Buckling behaviour of single pile and pile bent in the Scotch Road Bridge     

《Geomechanics and Geoengineering》2013,8(4):291-298

The buckling behaviour of the 360 × 152 steel H-piles supporting the integral abutments of the Scotch Road Bridge, located in Trenton, New Jersey, has been studied for the cases of single pile and pile bent. Three-dimensional finite-element models for single pile and pile bent have been developed to study the behaviour of these fully embedded piles under axial and lateral loading. An iterative analysis based on extracting the eigenvalues and eigenvectors (mode shapes) that correspond to the pile(s) critical buckling loads has been adopted. The pile(s) and the surrounding sand were modelled using solid continuum elements in the finite-element model. Material non-linearity is accounted for in both the piles and the soil in the base state of the model. A parametric study has been utilized to determine the effect of the geometric and material properties of the pile and the surrounding sand on the predicted critical buckling loads of the piles. The effects of four parameters have been studied: soil stiffness, pile length, type of connection, and combining vertical and lateral loads. The results from the parametric study showed that the variation of the percentage change in the sand stiffness, pile length, and combining vertical and lateral loads with the critical buckling loads of the 360 × 152 H-piles is nonlinear. Furthermore, the parameters studied are more influential in affecting the critical buckling load of a single pile than a pile bent, with the exception of the ‘type of connection’ parameter.  相似文献   

Stratigraphic delineation by three-dimensional clustering of piezocone data     

《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2013,7(2):102-119

Piezocone soundings are a fast and economical approach for geotechnical site characterization, providing three separate and continuous channels of data with depth, including: tip resistance q _T, porewater pressure u ₂ and sleeve friction f _s. Literally hundreds to thousands of data points are collected by a single sounding. Since these readings are functions of both soil type and soil behaviour, they can be used for the delineation of soil stratigraphy.

One way to process large amounts of data involves clustering. Cluster analysis is an efficient statistical way to analyse the stratigraphic vertical profiling of geomaterials and means to detect the inherent similarity between data sets and group them together. Clustering in previous geotechnical research was based on only two channels of piezocone data (q _T and u₂). The method works well for soils that are under the groundwater table and was applied to soundings in clay deposits.

In the present paper, a new cluster analysis approach is developed based on all three channels of data, thus extending the method to soils above the water table and applicable to sands, silts, and clays. Example soil profiles derived by three-channel cluster analysis are presented herein and compared with conventional soil boring and sampling data.  相似文献   

Geomorphic response to growing fault-related folds: example from the foothills of central Taiwan     

Bernard Delcaillau 《Geodinamica Acta》2013,26(5):265-287

Abstract

In this paper we concentrate particularly on the geomorphological indicators left by active tectonics. In the central foothills of Taiwan, we used topography, drainage pattern and structural data to perform quantitative morphometric analysis and to determine relative age of fault-related anticlines. The Tiehchen, Tatu and Pakua ridge belt is a fault-related anticline system located in the hanging wall of the Changhua fault along the western thrust front of the foothills. Geomorphic systems are analysed with intent to detect the various responses of landforms and drainage pattern to late Quaternary deformation. Topography and drainage basin register uplift and are valuable tools to discriminate lateral propagation of an active frontal fold. Geomorphic field evidence and quantitative morphometric parameters are used to define the evolution of the rising anticline ridges and to infer tectonism style along an active front. Geometry of alluvial fans, formed along the frontal side of the anticlines, and weathered terrace deposits provide relevant information on neotectonics. Knowledge concerning these younger anticline ridges, makes this area a good example of an actively forming mountain front. We discuss in detail the origin of N045°, N095 and N120° trending oblique fault scarps which delimite numerous fault blocks. The fault scarps morphology is characterized by imbricate talus facets. Steeper topography accompanied by breaks in the slope along some transverse profiles, seems to correspond to the traces of successive uplifts. © 2001 Éditions scientifiques et médicales Elsevier SAS  相似文献   

Paraglacial sedimentation and denudation processes in an Alpine valley of Switzerland. An approach to the quantification of sediment budgets     

Benjamin U. Müller 《Geodinamica Acta》2013,26(5):291-301

Abstract

As a result of recent drillings in the Walensee Valley (eastern Switzerland) a new facies model for the Quaternary filling of Alpine valleys has been developed. A detailed lithological model and some new radiocarbon dating allowed the calculation of regional sedimentation and denudation rates and their change during the Late- and Postglacial period. It is shown that these changes follow the paraglacial sedimentation model by Church and Ryder [1]. The absolute quantification of the sediment budgets between the Last Glaciation and today points to denudation rates in the order of 1.5 mm y^?1 for the catchment of the Lake of Walenstadt. This is 50 % higher than suggested from current tectonic and isostatic estimates up to now. In that case present day uplift of the Alps would not be in balance with denudation. © Elsevier, Paris  相似文献   

鄂尔多斯盐沼湿地土壤盐分特征对植物群落的影响          下载免费PDF全文

崔乔  何彤慧  全晓塞  陈向全  何玉实 《盐湖研究》2022,30(1):25-32

为研究内陆盐沼植物群落的分布对土壤盐分的响应特征,选取鄂尔多斯盐湖盐沼区作为研究区,筛选了肉质耐盐植物群落、苔草植物群落和禾草植物群落3类典型植物群落,开展了土壤含水量、pH、电导率以及Na+、K+、Mg2+、Ca2+、Cl-、SO42-、CO32-和HCO3-测定,分析了区内典型植物群落对土壤水盐因子的响应规律.探讨...  相似文献   

陆面模式中土壤冻融过程参数化研究进展   总被引：21，自引：0，他引：21  

王澄海  董文杰  韦志刚 《地球科学进展》2002,17(1):44-52

土壤冻融过程在寒区水文和气候系统中有着重要作用。陆面模式中土壤冻融过程的参数化对模式的设计和模拟结果有着关键作用。通过对广泛应用的Bucket，SIB，BATS，VIC，BEAS， LSM等几种主要的陆面模式中的冻融过程参数化方案进行了总结和比较。首先，详尽地描述了土壤冻融与气候变化的数值模拟研究，总结和评述了土壤冻融过程对气候变化的作用。其次，对几种主要的陆面过程模式在土壤水热参数化方案中对冻融过程的考虑及其特点进行了比较和讨论。还对冻结深度和冻结周期的预报模式进行了简介，最后对该领域当前面临的主要研究问题进行了探讨和阐述。  相似文献   

土壤侵蚀量预报模型研究进展   总被引：38，自引：0，他引：38  

符素华  刘宝元 《地球科学进展》2002,17(1):78-84

土壤侵蚀模型是定量评价水土资源发展动态、指导综合治理规划、评价治理方案和措施的技术工具。根据建模的手段和方法，土壤侵蚀量预报模型有经验模型和物理成因模型两大类。根据建模对象的不同，土壤侵蚀模型又有坡面土壤侵蚀模型和流域土壤侵蚀模型之分。主要从这4个方面入手，介绍了国内外土壤侵蚀量预报模型研究的主要成就，指出了现有模型的不足。在总结前人工作的基础上，提出了我国土壤侵蚀模型今后的发展方向。  相似文献   

全球变化条件下的土壤呼吸效应   总被引：52，自引：7，他引：52  

彭少麟  李跃林  任海  赵平 《地球科学进展》2002,17(5):705-713

土壤呼吸是陆地植物固定CO₂尔后又释放CO₂返回大气的主要途径，是与全球变化有关的一个重要过程。综述了全球变化下CO₂浓度上升、全球增温、耕作方式的改变及氮沉降增加的土壤呼吸效应。大气CO₂浓度的上升将增加土壤中CO₂的释放通量，同时将促进土壤的碳吸存；在全球增温的情形下，土壤可能向大气中释放更多的CO₂，传统的土地利用方式可能是引发温室气体CO₂产生的重要原因，所有这些全球变化对土壤呼吸的作用具有不确定性。认为土壤碳库的碳储量增加并不能减缓21世纪大气CO₂浓度的上升。据此讨论了该问题的对策并提出了今后土壤呼吸的一些研究方向。其中强调，尽管森林土壤碳固定能力有限，但植树造林、森林保护是一项缓解大气CO₂上升的可行性对策；基于现有田间尺度CO₂通量测定在不确定性方面的进展，今后应继续朝大尺度田间和模拟程序方面努力；着重回答全球变化条件下的土壤呼吸过程机理；区分土壤呼吸的不同来源以及弄清土壤呼吸黑箱系统中土壤微生物及土壤动物的功能。当然，土壤呼吸的测定方法尚有待改善。  相似文献   

Annual dissolved fluxes from Central Nepal rivers: budget of chemical erosion in the Himalayas   总被引：2，自引：0，他引：2  

Christian France-Lanord  Matthew Evans  Jean-Emmanuel Hurtrez  Jean Riotte 《Comptes Rendus Geoscience》2003,335(16):1131-1140

Annual dissolved element fluxes of Himalayan rivers from Central Nepal are calculated using published river discharge and a new set chemical data of rivers, including monsoon sampling. These are used to study the control on chemical erosion of carbonate and silicate over the whole basin. Chemical erosion of carbonate is mainly controlled by the river runoff but it can be limited by the availability of carbonate in limestone-free basin. Chemical erosion of silicate is well correlated to the runoff. However differences between High Himalayan and Lesser Himalayan basins suggest that physical erosion may also play an important control on silicate weathering. To cite this article: C. France-Lanord et al., C. R. Geoscience 335 (2003).  相似文献   

影响文山三七品质的土壤地质背景因素   总被引：6，自引：0，他引：6  

高宏光  杨双兰  曾群望 《云南地质》2001,20(2):195-202

应用农业地质学的理论和方法，初步探讨了影响云南文山地区的三七品质的土壤地质背景因素。结果表明：不同类型的土壤地质背景上种植出的三七，具有不同的品质特征。火山岩形成的土壤，种植出的三七，其总皂甙的得率高，碳酸盐形成的红壤，种植出的三七，则总皂甙得率最低，碎屑岩和碳酸岩形成的混合型土壤，种植出的三七，其总皂甙得率则居于二者之间。高钾的火山岩类土壤地质背景和高稀土的碳酸盐类土壤地质背景，是形成不同品质特征三七的根本原因，钾和稀土是形成三七不同品质特征的重要元素。  相似文献