倾斜荷载作用下层状非均质地基的极限承载力   总被引：1，自引：0，他引：1  

袁凡凡  栾茂田  闫澍旺  林源 《岩土力学》2004,25(Z2):564-567

通过一定的室内模型试验对倾斜荷载作用下层状非均匀地基的极限承载力进行了试验研究.引入荷载倾斜影响系数,对于层状非均质地基的极限承载力计算公式进行了修正,给出了倾斜荷载作用下的地基极限承载力计算公式.根据模型试验结果,对所建立的计算公式进行验证.结果表明,对于倾斜荷载作用下的层状非均匀地基,根据修正后的Meyerhof承载力公式所得到的计算结果能够较好地与试验结果吻合.  相似文献   

Elastic wave propagation in a radially anisotropic medium     

A. Boström  M. Johansson  T. Svedberg 《Geophysical Journal International》1994,118(2):401-410

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计算横向非均匀介质体波理论地震图的Maslov渐近法          下载免费PDF全文

朱良保 《地球物理学报》1989,(2)

本文运用Maslov渐近理论编写的二维横向非均匀介质中的理论地震图程序,与其它类型算法作了精确对比,结果表明,在层状介质模型中,本程序的结果无论振幅还是波形对比都与反射率法基本相同。对于二维横向非均匀模型,在射线理论的非奇点处,本算法与射线方法基本一致,在射线理论的奇异点处,Maslov方法消除了射线理论所固有奇点,提高了计算精度。  相似文献   

First-order P-wave ray synthetic seismograms in inhomogeneous weakly anisotropic media     

Ivan P&#;en&#;ík  Véronique Farra 《Geophysical Journal International》2007,170(3):1243-1252

We propose approximate equations for P -wave ray theory Green's function for smooth inhomogeneous weakly anisotropic media. Equations are based on perturbation theory, in which deviations of anisotropy from isotropy are considered to be the first-order quantities. For evaluation of the approximate Green's function, earlier derived first-order ray tracing equations and in this paper derived first-order dynamic ray tracing equations are used.
The first-order ray theory P -wave Green's function for inhomogeneous, weakly anisotropic media of arbitrary symmetry depends, at most, on 15 weak-anisotropy parameters. For anisotropic media of higher-symmetry than monoclinic, all equations involved differ only slightly from the corresponding equations for isotropic media. For vanishing anisotropy, the equations reduce to equations for computation of standard ray theory Green's function for isotropic media. These properties make the proposed approximate Green's function an easy and natural substitute of traditional Green's function for isotropic media.
Numerical tests for configuration and models used in seismic prospecting indicate negligible dependence of accuracy of the approximate Green's function on inhomogeneity of the medium. Accuracy depends more strongly on strength of anisotropy in general and on angular variation of phase velocity due to anisotropy in particular. For example, for anisotropy of about 8 per cent, considered in the examples presented, the relative errors of the geometrical spreading are usually under 1 per cent; for anisotropy of about 20 per cent, however, they may locally reach as much as 20 per cent.  相似文献   

Time-averaged and time-dependent energy-related quantities of harmonic waves in inhomogeneous viscoelastic anisotropic media     

Vlastislav &#;ervený  Ivan P&#;en&#;ík 《Geophysical Journal International》2007,170(3):1253-1261

The energy–flux vector and other energy-related quantities play an important role in various wave propagation problems. In acoustics and seismology, the main attention has been devoted to the time-averaged energy flux of time-harmonic wavefields propagating in non-dissipative, isotropic and anisotropic media. In this paper, we investigate the energy–flux vector and other energy-related quantities of wavefields propagating in inhomogeneous anisotropic viscoelastic media. These quantities satisfy energy-balance equations, which have, as we show, formally different forms for real-valued wavefields with arbitrary time dependence and for time-harmonic wavefields. In case of time-harmonic wavefields, we study both time-averaged and time-dependent constituents of the energy-related quantities. We show that the energy-balance equations for time-harmonic wavefields can be obtained in two different ways. First, using real-valued wavefields satisfying the real-valued equation of motion and stress–strain relation. Second, using complex-valued wavefields satisfying the complex-valued equation of motion and stress–strain relation. The former approach yields simple results only for particularly simple viscoelastic models, such as the Kelvin–Voigt model. The latter approach is considerably more general and can be applied to viscoelastic models of unrestricted anisotropy and viscoelasticity. Both approaches, when applied to the Kelvin–Voigt viscoelastic model, yield the same expressions for the time-averaged and time-dependent constituents of all energy-related quantities and the same energy-balance equations. This indicates that the approach based on complex-valued representation of the wavefield may be used for time harmonic waves quite universally. This study also shows importance of joint consideration of time-averaged and time-dependent constituents of the energy-related quantities in some applications.  相似文献   

滇西实验场及邻区前兆群体异常与成组中强震的关系     

杨芬  金明培  赵家本 《中国地震》2007,23(2):175-183

本文使用前兆群体异常信息提取的方法,即应用前兆群体非均匀度ID和前兆综合信息量S数学分析,以及相关计算软件,对滇西地震预报实验场及邻区(N24～28°,E98～102°)的断层形变和地下流体各种监测手段的多台项观测资料进行了系统计算分析。研究结果表明:多台多测项前兆群体异常的映震效果优于多台单测项前兆群体异常的应震效果;前兆群体异常与中强地震的对应关系较好,且一组前兆群体异常一般会对应2次以上中强地震,显示了前兆群体异常与地震成组对应关系,而不是以往单次前兆与单个地震一一对应关系。  相似文献   

A note on dynamic ray tracing in ray-centered coordinates in anisotropic inhomogeneous media   总被引：1，自引：0，他引：1  

V. Červený 《Studia Geophysica et Geodaetica》2007,51(3):411-422

Dynamic ray tracing plays an important role in paraxial ray methods. In this paper, dynamic ray tracing systems for inhomogeneous anisotropic media, consisting of four linear ordinary differential equations of the first order along the reference ray, are studied. The main attention is devoted to systems expressed in a particularly simple choice of ray-centered coordinates, here referred to as the standard ray-centered coordinates, and in wavefront orthonormal coordinates. These two systems, known from the literature, were derived independently and were given in different forms. In this paper it is proved that both systems are fully equivalent. Consequently, the dynamic ray tracing system, consisting of four equations in wavefront orthonormal coordinates, can also be used if we work in ray-centered coordinates, and vice versa. vcerveny@seis.karlov.mff.cuni.cz  相似文献   

RANDOM SEISMIC RESPONSES OF MULTI-SUPPORT STRUCTURES IN EVOLUTIONARY INHOMOGENEOUS RANDOM FIELDS     

JIAHAO LIN  JIANJUN LI  WENSHOU ZHANG  F. W. WILLIAMS 《地震工程与结构动力学》1997,26(1):135-145

An efficient approach is proposed for analysing the non-stationary random responses of complex structures located in an evolutionary inhomogeneous stochastic field. The approach is a kind of complete CQC method because the cross-correlation terms both between the participant modes and between the ground joint excitations are included in the response calculations. The effect of the loss of coherency between ground joints is also taken into account. For non-proportionally damped structures with many degrees of freedom, the order of the equations of motion can be reduced by using only real modes while structural non-stationary random responses can still be computed conveniently and accurately. © 1997 by John Wiley & Sons, Ltd.  相似文献   

复合加载情况下非均质地基上条形基础的极限承载力研究     

张其一  栾茂田 《岩土力学》2009,30(5):1281-1286

复合加载情况下精确求解非均质地基上条形基础的极限承载力以及评价影响极限承载力的相关因素,具有很强的工程实用与理论参考价值。基于极限平衡原理,在Mohr-Coulomb破坏准则的基础上,将非均质地基上条形基础极限承载力问题等价为一个边界待定的泛函极值问题。利用变分原理得到与平衡方程相等价的积分约束条件以及相应的欧拉方程与横截条件。引入问题边界条件,利用VC++6.0编制了数值计算程序,求得了复合加载情况下非均质地基破坏时的滑裂面函数与破坏包络曲线。从理论上研究了土体内摩擦角、土体黏聚力、土层强度比与地下水位变化等因素对地基破坏包络曲线的影响。研究结果表明,其解答是地基极限承载力真实解的某一最小上限。  相似文献   

地震大形势预测方法的预测效能与应用研究     

李志雄  陶本藻  吴婷  路鹏  李圣强  江在森  杨林章  泽仁志玛  赵晓燕 《地震》2007,27(2):17-29

采用地震非均匀度(GL值)预测方法, 在震例回朔性检验研究、 室内岩石破裂实验及GPS观测结果等三种途径对该方法预测效能进行评价研究的基础上, 开展对中国大陆未来1～3年强地震活动主体地区和危险性预测工作。 效能评价结果表明, 地震非均匀度(GL值)可以较好地刻画岩石失稳前因破裂成核导致的声发射活动在时间分布上的状态变化, 这种状态变化可能与强地震孕育进入末期、 强地震即将发生有关。 地震非均匀度时空扫描结果表明, 未来1～3年中国大陆强地震活动主体地区将集中在青藏块体中北部及新疆南天山地区, 上述区域在未来一个时期发生多次6.5级乃至7级以上地震的可能性较大。  相似文献