Effect of Compressive Load on Oblique Pull-out Capacity of Model Piles in Sand     

B. Krishna  N. R. Patra 《Geotechnical and Geological Engineering》2006,24(3):593-614

Model tests on steel piles embedded in sand were carried out in the laboratory to study the effects of compressive load (i.e. 0, 25, 50, 75, and 100% of their ultimate capacity in compression) on oblique pull-out capacity of piles. The model piles were of 20 mm × 20 mm cross section, which had an embedded length of 400 and 600 mm. The pull was applied at an inclination of 0°, 30°, 60° and 90° with vertical axis of the piles. The experimental results indicate that the net oblique pull-out capacity of piles decreases with increase in % of compressive load and the decrease depends on the magnitude of the compressive load. Semi-empirical methods, based on experimental results, have been suggested to determine the oblique pull-out resistance of piles subjected to static compressive loads. A comparison of predicted values of the ultimate oblique resistance by proposed methods of analysis with experimental values, and also with those reported by others, showed reasonably good agreement.  相似文献   

长江三峡库区干流水体主要污染负荷来源及贡献   总被引：6，自引：0，他引：6       下载免费PDF全文

朱俊  董辉  王寿兵  王祥荣  张浩  樊正球 《水科学进展》2006,17(5):709-713

目前三峡水库枯水期已有11.1%的监测断面水质超标。城区江段岸边水质已出现较为严重的污染带。利用面向环境问题的污染负荷计量方法,对长江三峡库区干流水体主要污染负荷来源及贡献进行了分析。结果表明,富营养化污染负荷2003年总量为2.79万t PO₄3-当量,其中总磷贡献量最大,占总量的45.8%。其次是总氮和COD_Cr,分别占37.9%和16.4%。城市生活污水和农业施肥是主要来源,分别占总量的61.0%和26.3%。水生生态毒性污染负荷为7 612.6t 1,4-二氯苯当量。其中挥发酚和汞贡献量分别占78.0%和21.2%。来自城市生活污水占76.52%,重点工业企业的占23.48%。富营养化污染负荷有逐年增加趋势。重点工业企业六价铬和铅,城市污水中挥发酚水生生态毒性污染负荷增加较快。  相似文献   

地表水非点源污染负荷计算方法探讨   总被引：4，自引：0，他引：4  

杨育红  沈万斌 《吉林大学学报(地球科学版)》2006,(Z1)

以多年河流统计监测资料为基础,运用两点法,考虑非点源影响,逆推计算,求得地表水非点源污染负荷。以吉林省为例,分析了吉林省4大水系15条河流65个监测断面2000~2004年统计资料,运用两点法确定吉林省主要河流COD衰减系数(K),逆推计算得到吉林省非点源污染负荷为1443.711m3/s,其中松花江水系802.93m3/s,图们江水系108.369m3/s,辽河水系372.392m3/s,浑江、鸭绿江水系160.02m3/s。非点源污染负荷是点源污染负荷的57.14倍,成为吉林省地表水环境主要污染源。  相似文献   

Study on stability of thin-walled circular pipe piles embedded shallowly under lateral loads     

JIN Qing  CUI Xin-zhuang  LIU Zheng-yin 《岩土力学》2006,27(Z1):839-843

The interaction between soil and rigid piles loaded laterally is analyzed with finite difference method. There is a little difference between computational and experimental value of bearing capacity of rigid piles. Effects of embedding dimensions of piles and mechanical parameters of soil on lateral bearing capacity of rigid piles are studied. It is found that the lateral bearing capacities of rigid piles have important relation with the elastic modulus of soil, have approximate linear relations with the cohesion of soil and the friction coefficient of pile-soil interface and increase obviously with the internal friction angle of soil. But the effects of dilation angle on the lateral bearing capacities of rigid piles are negligible. The relations of bearing capacities of rough piles with smooth piles and the friction coefficient of pile-soil interface are also obtained.  相似文献   

Human impact on land–ocean sediment transfer by the world's rivers   总被引：3，自引：1，他引：3  

D.E. Walling   《Geomorphology》2006,79(3-4):192

Land–ocean transfer of sediment by rivers is a key pathway for material transfer on Earth. Contemporary data on the sediment loads of rivers provide clear evidence of significant recent changes in the sediment fluxes of several rivers in response to human impact. The key drivers of increased sediment loads include land clearance for agriculture and other facets of land surface disturbance, including logging activity and mining. Although, programmes for soil conservation and sediment control can result in reduced sediment loads, the trapping of sediment by dams represents the dominant cause of reduced loads. This influence is currently assuming increasing importance at the global scale. Any attempt to link these drivers to changes in the global land–ocean sediment flux must take account of the aggregation and buffering effects that operate in larger basins, which can cause damping and even removal of signals of increasing flux within the upstream basin, and complicate the link between upstream and downstream response to human impact. Further work is required to provide a precise quantitative assessment of the human impact on global land–ocean sediment fluxes and the net effect of increasing and decreasing fluxes. Particular attention must be paid to the temporal perspective and the variation of impact trajectories in different areas of the globe and for river basins of different sizes.  相似文献   

A primitive pseudo wave equation formulation for solving the harmonic shallow water equations     

J. J. Westerink 《Advances in water resources》1987,10(4)

A finite element method formulation for solving the harmonic shallow water equations in their primitive or unmodified form is developed and analysed. The scheme, referred to as the Primitive Pseudo Wave Equation Formulation (PPWE), involves developing a weak weighted residual form of the continuity equation and furthermore forming a pseudo wave equation by substituting the discretized form of the momentum equation into the discretized form of the continuity equation. The final set of equations to be solved, the pseudo wave equation and the primitive momentum equations, deceptively resemble the discretized equations of the wave equation formulation of Lynch and Gray. Despite this resemblance, Fourier analysis indicates that the PPWE scheme is still fundamentally primitive.However, application of the PPWE scheme to a set of stringent test problems results in very good solutions with well controlled nodal oscillations. It is shown that this low degree of spurious oscillations is due to the treatment of the boundary conditions such that elevation is taken as an essential condition and normal flux is taken as a natural condition. This particular boundary condition treatment is suggested by the formation of the pseudo wave equation. Furthermore, even though the equation re-arrangement does not in itself effect the solutions, it does make the scheme much more efficient.  相似文献   

基于移去-恢复法的区域大气负荷影响精化——以滇西地区为例     

申龙杰  章传银  徐鹏飞  杨康 《大地测量与地球动力学》2022,42(6):631-636

传统的大气负荷改正根据全球大气压模型计算获取,但全球大气压模型中、长波信号占优,缺乏突显区域特征信息的短波信号,而在研究高精度的区域大气负荷影响时,空间信息中的短波信号不可忽视。为此,根据地球重力场理论,引入移去-恢复思想,结合ECMWF提供的全球大气压变化数据和区域高分辨率大气压变化数据（CLDAS-V2.0）,基于负荷球谐系数和区域负荷格林函数方法得到大气压变化对滇西地区的负荷影响。结果表明,得到的大气负荷形变场在空间和时间分变率上均有一定提高。利用移去-恢复法计算区域大气压负荷影响,可为固体地球形变和CORS站时序分析提供参考。  相似文献   

多层四流球谐函数算法的构建及在大气辐射传输模式中的应用   总被引：1，自引：0，他引：1  

张华  卢鹏 《气象学报》2014,72(6):1257-1268

为了在不大幅度增加计算成本的情况下提高大气辐射传输计算的精度,利用单层四流球谐函数结合多层二流累加法,构造了可用于多层大气的四流球谐函数算法。为了比较与其他辐射传输算法的差异,引入48流离散纵坐标算法作为比较标准,Eddington 近似、四流离散纵坐标算法作为比较对象。在真实大气廓线条件下,计算了晴空和有云大气顶向上辐射通量、地表向下辐射通量以及加热率廓线。得出以下结论：在晴空情况下,与作为标准的48流离散纵坐标法相比,Eddington 近似、四流离散纵坐标法和新构造的四流球谐函数方法加热率绝对误差都小于0?3 K／d;向上、向下辐射通量的相对误差分别小于1％和0?6％。这表明在晴空情况下,3种算法对加热率的计算精度差别不大;对辐射通量的计算精度,两种四流近似算法比传统的 Eddington 近似更为精确。在有云情况下,与48流离散纵坐标法相比,四流球谐函数和四流离散纵坐标法计算的云顶加热率相对误差小于1％,而 Eddington 近似计算的云顶加热率相对误差大于5％。结果表明：新构造的四流球谐函数算法可用于大气辐射传输模式,在不大幅度增加计算成本的同时,提高了晴空大气的整体辐射计算精度和有云大气辐射加热率的计算精度。  相似文献   

潮汐日不等显著区域深度基准面的确定研究          下载免费PDF全文

吕忠琨 《海洋测绘》2014,34(6):46-48

由于利用定义法独立求算验潮站的深度基准面对潮位观测资料、计算工具有较高的要求,并且由于潮汐调和常数存在季节变化,导致利用中、短期验潮资料求算的深度基准面稳定性不高。利用邻近验潮站传算验潮站深度基准面在海洋测绘中经常涉及,对各种传算方法的数学模型进行了分析,认为其实质均为"潮差比法"传算深度基准面,并对"潮差比法"确定深度基准面提出了改进的建议。  相似文献   

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