Microcracks in ultrabasic rocks under uniaxial compressive stress     

Ioannis Rigopoulos  Basilios Tsikouras  Panagiotis Pomonis  Konstantin Hatzipanagiotou 《Engineering Geology》2011,117(1-2):104-113

The initiation and propagation of microcracks under stress are highly dependent upon the mineralogical and textural characteristics of the various lithotypes. Detailed observation and quantification of microcracks before and after uniaxial compression test were conducted. A fresh olivine-rich harzburgite and a serpentinized dunite were analyzed, collected from the Pindos and Vourinos ophiolites (northern Greece) respectively, in order to compare their microcrack patterns. Quantitative analysis indicated that during uniaxial compression the intragranular microcracks, which are the dominating crack-type, are gradually transformed or organized into transgranular cracks. Some of the newly formed transgranular cracks may also be a result of the growth of existing grain-boundary cracks. The new intragranular microcracks in the olivine-rich harzburgite are oriented predominantly parallel to the compressive stress direction, while those in the serpentinized dunite show a scattered orientation presumably due to the mesh texture of this rock-type. The new transgranular cracks of both peridotites tend to be subparallel to the compressive stress direction, however, many of them show a random orientation due to the fact that they have been formed as a result of the propagation of grain-boundary cracks. The occurrence of the soft serpentine along fracture surfaces of olivine, when it is in assemblage with orthopyroxene, tends to absorb the applied stress hampering the development of microcracks in olivine. On the other hand in serpentinized peridotites, the microcracks are enhanced in olivine because it is surrounded by large amounts of the much softer and flexible serpentine. Microcracks are usually formed along the cleavage planes of orthopyroxene porphyroclasts, indicating that such crystallographic preferred orientations act as planes of weakness, controlling the direction of the crack paths. Cr-spinel grains likely comprise locations of initiation of microcracks due to their very hard nature and different mechanical behaviour relative to the surrounding silicate phases. Knowledge of the mineralogical and textural characteristics may assist in the prediction of potential development of failure surfaces of an ultrabasic rock in-service.  相似文献   

Visitors’ perceptions on the management of an important nesting site for loggerhead sea turtle (Caretta caretta L.): The case of Rethymno coastal area in Greece     

Nikoleta Jones  Kalliopi Panagiotidou  Ioannis Spilanis  Konstantinos I. EvangelinosPanayiotis G. Dimitrakopoulos 《Ocean & Coastal Management》2011,54(8):577-584

Tourism has important impacts, both positive and negative, on the management of coastal areas with high biodiversity value. It is therefore important to investigate visitors’ perceptions concerning environmental policy alternatives for these areas along with the factors influencing these perceptions. The present paper aims to investigate visitors’ perceptions of an important nesting ground for loggerhead sea turtles located in a highly touristic area of Greece (Rethymno, Crete) registered in the Natura 2000 network. The paper focuses on the level of environmental awareness of visitors and their perceptions of two proposed policy instruments which will secure funding for the improvement of the environmental management of the area: an entrance fee to the beach and a tax to be levied on local accommodation costs. The influence of social and institutional trust on these perceptions is also explored. According to the results of the study, awareness of the existence of the Natura 2000 site was low. Furthermore, the accommodation tax was regarded as a more effective policy when compared to the entrance fee. Average Willingness to Pay (WTP) was also explored for the two policies, estimated at €1.13 for the daily accommodation tax and €1.59 for the entrance fee. The influence of social and institutional trust had a significant influence both on the perceived level of effectiveness of the proposed policies and the stated Willingness to Pay. The study concludes that the accommodation tax would be a more appropriate policy for the management of Rethymno beach taking into consideration visitors’ perceptions and the current level of trust.  相似文献   

Three dimensional wave scattering by arrays of elliptical and circular cylinders     

Ioannis K. Chatjigeorgiou 《Ocean Engineering》2011,38(13):1480-1494

Recently, Chatjigeorgiou and Mavrakos (2009, 2010a) provided an analytic solution for the three dimensional wave scattering by arrays of elliptical cylinders. The present paper extends the contents of the existing study to tackle the problem of the hydrodynamic interactions between elliptical and circular cylinders. The main task is to derive an analytic solution for the total velocity potential for an arbitrary body of the array and accordingly, to express the hydrodynamic pressure, the exciting forces and the wave elevation in compact analytic closed-forms.The solution method is rather complicated as it considers the circular cylinders as different geometries and not special cases of elliptical cylinders with zero elliptic eccentricity. Nevertheless, the adopted procedure enhances the mathematical reconstruction of the physical subject as it requires the derivation and the employment of addition theorems that transform expressions from elliptic to polar coordinate systems in all four possible combinations.  相似文献   

An integrated GIS-based method for wind-power estimation: application to western Cyprus     

Ioannis Kastanas  Andreas Georgiou  Panagiotis Zavros  Evangelos Akylas 《Central European Journal of Geosciences》2014,6(1):79-87

This study presents an integrated method for the estimation and analysis of potential wind-energy resources in Cyprus, which is applied at selected sites on the western side of the island. Firstly, a statistical analysis of wind speed and direction data was conducted at six meteorological stations in western Cyprus, establishing daily, monthly and annual variations of wind speed. Also examined were the Weibull distributions of the wind at each site. These wind statistics serve as the basis for estimating corrected statistical distributions over the extended study areas, which were calculated using the Wind Atlas Analysis and Application Program (WAsP) that modifies wind flow estimates based on local topographic effects. As a result, a geographic and wind-resource database was formulated around each station. Aggregation of this data using statistical weighting methods allows the extrapolation of observed results and the visualization for selected hours of the day over the western part of Cyprus. The results indicate the strong influence of the sea-breeze on the island’s wind potential, and identify a number of areas of higher wind-energy potential suitable for wind-resource exploitation. It is hoped that both the methodology applied and results obtained can be further used by potential investors and wind-energy developers.  相似文献   

Paleostress magnitude in a fold-thrust belt （External Hellenides, Greece）： evidence from twinning in calcareous rocks     

Paraskevas Xypolias Ioannis Koukouvelas 《《幕》》2005,28(4):245-251

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The validity of the continuum limit in the gravitational N-body problem     

Ioannis V. Sideris 《Celestial Mechanics and Dynamical Astronomy》2004,90(1-2):147-162

This paper attempts to give quantitative as well as qualitative answers to the question of the analogy between smooth potentials and N-body systems. A number of simulations were performed in both integrable and nonintegrable smooth environments and their frozen N-body analogues, and comparisons were made using a number of different tools. The comparisons took place on both statistical and pointwise levels. The results of this study suggest that microscopic chaos associated with discreteness effects is always present in N-body configurations. This chaos is different from the macroscopic chaos which is associated with the bulk potential and persists even for very large N. Although the Lyapunov exponents of orbits evolving in N-body environments do not decrease as N increases, comparisons associated with the statistical properties, as well as with the power spectra of the orbits, affirm the existence of the continuum limit.  相似文献   

Analysis of Faults' Effect on the Stability of Surface Lignite Mining Areas Using the Distinct Element Method     

Al Heib  Marwan  Zevgolis  Ioannis E.  Theocharis  Alexandros I.  Koukouzas  Nikolaos C.  Coccia  Stella 《Geotechnical and Geological Engineering》2022,40(3):1307-1321

Geotechnical and Geological Engineering - 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...  相似文献   

Numerical Slope Stability Analysis of Deep Excavations Under Rainfall Infiltration     

Deliveris  Alexandros V.  Theocharis  Alexandros I.  Koukouzas  Nikolaos C.  Zevgolis  Ioannis E. 《Geotechnical and Geological Engineering》2022,40(8):4023-4039

Geotechnical and Geological Engineering - Rainfall leads to the deterioration of slope stability conditions, while intense rainfall has been commonly associated with landslides on natural or...  相似文献   

Petrography and geochemistry of the enriched basaltic shergottite Northwest Africa 2975          下载免费PDF全文

Qi He  Long Xiao  J. Brian Balta  Ioannis P. Baziotis  Weibiao Hsu  Yunbin Guan 《Meteoritics & planetary science》2015,50(12):2024-2044

We present a study of the petrology and geochemistry of basaltic shergottite Northwest Africa 2975 (NWA 2975). NWA 2975 is a medium‐grained basalt with subophitic to granular texture. Electron microprobe (EMP) analyses show two distinct pyroxene compositional trends and patchy compositional zoning patterns distinct from those observed in other meteorites such as Shergotty or QUE 94201. As no bulk sample was available to us for whole rock measurements, we characterized the fusion crust and its variability by secondary ion mass spectrometer (SIMS) measurements and laser ablation inductively coupled plasma spectroscopy (LA‐ICP‐MS) analyses as a best‐available proxy for the bulk rock composition. The fusion crust major element composition is comparable to the bulk composition of other enriched basaltic shergottites, placing NWA 2975 within that sample group. The CI‐normalized REE (rare earth element) patterns are flat and also parallel to those of other enriched basaltic shergottites. Merrillite is the major REE carrier and has a flat REE pattern with slight depletion of Eu, parallel to REE patterns of merrillites from other basaltic shergottites. The oxidation state of NWA 2975 calculated from Fe‐Ti oxide pairs is NNO‐1.86, close to the QFM buffer. NWA 2975 represents a sample from the oxidized and enriched shergottite group, and our measurements and constraints on its origin are consistent with the hypothesis of two distinct Martian mantle reservoirs: a reduced, LREE‐depleted reservoir and an oxidized, LREE‐enriched reservoir. Stishovite, possibly seifertite, and dense SiO₂ glass were also identified in the meteorite, allowing us to infer that NWA 2975 experienced a realistic shock pressure of ~30 GPa.  相似文献   

An agricultural flash flood loss estimation methodology: the case study of the Koiliaris basin (Greece), February 2003 flood   总被引：2，自引：1，他引：1  

Anthi-Eirini K. Vozinaki  George P. Karatzas  Ioannis A. Sibetheros  Emmanouil A. Varouchakis 《Natural Hazards》2015,79(2):899-920

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