求解弹性波方程的辛RKN格式   总被引：2，自引：2，他引：0       下载免费PDF全文

刘少林  李小凡  汪文帅  朱童 《地球物理学报》2015,58(4):1355-1366

将弹性波方程变换至Hamilton体系,构造适用于弹性波模拟的高效显式二阶辛Runge-Kutta-Nystrm(RKN)格式,运用根数理论得到此格式的阶条件方程组.通过给定系数的限定条件,得到方程的对称解.为了使时间离散误差达到极小,提出数值频率与真实频率比较,通过Taylor展开,得到关于辛系数的限定方程,求解方程组得到最小频散辛RKN格式.对比分析时间演进方程的稳定性,得到使库朗数达到极大值的限定方程,求解方程组得到最稳定辛RKN格式.发现此两种格式为同一格式.新得到的辛RKN格式不依赖于空间离散方法,为了对比的需要,选取有限差分法进行空间离散.在频散、稳定性分析中,与常见辛格式对比,从理论上分析了本文提出的格式在数值频散压制、稳定性提升等方面的优势,数值实验进一步证实了理论分析的正确性.  相似文献   

VTI介质纯P波混合法正演模拟及稳定性分析   总被引：3，自引：3，他引：0       下载免费PDF全文

杜启振  郭成锋  公绪飞 《地球物理学报》2015,58(4):1290-1304

各向异性介质纯P波方程完全不受横波的干扰,在一定程度上可以减缓由于介质各向异性引起的数值不稳定,本文推导了具有垂直对称轴的横向各向同性(VTI)介质纯P波一阶速度-应力方程.由于纯P波方程存在一个分数形式的伪微分算子,无法直接采用有限差分法求解.针对该问题,本文采用伪谱法和高阶有限差分法联合求解波动方程,重点分析了混合法求解纯P波一阶速度-应力方程的稳定性问题,并给出了混合法求解纯P波方程的稳定性条件.数值模拟结果表明纯P波方程伪谱法和高阶有限差分混合法能够进行复杂介质的正演模拟,在强变速度、变密度的地球介质中仍然具有较好的稳定性.  相似文献   

基于小生境遗传算法软土地基上加筋路堤稳定性分析     

陈昌富  龚晓南 《工程地质学报》2005,13(4):516-520

在软土地基加筋路堤稳定性分析方法中,传统分析方法(如瑞典法和荷兰法)因对加筋材料的加筋作用估计不足,导致计算结果过于保守,与实际不符。本文在充分考虑加筋体的加筋作用下,提出了新的加筋路堤稳定性分析计算方法,并采用小生境遗传算法搜索临界滑动面和最小安全系数。算例计算结果表明,本文提出的加筋路堤稳定性分析方法与工程实际情况吻合较好,并且小生境遗传算法能有效地搜索到边坡所有的临界滑动面。  相似文献   

Comparative analysis of contributing parameters for rainfall-triggered landslides in the Lesser Himalaya of Nepal   总被引：6，自引：0，他引：6  

Ranjan Kumar Dahal  Shuichi Hasegawa  Minoru Yamanaka  Santosh Dhakal  Netra Prakash Bhandary  Ryuichi Yatabe 《Environmental Geology》2009,58(3):567-586

In the Himalaya, people live in widely spread settlements and suffer more from landslides than from any other type of natural disaster. The intense summer monsoons are the main factor in triggering landslides. However, the relations between landslides and slope hydrology have not been a focal topic in Himalayan landslide research. This paper deals with the contributing parameters for the rainfall-triggered landslides which occurred during an extreme monsoon rainfall event on 23 July 2002, in the south-western hills of Kathmandu valley, in the Lesser Himalaya, Nepal. Parameters such as bedrock geology, geomorphology, geotechnical properties of soil, and clay mineralogy are described in this paper. Landslide modeling was performed in SEEP/W and SLOPE/W to understand the relationship of pore water pressure variations in soil layers and to determine the spatial variation of landslide occurrence. Soil characteristics, low angle of internal friction of fines in soil, medium range of soil permeability, presence of clay minerals in soil, bedrock hydrogeology, and human intervention were found to be the main contributing parameters for slope failures in the region.  相似文献   

Parametric studies of disturbed rock slope stability based on finite element limit analysis methods     

《Computers and Geotechnics》2017

This study employs the finite element upper bound and lower bound limit analysis methods to investigate the stability of inhomogeneous rock slopes. The differences in the stability numbers of the upper and lower bound solutions are bracketed within ±10.5% or better, and the stability numbers obtained are presented in rock slope stability charts. These stability charts can provide a convenient tool for preliminary stability designs of inhomogeneous rock slopes. Various recommended blasting damage zones are considered, and disturbance factors are used to represent damage levels. Results showed that rock mass disturbance could significantly influence the evaluation of rock slope stability.  相似文献   

2009年兰州市九州石峡口滑坡成因及其西侧高边坡稳定性研究          下载免费PDF全文

穆鹏  吴玮江  杨涛 《地震工程学报》2010,32(4):343-348

2009年5月16日兰州市九州石峡口小区西侧山体发生滑坡灾害,造成重大生命和财产损失。本文对石峡口滑坡的特征和成因进行了系统研究,认为滑坡区高陡的地形、不合理的绿化灌溉和不良的岩土体工程地质性质是诱发该滑坡的主要因素。在分析石峡口滑坡成因的基础上对与该滑坡相邻的西侧高边坡进行了稳定性研究,采用有限元强度折减法计算出潜在滑面的位置和稳定系数,并和极限平衡法计算结果做比较,结果表明有限元强度折减法与传统极限平衡法计算的稳定性系数很接近,增强了计算结果的可靠性。  相似文献   

冻土区输电线路塔基选位的影响因素分析   总被引：1，自引：0，他引：1  

程东幸  张建民  刘厚健  俞祁浩  刘志伟 《工程地质学报》2009,17(3):329-334

青海西藏500kV直流联网输电线路工程跨越整个青藏高原,其生存环境不可避免与冻土有着紧密联系,冻土特有的冻胀、融沉特性给线路的勘测、设计、施工及后期运营带来了极大挑战。本文对取自青藏高原的原状和重塑冻土样样品进行了物理力学试验。结果表明:同种土在不同含冰量下,随含冰量的增大,则冻融特性敏感性增强;不同性质的土,在含冰量相同的情况下,颗粒越细,则冻融特性越敏感。同时,分析认为:塔基地质环境、不良冻土现象、不同地貌单元、冻土的热稳定性特征及施工作业便捷性等都是影响塔基稳定性的重要因素。  相似文献   

岩盐物理力学性质及其工程稳定性应用现状及其展望          下载免费PDF全文

余冬梅  虎啸天  付江涛  李光莹  胡夏嵩 《盐湖研究》2013,(3):65-72

在分析国内外有关学者关于岩盐的物理力学性质及其工程稳定性应用研究现状基础上,分别从岩盐物理力学性质、岩盐孔隙度、渗透率、塑性变形能力和损伤恢复等物理特性方面,论述了近年来有关岩盐的短期强度特性、岩盐的蠕变性能、围压作用下的力学特性,以及温度效应对岩盐力学特性影响等有关岩盐工程应用中所表现出的物理力学特性;最后从岩盐在工程应用方面,提出了岩盐及其工程应用的发展方向。  相似文献   

Zonal shear flows with a free surface: Hamiltonian formulation and linear and nonlinear stability     

B.K. Shivamoggi  G.J.F. van Heijst 《地球物理与天体物理流体动力学》2013,107(4):293-301

General theoretical results via a Hamiltonian formulation are developed for zonal shear flows with the inclusion of the vortex stretching effect of the deformed free surface (equivalent barotropic model). These results include a generalization of the Flierl–Stern–Whitehead zero angular momentum theorem for localized nonlinear structures (whether or not on a β-plane), and sufficient conditions for linear and nonlinear stability in the Liapunov sense–the latter are given as estimates in terms of an L ²-type perturbation norm which are global in time and are derived via bounds on the equilibrium potential vorticity gradient.  相似文献   

On the nonlinear evolution of columnar vortices in a rotating environment     

P.G. Potylitsin  W.R. Peltier 《地球物理与天体物理流体动力学》2013,107(5):365-391

We examine the three-dimensional, nonlinear evolution of columnar vortices in a rotating environment. As the initial vorticity distribution, a wavetrain of finite amplitude Kelvin-Helmholtz vortices in shear is employed. Through direct numerical simulation of the Navier-Stokes equations we seek to better understand the process of maturation of the various three-dimensional modes of instability to which such vortical flows are subject, especially those which exist as a consequence of the action of the Coriolis force. In the absence of rotational influence, we thereby demonstrate that the nonlinear evolution of columnar vortices is most strongly controlled by one or the other of two mechanisms. One mechanism of instability is identifiable as a so-called elliptical instability, which promotes the initial bending of vortex tubes in a sinusoidal fashion, while the other is a hyperbolic mode, which is responsible for the development of streamwise vortex streaks in the "braids" between adjacent vortex cores. In the rotating case, anticyclonic vortices are strongly destabilized by weak background rotation, while rapid rotation stabilizes both the cyclones and anticyclones. The strong anticyclones are subject to two distinct forms of instability, namely a Coriolis force modified elliptical instability and an inertial (centrifugal) instability. The former instability is very similar to the nonrotating form of the elliptical instability as it promotes bending of vortex tubes, while the latter instability grows on the edge of the vortex core and generates streaks of vorticity, which surround the vortex core itself. These results of direct numerical simulation fully verify the results of previous linear stability analyses. Taken together, they provide a simple explanation for the broken symmetry that is often observed to be characteristic of the von Karman vortex streets that develop in the atmospheric lee of oceanic islands.  相似文献