Geotechnical and mineralogical properties of weak rocks from Central Greece     

Ilia Ioanna  Rozos Dimitrios  Perraki Theodora  Tsangaratos Paris 《Central European Journal of Geosciences》2009,1(4):431-442

Thirty bulk samples of hard soils-soft rocks such as marls, originating from Euboea Island and Peloponnesus area, were investigated to evaluate their geotechnical behavior. Specifically, by conducting a series of physical and geotechnical tests, such as liquid limit and plastic limit tests, along with the estimation of the grain size fraction, Slake Durability and Point Load Test. Certain parameters were determined and used for empirical correlations with their mineralogical characteristics. The mineralogical composition was determined by X-ray diffraction, thermo-gravimetric and thermal analysis, succeeded by textural analysis performed by Optical Microscope. With the help of the above mentioned tests, we interpreted the observed geotechnical behavior of the examined weak rocks by means of mineralogical composition and texture. Durability and the unconfined compressive strength was found to be influenced by high percentages in carbonate minerals. In addition, it was found that a decrease in clay content resulted in higher strength and durability values. The concluded empirical correlations verified the influence of these parameters and gave a general overview of the engineering behavior of the examined weak rocks.  相似文献   

Comparison of ten notable meteorological drought indices on tracking the effect of drought on streamflow     

Dimitrios Myronidis  Dimitrios Fotakis  Konstantinos Ioannou  Konstantina Sgouropoulou 《水文科学杂志》2013,58(15-16):2005-2019

ABSTRACT

Ten notable meteorological drought indices were compared on tracking the effect of drought on streamflow. A 730-month dataset of precipitation, temperature and evapotranspiration for 88 catchments in Oregon, USA, representing pristine conditions, was used to compute the drought indices. These indices were correlated with the monthly streamflow datasets of the minimum, maximum and mean discharge, and the discharge monthly fluctuation; it was revealed that the 3-month Z-score drought index (Z3) has the best association with the four streamflow variables. The Mann-Kendall trend detection test applied to the latter index time series mainly highlighted a downward trend in the autumn and winter drought magnitude (DM) and an upward trend in the spring and summer DM (p = 0.05). Finally, the Pettitt test indicated an abrupt decline in the annual and autumn DM, which began in 1984 and 1986, respectively.  相似文献   

Present climate trend analysis of the Etesian winds in the Aegean Sea     

Anastasia Poupkou  Prodromos Zanis  Panagiotis Nastos  Dimitrios Papanastasiou  Dimitrios Melas  Kleareti Tourpali  Christos Zerefos 《Theoretical and Applied Climatology》2011,104(3-4):459-472

Wildfires are a common experience in Alaska where, on average, 3,775?km² burn annually. More than 90% of the area consumed occurs in Interior Alaska, where the summers are relatively warm and dry, and the vegetation consists predominantly of spruce, birch, and cottonwood. Summers with above normal temperatures generate an increased amount of convection, resulting in more thunderstorm development and an amplified number of lightning strikes. The resulting dry conditions facilitate the spread of wildfires started by the lightning. Working with a 55-year dataset of wildfires for Alaska, an increase in the annual area burned was observed. Due to climate change, the last three decades have shown to be warmer than the previous decades. Hence, in the first 28?years of the data, two fires were observed with an area burned greater than 10,000?km², while there were four in the last 27?years. Correlations between the Palmer Drought Severity Index and the Canadian Drought Code, against both the number of wildfires and the area burned, gave relatively low but in some cases significant correlation values. Special emphasis is given to the fire season of 2004, in which a record of 27,200?km² burned. These widespread fires were due in large part to the unusual weather situation. Owing to the anticyclonic conditions of the summer of 2004, the composite anomaly of the 500?mb geopotential height showed above normal values. The dominance of a ridge pattern during summer resulted in generally clear skies, high temperatures, and below normal precipitation. Surface observations confirmed this; the summer of 2004 was the warmest and third driest for Interior Alaska in a century of climate observations. The fires lasted throughout the summer and only the snowfalls in September terminated them (at least one regenerated in spring 2005). Smoke from the forest fires affected the air quality. This could be demonstrated by measurements of visibility, fine particle matter, transmissivity of the atmosphere, and CO concentration.  相似文献   

Kinematic analysis and analogue modelling of the Passeier- and Jaufen faults: implications for crustal indentation in the Eastern Alps     

Stefan Luth  Ernst Willingshofer  Marten ter Borgh  Dimitrios Sokoutis  Jozua van Otterloo  Arno Versteeg 《International Journal of Earth Sciences》2013,102(4):1071-1090

Crustal deformation in front of an indenter is often affected by the indenter’s geometry, rheology, and motion path. In this context, the kinematics of the Jaufen- and Passeier faults have been studied by carrying out paleostress analysis in combination with crustal-scale analogue modelling to infer (1) their relationship during indentation of the Adriatic plate and (2) their sensitivity in terms of fault kinematics to the geometry and motion path of Adria. The field study reveals mylonites along the Jaufen fault, which formed under lower greenschist facies conditions and is associated with top-to-the-west/northwest shear with a northern block down component. In addition, a brittle reactivation of the Jaufen shear zone under NNW–SSE to NW–SE compressional and ENE–WSW tensional stress conditions was deduced from paleostress analysis. The inferred shortening direction is consistent with fission track ages portraying Neogene exhumation of the Meran-Mauls basement south of the fault. Along the Passeier fault, deformation was only brittle to semi-ductile and paleostress tensors record that the fault was subjected to E–W extension along its northern segment varying into NW–SE compression and sinistral transpression along its southern segment. In the performed analogue experiments, a rigid, triangular shaped indenter was pushed into a sand pile resulting in the formation of a Passeier-like fault sprouting from the indenter’s tip. These kinds of north-trending tip faults formed in all experiments with shortening directions towards the NW, N, or NE. Consequently, we argue that the formation of the Passeier fault strongly corresponds to the outline of the Adriatic indenter and was only little affected by the indenter’s motion path due to induced strain partitioning in front of the different indenter segments. The associated fault kinematics along the Passeier fault including both E–W extension and NNW to NW shortening, however, is most consistent with a northward advancing Adriatic indenter.  相似文献   

Application of the revised universal soil loss equation model on landslide prevention. An example from N. Euboea (Evia) Island, Greece   总被引：5，自引：2，他引：3  

Dimitrios Rozos  Hariklia D. Skilodimou  Constantinos Loupasakis  George D. Bathrellos 《Environmental Earth Sciences》2013,70(7):3255-3266

This study aims to evaluate the application of the Revised Universal Soil Loss Equation (RUSLE) on predicting of sites susceptible to slope failures caused by the soil erosion. It was carried out at the northern part of Euboea Island presenting one of the highest frequencies of landslide occurrence in Greece. All required datasets for the application of the RUSLE model were engaged to compile a potential soil erosion map of the study area. In addition, historical slope failure data were used to evaluate the produced map. Moreover, the frequency ratio statistical analysis was applied for the verification of the soil erosion map. The results showed a satisfactory agreement between the soil erosion intensity zones and distribution of landslides events. Therefore, the RUSLE model can be applied for the localization of sites susceptible to landslides that were prepared or triggered by the soil erosion. Finally, taking under consideration the contribution of erosion mechanisms over the landslides manifestation, a combination of measures were proposed for preventing and supporting these catastrophic phenomena.  相似文献   

Sustainable Soil Particle Size Characterization Through Image Analysis     

Hyon-Sohk Ohm  Andhika Sahadewa  Roman D. Hryciw  Dimitrios Zekkos  Nicholas Brant 《Geotechnical and Geological Engineering》2013,31(6):1647-1652

A rapid, clean, low-energy, image-based method for determining the grain size distribution of soils by image analysis has been developed. The method is called Sediment Imaging or “Sedimaging”. It develops the grain size distribution for particles in the range between a U.S. Standard Sieve No. 10 (2.0 mm openings) and U.S. Standard Sieve No. 200 (0.075 mm openings) range. The system utilizes a high resolution Nikon D7000 digital single lens reflex camera and image processing software developed specifically for interpreting the images and producing the resulting grain size distribution. The Sedimaging system is more sustainable and environmentally friendly than traditional sieving by virtue of its far lower power needs, less water consumption, longer equipment life and less maintenance. From the environmental and health perspectives, Sedimaging is less noisy, generates no vibrations and produces no airborne particulates. Sedimaging is also significantly faster than sieving and produces thousands of data points compared to typically 8 by sieving; it also automatically computes grain size distribution metrics such as the coefficients of uniformity and gradation.  相似文献   

Analysis of seafloor backscatter strength dependence on the survey azimuth using multibeam echosounder data     

Xavier?LurtonEmail authorView author&#;s OrcID profile  Dimitrios?Eleftherakis  Jean-Marie?Augustin 《Marine Geophysical Researches》2018,39(1-2):183-203

The sediment backscatter strength measured by multibeam echosounders is a key feature for seafloor mapping either qualitative (image mosaics) or quantitative (extraction of classifying features). An important phenomenon, often underestimated, is the dependence of the backscatter level on the azimuth angle imposed by the survey line directions: strong level differences at varying azimuth can be observed in case of organized roughness of the seabed, usually caused by tide currents over sandy sediments. This paper presents a number of experimental results obtained from shallow-water cruises using a 300-kHz multibeam echosounder and specially dedicated to the study of this azimuthal effect, with a specific configuration of the survey strategy involving a systematic coverage of reference areas following “compass rose” patterns. The results show for some areas a very strong dependence of the backscatter level, up to about 10-dB differences at intermediate oblique angles, although the presence of these ripples cannot be observed directly—neither from the bathymetry data nor from the sonar image, due to the insufficient resolution capability of the sonar. An elementary modeling of backscattering from rippled interfaces explains and comforts these observations. The consequences of this backscatter dependence upon survey azimuth on the current strategies of backscatter data acquisition and exploitation are discussed.  相似文献   

Recursive algorithms for the computation of the potential harmonic coefficients of a constant density polyhedron   总被引：1，自引：0，他引：1  

Dimitrios Tsoulis  Olivier Jamet  Jérôme Verdun  Nicolas Gonindard 《Journal of Geodesy》2009,83(10):925-942

The gravitational potential of a constant density general polyhedron can be expressed both in terms of a closed analytical expression and as a series expansion involving the corresponding spherical harmonic coefficients. The latter can be obtained from two independent algorithms, which differ not only in their algorithmic architecture but in their efficiency and overall performance, especially when computing the coefficients of higher degree and order. In the present paper a comparative study of all these three approaches is carried out focusing on the numerical implementation of the recursive relations appearing in the two algorithms for the computation of the polyhedral potential harmonic coefficients. The performed numerical investigations show that the linear algorithm proposed by Jamet and Thomas (Proceedings of the second international GOCE user workshop, ‘GOCE, The Geoid and Oceanography’, ESA-ESRIN, Frascati, Italy, 8–10 March 2004, ESA SP-569, 2004), but so far not implemented, achieves a reasonable accuracy at a computational expense that opens to practical applications, for instance in the field of satellite gravimetry/gradiometry interpretation. The convergence behavior of the linear recursion algorithm is studied thoroughly and a computational procedure is proposed that enables the stable computation of potential harmonic coefficients up to degree 60 when referring to an arbitrarily shaped polyhedral body.  相似文献   

Relation between mean stress,thermodynamic, and lithostatic pressure     

Evangelos Moulas  Stefan M. Schmalholz  Yury Podladchikov  Lucie Taj manov  Dimitrios Kostopoulos  Lukas Baumgartner 《Journal of Metamorphic Geology》2019,37(1):1-14

Pressure is one of the most important parameters to be quantified in geological problems. However, in metamorphic systems the pressure is usually calculated with two different approaches. One pressure calculation is based on petrological phase equilibria and this pressure is often termed thermodynamic pressure. The other calculation is based on continuum mechanics, which provides a mean stress that is commonly used to estimate the thermodynamic pressure. Both thermodynamic pressure calculations can be justified by the accuracy and applicability of the results. Here, we consider systems with low‐differential stress (<1 kbar) and no irreversible volumetric deformation, and refer to them as conventional systems. We investigate the relationship between mean stress and thermodynamic pressure. We discuss the meaning of thermodynamic pressure and its calculation for irreversible processes such as viscous deformation and heat conduction, which exhibit entropy production. Moreover, it is demonstrated that the mean stress for incompressible viscous deformation is essentially equal to the mean stress for the corresponding viscous deformation with elastic compressibility, if the characteristic time of deformation is five times longer than the Maxwell viscoelastic relaxation time that is equal to the ratio of shear viscosity to bulk modulus. For typical lithospheric rocks, this Maxwell time is smaller than c. 10,000 years. Therefore, numerical simulations of long‐term (>10 kyr) geodynamic processes, employing incompressible deformation, provide mean stress values that are close to the mean‐stress value associated with elastic compressibility. Finally, we show that for conventional systems the mean stress is essentially equal to the thermodynamic pressure. However, mean stress and, hence, thermodynamic pressure can be significantly different from the lithostatic pressure.  相似文献   

Geometry of growth strata in a transpressive fold belt in field and analogue model: Gosau Group at Muttekopf,Northern Calcareous Alps,Austria          下载免费PDF全文

Hugo Ortner  Andreas Kositz  Ernst Willingshofer  Dimitrios Sokoutis 《Basin Research》2016,28(6):731-751

The thrust sheets of the Northern Calcareous Alps were emplaced during Late Cretaceous thrust‐dominated transpression expressed by thrust sheets segmented by closely spaced tear faults. Thrust sheet‐top sediments were deposited during thrusting and associated fold growth and were controlled by active folding and tearing. We observe two types of angular unconformities: (1) Angular unconformities above folds between tear faults conform with the model of progressive unconformities. Across these unconformities dip decreases upsection. (2) Here, we define progressive unconformities that are related to tear faults and are controlled by both folding and tearing. Across these unconformities both strike and dip change. In growth strata overlying folds dissected by high‐angle faults, such unconformities are expected to be common. We used analogue modelling to define the geometry of the tear faults and related unconformities. Within the syn‐tectonic sediments, a steep, upward flattening thrust within a broader, roughly tulip‐shaped drag zone develops. The thrust roots in the tear fault in pre‐tectonic deposits and is curved upward toward the downthrown block. Vertical offset on the thrust is related to differential vertical uplift caused by, for example, growth of folds with different wavelength and amplitude on either side of the tear fault. Formation of progressive unconformities is governed by the relationship between the rates of deposition and vertical growth of a structure. Fault‐related progressive unconformities are additionally controlled by the growth of the vertical step across the tear fault. When the rates of vertical growth of two neighbouring folds separated by a tear fault are similar, the rate of growth across the tear fault is small; if the first differ, the latter is high. Episodic tear fault activity may create several angular unconformities attached to a tear fault or allow the generation of angular unconformities near tear faults in sedimentary systems that have a rate of deposition too high to generate classical progressive unconformities between the tear faults.  相似文献