Ring foundation on elastic subgrade: an analytical solution for computer modelling using the Lagrangian multiplier method          下载免费PDF全文

Shahin Nayyeri  Masood Hajali  Caesar Abi Shdid 《国际地质力学数值与分析法杂志》2016,40(14):2017-2030

In the practice of geotechnical engineering, the case of a ring footing carrying a set of concentrated point loads is a common problem. At times, the induced vertical and angular displacements for the ring footing need to be evaluated at a relatively precise level. By making use of the governing set of equations derived for the case of a general curved beam, expressions that can be easily implemented in modern computing software are derived for the vertical and angular displacements of a ring footing of rectangular cross section as functions of the radial position. The loading case considered is a vertical point load, and the soil is modelled as elastic. Estimates of the displacements have been shown for a common range of practical applications. The behaviour for a set of concentrated loads may be evaluated using the derived equations through direct superposition. Nonlinear finite element analysis is used to evaluate the vertical deflection and angular twist of the ring foundation. Numerical analysis performed for three ring foundations with different radii and cross sections is reported to validate the accuracy of the derived analytical solution. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

The Fourier Integral Method: An efficient spectral method for simulation of random fields   总被引：4，自引：0，他引：4  

E. Pardo-Igúzquiza  M. Chica-Olmo 《Mathematical Geology》1993,25(2):177-217

The Fourier Integral Method (FIM) of spectral simulation, adapted to generate realizations of a random function in one, two, or three dimensions, is shown to be an efficient technique of non-conditional geostatistical simulation. The main contribution is the use of the fast Fourier transform for both numerical calculus of the density spectral function and as generator of random finite multidimensional sequences with imposed covariance. Results obtained with the FIM are compared with those obtained by other classic methods: Shinozuka and Jan Method in 1D and Turning Bands Method in 2D and 3D, the points for and against different methodologies are discussed. Moreover, with the FIM the simulation of nested structures, one of which can be a nugget effect and the simulation of both zonal and geometric anisotropy is straightforward. All steps taken to implement the FIM methodology are discussed.  相似文献   

Distribution and migration of pesticide residues in mosquito control impoundments St. Lucie County, Florida, USA     

R. W. Parkinson  T. C. Wang  J. R. White  J. R. David  M. E. Hoffman 《Environmental Geology》1993,22(1):26-32

This project was designed to: (1) document the distribution and migration of organochlorine pesticide residues within marsh substrates of 18 St. Lucie County mosquito control impoundments located along the Indian River Lagoon estuary, and (2) evaluate the impact of water management techniques on residue mobility. Our results indicate that detectible concentrations of organochlorine compounds, applied between the late 1940s and early 1950s, are present in 16 of the 18 St. Lucie County mosquito control impoundments. These compounds are primarily restricted to the surficial, organic-rich wetland sediment, which, based upon geotechnical analysis, was exposed to the atmosphere at a time when the impoundments were subjected to pesticide treatment. Contaminated sediments are present below the surficial, organic-rich layer, suggesting that some vertical migration of pesticides has occurred. It is unlikely that leaching associated with the downward percolation of impounded water was responsible for this migration as pesticide residues were never detected within thein situ pore waters. An alternative explanation is that biological processes (e.g., rooting, burrowing) facilitated the downward flux of organochlorine compounds into sediment horizons not subjected to direct treatment. Eighty-eight surface water samples obtained from two impoundments subjected to contrasting water management techniques were analyzed for pesticide content. None of the surficial water samples collected in association with these impoundments contained detectible concentrations of organochlorine compounds. These samples were unfiltered and contained as much as 25 mg/1 of particulate organic matter. This suggests that the currently preferred management technique (RIM), which is designed to maintain water quality, limit mosquito production, and provide for ecological continuity, does not hydraulically mobilize pesticide residues into the Indian River Lagoon estuary.  相似文献   

纵观近代岩矿测试分析技术   总被引：1，自引：0，他引：1  

祖振杰  叶松 《地学前缘》1994,(Z1)

本文就近代岩矿测试分析技术作了较为全面的介绍。文章指出，地矿部从８０年代起，由于引进了大批现代先进仪器设备，使岩矿测试分析技术出现了崭新面貌，形成为多学科相结合的新格局，从而促进地质科学在理论上和实践上均取得显著进步，在某些学科领域已发生了根本性变化，并为地质或其它市场提供了大量信息，为促进科技成果转化为生产力作出了巨大贡献。纵观近代岩矿测试分析技术，文章提出了多机联用、整体分析和拓宽测试分析领域的建议，以更好地为祖国经济主战场服务。  相似文献   

利用SPACE LAB彩色红外影像及数据复合技术对藏北牧草资源进行计算机分类的研究     

舒宁  关泽群 《遥感学报》1990,(1)

本文就在藏北草资源调查中,应用空间实验室量测摄影机(MC)摄得的彩色红外影像,及根据遥感影像目视判读所利用的信息空间特点和草场分类原理进行计算机自动分类的理论与方法,对利用辅助数据和影像数据复合技术的几种尝试进行了讨论,并依实地调查资料和专家判读结果对各种分类结果进行了评价。说明利用这种航天遥感资料,辅以Landsat影像生物量指标、DTM和坡度、坡向数据以及计算机自动分类技术,进行资源调查是可行的,可以达到最佳效果。  相似文献   

数值天气预报中的两类反问题及一种数值解法──理想试验   总被引：14，自引：5，他引：14  

郜吉东  丑纪范 《气象学报》1994,52(2):129-137

针对数值预报中产生误差的两个来源提出了数值预报中存在着两类反问题。并在一维的非线性平流扩散方程上，用共轭方程的解法对提出的两类反问题作出了理想场的数值试验。试验结果表明，这种解反问题的方法非常有效。它利用＂观测资料＂所包含的时间演变的信息确定出了方程的初值或方程中误差订正项的空间分布状况。而且无论对＂观测资料＂的超定还是欠定都能得出较有意义的结果。因而有很大的利用前景。  相似文献   

A review of methods used to determine the fractal dimension of linear features   总被引：7，自引：0，他引：7  

Brian Klinkenberg 《Mathematical Geology》1994,26(1):23-46

An in-depth review of the more commonly applied methods used in the determination of the fractal dimension of one-dimensional curves is presented. Many often conflicting opinions about the different methods have been collected and are contrasted with each other. In addition, several little known but potentially useful techniques are also reviewed. General recommendations which should be considered whenever applying any method are made.  相似文献   

Tunnel blasting techniques in difficult ground conditions   总被引：1，自引：0，他引：1  

A. K. Chakraborty  J. L. Jethwa 《Geotechnical and Geological Engineering》1994,12(4):219-239

Summary The quality of tunnelling can be improved by proper blast design which takes into account the rock mass conditions. The effects of different rock mass properties on tunnel blast performance need to be assessed. The strength of the formation and joint orientation critically affected fragmentation and overbreak in a model study of blasting. Similar effects were noted in situ when the performance of a blast pattern in different rock mass conditions in the Tandsi inclines (Bihar, India) were analysed. Accordingly, the on-going blast pattern was modified for the poor ground conditions prevailing in the rest of the inclines. Improved fragmentation and smooth profile were obtained as a result; the rate of drivage improved considerably and the cost of excavation was reduced. Based on the observations in the model studies and the investigations at Tandsi, some guidelines for optimum blast design in difficult ground conditions are suggested.  相似文献   

Comparison of taxon calibrations,modern analogue techniques,and forest-stand simulation models for the quantitative reconstruction of past vegetation: A critique     

Allen M. Solomon 《地球表面变化过程与地形》1986,11(6):681-685

Taxon calibrations based on eastern North America or on the southeastern United States alone suggest a different forest composition from that based on Wisconsin/Michigan, which is argued as preferable. Questions are raised about how well comparison with modern analogues distinguishes forest characteristics. The simulation model used by Delcourt and Delcourt is thought to be inappropriate, partly because it is constrained by faulty climatic data. Models are seen as complementary to other techniques rather than as an alternative methodology.  相似文献   

微机图形开发与动画制作技术在波动仿真中的应用     

吴宝国 《华南地震》1995,15(1):43-48

波动的图形仿真技术的正问题和反问题的解决有着极为重要的意义，目前这项技术在地震工程界应用得还非常少，本文简要介绍了作为波动图形仿真基础的计算机图形学和动画制作的基本概念以及常用方法，这些概念及方法有助于工程界人士方便地掌握绘制图形与制作动画的要领。  相似文献