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排序方式： 共有1572条查询结果，搜索用时 31 毫秒
991.
Mahdi Taiebat Boris Jeremić Yannis F. Dafalias Amir M. Kaynia Zhao Cheng 《Soil Dynamics and Earthquake Engineering》2010
To predict the earthquake response of saturated porous media it is essential to correctly simulate the generation, redistribution, and dissipation of excess pore water pressure during and after earthquake shaking. To this end, a reliable numerical tool requires a dynamic, fully coupled formulation for solid–fluid interaction and a versatile constitutive model. Presented in this paper is a 3D finite element framework that has been developed and utilized for this purpose. The framework employs fully coupled dynamic field equations with a u–p–U formulation for simulation of pore fluid and solid skeleton interaction and a SANISAND constitutive model for response of solid skeleton. After a detailed verification and validation of the formulation and implementation of the developed numerical tool, it is employed in the seismic response of saturated porous media. The study includes examination of the mechanism of propagation of the earthquake-induced shear waves and liquefaction phenomenon in uniform and layered profiles of saturated sand deposits. 相似文献
992.
爆炸应力波作用下分支裂纹动态力学特性试验 总被引：1，自引：0，他引：1
应用爆炸加载的透射式动焦散线测试系统,分析了平板中预制贯通裂纹在爆炸应力波作用下端部衍生分支裂纹及爆炸主裂纹的扩展规律。预制贯通裂纹面在压缩应力波及反射拉伸波作用下表现出明显的张开和闭合交替变化,预制贯通裂纹减弱了爆炸主裂纹的动态扩展行为,爆炸主裂纹难以穿过预制贯通裂纹继续扩展。分支裂纹是爆炸应力波在预制贯通裂纹端部衍射效应形成应力集中而衍生、起裂、扩展,其开裂角与预制贯通裂纹、爆炸应力波入射角密切相关,分支裂纹尖端沿着最大能量释放率方向起裂,逐渐平行于最大主应力的方向稳定扩展,中后期扩展多表现为复合型断裂。爆炸分支裂纹的动态应力强度因子、扩展速度低于爆炸主裂纹,获得了分支裂纹起裂韧度为0.50～0.65 MN/m3/2、止裂韧度为0.25～0.35 MN/m3/2。 相似文献
993.
考虑地应力作用下节理扩展引起的煤岩物理力学性质改变,进而导致煤层应力、变形的重新分布,给出了煤岩单元节理扩展的计算方法,并分析了节理扩展与应力的相互作用关系。应用小波神经网络方法及逐级加载算法,提出节理扩展煤储层应力场的联合反演方法,并对沁水盆地晋城区块煤储层应力场分布规律进行分析。结果表明:晋城区块最大主应力为8～13 MPa,由西北向东南呈逐渐增大趋势;最小主应力为5～9 MPa,应力低值区集中在晋城南部区域。通过对比关键点的现场实测值与模拟计算结果,得知主应力大小与实测值最大误差仅为3%,方位误差小于1.3°,满足工程计算精度要求。利用联合反演分析煤储层应力场,具有计算精度高、速度快、建模简单等优点,适合于软件集成快速计算。 相似文献
994.
995.
996.
基底断层在沉积盖层中传播所形成的褶皱形态难以用平行膝折褶皱理论进行解释,这在于两者的流变学性质有很大差异。Erslev提出了三角剪切断层传播褶皱理论,认为下伏断层的脆性强破裂变形为向上变宽的三角形分布式剪切所调节,三角形顶点固定于断层端点。Hardy和Ford拓展了这一理论并成功地建立数字模拟模型,Allmendinger进一步建立与完善了三角剪切的正演模型与反演方法。通过运动学模型预测结果与天然构造观察和相似模拟实验结果的对比分析,以及通过一系列力学模型对运动学模型的检验,三角剪切断层传播褶皱理论被证实并获得了广泛应用。对前陆盆地、克拉通盆地和走滑盆地的基底卷入型构造与走滑或斜向滑动构造,都可以应用三角剪切断层传播褶皱理论来分析变形样式及其分布特征。该理论可以有效地预测隐伏断层的初始破裂点、断层传播量与发育部位,已成功地应用于工程地质与地震灾害预报等方面。 相似文献
997.
为了准确表征不同角度预制节理岩石在单轴压缩下的变形破坏模式，基于3D打印技术制作了节理模型用于模拟岩体中的结构面，通过水泥砂浆的浇筑得到含不同角度预制节理的岩石试件并进行单轴压缩试验，同时采用数字图像相关技术（DIC）观测、分析试验过程中试件裂纹产生、扩展以及贯通过程。结果表明：随着预制节理从0°增加到90°，试件强度与峰值应变均呈现先降低后升高的变化趋势，0°和45°试件弹性模量相对于完整试件有所降低。基于DIC检测结果，0°、30°、45°及60°试件裂纹皆从预制节理尖端部位起裂，各角度试件的起裂应力与试件强度变化规律一致。各角度试样起裂时在剪应力控制下以剪切翼型裂纹形式起裂，0°与45°试件裂纹在扩展过程由剪切发展为张拉型裂纹，30°和60°试件以剪切裂纹形式贯穿始终，90°试件从底部起裂并最终表现为张拉破坏。研究还发现，下翼起裂角θ2和上翼起裂角θ1之间存在明显的线性正相关关系，关系式为θ2 =0.828 6θ1 +12.185，且起裂应力大小变化与峰值应力变化一致，皆随节理角度的增加先减小后增大。 相似文献
998.
In this paper, a novel semi-analytical method, called Decoupled Equations Method (DEM), is presented for modeling of elastic wave propagation in the semi-infinite two-dimensional (2D) media which are involved surface topography. In the DEM, only the boundaries of the problem are discretized by specific subparametric elements, in which special shape functions as well as higher-order Chebyshev mapping functions are implemented. For the shape functions, Kronecker Delta property is satisfied for displacement function. Moreover, the first derivatives of displacement function with respect to the tangential coordinates on the boundaries are assigned to zero at any given node. Employing the weighted residual method and using Clenshaw–Curtis numerical integration, coefficient matrices of the system of equations are transformed into diagonal ones, which leads to a set of decoupled partial differential equations. To evaluate the accuracy of the DEM in the solution of scattering problem of plane waves, cylindrical topographical features of arbitrary shapes are solved. The obtained results present excellent agreement with the analytical solutions and the results from other numerical methods. 相似文献
999.
Maurizio Mazzoleni Francesco Dottori Luigia Brandimarte Shewandagn Tekle Mario L. V. Martina 《水文科学杂志》2017,62(6):892-910
The reliability of a levee system is a crucial factor in flood risk management. In this study we present a probabilistic methodology to assess the effects of levee cover strength on levee failure probability, triggering time, flood propagation and consequent impacts on population and assets. A method for determining fragility curves is used in combination with the results of a one-dimensional hydrodynamic model to estimate the conditional probability of levee failure in each river section. Then, a levee breach model is applied to calculate the possible flood hydrographs, and for each breach scenario a two-dimensional hydrodynamic model is used to estimate flood hazard (flood extent and timing, maximum water depths) and flood impacts (economic damage and affected population) in the areas at risk along the river reach. We show an application for levee overtopping and different flood scenarios for a 98 km reach of the lower Po River in Italy. The results show how different design solutions for the levee cover can influence the probability of levee failure and the consequent flood scenarios. In particular, good grass cover strength can significantly delay levee failure and reduce maximum flood depths in the flood-prone areas, thus helping the implementation of flood risk management actions.
EDITOR D. KoutsoyiannisASSOCIATE EDITOR A. Viglione 相似文献
1000.
Morteza Eskandari‐Ghadi Ammar Mirzapour Azizollah Ardeshir‐Behrestaghi 《国际地质力学数值与分析法杂志》2011,35(14):1587-1603
In this paper, forced rocking vibration of a rigid circular disc placed in a transversely isotropic full‐space, where the axis of material symmetry of the full‐space is normal to the surface of the plate, is analytically investigated. Because of using the Fourier series and Hankel integral transforms, the mixed boundary‐value problem is transformed into two separate pairs of integral equations called dual integral equations. The dual integral equations involved in this paper are reduced to Fredholm integral equations of the second kind. With the aid of contour integration, the governing integral equation is numerically evaluated in the general dynamic case. The reduced static case of the dual integral equations is solved analytically and the vertical displacement, the contact pressure and the static impedance/compliance function are explicitly determined, and it is shown that the pressure in between the plate and the full‐space and the compliance function reduced for isotropic half‐space are identical to the previously published solutions. The dynamic contact pressure in between the disc and the space and also the related impedance function are numerically evaluated in general dynamic case and illustrated. It is shown that the singularity exists in the contact pressure at the edge of the disc is the same as the static case. To show the effect of material anisotropy, the numerical evaluations are given for some different transversely isotropic materials and compared. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献