring and countermeasures, while various studies were conducted. The present work aims to revisit the case study of Mavropigi from a different than the previous perspectives. Previous studies were based only on continuum approaches, thus understating or ignoring the effect of discontinuities. Nevertheless, the area has an intense tectonic past and faults that interact with soil movements. In this work, advanced, discontinuous numerical modelling through the distinct element method was used to understand better the role of slope-fault interaction in the case study of Mavropigi and assess the faults' effect on the area's response. The results emphasised the influence of faults on ground movements. The fault's existence increases the impact of the mine operations on the surrounding area significantly and intensifies the possibility of structural damage in nearby constructions. The analysis confirms that the open-pit mine's effect on the surrounding area can be amplified under complex geological conditions, in this case, the presence of faults nearly parallel to the slope inclination. [ABSTRACT FROM AUTHOR]

A reliability analysis framework for the stochastic simulation of slope progressive failure is proposed in the current work. Progressive failure is addressed as a local failure propagation process that takes place along individual segments upon a critical slip surface. The probabilities of progressive failure are evaluated by transition probabilities and Markov chains theory. Slope stability computations are performed by elastoplastic finite element models. The point estimate method is used for the direct integration of geotechnical uncertainty within stability computations. For the various safety states during local failure advancement, progressive failure probabilities are expressed through a transition probability matrix. The effect of certain factors, such as the cross-correlation between shear strength components, the performance function's probability distribution, and the initial stress ratio at rest, are also investigated and discussed. [ABSTRACT FROM AUTHOR]

A methodology for the probabilistic evaluation of slope stability, capable of disclosing local reliability levels for a certain failure mode of an excavated slope, is proposed in the present work. Probabilistic slope evaluation is conducted upon a deterministically defined slip surface, exposed by the strength reduction method. Computations are performed by combining the probabilistic point estimate method with finite elements. Soil shear strength parameters, φ′ and c′, are treated as random variables of assumed constant variation, following normal distributions. The disclosure of remarkable variation of local slope reliability levels along its critical slip surface, highlights the potential for occurrence of local overstress, in cases where global slope stability is secured. High local probabilities of failure in the overstressed areas of the slope are manifested, despite its low global slope probability of failure. The noteworthy influence of cross-correlation between shear strength parameters, as well as the impact of their uncertainty level on the local probability of failure is discussed. The updated local and global reliability levels, during progressive failure propagation, are also obtained by the model. [ABSTRACT FROM AUTHOR]

Olive mill wastewater (OMW) is characterized as a high-strength effluent due to the high organic load, low biodegradability, and presence of phytotoxic compounds. Most of the OMW treatment methods proposed, including adsorption, focus mainly on the reduction of chemical oxygen demand and recovery of polyphenols. Adsorption studies aiming at nutrient removal from OMW are very limited. In the present work, Ca(OH)2-treated zeolite (CaT-Z) in a granular form was used for simultaneous recovery of phosphate (PO43−) and potassium (K+) ions from two samples of anaerobically digested OMW. Nutrient adsorption was investigated as a function of contact time, pH and dilution of OMW with deionized water. The lower removal efficiency of phosphorus (P) by CaT-Z was observed at higher dilution ratios consisted of 3.125–6.25% OMW-1 and 5% OMW-2. The maximum P removal was 73.9% in 25% OMW-1 and 85.9% in 10% OMW-2. Potassium removal, as the predominant cation of OMW samples, increased from 17.3 to 46.1% in OMW-1 and from 15.1 to 57.7% in OMW-2 with increasing dilution. The maximum experimental adsorption capacities were 15.8 mg K and 2.14 mg P per gram of CaT-Z. Five sequential treatments of 50% OMW-2 with fresh CaT-Z at each stage ensured a cumulative removal of 87.5% for P and 74.9% for K. Adsorption kinetics were faster for K than for P. The plant-available P was found to be the predominant fraction on the loaded CaT-Z. Electron Probe Micro-analysis confirmed the enhanced content of K and P on the loaded CaT-Z, whereas X-ray mapping revealed the co-distribution of Ca and P. This study demonstrates the potential usage of CaT-Z as an immobilization medium of P and K from anaerobically treated OMW. [ABSTRACT FROM AUTHOR]

Coal mine discharges in several European countries were investigated as part of the European Commission's MANAGER project. The emphasis of the project was identification of priority pollutants and potential remedial approaches. The main identified priority pollutants were sulphate (all countries) and iron (all countries except Greece). High concentrations of chloride (particularly in Germany and Poland) were associated with discharge of saline mine waters linked to the presence of fossil sea water; these mine waters also had high boron concentrations, in contrast to chloride-rich waters in UK that are linked to recent sea water inflow. Concentrations of trace metals vary among countries, but radium is an important contaminant in barium-rich waters with low sulphate concentrations, essentially in Poland. Concentrations of trace metals and metalloids were generally low because of their relative scarcity in coal strata and adsorption onto ferric oxides and hydroxides, but they still often exceeded the environmental quality thresholds. [ABSTRACT FROM AUTHOR]

This paper presents the outcome of a feasibility study on underground coal gasification (UCG) combined with direct carbon dioxide (CO) capture and storage (CCS) at a selected site in Bulgaria with deep coal seams (>1,200 m). A series of state-of-the-art geological, geo-mechanical, hydrogeological and computational models supported by experimental tests and techno-economical assessments have been developed for the evaluation of UCG-CCS schemes. Research efforts have been focused on the development of site selection requirements for UCG-CCS, estimation of CO storage volumes, review of the practical engineering requirements for developing a commercial UCG-CCS storage site, consideration of drilling and completion issues, and assessments of economic feasibility and environmental impacts of the scheme. In addition, the risks of subsidence and groundwater contamination have been assessed in order to pave the way for a full-scale trial and commercial applications. The current research confirms that cleaner and cheaper energy with reduced emissions can be achieved and the economics are competitive in the future European energy market. However the current research has established that rigorous design and monitor schemes are essential for productivity and safety and the minimisation of the potential environmental impacts. A platform has been established serving to inform policy-makers and aiding strategies devised to alleviate local and global impacts on climate change, while ensuring that energy resources are optimally harnessed. [ABSTRACT FROM AUTHOR]

Eight types of A356 Al-fly ash composites were produced by pressure infiltration of high-Ca lignite fly ash. This type of ash was used for the first time in Al-composites synthesis, and particularly by liquid metal infiltration techniques. After examining mineralogy and chemistry, specific, narrow ash size fractions were used for the synthesis of composites, and properties linked to microstructure and wear strength of the materials. The effect of using ground ash particles on the microstructure and tribological performance of the composites was also investigated. It was concluded that using fine, high-Ca ash particles can improve the properties of composites, and that using ash particles in a ground form can better facilitate the production process of MMCs. [ABSTRACT FROM AUTHOR]

The aim of this work was to test CFB-derived fly ash for its potential to get utilised in ceramic tiles-manufacturing by applying the sintering technique. The tested specimens were moulded using extrusion and fired at 1,050°C; a laboratory pilot-plant simulation of the industrial brick fabrication process was applied and the produced materials were afterwards tested for their microstructure and physical properties. Different types of clays were selected and characterised and various clay-ash mixtures were prepared. Plasticity after mixing with water as well as extrusion of the compact specimens and their drying behaviour were evaluated. Water absorption and mechanical strength of fired specimens were determined and evaluated as a function of the percentage FA content. Results showed that large-scale production of CFB FA-containing bricks is feasible, as their mechanical properties were not significantly harmed, while any possible detrimental effect on the other properties of the synthetic bricks appeared to be relatively restricted. [ABSTRACT FROM AUTHOR]

In the current study, the evolution of the composition of fly ash (FA), since the beginning of operation of the lignite-fired power station of Amynteon-Filotas [Steam Electric Station (SES) Amynteon-Filotas] in Greece, is presented. The respective evolution of the feedcoal-composition is also showed. This power station began to operate in 1987. Before that, it was predicted that lignite fly ash would turn from strongly calcareous to barely pozzolanic. Moreover, the variation of sulphur (%) (both total and volatile) in feedcoal had revealed that fly ash would not often meat the specifications to be used in the production process of concrete, due to the excessive percentage presence of SO. These predictions were eventually confirmed in the 23 years of operation of the power station. During these years SO (%) kept alternating, rendering-in some cases-fly ash suitable for use in cement industry applications. The periodical changes of the SO concentration in fly ash were attributed to the free (volatile) sulphur of feedcoal as well as to the excess of FeS, which had also a serious effect on the daily power production process (severe erosion of the metallic surfaces of boiler). A number of solutions for tackling this phenomenon are suggested in this study: discard of specific FA grain fractions, intense monitoring of the material and its effective mixture-homogenization and selective mining of lignite. [ABSTRACT FROM AUTHOR]

Correct values for radium have been rewritten in Table 1 and Table 2. Correct radium units in Figure 2(c) are Bq/L (Becquerel per liter). The same applies to discussion about radium in the text (page 21). [ABSTRACT FROM AUTHOR]

The large amount of spoil material produced during the mining process imposes a significant economic and environmental liability on lignite producers. In this context, the present paper provides an overview of the geotechnical characteristics of European lignite mine spoil heaps and discusses their significance to the stability of the heaps. In order to achieve this, samples collected from spoil heaps of Polish, Czech and Greek mines are analysed and the results are compiled with data from the literature. A major conclusion drawn is that both physical and engineering properties of spoil heaps indicate a noteworthy variability, which is larger than typical in situ ground material. This is because of the additional factors affecting spoil heap deposition, such as the transportation and dumping method. Furthermore, failure mechanisms and case histories of large instabilities in lignite spoil heaps are critically discussed in order to better understand triggering failure mechanisms. It is concluded that classical assumptions made for natural soil slopes and relevant limit equilibrium models should be cautiously applied to spoil heaps. The challenges associated with numerical and probabilistic modelling of spoil heap stability, such as the inherent spatial variability of spoils and the time-dependent changes in their geotechnical properties, are also critically discussed. Finally, important research gaps in design and analysis of spoil heap stability, such as the absence of appropriate constitutive models developed specifically for spoil materials, are summarised. [ABSTRACT FROM AUTHOR]