利用“3S”技术进行北京地区土壤水分监测应用技术研究   总被引：13，自引：4，他引：13       下载免费PDF全文

王晓云  张文宗等 《应用气象学报》2002,13(4):422-429

该文主要对适合于北京地区的土壤水分卫星遥感监测方法，利用GIS及GPS工具，提高对土壤水分卫星遥感监测结果的分析能力进行了探讨。在分析研究北京地区土壤水分卫星遥感监测模式及适宜使用的下垫面状况和时段的基础上，提出了一批具有一定物理意义和应用价值的遥感模式。利用GIS和GPS技术实现包括遥感信息在内的多种数据的复合，以影像的方式，将地表地理状况与土壤水分卫星遥感监测结果结合起来，实现了RS、GIS及GPS的融合，提高了土壤水分卫星遥感监测的精度。  相似文献   

基于土体中结构面的岩土工程问题探讨   总被引：10，自引：2，他引：10  

蒋建平  章杨松  罗国煜 《工程地质学报》2002,10(2):160-165

土体中也存在结构面，并且结构面的存在与很多的岩土问题有关。为使土体中的结构面受到足够的重视，本文就其中的几个主要岩土工程问题进行了探讨，它们是：结构面对土体力学性质的影响、土体结构面对土体破坏的控制作用、有时可尝试用离散元等模型分析土体变形、土体中结构面上水的渗流和污染物的运移、结构面上土体力学参数问题、土坡稳定性问题、土与结构物的相互作用问题、土体中结构面与环境岩土工程问题等。  相似文献   

静压预制桩工程性状研究──以河南某电厂技改工程为例   总被引：1，自引：1，他引：1  

蒋孝成  黄志全  张长存 《工程地质学报》2002,10(3):288-292

以河南某电厂技改工程为例 ,根据现场检测结果 ,探讨了影响静压预制桩沉桩深度成因 ,分析了静压桩承载力的分布规律。研究结果证明静压桩的沉桩深度和承载力与地基土的性状密切相关。对于河南某电厂技改工程场地 ,尽管桩端进入砂较小深度 ,却可以在桩端平面附近良好土层的作用下提供较大的端阻力。  相似文献   

土壤离子电导率测量在可地浸砂岩铀矿找矿勘查中的实验研究     

侯林慧  谭克仁 《大地构造与成矿学》2002,26(4):447-451

土壤离子电导率测量是隐伏金属矿床、贵金属矿床普查找矿的重要技术方法,本研究应用该方法对隐伏可地浸砂岩铀矿进行普查找矿实验研究。实验表明,本区土壤离子电导率背景值为22.91μs/cm,异常平均值为513.96μs/cm,最高异常值达1349.30μs/cm。它可以圈定舌状蚀变砂岩体与未蚀变砂岩的接触边界,从而可以圈定隐伏砂岩铀矿的产出位置,是隐伏可地浸砂岩铀矿普查找矿的既经济又有效的方法。  相似文献   

A method to predict the group fissuring and faulting caused by regional groundwater decline     

E. Rojas  J. Arzate  M. Arroyo   《Engineering Geology》2002,65(4):20-260

Ground fissuring is a recurrent problem in many countries where water extraction surpasses the natural recharge of aquifers. Due to differential settlement, the soil layer undergoes deformation and cracks with serious consequences for civil infrastructure. Here, we propose an approximate analysis of the fissuring process that can be used to predict the location of cracks, which increasingly affect some middle- and large-sized cities in the world. For that purpose, the ground loss theory is applied to sediments overlying a sinusoidal-shaped graben. This analysis shows the existence of a tensile zone at the border of the graben with maximal values on its shoulder where tension cracks are more likely to appear. It also shows that soil deformation under differential settlement may evolve into ground faulting if water withdrawal continues. Finally, when a crack has completely developed, the tensile zone shifts towards the center of the graben, creating a new area for potential cracking and faulting.  相似文献   

EFFECTS OF SOIL CRUSTING ON SOIL MOISTURE, RUNOFF AND EROSION: FIELD OBSERVATIONS     

Tongxin ZHU 《国际泥沙研究》2002,17(4)

1 INTRODUCTION Soil crusting, or soil sealing, is one of the common phenomena in agricultural lands or semi-arid and arid soils. Due to the breakdown of soil aggregates by raindrops, soil surface develops a very thin, often less than a few millimeters, dense layer. Many studies indicated that such a thin layer significantly reduces infiltration capacity and increases surface runoff (i.e. McIntyre, 1958; Edward and Larson, 1969; Agassi et al., 1985; Bradford et al., 1986; Romkens et al.,…  相似文献   

Fuzzy neural network models for liquefaction prediction   总被引：1，自引：0，他引：1  

M. S. Rahman  Jun Wang 《Soil Dynamics and Earthquake Engineering》2002,22(8)

Integrated fuzzy neural network models are developed for the assessment of liquefaction potential of a site. The models are trained with large databases of liquefaction case histories. A two-stage training algorithm is used to develop a fuzzy neural network model. In the preliminary training stage, the training case histories are used to determine initial network parameters. In the final training stage, the training case histories are processed one by one to develop membership functions for the network parameters. During the testing phase, input variables are described in linguistic terms such as ‘high’ and ‘low’. The prediction is made in terms of a liquefaction index representing the degree of liquefaction described in fuzzy terms such as ‘highly likely’, ‘likely’, or ‘unlikely’. The results from the model are compared with actual field observations and misclassified cases are identified. The models are found to have good predictive ability and are expected to be very useful for a preliminary evaluation of liquefaction potential of a site for which the input parameters are not well defined.  相似文献   

The significance of rock structure,lithology and pre‐glacial deep weathering for the shape of intermediate‐scale glacial erosional landforms     

Mats Olvmo  Magnus Johansson 《地球表面变化过程与地形》2002,27(3):251-268

The main landforms within the glacially scoured Precambrian rocks of the Swedish west coast are closely connected to the principal structural pattern and have lately been explained as mainly a result of etch processes, probably during the Mesozoic and with a possible second period of etching during the Neogene. To explore the effect of multiple glacial erosion on the rock surfaces, an island with two different lithologies and with striae from different directions was selected for a detailed study, focusing on the shape of roches moutonnées. Air‐photo interpretation of bedrock lineaments and roches moutonnées combined with detailed field mapping and striae measurements are used to interpret the structural and lithological control on the resulting shape. The study reveals a significant difference in shape between roches moutonnées in augen‐granite and orthogneiss. Low elongated and streamlined roches moutonnées occur in the gneiss area, striated by a Late Weichselian ice flow from the NE. This ice flow is subparallel with both the local dominant trend of topographically well‐expressed joints and the schistosity of the gneiss. Frequently, there are no signs of quarrying on the lee‐sides of the gneiss roches moutonnées and hence they resemble the shape of whalebacks, or ruwares, as typically associated with the exposed basal weathering surface found in tropical areas. The granite roches moutonnées were formed by an older ice flow from the ESE, which closely followed the etched WNW–ESE joint system of the granite. Late Weichselian ice flow from the NE caused only minor changes of the landforms. On the contrary, marks of the early ESE ice flow are poorly preserved in the gneiss area, where it probably never had any large effect as the flow was perpendicular to both schistosity and structures and, accordingly, also to the pre‐glacial relief. The study demonstrates that coincidence between ice flow direction and pre‐glacially etched structures is most likely to determine the effects of glacial erosion. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

A model of equilibrium bed topography for meander bends with erodible banks     

Stephen E. Darby  Ivana Delbono 《地球表面变化过程与地形》2002,27(10):1057-1085

Channel curvature produces secondary currents and a transverse sloping channel bed, along which the depth increases towards the outer bank. As a result deep pools tend to form adjacent to the outer bank, promoting bank collapse. The interaction of sediment grains with the primary and secondary flow and the transverse sloping bed also causes meanders to move different grain sizes in different proportions and directions, resulting in a consistent sorting pattern. Several models have been developed to describe this process, but they all have the potential to over‐predict pool depth because they cannot account for the influence of erodible banks. In reality, bank collapse might lead to the development of a wider, shallower cross‐section and any resulting flow depth discrepancy can bias associated predictions of flow, sediment transport, and grain‐size sorting. While bed topography, sediment transport and grain sorting in bends will partly be controlled by the sedimentary characteristics of the bank materials, the magnitude of this effect has not previously been explored. This paper reports the development of a model of flow, sediment transport, grain‐size sorting, and bed topography for river bends with erodible banks. The model is tested via intercomparison of predicted and observed bed topography in one low‐energy (5·3 W m^?2 specific stream power) and one high‐energy (43·4 W m^?2) study reach, namely the River South Esk in Scotland and Goodwin Creek in Mississippi, respectively. Model predictions of bed topography are found to be satisfactory, at least close to the apices of bends. Finally, the model is used in sensitivity analyses that provide insight into the influence of bank erodibility on equilibrium meander morphology and associated patterns of grain‐size sorting. The sensitivity of meander response to bank cohesion is found to increase as a function of the available stream power within the two study bends. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Development of site-specific design ground motions in Western and Eastern North America     

Walter Silva  Carl Costantino   《Soil Dynamics and Earthquake Engineering》2002,22(9-12):755-764

This paper presents results recently obtained for generating site-specific ground motions needed for design of critical facilities. The general approach followed in developing these ground motions using either deterministic or probabilistic criteria is specification of motions for rock outcrop or very firm soil conditions followed by adjustments for site-specific conditions. Central issues in this process include development of appropriate attenuation relations and their uncertainties, differences in expected motions between Western and Eastern North America, and incorporation of site-specific adjustments that maintain the same hazard level as the control motions, while incorporating uncertainties in local dynamic material properties. For tectonically active regions, such as the Western United States (WUS), sufficient strong motion data exist to constrain empirical attenuation relations for M up to about 7 and for distances greater than about 10–15 km. Motions for larger magnitudes and closer distances are largely driven by extrapolations of empirical relations and uncertainties need to be substantially increased for these cases.

For the Eastern United States (CEUS), due to the paucity of strong motion data for cratonic regions worldwide, estimation of strong ground motions for engineering design is based entirely on calibrated models. The models are usually calibrated and validated in the WUS where sufficient strong motion data are available and then recalibrated for applications to the CEUS. Recalibration generally entails revising parameters based on available CEUS ground motion data as well as indirect inferences through intensity observations. Known differences in model parameters such as crustal structure between WUS and CEUS are generally accommodated as well. These procedures are examined and discussed.  相似文献