Flood hazard assessment for extreme flood events     

Davor Kvočka  Roger A. Falconer  Michaela Bray 《Natural Hazards》2016,81(3):1569-1588

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Mineralogy of the P-12 K-Ti-richterite diopside olivine lamproite from Wajrakarur,Andhra Pradesh,India: implications for subduction-related magmatism in eastern India     

Gurmeet Kaur  Roger H. Mitchell 《Mineralogy and Petrology》2016,110(2-3):223-245

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Meeting the Challenge of Systemic Change in Geography Education: Lucy Sprague Mitchell’s Young Geographers     

Roger M. Downs 《The Journal of geography》2016,115(1):3-11

The history of K–12 geography education has been characterized by recurrent high hopes and dashed expectations. There have, however, been moments when the trajectory of geography education might have changed to offer students the opportunity to develop a thorough working knowledge of geography. Lucy Sprague Mitchell’s geography program developed in the 1920s and 1930s was brilliant in its conception and execution but it did not lead to large-scale systemic change. Analyzing the origins, development, and outcome of her program suggests the conditions that facilitate and inhibit systemic change, and therefore perhaps we can learn to capitalize on comparable moments in the future.  相似文献   

Psychoanalytic Geographies          下载免费PDF全文

Roger M. Downs 《Geographical review》2016,106(4):e54-e57

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Use of Recycled Polyethylene Terephthalate Strips in Soil Improvement     

Castilho  Tayane Westermann  Rodrigues  Roger Augusto  Lodi  Paulo César 《Geotechnical and Geological Engineering》2021,39(8):5943-5955

Geotechnical and Geological Engineering - Many studies have investigated polyethylene terephthalate (PET) and polypropylene fibers in soil improvement. However, there is a lack of research using...  相似文献   

The Flat Dilatometer Test in an Unsaturated Tropical Soil Site     

Rocha  Breno Padovezi  Rodrigues  Roger Augusto  Giacheti  Heraldo Luiz 《Geotechnical and Geological Engineering》2021,39(8):5957-5969

The site characterization of unsaturated soils is well stablished based on laboratory tests, which are expensive and time-consuming. In-situ testing methods, such as the flat dilatometer test (DMT), are an alternative to the traditional approach of drilling, sampling, and laboratory testing. The literature on DMT interpretation is well established on saturated and well-behaved soils. Only few studies deal with DMT interpretation in unusual soils, and little is known about the influence of soil suction on this test. This paper presents and discusses the influence of soil suction on four DMT campaigns carried out in an unsaturated tropical soil site, also incorporating the soil suction influence on the DMT interpretation. Soil suction was estimated by the soil–water characteristic curve (SWCC) and water content profiles. The water content profiles range from 11.3 to 19.7% which corresponds to a suction range estimated by SWCCs mostly between 6 and 200 kPa. Soil suction significantly influenced DMT data up to 5 m depth at the studied site (the unsaturated active zone) increasing the intermediate DMT parameters. The average horizontal stress index (K_D) was equal to about 1.7 and the average dilatometer modulus (E_D) was about 4.7 MPa in the active zone and practically doubled their values due to in situ soil suction. The estimated peak friction angle (?) was 20–30% higher due to soil suction influence on DMT assuming the soil behaves as a sand like material. Soil suction must be considered to assess the behavior of the investigated soil by the DMT. The suction influence should be incorporated in the effective stress and this approach considerably improved the site characterization of the studied site.

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Regional subglacial quarrying and abrasion below hard-bedded palaeo-ice streams crossing the Shield–Palaeozoic boundary of central Canada: the importance of substrate control     

Syed Bukhari  Nick Eyles  Shane Sookhan  Riley Mulligan  Roger Paulen  Maarten Krabbendam  Niko Putkinen 《Boreas: An International Journal of Quaternary Research》2021,50(3):781-805

Three-dimensional surface visualization models derived from high-resolution LiDAR data provide new information about the type and scale of erosional processes below Late Wisconsin palaeo-ice streams traversing the boundary between Canadian Shield crystalline rocks with offlapping Palaeozoic limestones in central Ontario. The hard bed is directly analogous to that found below ice streams in East Antarctica and East Greenland and provides insight into the effects of abrupt changes in substrate type on subglacial processes. Erosion of hard crystalline Canadian Shield rock was largely ineffectual consisting of areal abrasion of rounded whalebacks and local lee side plucking. In contrast, fast flow over the strike of gently dipping well-bedded and jointed Palaeozoic limestones cut large flow-parallel grooves and ridges akin to mega-scale glacial lineations reflecting intense abrasion below narrow streams of subglacial debris dominated by hard crystalline Shield clasts (erodents). Regionally extensive plucking of structurally weak, well-jointed and bedded limestone produced large volumes of rubbly carbonate debris leaving a 25-km-wide belt of uncontrolled hummocky rubble terrain (long known as the Dummer Moraine in Southern Ontario) some 350 km long and locally as much as 10 m thick. Subglacial plucking and abrasion under fast flowing ice were highly effective in stripping limestone cover rocks from Precambrian basement, and over many glacial cycles, may have played a role in the location and excavation of numerous large and deep lake basins around the Shield–Palaeozoic boundary zone in North America.  相似文献   

Pyroxene-melt equilibria: an updated model     

Roger L. Nielsen  Paula M. Davidson  Timothy L. Grove 《Contributions to Mineralogy and Petrology》1988,100(3):361-373

An updated model for pyroxene-melt equilibria at 1 atm has been developed and calibrated using new and existing experimental data in order to refine calculations of liquid lines of descent, which simulate the effect of igneous differentiation processes. We combine the Davidson and Lindsley (1985) model for activities of components in clinopyroxene and orthopyroxene solid solutions, a _i ^p , where i represents a quadrilateral endmember, with the Nielsen and Drake (1979) expressions for component activities in the melt, a _i ^L (two-lattice melt model). The chemical potential differences for pyroxene-melt equilibria are expressed in the form: $$\Delta \mu _{\iota } = 0 = In \left( {{{a_i^p } \mathord{\left/{\vphantom {{a_i^p } {a_i^L }}} \right.\kern-\nulldelimiterspace} {a_i^L }}} \right) + A_i + {{B_i } \mathord{\left/{\vphantom {{B_i } T}} \right.\kern-\nulldelimiterspace} T}$$ Pyroxene compositions were projected to quadrilateral compositions with the method of Lindsley and Anderson (1983). The regression constants A _i and B _i were calculated from experimental data that consists of 282 pyroxene-melt pairs, including 83 orthopyroxene-melt pairs. These experiments were all performed at 1 atm and represent compositions ranging from basalts (alkali to lunar) to dacites (42–66 wt% SiO₂). The model is calibrated for 1000相似文献   

Revealing hydrocarbon migration pathways     

Ulrich Mann 《International Journal of Earth Sciences》1989,78(1):337-348

In this paper a general concept for revealing hydrocarbon migration pathways in rock sequences is introduced. The concept uses a multidisciplinary approach based on a geochemical and a petrophysical (or mineralogical) index. These two indices provide together the migration plot which shows the direction of hydrocarbon movement.With the help of this technique, serrerai hydrocarbon migration effects were established for a sequence of continous cores from the Upper Carboniferous. The results were verified by comparing gradients of hydrocarbon concentrations relative to pore volume. In this way the relative importance of individual migration pathways were recognized, as well as presently or formerly active migration pathways.The strong influence of permeability changes on hydrocarbon movement in source beds requires the use of the »atypical pore network« model to supplement the kerogen network model. Both models help in understanding the mechanisms of primary migration, but in certain stiuations, one might be more effective than the other.

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Zusammenfassung In diesem Aufsatz wird ein Konzept vorgestellt zur Erkennung von Erdölmigrationsbahnen in Gesteinsabfolgen. Das Konzept ist multidisziplinär ausgerichtet und beruht auf der Anwendung eines geochemischen und eines petrophysikalischen (oder mineralogischen) Parameters. Beide zusammen genommen erlauben die Erstellung eines Migrationsdiagramms, das angibt in welche Richtung sich die Kohlenwasserstoffe bewegen.Mittels dieser Methode wurden in einer fortlaufenden Abfolge von Bohrkernen aus dem Oberkarbon mehrere Trends für die Migrationsrichtung von Erdöl erkannt. Diese Trends wurden durch Vergleich mit Kohlenwasserstoffkonzentrationsgradienten, bezogen auf das Porenvolumen des Gesteins, verifiziert. Auf diese Art und Weise ließ sich sowohl die Bedeutung der einzelnen Migrationsbahnen relativieren als auch zwischen jetzigen und früheren Migrationswegen unterscheiden.Der starke Einfluß von Permeabilitätsänderungen auf die Bewegung von Kohlenwasserstoffen auch in Erdölmuttergesteinen fordert die Anwendung des »Atypischen Porennetzwerk-Modells« als Ergänzung zum Kerogennetzwerk-Modell. Beide Modelle tragen wesentlich zum Verständnis der Mechanismen der primären Migration von Erdöl bei, jedoch kann im Einzelfall die Verwendung des einen Modells effektiver sein als die des anderen.

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Résumé L'auteur présente une méthode générale permettant de déterminer le chemin suivi par les hydrocarbures lors de leur migration à travers les roches. Cette méthode utilise une approche multidisciplinaire basée sur un indice géochimique et un indice pétrophysique (ou minéralogique). Ces deux indices combinés fournissent l'indice de migration, qui indique la direction du déplacement des hydrocarbures.Cette méthode a permis d'établir les effets de plusieurs migrations d'hydrocarbure dans une série continue de carottes du Carbonifère supérieur. Les résultats obtenus ont été vérifiés en comparant les gradients du rapport concentration d'hydrocarbure/volume des pores. On peut reconnaître, de cette manière, l'importance relative des voies individuelles de migration, ainsi que celle des voies de migration actives aujourd'hui ou dans le passé.Etant donné le rôle important joué par les différences de perméabilité dans le déplacement des hydrocarbures au sein des roches, on se réfère au modèle Atypical Pore Network, qui complète le modèle Kerogene Network. Les deux modèles sont utilisés de manière complémentaire pour comprendre les mécanismes de la migration primaire; dans des cas extrêmes, l'un d'eux peut être plus effectif que l'autre.Cette approche constitue un nouveau pas vers une meilleure identification et une meilleure quantification des effets de la migration; elle offre des avantages considérables en raison de la diversité des paramètres qui peuvent être utilisés. Comme n'importe quel autre outil d'exploration, elle ne peut être utilisée seule dans les travaux d'évaluation et d'interprétation. Pour porter tous ses fruits, elle doit être intégrée aux données géologiques, géophysiques et surtout hydrodynamiques.

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Evolution of sedimentary basins — the integrated modeling approach     

H. S. Poelchau  U. Mann 《International Journal of Earth Sciences》1989,78(1):1-5

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