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991.
Monitored and simulated variations in matric suction during rainfall in a residual soil slope 总被引:1,自引:0,他引:1
Aurelian C. Trandafir Roy C. Sidle Takashi Gomi Toshitaka Kamai 《Environmental Geology》2008,55(5):951-961
This research combines field, laboratory and numerical investigations to estimate the development of a wetting front within
a 1.2 m residual soil mantle on a steep forested slope during rainfall events. The field-monitored variations in matric suction
due to rain-water infiltration during various events revealed that the maximum infiltration rate was much higher when the
wetting front resided in the upper 20 cm of soil compared to the case when the wetting front advanced to depths > 20 cm. Laboratory
investigations on soil hydraulic properties (i.e., soil water characteristic curve, and hydraulic conductivity) were useful
to establish the parameters of a multilayer finite-element model for one-dimensional vertical infiltration. These parameters
were subsequently calibrated by matching the predicted and field measured transient pore water pressure responses during actual
rainstorms with irregular rainfall patterns. The calibrated simulation model was used to assess the migration of the wetting
front under uniform rainfall with different intensities. Based on the numerical results, a hyperbolic equation was developed
to predict the duration of uniform rainfall required for the propagation of wetting front to a certain depth for a given rainfall
intensity. The proposed equation was subsequently tested against field-monitored advancements of the wetting front during
real rainstorms with variable rainfall intensity. 相似文献
992.
Temporal-spatial climate change in the last 35 years in Tibet and its geo-environmental consequences 总被引:4,自引:0,他引:4
The climate change in Tibet has induced complex water resource and geo-environmental changes. Tibet is located in a unique
geographical zone with the characteristics of middle-low latitude, high altitude and very low average air temperature, and
the climate there has been changed both in time and in space under the effect of global warming. Except for two regions without
data, the changes of both air temperature and rainfall in the last 35 years in Tibet exhibit evident zonational patterns.
In general, air temperature increases higher from east to west, whereas rainfall changes from decrease to increase from south
to north. Except for some areas in southern Tibet, the general increase of rainfall accelerated the rate of water cycle, and
caused an increase in the gross amount of water resources in Tibet. Moreover, under the impact of climate change, the frequency
of occurrence of landslide and debris flow has slightly increased in the high mountain–canyon regions of eastern Tibet. Also,
the debris flow due to ice lake outburst has evidently increased in the plateau mountain–lake basin regions of southern Tibet.
By contrast, desertification in the western plateau–lake basin regions of northern Tibet has been intensified. 相似文献
993.
994.
D. L. Dunkerley 《地球表面变化过程与地形》1995,20(3):207-218
Surface stones are a common feature of desert hillslopes. They influence slope processes ranging from the interception and partitioning of rainwater to the dislodgement and transport of regolith particles. The aspects of a stone mantle which relate to these various influences are diverse, and include surface cover fraction, dimensions of the infiltration annulus, and geometric and packing effects. Analyses of the characteristics of stone cover at two study sites were made using photographic methods and are used to evaluate different means of reporting mean stone sizes. It is found that mean diameter based on weight, as conventionally employed in sieve analysis, is insensitive to important stone cover characteristics and may be influenced greatly by uncommon, large stones. Similarly, mean diameters based on count become inappropriate if large numbers of small stones dominate the calculated mean, concealing other site-to-site differences in stone cover. As a more appropriate parameterization of stone geometry, the use of mean diameters weighted by stone surface area and perimeter length are proposed. These weighting factors have the advantage that they relate closely to stone characteristics relevant to slope hydrology and erosion processes. 相似文献
995.
MATHEMATICALMODELOFOVERLANDFLOWANDMECHANISMOFSOILCONSERVATIONFORFORESTEDSTEEPHILLSLOPE--(II)MechanismofSoilConservationOverSt... 相似文献
996.
Abstract The metamorphic history of the Archaean Superior Province crystalline basement in the Palaeoproterozoic Ungava Orogen attests to the importance of structural and geohydrological controls on a retrograde amphibolite-granulite transition. Two distinct metamorphic suites, separated in age by nearly one billion years, are recognized in extensively exposed tonalitic to dioritic metaplutonic gneisses. The older suite comprises c. 2.7-Ga granulite facies assemblages (orthopyroxene-clinopyroxene-hornblende-plagioclase-ilmenite ± biotite ± quartz) that record moderate pressures (±5 kbar) and high temperatures (±800° C). A younger, c. 1.8-Ga suite resulted from amphibolitization of the granulites and is characterized by regionally extensive amphibolite facies mineral zones that broadly parallel the basal décollement of the overlying Proterozoic Cape Smith Thrust Belt. Deformation/mineral growth relationships in the amphibolitized basement indicate that extensive hydration and re-equilibration of the Archaean granulites occurred during thrust belt deformation. The transition from granulite facies to amphibolite facies assemblages is characterized by the growth of garnet-hornblende-quartz ° Cummingtonite coronas between plagioclase and orthopyroxene-clinopyroxene, as well as titanite coronas on ilmenite. Multi-equilibrium thermobarometry on the coronitic assemblages documents re-equilibration of the granulitic gneiss to 7.7 kbar at 644° C in the south and 9.8 kbar at 700° C in the north. The variably deformed, amphibolite facies domain sandwiched between the coronitic garnet zone and the basal décollement is marked by significant metasomatic changes in major element concentrations within tonalite. These changes are compatible with equilibrium flow of an aqueous-chloride fluid down a temperature gradient. The source of fluids for basement hydration/metasomatism is interpreted to be dehydrating clastic rocks in the overlying thrust belt, with fluid flow probably focused along the basal décollement. 相似文献
997.
Yu Chongwen 《中国地质大学学报(英文版)》1995,(1)
Dissolution Precipitation Wave Structure ofHydrothermal Ore Zoning¥YuChongwen(FacultyofEarthSciences,ChinaUniversityofGeoscie... 相似文献
998.
Rates of splash detachment from a sandy soil of the Cottenham Series, subjected to a five-minute design storm of 50 mm/h with a kinetic energy of 127 J/m2 and a median volume drop size of 3·2 mm supplied from a rotating-disc rainfall simulator, are determined without a plant cover and with the cover of a single Brussels sprouts plant. Measurements are made at regular intervals throughout the growing season. Plant canopies of 10 to 25 per cent result in reductions of 10 to 25 per cent in rainfall volume and 10 to 81 per cent in rainfall energy. The volume and energy of the rain beneath the plant are significantly (P < 0·05) correlated with its number of leaves (r = ?0·84 and ?0·92 respectively for n = 49). No reduction was observed in the rate of splash detachment which averages 1·2 kg/m2 for the design storm with and without the plant. The detachment rate was found rather surprisingly to be inversely related to the energy of the rainfall under the plant and positively related to the number of leaves. As the number of leaves increases, so does the detachment rate per unit of rainfall energy. 相似文献
999.
文章从介绍扩散和渗滤作用一般概念着手,根据德兴铜厂斑岩铜矿床之细矿脉形成过程中元素自矿脉向围岩发生迁移的这一事实,应用扩展的一维费克定律来模拟这一真实过程。并讨论了铜厂铜矿床形成过程中离子、络离子具线性等温线的纯扩散、纯渗滤和扩散与渗滤重叠情况,以及非线性等温线的纯扩散作用。 相似文献
1000.
Two methods for sampling aggregates in the soil surface under simulated rain were compared using two soil types. Results showed that aggregate size distributions obtained by spatula sampling were not significantly different from those obtained using rings buried in the soil surface, provided both were sampled to the same depth. The effect of transporting samples over a distance of 60 km was non-significant when samples were placed in bottles half-filled with rainwater and transported in an upright position. The per cent aggregates > 0.125 mm was found to be the most suitable index of aggregate stability for both soils. 相似文献