Analytical modelling of a large‐scale dynamic testing facility     

P. Ceresa  F. Brezzi  G. M. Calvi  R. Pinho 《地震工程与结构动力学》2012,41(2):255-277

An analytical model, which aims at reproducing the response of a large‐scale dynamic testing facility, that is a system composed of the specimen/shaking table/reaction‐mass/airbags/dampers/soil is developed. The Lagrangian of the system is derived, under the assumption of large displacements and rotations. A set of four nonlinear differential equations is obtained and solved with numerical methods. Preliminary verifications of the derived model are carried out by reproducing both well‐known results in the literature as well as those of a lumped model employed in the design of an existing dynamic testing facility. The case‐study for validating the nonlinear equations of motion is the shaking table of the EUCENTRE Laboratory. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

重力时序变化系统稳定性的研究     

郭树松  祝意青 《大地测量与地球动力学》2011,31(5):61-64

把重力时序系统视为慢时变系统,根据线性系统分析的理论方法,用差分方程描述该系统的等价参数模型, 通过判断参数序列的稳定性来探索前兆异常。对河西流动重力观测网1994—2009年3个测点的观测数据的计算分析验证了该方法的有效性,但失稳与地震前兆的关系还需进一步研究。  相似文献   

层状非饱和土地基的轴对称稳态动力响应     

徐明江  魏德敏  何春保 《岩土力学》2011,32(4):1113-1118

考虑土颗粒、孔隙流体的压缩性及各相物质间的黏性、惯性耦合作用,采用理论上更加严谨的饱和度本构关系式,建立了非饱和土的动力控制方程。该组方程与饱和土的经典Biot波动方程完全兼容,因此,具有更广泛的适用性。通过引入一组状态向量,在圆柱坐标系下将非饱和土满足的波动方程转化为状态方程组,利用Hankel变换,求解状态方程组,得到了传递矩阵。结合边界条件及层间接触连续条件,求解了层状非饱和地基的稳态动力响应问题。数值算例表明：土层对地表动位移的影响主要集中在临界深度范围内;软硬土层的相对次序对地表动位移幅值有显著影响;饱和度增大会引起土的物理参数发生相应的改变,尤其是动剪切模量通常降幅较大,而动剪切模量是决定位移幅值的关键因素,最终的结果是导致地表动位移幅值明显增大。  相似文献   

A SANISAND model with anisotropic elasticity     

Ali Lashkari 《Soil Dynamics and Earthquake Engineering》2010

Numerous experimental studies indicate that as a result of shear stress, the elastic behavior of granular media becomes both non-linear and anisotropic. This paper presents a simple constitutive model for sands with respect to anisotropic elasticity. To this aim, using the concept of second order fabric tensor, a simplified elasticity theory is presented which is capable of considering the effect of induced anisotropy on the elastic response. SANISAND is the name used for a family of simple anisotropic sand models developed in the framework of critical state soil mechanics and bounding surface plasticity. An existing SANISAND model is modified in order to include the proposed anisotropic elasticity. The modified model simulations are compared with those obtained from the other members of this family. It is shown that considering anisotropic elasticity can take part in explanation of drastic loss of mean principal stress when sand is subjected to reverse loading in dilative branch of behavior and as a result, improve the liquefaction simulations.  相似文献   

Well-balanced high-order centered schemes on unstructured meshes for shallow water equations with fixed and mobile bed     

Alberto Canestrelli  Michael Dumbser  Annunziato Siviglia  Eleuterio F. Toro 《Advances in water resources》2010

In this paper, we study the numerical approximation of the two-dimensional morphodynamic model governed by the shallow water equations and bed-load transport following a coupled solution strategy. The resulting system of governing equations contains non-conservative products and it is solved simultaneously within each time step. The numerical solution is obtained using a new high-order accurate centered scheme of the finite volume type on unstructured meshes, which is an extension of the one-dimensional PRICE-C scheme recently proposed in Canestrelli et al. (2009) [5]. The resulting first-order accurate centered method is then extended to high order of accuracy in space via a high order WENO reconstruction technique and in time via a local continuous space–time Galerkin predictor method. The scheme is applied to the shallow water equations and the well-balanced properties of the method are investigated. Finally, we apply the new scheme to different test cases with both fixed and movable bed. An attractive future of the proposed method is that it is particularly suitable for engineering applications since it allows practitioners to adopt the most suitable sediment transport formula which better fits the field data.  相似文献   

Numerical modelling of coupled surface and subsurface flow systems     

Prince Chidyagwai  Beatrice Rivière 《Advances in water resources》2010

This paper presents and compares several numerical solutions of the coupled system of Navier–Stokes and Darcy equations. The schemes are based on combinations of the finite element method and the discontinuous Galerkin method. Accuracy and robustness of the methods are investigated for heterogeneous porous media. The importance of local mass conservation for filtration problems is also discussed.  相似文献   

断层防水煤柱可靠度分析   总被引：3，自引：3，他引：0  

杜文堂 《煤田地质与勘探》2001,29(1):34-36

为了合理设计防水煤岩柱的宽度,使用了可靠度分析的“JC”方法,分析了水压力、煤层抗张强度及突水系数的不确定性,建立了防水煤柱可靠度分析的极限状态方程。并计算了与防水煤柱有关的可靠度指标、失效概率和安全系数。参考其它事故的死亡率,防水煤柱的失效概率为1× 10 -5~1× 10 -6比较合适。   相似文献   

泥石流的二维数学模型   总被引：5，自引：2，他引：3  

王纯祥  白世伟  江崎哲郎  三谷泰浩 《岩土力学》2007,28(6):1237-1241

泥石流是在重力作用下,由砂粒石块和水等组成的固液混合物,是一种发生于山区的复杂的地质灾害现象。泥石流主要是由暴雨诱发引起的,它沿着复杂的三维地形高速流动,具有流体流动的特性。为了模拟泥石流的运动规律,预测降雨诱发的泥石流的到达距离和泛滥范围,减少和避免泥石流引起的灾害,把泥石和雨水组成的固液混合物假定为遵循均匀、连续、不可压缩的、非定常的牛顿流体运动规律。基于质量守恒方程和Naiver-stokes方程,采用深度积分方法,推导出了一个模拟泥石流运动的二维数学模型。所有方程式可用有限差分法来求解。结合GIS,该模型可用于预测泥石流的流动距离和泛滥范围,以及泛滥范围内的危险房屋和路段,也可以用于泥石流灾害的风险性分析。  相似文献   

基于免疫遗传算法解算GPS病态方程     

屈利娜  任超  许本意  刘源璋  王浩宇 《海洋测绘》2011,31(5):9-11

介绍了利用免疫遗传算法解决GPS快速动态定位中法矩阵的病态问题,将其求解问题转化成一个函数优化问题。在遗传算法中加入免疫因子,使在抗体的选择过程中避免了退化现象的发生,提高了算法的整体性能。理论分析和算例结果表明,方法能够有效提高定位效率。  相似文献   

Symbolic analytical solution of N‐dimensional radially symmetric polytropes     

A. S. Saad 《Astronomische Nachrichten》2004,325(9):733-739

In this paper, accelerated power series solutions are developed for N‐dimensional symmetric radially polytropes. The solutions are valid for any geometric and polytropic index. The implementation of Padé technique and changing of the independent variable give us identical polytrope solutions to the numerical one. Physical parameters are presented for Ndimensional radially polytropes. In case of the isothermal sphere, the density profile is accurate to 10^–5 per cent whatever the value of ξ is. All the computations are performed using Mathematica software. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献