B. Christaras

Evaluating urban land cover change in the Hurghada area, Egypt, by using GIS and remote sensing.

The rapid urban development in the Hurghada area since the 1980s has dramatically enhanced the potential impact of human activities. To inventory and monitor this urban development effectively, remote sensing provides a viable source of data from which updated land cover information can be extracted efficiently and cheaply. In this study, data from three satellite datasets, Landsat Thematic Mapper (Landsat 5 TM), Landsat Enhanced Thematic Mapper Plus (Landsat 7 ETM+) and Terra/Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), acquired during 1987, 2000 and 2005, respectively, were used to detect and evaluate Hurghadas urban expansion. Five change detection techniques were tested to detect areas of change. The techniques considered were image differencing, image ratioing, image overlay, multidate principal component analysis (PCA) and post-classification comparison. The post-classification comparison was found to be the most accurate procedure and produced three land use/land cover (LULC) maps of the years 1987, 2000 and 2005 with overall accuracies of 87.8%, 88.9% and 92.0%, respectively. The urban expansion analysis revealed that the built-up area has expanded by ∼40 km2 in 18 years (1987–2005). In addition, 4.5 km2 of landfill/sedimentation was added to the sea as a result of the coastal urban development and tourist activities. The booming coastal tourism and population pressure were considered to be the main factors driving this expansion, and some natural and artificial constraints constrained the physical shape of the city. The expansion is represented by urban fringe development, linear, infill and isolated models. Topography, lithology and structures were also analysed as possible factors that influenced the expansion. The understanding of the spatial and temporal dynamics of Hurghadas urban expansion is the cornerstone for formulating a view about the future urban uses and for making the best use of the limited resources that are available.

Estimation Of Damage At The Surface Of StonesUsing Non Destructive Techniques

The investigation of the physical and mechanical properties of stones in monuments needs non destructive methods and small quantity of testing material. In this framework, P & S wave ultrasonic velocities can be used for both in situ and laboratory measurements. In the present paper the above methods was used for the study of properties like the mechanical anisotropy, weathering degree, mechanical strength and deformation ability of stones, using data from different countries, like France, Italy and Greece. The P-waves were also used, in indirect mode, for the estimation of the depth of weathering at the stone surfaces of three representative monuments in Greece.

Landslides in iliolitic and marly formations : Examples from north-westem Greece

Abstract Landslides in iliolitic and marly formations are investigated at two representative sites in northern Greece. The first case concerns an iliolitic tectonic formation between Pindos and Ionian flysch while the second concerns the marls of the molasses of the Mesohellenic Basin. Both areas present a high relief, with steep slopes and significant rainfall. The above formations were studied using both in situ and laboratory techniques. According to our study, these formations present more or less similar mechanical properties, but different behaviour in relation to landslide occurrence; they are very hard in dry conditions but lose their resistance rapidly under wet conditions. In the first case, the rainwater penetrates the iliolite causing landslides of soil type. In the second the rainwater does not penetrate the marl creating a surface saturated zone. The material drys rapidly creating cracks and flakes which accumulate at the toe of the slope. This weathering causes caving at the base of the overlying sandstone which presents toppling and sliding phenomena.

The role of organic matter of carbonate rocks in the reactivity of the produced quicklime

The gray and white crystalline limestones from Agios Panteleimonas Florina have almost the same mineralogical composition. They are mainly composed of calcite (96%), while the percentage of the contained organic matter is 0.8% in the gray and 0.09% in the white crystalline limestone. After heating both crystalline limestones at 500°C no serious change was observed concerning their mineralogical composition. However, the velocity of P waves and the porosity in the gray limestone are changed significantly while this trend is not noticed in the white limestone. These changes are mainly attributed to the burning of organic matter, which is contained with greater percentage in the gray crystalline limestone. At 1000°C both crystalline limestones are completely calcined. The dissociation of calcite and dolomite increases significantly the porosity of the produced quicklime. The quicklime from gray crystalline limestone presents higher porosity value (by 5.2 percentage units) and it is more reactive (by 4.9 percentage units) in comparison with the quicklime from white crystalline limestone. This difference in the reactivity is mainly attributed to the difference in the percentage of organic matter contained in the two crystalline limestones.RésuméLes calcaires cristallins, gris et blancs, de Agios Panteleimonas Florinas, ont à peu près la même composition minéralogique. Ils sont composés essentiellement de calcite (96%), tandis que le pourcentage de la matière organique contenue est de 0,8% dans le gris et 0,09% dans le calcaire cristallin blanc. Le chauffage de ces deux calcaires cristallins à 500°C n’apporte aucun sérieux changement concernant leur composition minéralogique. Toutefois, la vitesse des ondes P et la porosité du calcaire gris ont considérablement changé, tandis que cette tendance n’est pas notée dans le calcaire blanc. Ces changements sont attribués à la combustion de la matière organique, dont le pourcentage est plus élevé dans le calcaire cristallin gris. À 1000°C les deux calcaires cristallins sont complètement calcinés. La destruction de la calcite et de la dolomite augmente considérablement la porosité de l’asbeste produit. L’asbeste produit par le calcaire cristallin gris présente une valeur de porosité supérieure de 5,2% et il est plus réactif (de 4,9%) en comparaison avec l’asbeste produit par le calcaire cristallin blanc. Cette différence de réactivité est essentiellement attribuée à la différence du pourcentage de matière organique contenue dans les deux calcaires cristallins.

Soil quality as a factor of the distribution of damages at the meizoseismal area of the Kozani-Grevena 1995 earthquake, in Greece (Ms = 6.6)

The physical and mechanical properties of the soil formations were related to the damages observed in Kozani and Grevena area, in Northern Greece, after the earth-quake of 13th May 1995 (Ms = 6.6). Properties such as grain size distribution, plasticity, shear strength, compression index, permeability and ultrasonic velocity were measured in order to classify the suitability of the soil formations, for urban planning, and correlate their mechanical behaviour with the damages observed in the construction. According to our observations, a great number of recent buildings were damaged also in areas far away from the seismotectonic zones, where silty and clayey soils dominate, presenting very low permeability, low ultrasonic velocity together with high plasticity and compressibility.

Support of unstable wedges along the Platamon railway tunnel under construction, in northern Greece

Abstract In this paper, support measures obtained with the RMR classification method were used for estimating the support capacity of wedges found in relatively shallow tunnels. This was done for the Platamon railway tunnel, in northern Greece, which is at present, under construction. According to our investigation, the safety factors, which were calculated using the above mentioned support measures, were much higher than the theoretically needed safety factor. In cases where the height of the wedges is much greater than their base and the rockmass quality is very poor, the proposed RMR support measures could be introduced. In these cases, additional techniques, which include steel ribs and shotcrete (together with rock bolts), could be used.

Application of Non Destructive Ultrasonic Techniques for the Analysis of the Conservation Status of Building Materials in Monumental Structures

Some examples of application of ultrasonic methods were chosen in different test areas located in Southern Sardinia (Italy) and Northern Greece coastal areas: (1) Cagliari town (Southern Sardinia—Italy), masonry structure and architectural element of an ancient monument. (2) Dion archeaological site (N. Greece). The study on the above mentioned monument was focused on the application of ultrasonic techniques in the low frequency range (24–54 kHz), with the aim to verify the conservation status of their building materials by means of the study of the longitudinal ultrasonic pulses propagation. Compressional velocity has been related to the physical, textural and mineralogical-petrographic features of the investigated materials, to correlate their intrinsic properties with the elastic ones. On the base of the laboratory ultrasonic measures, in situ investigations have been performed to identify the areas affected by degradation, quantify the intensity of weathering and monitoring his evolution. In addition, the methodological approach used in this study has proved to be useful also to reconstruct the texture of walls under the plaster or in the outcropping masonry structures, where the degradation makes it difficult the macroscopic identification of building materials.

Environmental effects on the Monasteries of Mount Athos; the case of Symonos Petra Monastery

Abstract The Monastery of Symonos Petra, located in Athos mountain (Greece) was studied for geotechnical site investigation and building material weathering conditions. The site investigation comprised rockmass description and rock slope stability analysis. The interpretation of the collected data determined the probable surfaces of sliding that can be activated under specific conditions. Building stones and different types of mortar, used as cementing material, were collected from the older parts of the Monastery (13th and 16th century). These samples were examined regarding their origin so as the most suitable measures for preservation may be taken.

Support capacity of wedges along tunnels of Egnatia highway

Abstract Four tunnels along the under construction Egnatia highway, were studied in N. Greece (Polymylos and Vassilikos areas). The concept was to investigate the changes of the safety factors and the support ability of the wedges, regarding to their dimensions, taking also into account the spacing of the discontinuities. The safety factors of the wedges, as well as their ration before and after support, were correlated significantly with the weights and the volumes of the wedges, using powered regressions. According to these results the efficiency of the support ability of the shotcrete is very high in cases where the rock mass is cracked. There is no difference in safety factor between using only shotcrete and using shotcrete and rockbolts for supporting relatively small wedges. This ability decreases dramatically for bigger wedge volumes, over 20m3 and of weights in cases where these are over about 40tns. In these cases, the shotcrete presents low efficiency and bolting is the main support measure performed.

Predicting the average size of blasted rocks in aggregate quarries using artificial neural networks

The prediction of the average size of fragments in blasted rock piles produced after blasting in aggregate quarries is essential for decresing the cost of crushing and secondary breaking. There are several conventional and advanced processes to estimate the size of blasted rocks. Among these, the empirical prediction of the expected fragmentation in most cases is carried out by Kuznetsov’s equation (Sov Min Sci 9:144–148, 1973), modified by Lilly (1986) and Cunningham (1987). The present research focuses on the effect of the engineering geological factors and blasting process on the blasted fragments using a more powerful, advanced computational tool, an artificial neural network. In particular, the blast database consists of the blastability index of limestone on the pit face, the quantities of the explosives and of the blasted rock pile, assessing the interaction of these parameters on the blasted rocks. The data were collected from two aggregate quarries, Drymos and Tagarades, near Thessaloniki, in the Central Macedonia region of Greece. This approach indicates significant performance stability, providing the fragmentation size with high accuracy.