The Influence of Porosity on Tensile and Compressive Strength of Porous Chalks   总被引：9，自引：4，他引：9  

V. Palchik  Y. H. Hatzor 《Rock Mechanics and Rock Engineering》2004,37(4):331-341

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Bearing capacity of unsaturated expansive soils     

Yongfu Xu 《Geotechnical and Geological Engineering》2004,22(4):611-625

It is difficult to determine the bearing capacity of a foundation in unsaturated expansive soil, although this is most important. The bearing capacity of unsaturated expansive soil is related to the drying and wetting environment. Swelling pressure occurs when the soil volume change is constrained as an expansive soil is inundated. The expansive lateral pressure, induced by the swelling pressure is similar to the passive earth pressure. By considering the effect of the expansive lateral pressure in Terzaghi's bearing capacity formula, the bearing capacity of unsaturated expansive soil is derived. Because it is very difficult to measure suction in situ, the bearing capacity is expressed using the expansive lateral pressure offers a feasible approach to calculate the bearing capacity of a foundation in unsaturated expansive soil, when suction is not measured. Plate load tests to measure the bearing capacity in situ were performed for the foundation in natural soil and saturated soil immersed by water. The verification of the bearing capacity formulae presented in this paper is conducted by comparing the predicted results with the results of the plate load tests on unsaturated expansive soils in Handan and Bingxia, China.  相似文献   

Curie Point Depths Beneath Precordillera Cuyana and Sierras Pampeanas Obtained from Spectral Analysis of Magnetic Anomalies   总被引：1，自引：0，他引：1  

Francisco Ruiz  Antonio Introcaso   《Gondwana Research》2004,7(4):1133-1142

A gravity and magnetic survey has been carried out with the purpose of investigating geophysical features of the crusts beneath three geological provinces in western Argentina: Cuyo Precordillera, the Sierras Pampeanas of San Juan and La Rioja, and Famatina System, the results of which are displayed in three maps: Bouguer anomaly, total field magnetic anomaly and total field reduced to the pole.

The top and bottom boundaries of the magnetized crust were calculated from power-density spectra of the total-field anomalies from our terrestrial database in 90 2D windows. The depths obtained for the bottom of magnetized crust are assumed to correspond to Curie point depths. The values thus obtained for the Precordillera range between 29 and 40 km, whereas for the Sierras Pampeanas, in the Sierra de Pie de Palo, and other mountain chains along the Bermejo-Desaguadero lineament or Valle Fértil lineament, such depth ranges between 20 and 35 km. These results are consistent with Curie point depths determined on different continental regions in the world.

A map of regional heat flow has been prepared in the present work based on the depth of the Curie point isotherm, which shows that heat flow patterns in Precordillera are different from those found in Sierras Pampeanas.

A significant heat flow extending in Northeast-Southwest direction seems to be directly related to Juan Fernández Ridge trace.

The results of the present investigations also point out a possible relationship between the base of the magnetized crust and the boundary separating the brittle from the ductile crustal regime.  相似文献   

长江干流主要营养盐含量的变化特征——1998~1999年日中合作调查结果分析   总被引：18，自引：0，他引：18  

徐开钦  林诚二  牧秀明  村上正吾  徐保华  渡边正孝 《地理学报》2004,59(1):118-124

根据1998年和1999年秋季在长江干流从重庆至长江口进行的纵向采样和分析,对长江干流的各态氮、磷含量的沿江变化进行研究。从整体上了解长江干流的水质变化特性,特别是营养盐含量的分布状况。研究结果表明,长江干流的SS浓度很高,介于50~400 mg/l。TN、TP浓度分别在70~110 滋mol/L、2~25 滋mol/L之间,前者以NO3-N为主,后者以PTP为主,PO4-P含量仅占TP的10%~20%。DIN/PO4-P的比值在70~160之间,远高于浮游植物生长P限制值,表明长江口及临近海域中P可能是生物生命活动的主要限制因素。葛洲坝水库对SS、TP、TN、NH4-N、BOD、COD等水质有一定的净化作用。长江水体在通过各大城市以及两大湖泊时,BOD、NH4-N负荷的增加迅速,特别是通过重庆、武汉、南京、上海及洞庭湖和鄱阳湖之后尤为明显。N、P含量的上升与人口增长、生活污水排放量及流域内化肥施用量增加有关。洞庭湖和鄱阳湖水系以及周围的面源负荷,对长江流域的营养盐变动有很大的影响。  相似文献   

幂函数对建筑物沉降的回归分析     

于春生 《现代测绘》2004,27(4):33-34

通过实例推导幂函数对建筑物沉降进行回归分析，并且得出较为精确的结果，同时也说明在选择回归函数的时候，还会受到很多条件影响。  相似文献   

图像控制点数据库的设计与实现   总被引：4，自引：0，他引：4  

朱彩英李新慧  杨培章靳国旺 何钰 《测绘学院学报》2004,21(4):282-285

地面控制点数据是航天航空图像摄影测量几何处理的必需数据。文中首先比较了控制点数据的存储管理方式，即采用文件系统方式与数据库方式的优缺点；接着分析了控制点图像数据的特征，从而提出了图像控制点数据的数据库存储方案，讨论了图像控制点数据库的查询方法；最后结合文中的方法，设计并且实现了一个控制点图像数据库管理与应用实验系统。通过分析认为，建立控制点图像数据库是重复利用控制点资源的有效途径。  相似文献   

基于EM算法和单幅雷达图像阴影的控制点坡度校正   总被引：1，自引：0，他引：1  

钱俊  舒宁 《武汉大学学报(信息科学版)》2004,29(12):1089-1092

对在我国现有的条件下进行控制点坡度校正的必要性进行了阐述，并分析了EM算法。根据EM算法以及基于区域增长的余弦散射模型建立了控制点坡度校正模型，并用河北省张北地区的雷达影像进行了实验，取得了较高的精度初值。  相似文献   

Long-term bed load transport rate based on aerial-photo and ground penetrating radar surveys of fan-delta growth, Coast Mountains, British Columbia     

Channa P. Pelpola  Edward J. Hickin   《Geomorphology》2004,57(3-4):169-181

Sequential aerial photography, sonar bathymetry, ground-penetrating radar (GPR), and sediment sampling and analysis provide the basis for calculating the volumetric and mass rate of progradation of the delta of Fitzsimmons Creek, a steep, high-energy, debris-flow-dominated channel draining about 100 km² of the southern Coast Mountains of British Columbia. Fitzsimmons Creek is typical of small mountain rivers in the region. GPR imaging is used to define the pre-depositional morphology of the receiving basin, a technique that improves the accuracy of the volumetric survey. The 52-year record (1947–1999) of progradation yielded an average annual volumetric transport rate of 1.00±0.16×10⁴ m³ year⁻¹ for bed load, corresponding to a mass transport rate of 1.60±0.28×10⁴ Mg year⁻¹. Bed load yields are consistent with those obtained in hydrogeomorphically similar basins in the region and elsewhere. Decade-based annual rates, which vary from 0.64±0.11×10⁴ to 2.85±0.38×10⁴ Mg year⁻¹, provide poor estimates of the 52-year average. Indeed, the 52-year record may also not be long enough to fully integrate the significant fluctuations in the sediment efflux from Fitzsimmons Creek. The methodology proposed in this paper can be transferred to other comparable mountain environments worldwide.  相似文献   

The effect of bed mobility on resistance to overland flow     

Shixiong Hu  Athol D. Abrahams 《地球表面变化过程与地形》2005,30(11):1461-1470

When sediment grains are transported as bed load in overland flow, there is a net transfer of momentum from the flow to the grains. When these grains collide with other grains, whether on the bed or in the flow, streamwise flow velocity decreases and resistance to flow increases. Resistance to flow generated in this manner is termed bed‐load transport resistance. Resistance to flow f over a plane bed may be partitioned into grain resistance f_g and bed‐load transport resistance f_bt. We use the symbols f_btf and f_btm to denote f_bt for flows over fixed beds and over mobile beds, respectively, and we compute the effect of bed mobility on flow resistance f_mob by subtracting f_btf from f_btm. The data for this study come from 54 flume experiments with fixed beds and 38 with mobile beds. On average f_mob is approximately equal to half of f_btm, which is about one‐quarter of f. Hence, f_mob is about one‐tenth of f. Predictive equations are developed for f_btf, f_btm and f_mob using dimensional analysis to identify the relevant independent variables and regression analysis to evaluate the coefficients associated with these variables. Values of f_mob are always positive which implies that mobile beds offer greater resistance to flow than do fixed beds. Evidently bed‐load grains colliding with mobile beds lose more momentum to the bed than do grains colliding with fixed beds. In other words, grain collisions with mobile beds are less elastic than those with fixed beds. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Green''''s functions for uniformly distributed loads acting on an inclined line in a poroelastic layered site   总被引：4，自引：0，他引：4  

梁建文  尤红兵 《地震工程与工程振动(英文版)》2005,(2)

Based on one type of practical Biot's equation and the dynamic-stiffness matrices of a poroelastic soil layer and half-space, Green's functions were derived for uniformly distributed loads acting on an inclined line in a poroelastic layered site. This analysis overcomes significant problems in wave scattering due to local soil conditions and dynamic soil-structure interaction. The Green's functions can be reduced to the case of an elastic layered site developed by Wolf in 1985. Parametric studies are then carried out through two example problems.  相似文献