两相饱和介质中的集中力点源位移场解与应用

通过两相饱和介质Ｂｉｏｔ方程变换,利用势场分解较好地解决了饱和两相介质中Ｐ１和Ｐ２波的耦合问题．再由Ｐｏｉｓｓｏｎ方程和Ｈｅｌｍｈｏｔｚ方程的特性,求解得到两相饱和介质在集中力点源作用下的位移场Ｇｒｅｅｎ函数,进而通过阶跃函数和Ｆｏｕｒｉｅｒ逆变换,求得两相介质在集中力．作用下的波场．由上述结果,根据扩容进水模型,合理地解释了孕震前各主要阶段在地震记录中垂直向振幅与振幅比统计值的变化．最后结合工作实例,利用两相介质波场理论求得由一般弹性介质理论不易求得的骨架固体力学参数．     

两相饱和介质中的集中力点源位移场解与应用

通过两相饱和介质Ｂｉｏｔ方程变换,利用势场分解较好地解决了饱和两相介质中Ｐ１和Ｐ２波的耦合问题．再由Ｐｏｉｓｓｏｎ方程和Ｈｅｌｍｈｏｔｚ方程的特性,求解得到两相饱和介质在集中力点源作用下的位移场Ｇｒｅｅｎ函数,进而通过阶跃函数和Ｆｏｕｒｉｅｒ逆变换,求得两相介质在集中力．作用下的波场．由上述结果,根据扩容进水模型,合理地解释了孕震前各主要阶段在地震记录中垂直向振幅与振幅比统计值的变化．最后结合工作实例,利用两相介质波场理论求得由一般弹性介质理论不易求得的骨架固体力学参数．     

二维土坝的两相动力分析

提出了一种分析饱和土坝动力反应的方法,考虑了土坝的两相介质特性,在固液耦联动力方程的基础上,选取固相位移,液相位移、孔隙水压作为场变量,采用伽辽金加权残数法进行有限元空间离散化,然后在时域上采用Ｗｉｌｓｏｎ－θ法进行逐步积分。该方法不仅能计算出固相位移和液相位移,而且能直接得到孔隙水压的反应过程。文中以一饱和土坝模型进行算例分析,并与将其作为单相介质时的结果进行了比较。该法可用于分析饱和介质的地震     

二维饱和孔隙介质的三场有限元方法

根据流固两相混合物连续介质力学理论,采用伽辽金加权残值法,选取固相位移,液相位移,孔隙不压作为场变量,对固液两相耦联方程进行有限元离散化,得到解耦方程组。然后在时域上采用Ｗｉｓｏｎ－θ进行了逐步积分,得到一种分析二维饱和孔隙介质地震反应的三场有限元方法。     

关于两相饱和介质中流相Green函数的解析解

自然界中许多动力学问题需要用两相饱和介质Green函数求得解答,本文在两相饱和介质位移场Green函数解答的基础上,求得的有关饱和流体孔隙压力,进、排流体流量等三个Green函数.从而使两相饱和介质涉及流体问题的Lamb方程能完整地使用.论文在推导过程中详细地阐述了流体三个Green函数的物理意义,并将所得结果与Chen（1994）的纯数学的结果作了对比.最后文章讨论了解析解的稳定性.     

二维非均匀饱和土体的地震反应分析

将饱和土体视为由弹性骨架和不可压缩流体组成的两相孔隙介质,取固相位移,液相位移,孔隙水压力为场变量。从两相孔介质的动力耦合微分方程出发,利用伽辽金原理和Ｗｉｌｓｏｎ－θ法导出了三场有限元积分方法,该方法可进行二维非均匀饱和土体的地震反应分析,文中通过算例讨论了非均匀饱和土体地震反应的一些特征。     

流体饱和多孔隙介质弹性波方程边界元解法研究

基于流体饱和多孔隙各向同性介质模型,本文首先推导了流体饱和多孔隙介质中弹性波传播的频率域系统动力方程及边界积分方程,然后给出了流体饱和多孔隙介质弹性波方程的基本解,最后,利用本文给出的边界元方法对流体饱和多孔隙各向同性介质中的弹性波传播进行了数值模拟.结果表明：不论是从固相位移,还是液相位移的地震合成记录都能看到明显的慢速P波,本文提出的流体饱和多孔隙介质弹性波边界元法是有效可行的.     

层状饱水软土地基三维非轴对称动力响应分析方法

将饱水软土地基视为两相介质、考虑水的渗流和土骨架9变形的耦合作用，用Fourier展开和Hankel积分变换分析三维非称对称饱和弹性土层波动方程，用刚度矩阵方法，建立了层状饱和软土地基三维非轴对称动力响应的解析分析方法。以数值算例对比分析了单相土介质与两相饱和土介质三维非轴对称稳态动力响应，结果表明：在饱水软土地基动力响应分析中应该考虑土体中孔隙流体的影响。     

基于Comsol的饱和多孔介质动力方程的数值模拟及应用

两相饱和多孔介质的动力响应问题在地震工程领域具有重要的研究意义,由于涉及到固相和液相的动力耦合,使得该问题的求解尤为复杂。本文利用Comsol在求解多场耦合问题上的优点,针对Biot饱和多孔介质u-U耦合形式下的波动方程特征,经过一系列微分算子运算和矩阵变换得到导数形式下的波动方程,基于Comsol Multiphysics提供的广义偏微分方程模式对变形后的波动方程进行求解,并把改进后的无限元边界应用到无限域动力问题的模拟中。通过与饱和多孔介质动力响应的解析解进行对比,验证模型求解技术的可行性和正确性,并在此基础上讨论饱和土地基中空沟隔振效果与饱和土体参数孔隙率、泊松比的关系。通过研究分析,可以为饱和土地基中空沟隔振设计提供一些有价值的参考。     

两相饱和介质的弹性位错震源矢量与静态位移场

根据两相饱和介质Biot理论,利用函数与Green函数性质,求得集中力点源作用下的Green函数．通过两相饱和介质场中的Betti定理,对两相饱和介质的弹性位错震源矢量与静态位移场作了全面的探讨．     

地震和波浪作用下表面波条件对海水动水压力的影响

地震动斜入射条件下海洋场地简化为理想流体海水-两相介质海床-弹性固体基岩系统模型,通常假定为静水液面条件。本文以地震动SV波为例,推导了表面波条件下海洋场地动力反应解析解,研究了表面波条件对海水动水压力的影响。研究表明,表面波频率在大于0.5Hz时对海水动水压力几乎无影响,在小于0.5Hz范围内有影响,且越接近水面、频率越低时影响越显著。实际地震动卓越频率通常大于0.5Hz,因而地震动作用下采用忽略表面波条件的静水液面假定是合理的。进一步结合线性波浪理论,研究SV波和波浪联合作用下表面波条件对海水动水压力的影响。研究表明,由于波浪属于低频荷载且频率通常小于0.5Hz,在地震和波浪联合作用下表面波条件的影响较地震单独作用更为显著。     

Combined effect of rheology and confining boundaries on spreading of gravity currents in porous media

One-dimensional flows of gravity currents within horizontal and inclined porous channels are investigated combining theoretical and experimental analysis to evaluate the joint effects of channel shape and fluid rheology. The parameter $\beta$ governs the shape of the channel cross section, while the fluid rheology is characterised by a power-law model with behaviour index n. Self-similar scalings for current length and height are obtained for horizontal and inclined channels when the current volume increases with time as $t^{\alpha }$.For horizontal channels, the interplay of model parameters $\alpha \text{,}n$, and $\beta$ governs the front speed, height, and aspect ratio of the current (ratio between the average height and the length). The dependency is modulated by two critical values of $\alpha \text{,}{\alpha }_{\beta }=n/(n+1)$ and ${\alpha }_n=(2\beta +1)/\beta$. For all channel shapes, ${\alpha }_{\beta }$ discriminates between currents whose height decreases ($\alpha <{\alpha }_{\beta }$) or increases ($\alpha >{\alpha }_{\beta }$) with time at a particular point. For all power-law fluids, ${\alpha }_n$ discriminates between decelerated currents, with time-decreasing aspect ratio ($\alpha <{\alpha }_n$), and accelerated currents, with time-increasing aspect ratio ($\alpha >{\alpha }_n$). Only currents with time-decreasing height ($\alpha <{\alpha }_{\beta }$) and aspect ratio ($\alpha <{\alpha }_n$) respect model assumptions asymptotically; the former constraint is more restrictive than the latter.For inclined channels, a numerical solution in self-similar form is obtained under the hypothesis that the product of the channel inclination $\theta$ and the slope of the free-surface is much smaller than unity; this produces a negligible error for $\theta >2°$, and is acceptable for $\theta >0.5°$. The action of gravity in inclined channels is modulated by both the behaviour index n and the shape factor $\beta$. For constant flux, the current reaches at long times a steady state condition with a uniform thickness profile. In steep channels and for sufficiently long currents, the free-surface slope becomes entirely negligible with respect to channel inclination, and the constant thickness profile depends only on n.Theoretical results are validated by comparison with experiments (i) in horizontal and inclined channels with triangular or semicircular cross-section, (ii) with different shear-thinning fluids, and (iii) for constant volume and constant flux conditions. The experimental results show good agreement with theoretical predictions in the long-time regime.Our analysis demonstrates that self-similar solutions are able to capture the essential long-term behaviour of gravity currents in porous media, accounting for diverse effects such as non-Newtonian rheology, presence of boundaries, and channel inclination. This provides a relatively simple framework for sensitivity analysis, and a convenient benchmark for numerical studies.     

黑龙江镜泊湖火山地区电性结构初步研究

在黑龙江镜泊湖火山地区做了 30个点的大地电磁测深工作。结果表明 :测区为非一维结构 ,中部为二维结构 ,走向为北东向。上下大致可分为 3个电性层 ,电阻率上部为中阻 ,中部为高阻 ,下部为低阻。测区四周电阻率高 ,中部有一个截面不规则的北东向拉长的低阻立式柱状体 ,该柱体的电阻率从上到下也呈“中 -高 -低”形式     

Is fractal dispersion subdiffusive or superdiffusive? A theoretical investigation

A probabilistic approach is used to simulate particle tracking along a fractal path. The particle tracking is modelled as the sum of elementary steps with independent random variables. An exponential distribution is obtained for each elementary step and a Gamma distribution or probability density function is then deduced. The relationship between fractal dispersivity and the elementary step is given. It is theoretically demonstrated that the fractal dispersion is subdiffusive and that the linear dispersion coefficient and the linear dispersivity decrease with the mean travel distance. A review of some fractal models showing an increase of the linear dispersivity is given and an explanation that shows why these models may be not correct is proposed. It is shown that the results presented are in agreement with other studies relating to the application of the fractional calculus to diffusion transport. Lastly, a relation between the fractal dimension and the order of the fractional Langevin equation is proposed. Copyright © 2007 John Wiley & Sons, Ltd.     

Determining anti-plane responses induced by oblique-truncated semicircular canyon using systematic hybrid method with mapping function

This paper proposes a novel strategy for the investigation of displacement amplitude ($\left|u_y\right|$) near and along an oblique-truncated semicircular canyon subjected to shear horizontal (SH) waves. Transfinite interpolation (TFI) was used to obtain the coordinates of nodes and determine the sequence of node numbering in the inner finite region including the canyon. The hybrid method, comprising finite element method and a Lamb series, was applied in conjunction with TFI to study the effects of canyon geometry, incident angle of SH waves ($\theta$), and dimensionless frequency ($\eta$) on $\left|u_y\right|$. We detailed the amplification of $\left|u_y\right|$ in the illuminated zone and variations in $\left|u_y\right|$ due to canyon-decay-effect along the canyon surface as well as the decay of $\left|u_y\right|$ resulting from the shield effect in the shadow zone. Interestingly, oblique-effects play an important role in the magnification of $\left|u_y\right|$ along the inclined bottom of canyons, and variations in $\theta$ and $\eta$ dominate the patterns of $\left|u_y\right|$.     

加卸载响应比的自然概率分布

从Ｇｕｔｅｎｂｅｒｇ－Ｒｉｃｈｔｅｒ的分布关系出发，以应用最多的以√Ｅ为响应量的Ｙ３为例，对模拟生成的满足Ｇ－Ｒ关系和均匀随机分布的事件探讨了加卸载响应比的自然概率分布，同时，还与首都圈地区的一组实际资料得到的自然概率进行了对比分析，结果表明，在样本量有保证的情况下，反映系统临近失稳程度的加卸载响应比Ｙ３的自然概率分布基本稳定，随机出现加卸载响应比高值的自然概率很低，因此，实际观测到的高响应经值确     

基于ABAQUS的真空-堆载联合预压法的仿真研究

利用有限元分析软件ABAQUS在仿真过程中直接模拟真空度,并通过ABAQUS的二次开发平台编写排水板单元子程序,对软土地基的真空-堆载联合预压进行仿真和固结分析,并与真空荷载换算为堆载方法进行对比。结果表明这种仿真模型更接近实际,分析地基变形与实际情况一致;塑料排水板单元子程序合理,可以有效减小分析误差。对天津港某软基的加固工程进行了建模仿真,其结果与实测数据相吻合,在误差允许范围内。通过计算不同泊松比、加固区宽度条件下真空-堆载联合预压的最终沉降量,分析得到了相应泊松比、加固区宽度的沉降修正系数,对类似的工程有一定的指导意义。