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41.
Jesús Díaz-Curiel Sandra Rueda-Quintero Bárbara Biosca Georgina Doñate-Matilla 《Acta Geotechnica》2017,12(5):1119-1127
In this paper, we present a modification of the existing mathematical formulation used to obtain the allowable bearing pressure from dynamic penetration tests in order to extend its applicability to the design of shallow foundations. The conventional relationships adopted to obtain the allowable bearing pressure from penetrometer tests have a discontinuous gradient, and they are limited to a depth less than the footing width. The aim of this work was to find a relationship that permits the estimation of this pressure in cohesionless soils, from the results of dynamic probing super heavy tests, through a single non-piecewise and continuous relationship that remains valid up to depths several times the footing width. This equation was applied as part of the geomechanical characterization survey undertaken for the construction of an elevated helipad in the centre of the Iberian Peninsula. The survey results were considered satisfactory, and the construction was completed without structural problems. 相似文献
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Drought, desiccation and discourse: missionary correspondence and nineteenth-century climate change in central southern Africa 总被引：1，自引：0，他引：1
This paper examines the role that representatives of the London Missionary Society in central southern Africa during the nineteenth century may have played in the development of geographical debates concerning the long-term desiccation of the African continent. Observations on climate included within missionary documents are used to reconstruct a chronology of intra-decadal climatic variability for the period 1815–1900. This reveals six drought periods and seven wet phases that affected large areas of the region, but identifies no evidence for progressive desiccation. The chronology is then used as a framework within which to view missionary perspectives on drought and desiccation. Major influences upon the development of desiccationist theory appear to include the prevalence of contemporary moral economic explanations of climatic variability, as well as the uptake and acceptance of indigenous understanding of climate change. Significantly, many of the key observations by eminent missionaries used as supporting evidence for progressive desiccation are identified as having been made during periods of severe drought. This is used to suggest that the most widely propagated evidence for desiccation may, therefore, simply be the end-product of periods of short-term drought rather than long-term climatic deterioration. 相似文献
44.
Unusually severe or prolonged drought ranks among the most devastating and calamitous of all extreme climate events, contributing
to wildfires, crop failure, livestock death, food shortages and famine. The response of human activities and the natural environment
to such historical weather perturbations provides a guide to where the most critical sensitivities to future climate changes
may lie (McCarthy et al., 2001, ‘Climatic change 2001: Impact adaptation, and vulnerability’, from 3rd Assesment Report of
IPCC). The reconstruction of regional climatic histories and investigations of the impacts of – and social response to – extreme
droughts in history are thus of crucial significance if we are to understand and anticipate the potential repercussions of
future events (Wigley, 1985, Nature 316, 106–107; Grove and Conterio, 1995, Clim. Change 30, 223).
Chihuahua, in the arid Northwest of Mexico, is one of the most seriously and frequently drought affected regions of the country
(Garcia, 2000, available at www.sequia.edu.mx/proyectos/vulnera.html). Prolonged drought in the 1930s, 1950s and 1990s contributed
to water scarcity, harvest failure, illness, livestock disease, abandonment and water conflict and served to highlight the
particular vulnerability of agrarian society in this region to climatic variability (Sandoval, 2003, Ingeneria Hidraulica en Mexico 18(2), 133–155). Recent investigations using tree ring analysis have identified several phases of such prolonged drought over
the last seven centuries. In this paper we use archival documents to investigate the impacts of such periods in late colonial
Chihuahua and to explore how society in the region responded to and coped with them. 相似文献
45.
46.
Geometric modelling and object-oriented software concepts applied to a heterogeneous fractured network from the Grimsel rock laboratory 总被引：2，自引：0，他引：2
Thomas Kalbacher Ralph Mettier Chris McDermott Wenqing Wang Georg Kosakowski Takeo Taniguchi Olaf Kolditz 《Computational Geosciences》2007,11(1):9-26
Discrete fracture network simulations are computationally intensive and usually time-consuming to construct and configure.
This paper presents a case study with techniques for building a 3D finite element model of an inhomogeneous fracture network
for modelling flow and tracer transport, combining deterministic and stochastic information on fracture aperture distributions.
The complex intersected fractures represent a challenge for geometrical model design, mesh quality requirements and property
allocations. For the integrated and holistic modelling approach, including the application of numerical and analytical simulation
techniques, new object-oriented concepts in software engineering are implemented to ensure a resourceful and practicable software
environment. 相似文献
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49.
Steven J. Balogh Daniel R. Engstrom James E. Almendinger Charlene McDermott Jie Hu Yabing H. Nollet Michael L. Meyer D. Kent Johnson 《Journal of Paleolimnology》2009,41(4):623-639
Sediment cores from Lake Pepin, a natural lake on the Upper Mississippi River, reveal the historical trends in trace metal
use and discharge in the watershed. Lead-210 dated concentration profiles of trace metals (Ag, Cd, Cr, Cu, Hg, Pb, V, Zn)
in sediment cores from throughout the lake generally showed low and stable concentrations prior to settlement (circa 1830),
peak concentrations between 1940 and 1975, and substantial decreases thereafter. Whole-lake sediment accumulation rates increased
greatly over the period of record, from 79,000 metric tons year−1 prior to 1830, to 876,000 metric tons year−1 during the 1990s. Whole-lake accumulation rates of most trace metals peaked in the 1960s but decreased sharply after that.
Sediment and trace metal accumulation rates decreased in the downstream direction, and approximately two-thirds of the sediment
and trace metal mass accumulated in Lake Pepin since 1800 was deposited in the upper 30% (by area) of the lake. The dramatic
declines in trace metal concentrations and accumulation rates in Lake Pepin sediments since 1970 coincide with increased pollution
control and prevention efforts throughout the watershed, including the implementation of secondary treatment at a large municipal
wastewater treatment plant upstream.
This is one of eight papers dedicated to the “Recent Environmental History of the Upper Mississippi River” published in this
special issue of the Journal of Paleolimnology. D.R. Engstrom served as guest editor of the special issue. 相似文献
50.