Dual simulations of fluid flow and seismic wave propagation in a fractured network: effects of pore pressure on seismic signature   总被引：1，自引：0，他引：1  

S. Vlastos  E. Liu  I. G. Main  M. Schoenberg  C. Narteau  X. Y. Li  B. Maillot 《Geophysical Journal International》2006,166(2):825-838

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Comparison of methods to model the gravitational gradients from topographic data bases   总被引：7，自引：0，他引：7  

Christopher Jekeli  Lizhi Zhu 《Geophysical Journal International》2006,166(3):999-1014

A number of methods have been developed over the last few decades to model the gravitational gradients using digital elevation data. All methods are based on second-order derivatives of the Newtonian mass integral for the gravitational potential. Foremost are algorithms that divide the topographic masses into prisms or more general polyhedra and sum the corresponding gradient contributions. Other methods are designed for computational speed and make use of the fast Fourier transform (FFT), require a regular rectangular grid of data, and yield gradients on the entire grid, but only at constant altitude. We add to these the ordinary numerical integration (in horizontal coordinates) of the gradient integrals. In total we compare two prism, two FFT and two ordinary numerical integration methods using 1" elevation data in two topographic regimes (rough and moderate terrain). Prism methods depend on the type of finite elements that are generated with the elevation data; in particular, alternative triangulations can yield significant differences in the gradients (up to tens of Eötvös). The FFT methods depend on a series development of the topographic heights, requiring terms up to 14th order in rough terrain; and, one popular method has significant bias errors (e.g. 13 Eötvös in the vertical–vertical gradient) embedded in its practical realization. The straightforward numerical integrations, whether on a rectangular or triangulated grid, yield sub-Eötvös differences in the gradients when compared to the other methods (except near the edges of the integration area) and they are as efficient computationally as the finite element methods.  相似文献   

Traction image method for irregular free surface boundaries in finite difference seismic wave simulation   总被引：16，自引：1，他引：16  

Wei Zhang  Xiaofei Chen 《Geophysical Journal International》2006,167(1):337-353

In this study, we propose a new numerical method, named as Traction Image method, to accurately and efficiently implement the traction-free boundary conditions in finite difference simulation in the presence of surface topography. In this algorithm, the computational domain is discretized by boundary-conforming grids, in which the irregular surface is transformed into a 'flat' surface in computational space. Thus, the artefact of staircase approximation to arbitrarily irregular surface can be avoided. Such boundary-conforming gridding is equivalent to a curvilinear coordinate system, in which the first-order partial differential velocity-stress equations are numerically updated by an optimized high-order non-staggered finite difference scheme, that is, DRP/opt MacCormack scheme. To satisfy the free surface boundary conditions, we extend the Stress Image method for planar surface to Traction Image method for arbitrarily irregular surface by antisymmetrically setting the values of normal traction on the grid points above the free surface. This Traction Image method can be efficiently implemented. To validate this new method, we perform numerical tests to several complex models by comparing our results with those computed by other independent accurate methods. Although some of the testing examples have extremely sloped topography, all tested results show an excellent agreement between our results and those from the reference solutions, confirming the validity of our method for modelling seismic waves in the heterogeneous media with arbitrary shape topography. Numerical tests also demonstrate the efficiency of this method. We find about 10 grid points per shortest wavelength is enough to maintain the global accuracy of the simulation. Although the current study is for 2-D P-SV problem, it can be easily extended to 3-D problem.  相似文献   

Redistribution of recent collision push and ridge push in Central Europe: insights from FEM modelling   总被引：2，自引：0，他引：2  

M. Jarosi&#;ski  F. Beekman  G. Bada  S. Cloetingh 《Geophysical Journal International》2006,167(2):860-880

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Effects of mode coupling and location of rotational axis on glacial induced rotational deformation in a laterally heterogeneous viscoelastic earth     

Patrick Wu  Hansheng Wang 《Geophysical Journal International》2006,167(2):853-859

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A traveltime reciprocity discrepancy in the Podvin & Lecomte time3d finite difference algorithm     

Ari Tryggvason  Björn Bergman 《Geophysical Journal International》2006,165(2):432-435

We have found that the extensively used finite difference scheme time3d produces time fields which are 'asymmetric' in the sense that traveltimes computed to the right of the source are faster than traveltimes computed to the left. All finite difference schemes will, as they are approximations to the wave equation, to some extent fail to obey reciprocity perfectly. We show, however, that the errors in time3d may be significant—and unnecessarily large. An asymmetry in the point source initialization has been identified, and after correction time3d produces time fields with an improved reciprocity.  相似文献   

基于有限差分法的抗滑桩计算机辅助设计   总被引：3，自引：0，他引：3  

杨佑发  黄小鹏 《中国地质灾害与防治学报》2006,17(2):95-98

基于地基系数“m-m”法、“m-k”法、“k-k”法的原理,考虑桩顶和桩底边界条件以及桩在滑动面处位移、转角、弯矩和剪力的连续条件,可解得桩身各节点的位移和内力,提出了进行抗滑桩全桩内力计算的有限差分法。根据差分方程并用VB6.0编制了实用的计算程序,既可避免繁琐的查表计算,提高计算速度,又可提高计算精度,直观生动,真正实现了人机交互,在界面的引导下,设计人员可完成全部计算,并绘出内力图形和抗滑桩截面配筋图,使设计更方便快捷,该软件可以极大地提高生产效率,降低工程造价,从而实现抗滑桩的优化设计。最后采用上述方法对某滑坡的悬臂抗滑桩进行了设计与计算。  相似文献   

燕山水库坝基防渗墙优化设计   总被引：1，自引：0，他引：1  

张宜虎  尹红梅  杨裕云  王亮清 《岩土力学》2005,26(7):1161-1164

因现场资料不足或分析手段落后等原因,当前进行水库坝基防渗墙设计,往往存在过于保守的倾向。以河南省燕山水库为例,基于优化设计的思路,采用目前较为成熟的二维有限单元法,对不同防渗条件下的坝基渗流场分别进行了模拟,并将计算所得比降、流量与允许比降、允许流量做了对比,从定量的角度提出了既安全、又经济的防渗方案:防渗墙厚度取0.8m,深度取打入破碎带5m。  相似文献   

三峡深水高土石围堰工程的渗流研究          下载免费PDF全文

戴会超  王玲玲 《水科学进展》2005,16(6):849-852

为了对三峡工程二期高土石围堰防渗设施的布置方案及其阻渗效果进行比较,采用有限元法对二期高土石围堰在不利的运行工况下的渗流场进行数值分析.比较了双排混凝土防渗墙方案、单排塑性混凝土低防渗墙加土工膜斜墙和单排厚塑性混凝土防渗墙等3种方案,分别采用恒定与非恒定模型计算,对立面二维和三维绕渗及防渗墙局部开裂等不利工况分别进行了数值模拟.结果表明:三方案均可有效抑制渗流场,双排混凝土防渗墙的防渗效果最好;墙体的局部开裂仅对局部区域的流场有影响.非恒定数值分析表明,堰体、基础不均匀沙石料及基坑抽水速度对渗流场影响极大,为保证堰体稳定,应限制基坑水位降落速度小于2 m/d.  相似文献   

遗传算法在边坡数值计算中的应用   总被引：4，自引：0，他引：4  

安关峰  殷坤龙等 《地球科学》2002,27(2):177-180

改进了进化方向的遗传算法与有限元数值法，结合并研制了相应的软件。应用该软件对多类型岩土边坡进行弹性模量、内聚力、内摩擦角等参数反演分析，显示误差很小，收敛速度也很快，这说明改进进化方向遗传算法这种新型的优化算法在多类型岩土参数优化估计中具有独特的优势。  相似文献