风沙地区遥感图像分析及其对选线的意义   总被引：1，自引：0，他引：1  

卓宝熙 《国土资源遥感》2003,14(4):1-5

简要叙述了利用遥感图像进行沙丘研究的优越性,重点介绍了沙漠地区各种类型沙丘的影像特征,并以其形态特征分析为依据,对某些类型沙丘的成因提出了看法,同时指出遥感图像沙丘判释对线路选线的意义及风沙与铁路、公路选线的关系等。  相似文献   

The response of subaqueous dunes to floods in sand and gravel bed reaches of the Dutch Rhine   总被引：4，自引：0，他引：4  

A.W.E. Wilbers  W.B.M. Ten Brinke† 《Sedimentology》2003,50(6):1013-1034

Abstract The branches of the River Rhine in the Netherlands, characterized by a sand–gravel bed in the upstream part and a sand bed in the downstream part of the river system, show migrating dunes, especially during floods. In the last 20 years, these dunes have been studied extensively. High-resolution echo-sounding measurements of these dunes, made with single and multibeam equipment, were analysed for three different sections of the Rhine river system during several floods. This analysis was done to quantify the growth, decay and migration rates of the dunes during floods. In addition, the migrating dunes were used to calculate bedload transport rates with dune tracking. The results of dune growth and decay and migration rate are shown to be very different for the various sections during the various floods, and these differences are related to differences in grain size of the bed and to differences in the distribution of discharge over the main channel and the floodplain. The relations are used to show that the growth and migration rate of dunes, and the calculated bedload transport rates during the rising stage of a flood wave can be predicted from the mobility of the bed material with simple power relations.  相似文献   

Multiscale Roughness Analysis of Particles: Application to the Classification of Detrital Sediments     

Hervé Drolon  Bernard Hoyez  Fabrice Druaux  Alain Faure 《Mathematical Geology》2003,35(7):805-817

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岩浆驱动破裂的形态研究     

栾锡武  秦蕴珊  宋海斌  石耀霖 《地球物理学进展》2003,18(1):138-141

轴地壳岩浆房是活动扩张中心海洋地壳结构的一个重要组成部分，轴地壳岩浆房通过深部岩浆源的补充，内部岩浆的同化熔融、结晶分异等岩浆房过程，其中的岩浆会破裂上覆的岩石层形成岩浆破裂，并沿岩浆破裂继续向上迁移。本文建立了岩浆迁移的层流模型，从理论上对岩浆迁移问题进行了探讨，并将遗传算法引入到该问题中来，用遗传算法求解了描述岩浆驱动破裂传播的积分方程。如果假设岩浆破裂在远离破裂末梢处的权限宽度为1M，则靠近末梢，破裂的宽度逐渐加大，在末梢处宽度为2m左右。并根据文献对岩浆流体的一些观测参数计算得出，岩浆破裂权限宽度不会很大，一般在1m左右的量级。  相似文献   

Geotechnical Hazards Associated with Desert Environment     

Shehata  W.M.  Amin  A.A. 《Natural Hazards》1997,16(1):81-95

The aridity of the Arabian Peninsula's deserts ranges between arid to hyperarid with hot dry climate, scarce precipitation and sparse vegetation. These harsh environmental conditions enhance some geomorphologic processes more than others, cause specific geotechnical problems, and increase desertification.From west to east, the general physiography of Saudi Arabia shows the Red Sea coastal plains and the escarpment foothills called Tihama followed by the Arabian Shield mountains, the Arabian Shelf plateau and finally the Arabian Gulf coastal plains. Sand moves by wind either as drifting sand or migrating dunes in four major sand seas, over the Arabian Shelf, and in the inter-mountain valleys, in the Arabian Shield causing problems of erosion and deposition. Human activities in the deserts may cause more instability to the sand bodies, enlarging the magnitude of the problem. Fine silty soil particles also move by wind, depositing loess mainly in selected areas downwind in the Tihama. These loess deposits subside and may form earth fissures by the process of hydrocompaction upon wetting. The addition of water can be either natural through storms or man-made through human agricultural or civil activities. Extensive sabkhas exist along the coastal plains of both the Red Sea and Arabian Gulf. The sabkha soil may also heave by salt re-crystallization or collapse by wetting. The shallow groundwater brines present in sabkhas also attack and corrode civil structures. Urbanization and excessive groundwater pumping may also deplete the fresh groundwater resources and may cause subsidence, ground fissuring and surface faulting as observed in some locations in the Arabian Shield. Although the average annual precipitation is very low, rain usually falls in the form of torrential storms, collected by dry valley basins and causing floods to unprotected downstream areas on the coastal plains of the Red Sea.The desert environment, being a fragile echo system, needs to be treated with care. Intercommunications between different national and international agencies and education of the layman should help to keep the system balanced and reduce the resulting environmental hazards. In addition, any suggested remedial measures should be planned with nature and engineered with natural materials.  相似文献   

SMA-MR复合型阻尼器   总被引：5，自引：0，他引：5  

卞晓芳  薛素铎 《世界地震工程》2004,20(2):23-29

利用形状记忆合金超弹性、形状记忆特性和MR液的材料特性，提出了SMA-MR复合阻尼器，建立了阻尼器的理论模型。通过输入正弦波得到小震、大震时相应的滞回曲线，并对一单层框架进行输入El Centro地震波下的减震效果分析，比较了SMA-MR阻尼器、仅有SMA和仅有MR作用下的减震效果。结果表明，所设计的SMA-MR阻尼器具有卓越的阻尼性能，对大震、小震的控制实现了自适应的智能性。  相似文献   

Modelling transverse dunes     

Veit Schwmmle  Hans Herrmann 《地球表面变化过程与地形》2004,29(6):769-784

Transverse dunes appear in regions of mainly unidirectional wind and high sand availability. A dune model is extended to two‐dimensional calculation of the shear stress. It is applied to simulate dynamics and morphology of three‐dimensional transverse dunes. In the simulations they seem to reach translational invariance and do not stop growing. Hence, simulations of two‐dimensional dune ?elds have been performed. Characteristic laws were found for the time evolution of transverse dunes. Bagnold's law of the dune velocity is modi?ed and reproduced. The interaction between transverse dunes led to the interesting conclusion that small dunes can travel over bigger ones. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Aeolian abrasion and modes of fine particle production from natural red dune sands: an experimental study   总被引：3，自引：0，他引：3  

Joanna E. Bullard  Grant H. McTainsh†  Christa Pudmenzky† 《Sedimentology》2004,51(5):1103-1125

A series of experiments was conducted to determine the potential for aeolian abrasion of natural dune sands to produce fine particles (< 125 µm) by (1) the release of resident fines; (2) spalling, chipping and breakage of particles; and (3) the removal of grain surface coatings. Parent samples were obtained from the surfaces of four active continental dunes and abraded using a glass ‘test tube’ chamber for up to 120 h. The fine particles produced by this abrasion process were trapped at varying time intervals and subject to detailed particle‐size analyses using a Coulter Multisizer. The abrasion of untreated parent samples produced fine particles in one of two main size classes, < 10 µm and > 50 µm, but when the parent sample was sieved to exclude particles < 250 µm, relatively more material in the range 10–50 µm was produced. For unsieved parent samples, the size range associated with the dominant mode varied according to the length of the abrasion time. The coarsest mode (> 63 µm) was dominant during the first 16 h of abrasion, then became less significant and is thought to be associated with the release of resident fines into suspension. The finest mode (< 10 µm) was absent or very weak during the first 16 h of abrasion, then became more significant and, in some instances, dominated the distribution as abrasion continued. Removal of grain surface coatings is the main source of fine material < 10 µm, and this may be a significant source of fine material in areas where sands are dominated by subrounded and rounded particles. By comparison with previous studies of aeolian particle abrasion, these natural dune sands produced very low quantities of fine material (by weight), but their spatial extent makes them potentially a significant source of dust‐sized particles at the global scale.  相似文献   

Transport rate of calcareous sand in unidirectional flow     

DAVID A. SMITH  KWOK FAI CHEUNG 《Sedimentology》2005,52(5):1009-1020

This paper examines the transport of calcareous sand in unidirectional flow and its prediction through existing sediment transport models. A flume experiment of four sand samples collected on Oahu, Hawaii, provides 29 sets of sediment transport data in the bed-form and suspended transport stages. The measured transport data are compared with direct predictions from four energy-based transport models developed for siliceous particles. Corrections for the grain-size, fall velocity, and critical velocity of calcareous sand based on recent research are applied to the models and the results are compared with the direct calculations and measured data. The comparison illustrates the important role particle shape plays in the transport of calcareous sand. All four sediment transport models give consistent predictions and good agreement with the majority of the measured data. Two of the models respond positively to the corrections in both the bed-form and suspended transport stages indicating that such an approach may provide an interim solution for the transport of calcareous sand.  相似文献   

Influence of vegetation on aeolian sand transport rate from a backshore to a foredune at Hasaki, Japan   总被引：1，自引：0，他引：1  

YOSHIAKI KURIYAMA  NORIO MOCHIZUKI†  TSUYOSHI NAKASHIMA‡ 《Sedimentology》2005,52(5):1123-1132

The influence of vegetation on aeolian sediment transport rate in the region from a backshore to a foredune was investigated at the Hasaki Coast in Japan, where an onshore wind was predominant and the creeping beach grasses Carex kobomugi and Calystegia soldanella were major species. The comparison of cross-shore distributions of the cross-shore component of aeolian sand transport rate with and without vegetation, which were estimated on the basis of the beach profile changes and a mass conservation equation, showed that the creeping grasses influenced the aeolian sand transport rate. The landward aeolian sand transport rate rapidly decreased landward from the seaward limit of vegetation when the grasses grew. The aeolian sand transport rate reduced by 95% with a vegetation cover of 28%. On the other hand, when the grasses were absent, the landward aeolian sand transport rate did not decrease near the seaward vegetation limit, but near the foot of the foredune.  相似文献