Book reviews     

Dieter Richter  Axel Borsdorf  Olusegun Areola  Risto Laulajainen  L. Wahlstroem  Reinhard Stewig  Jonathan B. Laronne  Gösta A. Eriksson  Cesar N. Caviedes  John Gunn  Karl Mauder  G. Kunkel  John T. Pierce  Leszek A. Kosinski  G.orge H. Kakiuchi  Reiner Herrmann  W. M. Sackinger 《GeoJournal》1982,6(6):581-588

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Temporal variability of throughfall as a function of the canopy development stage: from seasonal to intra-event scale     

José Bandeira Brasil  Eunice Maia de Andrade  Helba Araújo de Queiroz Palácio  Julio Cesar Neves dos Santos  Pedro Henrique Augusto Medeiros 《水文科学杂志》2020,65(10):1640-1651

ABSTRACT

The interception process impacts rainfall magnitude and intensity under the canopy. In this study, the effect of plant interception on throughfall characteristics was assessed in the deciduous Caatinga vegetation, at different canopy development stages and for temporal scales ranging from seasonal to the intra-event scale. Throughfall and stemflow percentages were slightly higher at the onset of the rainy season, when leaf area density is low, with resulting lower interception losses. However, there was no statistical difference among the variables at the seasonal scale. At the intra-event scale, average and maximum throughfall intensity at different time intervals showed statistical difference between the stages of canopy development. Regardless of leaf area density and rainfall depth, vegetation is able to retain all the water up to 2 min in the beginning of each rainfall event with accumulated rainfall smaller than 0.6 mm. Furthermore, the Caatinga vegetation attenuates the rainfall intensity by 30–40%.  相似文献   

Influence of hydropower outflow characteristics on riverbank stability: case of the lower Osage River (Missouri,USA)   总被引：1，自引：0，他引：1  

Wesam Mohammed-Ali  Cesar Mendoza  Robert R. Holmes Jr. 《水文科学杂志》2020,65(10):1784-1793

ABSTRACT

This research examined the influences of outflow characteristics affecting riverbank stability. The 130-km stretch of the Lower Osage River downstream from Bagnell Dam (Missouri, USA) provided an excellent case study for this purpose. The integrated BSTEM model with the HEC-RAS model was accurately calibrated and validated with data from the US Geological Survey. Then, the outflow characteristics (peak flow duration, flow drawdown rate, and low flow duration) were investigated individually. The results of this study showed that: (1) riverbank stability is little affected by the duration time of the peak flow, especially on the reaches far from the dam; (2) sudden flow drawdown significantly reduces riverbank stability; however, the impact of the drawdown rate decreases with distance from the dam; and (3) the duration of the low flow after peak flow influences the riverbank stability value proportional to the distance from the dam. The time of low flow before failure increases as the distance from the dam increases.  相似文献   

Considerations on regional development and the spatial location of economic activities in the developing countries     

Bertha K. Becker  Nilo Bernardes 《Geoforum》1976,7(3):223-232

In 1956, in view of the growing international disparities in rates of development, Myrdal asserted that it was risky to maintain that there had been economic progress in the last few decades for mankind as a whole. Today, after three decades of efforts to examine in greater depth the theory and practice of regional development, efforts of which the papers of the I.G.U. Commission on Regional Aspects of Development represent part, w can permit ourselves to re-examine the question which he posed. The aim of the present paper, then, is to attempt to set out the contribution of the contemporary theory of regional growth to the analysis and solution of the problems facing the developing countries. The first section reviews the important achievements of this contemporary theory, which provided the context out of which the papers of the Committee have developed. The second section analyses the contribution made by the I.G.U. Commission, while that third deals with limitations of the theory in the light of the actual situation in the developing countries.  相似文献   

The use of conic sections for the geometrical analysis of folded surface profiles     

Jesús Aller  Fernando Bastida  Noel C. Toimil  Nilo C. Bobillo-Ares 《Tectonophysics》2004,379(1-4):239-254

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Hot-fluid Driven Metasomatism of Samalpatti Carbonatites, South India: Evidence from Petrology, Mineral Chemistry, Trace Elements and Stable Isotope Compositions     

Rajesh K. Srivastava  Anand Mohan  Cesar Fonseca Ferreira Filho 《Gondwana Research》2005,8(1):77-85

The magmatic heritage of carbonatites can be identified on the basis of a combination of geological criteria such as, their mode of occurrence, the nature of associated igneous rocks, the presence of minerals of igneous origin, fenitization, characteristic trace element contents and isotopic composition. Late Proterozoic Samalpatti carbonatites were studied in view of these criteria, and were found to contain metamorphic minerals that normally form under thermal metamorphic conditions and which have unusual chemical compositions. A combination of criteria points clearly to a magmatic origin for these carbonatites. Field relations indicate that the dominant modes of intrusion of carbonatite into the encompassing pyroxenites and syenites include small dykes, veins, or lenses. The igneous nature of these carbonatites has been described elsewhere and chemically they are classified as calico-carbonatites. Currently, very little is known about the metamorphic textures and mineralogy observed in the Samalpatti carbonatites. In this study, several metamorphic minerals are reported including diopside, grossularite, vesuvianite, K-feldspar and wollastonite, and a hornfelsic texture is described. These mineral phases and texture characterize thermal metamorphism under low pressure and high temperature (LP-HT) metamorphic conditions (650°_750°C) or metasomatism aided by hot-fluid advection. The metamorphic nature of minerals reported is also confirmed by electron microprobe study. The Samalpatti carbonatite samples show much lower values of characteristic trace elements (P, Sr, Ba, Zr, Nb, Th, Y and REEs) than average concentrations for magmatic carbonatite. Stable isotopic (d¹³C and d¹⁸O) compositions of Samalpatti carbonatites do not fall in the primary igneous carbonatite (PIC) domain. The petrological and chemical signatures of these carbonatites suggest metasomatism in conjunction with fluid advection. Such a metasomatic process may drastically change the chemistry of the rocks in addition to enrichment of heavier stable isotopes. During this metasomatic process, characteristic elements would be dissolved in the high d¹⁸O fluid, and together with Rayleigh fractionation would contribute to enhanced concentrations of ¹³C and ¹⁸O in Samalpatti carbonatites.  相似文献   

Mapping method of rainfall-induced landslide hazards by infiltration and slope stability analysis     

Dolojan  Nilo Lemuel J.  Moriguchi  Shuji  Hashimoto  Masakazu  Terada  Kenjiro 《Landslides》2021,18(6):2039-2057

Landslides - By utilizing the Green-Ampt infiltration equation and the infinite slope stability model, a method for analyzing shallow slope failures caused by rainfall is developed. With rainfall...  相似文献   

A new approach for stabilization of lateritic soil with Portland cement and sand: strength and durability     

Consoli  Nilo Cesar  Párraga Morales  Durval  Saldanha  Rodrigo Beck 《Acta Geotechnica》2021,16(5):1473-1486

The presence of lateritic soils occurs in tropical and subtropical regions. The improvement of lateritic soils that are not suitable for a particular purpose through techniques that combine modification of grain size through the insertion of sand, incorporation of Portland cement and densification through compaction is seen as an alternative. In this context, a dosage method to use a local lateritic soil as construction material in a most rational way reducing the economic and environmental impacts related to this activity is still missing. Therefore, the current research aims to evaluate the performance of a lateritic soil via modification of grain size through the insertion of sand, incorporation of Portland cement and densification through compaction. For this, unconfined compression, and durability (wetting and drying) tests were carried out on specimens of compacted clayey gravel lateritic soil, whose granulometry was modified by the insertion of distinct amounts (from zero to 45%) of weathered sand, treated with distinct Portland cement contents (from 4 to 10%), molded at different dry unit weights (from 16.8 to 20.1 kN/m³) and cured for 7 and 28 days. Results of the mechanical tests have shown the significant influence exerted by cement content and dry unit weight of the blend, followed by curing time and finally sand insertion. Satisfactory correlations between the response variables (q_u and ALM) and the adjusted porosity/cement index (η/C_v) were obtained. Furthermore, an innovative approach to replacing the laborious durability test is proposed.

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The Hyperstatic Reaction Method for the Analysis of the Sprayed Concrete Linings Behavior in Tunneling     

Pierpaolo Oreste  Giovanni Spagnoli  Cesar Alejandro Luna Ramos  Lisa Sebille 《Geotechnical and Geological Engineering》2018,36(4):2143-2169

Hyperstatic Reaction Method considers the interaction between the shotcrete lining and the rock mass modelling half tunnel section by beam elements connected by nodes, which can develop bending moments, axial forces and shear forces. The interaction between ground and support is represented by Winkler type springs in the nodes of the numerical model, in the normal and tangential direction. 1944 analyses were developed considering three different tunnel radius values (2.0, 4.5 and 7.0 m), three different rock types (RMR = 40, RMR = 60 and RMR = 80), three different stress ratios acting on the linings (\(K = 1, \,K = 0.5\) and \(K = 0\)), three different lining thickness values (0.1, 0.2 and 0.3 m) and three values of the average elastic modulus of the shotcrete (6000, 9000 and 12,000 MPa). Besides, also two different stiffness values of the tangential springs at nodes were considered. Results show that the lining thickness and the elastic modulus of the shotcrete have a strong influence on the bending moment values which develop inside. The maximum axial force is not practically influenced by the lining elastic modulus and thickness. Both maximum bending moments and maximum axial forces increase in a linear way with the vertical load value; tunnel radius, \(K\) and RMR values of the rock mass have also a great influence on the maximum bending moment and axial force. Besides, it is possible to note how the absence of shear interaction between the lining and the rock mass causes bending moment values in the lining higher with respect to the case where the stiffness of the tangential springs at nodes equals to half the stiffness of the normal springs. For this reason, the neglectance of the shear interaction between the lining and the tunnel wall leads to an overdesign of the SC lining.  相似文献   

Development of microbial carbonates in the Lower Cretaceous Codó Formation (north‐east Brazil): Implications for interpretation of microbialite facies associations and palaeoenvironmental conditions          下载免费PDF全文

Anelize M. Bahniuk  Sylvia Anjos  Almério B. França  Nilo Matsuda  John Eiler  Judith A. Mckenzie  Crisogono Vasconcelos 《Sedimentology》2015,62(1):155-181

The study of microbial carbonates has acquired new significance with the recognition that they retain valuable information related to biomineralization processes associated with microbial activity throughout geological time. Additionally, microbialites have a demonstrated economic potential to serve as excellent hydrocarbon reservoirs. The Lower Cretaceous Codó Formation, located in the Parnaiba Basin of north‐east Brazil, comprises a unique stratigraphic sequence of up to 20 m thick, well‐preserved carbonate microbialites. Deposited in a continental basin during the initial break up and separation of South America from Africa in the Early Cretaceous, this lacustrine carbonate sequence provides an excellent example to investigate the palaeoenvironmental conditions controlling microbialite facies development. Based on macroscopic and microscopic observations of outcrop and drill core samples, four microbialite facies (stromatolite, lamina, massive and spherulite) were defined and distinguished by textures and microbial fossil content. Changes in facies type are related to alternating palaeo‐water depths, as reflected by ⁸⁷Sr/⁸⁶Sr cycles resulting from fluctuations in the sources of meteoric water. Clumped isotope measurements of stromatolitic fabrics yield precipitation palaeo‐temperatures with an average value of 35°C. The δ¹⁸O values of bulk carbonate (?6·8 to ?1·5‰ Vienna Pee Dee Belemnite) imply precipitation from water with calculated δ¹⁸O values between ?1·6‰ and 1·8‰ Vienna Standard Mean Ocean Water, reflecting precipitation from variably modified meteoric waters. The δ¹³C values of bulk carbonate (?15·5 to ?7·2‰ Vienna Pee Dee Belemnite) indicate a significant input of carbon derived from aerobic or anaerobic respiration of organic matter. Combined, the data indicate that the evolution of the Codó Formation occurred in a closed lacustrine palaeoenvironment with alternating episodes of contracting and expanding lake levels, which led to the development of specific microbialite facies associations. The results provide new insights into palaeoenvironmental settings, biogenicity and early diagenetic processes involved in the formation of ancient carbonate microbialites and, by extension, improve the knowledge of the reservoir geology of correlative units in deep waters offshore Brazil.  相似文献