模拟试验法确定桩基承载力   总被引：3，自引：0，他引：3  

亓宾  佴磊  江娟 《吉林大学学报(地球科学版)》2004,(Z1)

通过室内中型剪切摩擦试验确定桩与地层间的C、Φ值,依据莫尔—库仑准则确定桩侧摩阻力。桩侧法向应力采用桩土上部荷载引起的作用于桩身的侧向应力,桩端承载力通过室内三轴试验确定,两者之和即为单桩承载力。该方法用于肇源松花江大桥桩基承载力的测试,得出的桩承载力与实测值吻合较好,取得了预期的效果。  相似文献   

塔里木河南岸地下淡水资源分布特征及成因分析--以哈得4油田水源地为例     

叶义生  张鸿义  陈萍莉  刘平  侯谦儒  李强  喜英 《新疆地质》2004,22(3):244-247

塔里木河南岸地下水资源，卡要为受塔里水河控制的具有高矿化背景的地下水，在塔里木河洪水的淡化影响下，形成了一定范围的地下水淡化带．这种淡化水对油田供水具有战略意义，在一定程度上制约着油田建设的发展．通过对塔埋木河南岸地下淡水资源的分布特征与成因分析．为塔河南岸地下淡水资源的合理开发与利用指明了方向．  相似文献   

黄河水下三角洲沉积物强度变化原位测试研究   总被引：14，自引：8，他引：14  

贾永刚  霍素霞  许国辉  单红仙  郑建国  刘红军 《岩土力学》2004,25(6):876-881

研究区位于1964～1976年黄河由刁口入海时形成的水下三角洲叶瓣上。1995年为石油开采在潮坪上构筑的交通设施对波浪形成良好的屏障。在屏障两侧各选一典型研究区，于1999年和2002年进行了大量对比性现场原位土工测试，探讨了波浪对黄河口沉积物的次生改造作用，结果表明：(1)较强的波浪荷载作用，不会提高海底沉积物的表层强度，只是导致不均匀程度随水动力作用的时间增长有所加大：(2)较强的波浪荷载作用，使得海底表层沉积物之下一定深度范围内土体强度提高，形成强度硬层：(3)海底沉积物强度沿着剖面线在平面上呈现周期性或间隔性变化。  相似文献   

开发MapObjects为城市绿地管理服务   总被引：1，自引：0，他引：1  

李娟  卢文喜 《世界地质》2004,23(2):192-194

从控件技术出发，介绍了对象链接与嵌入技术—Activex控件技术，并将GIS控件MapObjects应用到长春市城市绿地管理领域中。开发出的长春市城区绿地地理信息系统具有地图管理和信息查询及修改功能，实现了地图的放大、缩小、平移以及由空间查属性和由属性查空间的双向查询功能，并以多媒体形式展示长春市绿化情况，为长春市实现科学管理绿地提供了技术支撑工具。  相似文献   

煤层气在煤储层中的扩散及其影响因素   总被引：4，自引：0，他引：4  

曹成润  牛伟  张遂安  霍永忠  陈秀艳  孙英男 《世界地质》2004,23(3):266-269

煤层气在煤储层中的扩散是指从煤基质孔隙表面上解吸的煤层气运移到割理系统的主要过程。发生扩散的前提条件是气体浓度差的出现，衡量扩散能力大小的重要参数是扩散系数。前者为由解吸速度、解吸气量和煤层气产量、井孔压力降等因素控制的动态参数，而后者为主要受扩散物质性质、扩散介质特征、扩散系统的温度、压力和孔隙结构形态等因素影响的静态参数。煤层气在煤储层中的扩散量与煤层气浓度差和扩散系数呈正比关系。  相似文献   

Crustal and mantle strengths in continental lithosphere: is the jelly sandwich model obsolete?     

Juan Carlos Afonso  Giorgio Ranalli 《Tectonophysics》2004,394(3-4):221-232

The relative importance of the contribution of the lower crust and of the lithospheric mantle to the total strength of the continental lithosphere is assessed systematically for realistic ranges of layer thickness, composition, and temperature. Results are presented as relative strength maps, giving the ratio of the lower crust to upper mantle contribution in terms of crustal thickness and surface heat flow. The lithosphere shows a “jelly sandwich” rheological layering for low surface heat flow, thin to average crustal thickness, and felsic or wet mafic lower crustal compositions. On the other hand, most of the total strength resides in the seismogenic crust in regions of high surface heat flow, crust of any thickness, and dry mafic lower crustal composition.  相似文献   

Effects of spatially structured vegetation patterns on hillslope erosion in a semiarid Mediterranean environment: a simulation study   总被引：1，自引：0，他引：1  

Matthias Boer  Juan Puigdefbregas 《地球表面变化过程与地形》2005,30(2):149-167

A general trend of decreasing soil loss rates with increasing vegetation cover fraction is widely accepted. Field observations and experimental work, however, show that the form of the cover‐erosion function can vary considerably, in particular for low cover conditions that prevail on arid and semiarid hillslopes. In this paper the structured spatial distribution of the vegetation cover and associated soil attributes is proposed as one of the possible causes of variation in cover–erosion relationships, in particular in dryland environments where patchy vegetation covers are common. A simulation approach was used to test the hypothesis that hillslope discharge and soil loss could be affected by variation in the spatial correlation structure of coupled vegetation cover and soil patterns alone. The Limburg Soil Erosion Model (LISEM) was parameterized and verified for a small catchment with discontinuous vegetation cover at Rambla Honda, SE Spain. Using the same parameter sets LISEM was subsequently used to simulate water and sediment fluxes on 1 ha hypothetical hillslopes with simulated spatial distributions of vegetation and soil parameters. Storms of constant rainfall intensity in the range of 30–70 mm h^?1 and 10–30 min duration were applied. To quantify the effect of the spatial correlation structure of the vegetation and soil patterns, predicted discharge and soil loss rates from hillslopes with spatially structured distributions of vegetation and soil parameters were compared with those from hillslopes with spatially uniform distributions. The results showed that the spatial organization of bare and vegetated surfaces alone can have a substantial impact on predicted storm discharge and erosion. In general, water and sediment yields from hillslopes with spatially structured distributions of vegetation and soil parameters were greater than from identical hillslopes with spatially uniform distributions. Within a storm the effect of spatially structured vegetation and soil patterns was observed to be highly dynamic, and to depend on rainfall intensity and slope gradient. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

The role of vegetation patterns in structuring runoff and sediment fluxes in drylands   总被引：4，自引：0，他引：4  

Juan Puigdefbregas 《地球表面变化过程与地形》2005,30(2):133-147

The dynamics of vegetation‐driven spatial heterogeneity (VDSH) and its function in structuring runoff and sediment fluxes have received increased attention from both geomorphological and ecological perspectives, particularly in arid regions with sparse vegetation cover. This paper reviews the recent findings in this area obtained from field evidence and numerical simulation experiments, and outlines their implications for soil erosion assessment. VDSH is often observed at two scales, individual plant clumps and stands of clumps. At the patch scale, the local outcomes of vegetated patches on soil erodibility and hydraulic soil properties are well established. They involve greater water storage capacity as well as increased organic carbon and nutrient inputs. These effects operate together with an enhanced capacity for the interception of water and windborne resources, and an increased biological activity that accelerates breakdown of plant litter and nutrient turnover rates. This suite of relationships, which often involve positive feedback mechanisms, creates vegetated patches that are increasingly different from nearby bare ground areas. By this way a mosaic builds up with bare ground and vegetated patches coupled together, respectively, as sources and sinks of water, sediments and nutrients. At the stand scale within‐storm temporal variability of rainfall intensity controls reinfiltration of overland flow and its decay with slope length. At moderate rainfall intensity, this factor interacts with the spatial structure of VDSH and the mechanism of overland flow generation. Reinfiltration is greater in small‐grained VDSH and topsoil saturation excess overland flow. Available information shows that VDSH structures of sources and sinks of water and sediments evolve dynamically with hillslope fluxes and tune their spatial configurations to them. Rainfall simulation experiments in large plots show that coarsening VDSH leads to significantly greater erosion rates even under heavy rainfall intensity because of the flow concentration and its velocity increase. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

A comparative study of concentrated plasticity models in dynamic analysis of building structures     

Maurice A. Dides  Juan C. de la Llera 《地震工程与结构动力学》2005,34(8):1005-1026

Concentrated plasticity (CP) models are frequently used in static and dynamic building analysis and have been implemented in available commercial software. This investigation deals with three different CP‐models, a simplified macroelement model (SEM) for a complete building story, a frame element with elasto‐plastic interaction hinges (PH), and a frame element with fiber hinges (FB). The objectives of this work are to evaluate the quality of the earthquake responses predicted by these models and to identify important aspects of their implementation and limitations for their use in dynamic analysis. The three elements are tested in a single‐story asymmetric plan building and in a three‐story steel building. Results show that base shear and global response values are usually computed with better accuracy than interstory deformations and local responses. Besides, the main limitation of elasto‐plastic CP models is to control the displacement offsets that result from perfect elasto‐plastic behavior. On the other hand, calibration of the SEM‐model shows that global responses in steel structures may be computed within 20% error in the mean at a computational cost two orders of magnitude smaller than that of the other CP elements considered. However, the three element models considered lead to increasing levels of accuracy in the dynamic response and their use depends on the refinement of the analysis performed. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

An approach for quantifying geomorphological impacts for EIA of transportation infrastructures: a case study in northern Spain   总被引：2，自引：0，他引：2  

Jaime Bonachea  Viola Maria Bruschi  Juan Remondo  Alberto Gonzlez-Díez  Luis Salas  Jurjen Bertens  Antonio Cendrero  Csar Otero  Cecilia Giusti  Andrea Fabbri  Jos Ramn Gonzlez-Lastra  Jos María Aramburu 《Geomorphology》2005,66(1-4):95

A methodological proposal for the assessment of impacts due to linear infrastructures such as motorways, railways, etc. is presented. The approach proposed includes a series of specific issues to be addressed for each geomorphological feature analysed—both ‘static’ and ‘dynamic’—as well as a series of steps to be followed in the process.Geomorphic characteristics potentially affected were initially identified on the basis of a conceptual activities/impacts model that helps to single out geomorphic impacts related to environmental concerns for the area. The following issues were addressed for each individual impact: nature of potential effects; indicators that can be used to measure impacts; criteria of ‘geomorphologic performance’; procedure for measurement/prediction of changes; translation of geomorphologic impacts into significant terms from the viewpoint of human concerns; possible mitigation and/or compensation measures.The procedure has been applied to a case study corresponding to a new motorway in the Basque Country, northern Spain. Geomorphological impacts considered in this analysis included: (1) consumable resources; (2) sites of geomorphological interest; (3) land units with high potential for use, high productivity or value for conservation; (4) visual landscape; (5) slope instability processes. The procedure has been designed for implementation in a Geographic Information System (GIS) environment. Details are given on the application of the method to each individual impact analysed and results are presented in both numerical and map form.Impacts assessed were initially expressed by means of heterogeneous magnitudes, depending on the geomorphological feature considered. Those geomorphological impacts were then translated into significant terms and homogeneous magnitudes. Integration was carried out on the basis of impact values thus obtained. Final integrated results were also expressed in numerical and map form.The method proposed enables comparison of alternatives as well as ‘prediction’ and assessment of impacts in terms directly related to geomorphic characteristics. It also facilitates the expression of those impacts in terms that allow integration with other types of environmental impacts.  相似文献