NUMERICAL SIMULATION OF INUNDATION IN SHENZHEN CITY BY FINTE DIFFERENCE MODEL MIXED WITH 1D AND 2D UNSTEADY FLOW

ＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＯＦＩＮＵＮＤＡＴＩＯＮＩＮＳＨＥＮＺＨＥＮＣＩＴＹＢＹＦＩＮＴＥＤＩＦＦＥＲＥＮＣＥＭＯＤＥＬＭＩＸＥＤＷＩＴＨ１ＤＡＮＤ２ＤＵＮＳＴＥＡＤＹＦＬＯＷ￥ＣＨＥＮＧＸｉａｏｔａｏ；ａｎｄＱＩＵＪｉｎｗｅｉ（Ｓｅｎ...     

THE RIVER CHANNEL ADJUSTMENT AS INFLUENCED BY THE FLOODPLAIN GEOECOSYSTEM： AN EXAMPLE FROM THE HONGSHAN RESERVOIR

ＴＨＥＲＩＶＥＲＣＨＡＮＮＥＬＡＤＪＵＳＴＭＥＮＴＡＳＩＮＦＬＵＥＮＣＥＤＢＹＴＨＥＦＬＯＯＤＰＬＡＩＮＧＥＯＥＣＯＳＹＳＴＥＭ：ＡＮＥＸＡＭＰＬＥＦＲＯＭＴＨＥＨＯＮＧＳＨＡＮＲＥＳＥＲＶＯＩＲ￥ＸＵＪｉｏｎｇｘｉｎ；ＳＨＩＣｈａｎｇｘｉｎｇ（Ｐｒ...     

APPLICATION OF RELIABILITY THEORY TO ASSESS THE INFLUENCE OF STOCHASTIC INPUT PARAMETERS ON DETERMINISTIC SEDIMENT TRANSPORT FORMULAS

ＡＰＰＬＩＣＡＴＩＯＮＯＦＲＥＬＩＡＢＩＬＩＴＹＴＨＥＯＲＹＴＯＡＳＳＥＳＳＴＨＥＩＮＦＬＵＥＮＣＥＯＦＳＴＯＣＨＡＳＴＩＣＩＮＰＵＴＰＡＲＡＭＥＴＥＲＳＯＮＤＥＴＥＲＭＩＮＩＳＴＩＣＳＥＤＩＭＥＮＴＴＲＡＮＳＰＯＲＴＦＯＲＭＵＬＡＳ￥Ｗｉｌｈｅｌｍ...     

SUSTAIN RESERVOIR USEFUL LIFE BY FLUSHING SEDIMENT

ＳＵＳＴＡＩＮＲＥＳＥＲＶＯＩＲＵＳＥＦＵＬＬＩＦＥＢＹＦＬＵＳＨＩＮＧＳＥＤＩＭＥＮＴ￥ＨｓｉｅｈＷｅｎＳｈｅｎａｎｄＪｉｈｎ－ＳｕｎｇＬａｉ（Ｐｒｏｆｅｓｓｏｒ，ＵｎｉｖｅｒｓｉｔｙｏｆＣａｌｉｆｏｒｎｉａａｔＢｅｒｋｅｌｅｙ，Ｄｅｐａｒｔｍｅｎ...     

WATER QUALITY SIMULATION OF HEAVY METAL TRANSPORTATION IN THE YELLOW RIVER

ＷＡＴＥＲＱＵＡＬＩＴＹＳＩＭＵＬＡＴＩＯＮＯＦＨＥＡＶＹＭＥＴＡＬＴＲＡＮＳＰＯＲＴＡＴＩＯＮＩＮＴＨＥＹＥＬＬＯＷＲＩＶＥＲＳＨＥＮＸｉａｎｃｈｅｎ１,ＦＥＮＧＨｕｉｈｕａ２,ＷＡＮＧＦｅｎｇｒｏｎｇ３ａｎｄＬＩＵＬｉｎｈｕａ４ＡＢＳＴＲＡＣＴＡ...     

THE FLUCTUATING CHARACTERISTICS OF HYDRODYNAMIC FORCES ON BED PARTICLE

ＴＨＥＦＬＵＣＴＵＡＴＩＮＧＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳＯＦＨＹＤＲＯＤＹＮＡＭＩＣＦＯＲＣＥＳＯＮＢＥＤＰＡＲＴＩＣＬＥ￥ＷＡＮＧＸｉｎｇｋｕｉａｎｄＡＮＦｅｎｇｌｉｎｇ（ＴｈｅＦｉｎａｎｃｅｗａｓＳｕｐｐｏｒｔｅｄｂｙＮａｔｉｏｎａｌＳｃｉｅｎ...     

EFFECTS OF EXISTENCE OF SEDIMENT PARTICLES ON THE ENERGY LOSS OF FLOW

ＥＦＦＥＣＴＯＦＥＸＩＳＴＥＮＣＥＯＦＳＥＤＩＭＥＮＴＰＡＲＴＩＣＬＥＳＯＮＴＨＥＥＮＥＲＧＹＬＯＳＳＯＦＦＬＯＷ￥ＬＩＵＱｉｎｇｑｕａｎ；ＣＨＥＮＬｉａｎｄＬＩＵＤａｙｏｕ（Ａｓｓｏｃ．ＲｅｓｅａｒｃｈＦｅｌｌｏｗ，ＩｎｓｔｉｔｕｔｅｏｆＭｅｃｈａ...     

Observation and research on ULF and VLF seismo－electromagnetic radiation

ＯｂｓｅｒｖａｔｉｏｎａｎｄｒｅｓｅａｒｃｈｏｎＵＬＦａｎｄＶＬＦｓｅｉｓｍｏ－ｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｒａｄｉａｔｉｏｎＪＩＡ－ＺＨＩＹＵＡＮ（袁家治）；ＫｏｚｏＴａｋａｈａｓｈｉ；ＳＨＵ－ＱＩＮＧＱＩＡＮ（钱书清），ＹｏｋｉｏＦｕｊｉｎａｗ...     

EVOLUTIONAL CHARACTERISTICS OF HYPER－CONCENTRATED FLOW IN BRAIDED CHANNEL OF THE YELLOW RIVER

ＥＶＯＬＵＴＩＯＮＡＬＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳＯＦＨＹＰＥＲ－ＣＯＮＣＥＮＴＲＡＴＥＤＦＬＯＷＩＮＢＲＡＩＤＥＤＣＨＡＮＮＥＬＯＦＴＨＥＹＥＬＬＯＷＲＩＶＥＲ￥ＱＩＰｕ；ＬＩＷｅｎｘｕｅ（Ｓｅｎｉｏｒｅｎｇｉｎｅｅｒ，ＩｎｓｔｉｔｕｔｅｏｆＨｙ...     

STUDY ON THE MATHEMATICAL MODEL OF HEAVY－METAL POLLUTANT TRANSPOPT－TRANSFORMATION IN RIVERS

ＳＴＵＤＹＯＮＴＨＥＭＡＴＨＥＭＡＴＩＣＡＬＭＯＤＥＬＯＦＨＥＡＶＹ－ＭＥＴＡＬＰＯＬＬＵＴＡＮＴＴＲＡＮＳＰＯＰＴ－ＴＲＡＮＳＦＯＲＭＡＴＩＯＮＩＮＲＩＶＥＲＳ￥Ｓｕｉ－ｌｉａｎｇＨｕａｎｇａｎｄＺｈａｏ－ｈｕｉＷａｎ（ＰｏｓｔｄｏｃｔｏｒａｌＦｅ...     

Nonlinear response analyses of a soil–structure interaction system using transformed energy transmitting boundary in the time domain

The energy transmitting boundary used in programs such as FLUSH and ALUSH is a very accurate and useful technique for the earthquake response analysis of soil–structure interaction systems. However, it is applicable only to linear analyses or equivalent linear analyses, because it can be calculated only in the frequency domain. The author has proposed methods for transforming frequency-dependent impedance into the time domain. In this paper, an earthquake response analysis method for a soil–structure interaction system, using the energy transmitting boundary in the time domain, is proposed. First, the transform of the transmitting boundary matrices to the time domain using the methods proposed by the author is studied. Then, linear and nonlinear time history earthquake response analyses using the boundary are performed. Through these studies, the validity and efficiency of the proposed methods are confirmed.     

A local time-domain transmitting boundary for simulating cylindrical elastic wave propagation in infinite media

Finite element simulation of the time-dependent wave propagation in infinite media requires enforcing the transmitting boundary to replace the truncated far-field infinite domain so as to model the effect of the wave radiation towards infinity. This paper proposed a novel local time-domain transmitting boundary for simulating the cylindrical elastic wave radiation problem. This boundary is a mechanical model consisting of the spring, dashpot and mass elements, with the auxiliary degrees of freedom introduced, which is dynamically stable and easily implemented into the commercial finite element codes. Numerical analysis of the cylindrical elastic wave radiation problem indicates that the proposed transmitting boundaries with the order N=3 for cylindrical P and SV waves and with the order N=4 for cylindrical SH wave have very high accuracy, even when the artificial boundary at wave source. The proposed transmitting boundary with order N=0 can be applied approximately to the general two-dimensional infinite elastic wave problems that contain the more complex outgoing wave fields at artificial boundary than the cylindrical waves. The plane-strain Lamb problem is analyzed with the acceptable engineering accuracy achieved. On the other hand, the proposed transmitting boundary with higher order can be a tool to localize the temporal convolution that appears in an exact time-domain transmitting boundary for the general infinite wave problems. This potential applicability is mentioned.     

A high-order time-domain transmitting boundary for cylindrical wave propagation problems in unbounded saturated poroelastic media

Based on the u–p formulation of Biot equation with an assumption of zero permeability coefficient, a high-order transmitting boundary is derived for cylindrical elastic wave propagation in infinite saturated porous media. By this transmitting boundary the total stresses on the truncated boundaries of a numerical model, such as a finite element model, are replaced by a set of spring, dashpot and mass elements, with some additionally introduced auxiliary degrees of freedom. The transmitting boundaries are incorporated into the DIANA SWANDYNE II program and an unconditionally stable implicit time integration algorithm is adopted. Despite the assumption made in the derivation of the transmitting boundary, numerical examples show that it can provide highly accurate results for cylindrical elastic wave propagation problems in infinite saturated porous medium in case the u–p formulation is applicable. Although the direct applications of the proposed transmitting boundary to general two dimensional wave problems in infinite saturated porous media are not highly accurate, acceptable accuracy can still be achieved by placing the transmitting boundary at relatively large distance from the wave source.     

Application of a second-order paraxial boundary condition to problems of dynamics of circular foundations on a porous layered half-space

A half-space finite element and a consistent transmitting boundary in a cylindrical coordinate system are developed for analysis of rigid circular (or cylindrical) foundations in a water-saturated porous layered half-space. By means of second-order paraxial approximations of the exact dynamic stiffness for a half-space in plane-strain and antiplane-shear conditions, the corresponding approximation for general three-dimensional wave motion in a Cartesian coordinate system is obtained and transformed in terms of cylindrical coordinates. Using the paraxial approximations, the half-space finite element and consistent transmitting boundary are formulated in a cylindrical coordinate system. The development is verified by comparison of dynamic compliances of rigid circular foundations with available published results. Examination of the advantage of the paraxial condition vis-á-vis the fixed condition shows that the former achieves substantial gain in computational effort. The developed half-space finite element and transmitting boundary can be employed for accurate and effective analysis of foundation dynamics and soil–structure interaction in a porous layered half-space.     

A viscous-spring transmitting boundary for cylindrical wave propagation in saturated poroelastic media

Based on the u–U formulation of Biot equation and the assumption of zero permeability coefficient, a viscous-spring transmitting boundary which is frequency independent is derived to simulate the cylindrical elastic wave propagation in unbounded saturated porous media. By this viscous-spring boundary the effective stress and pore fluid pressure on the truncated boundary of the numerical model are replaced by a set of spring, dashpot and mass elements, and its simplified form is also given. A u–U formulation FEA program is compiled and the proposed transmitting boundaries are incorporated therein. Numerical examples show that the proposed viscous-spring boundary and its simplified form can provide accurate results for cylindrical elastic wave propagation problems with low or intermediate values of permeability or frequency content. For general two dimensional wave propagation problems, spuriously reflected waves can be greatly suppressed and acceptable accuracy can still be achieved by placing the simplified boundary at relatively large distance from the wave source.     

Implementation of a second‐order paraxial boundary condition for a water‐saturated layered half‐space in plane strain

A half‐space finite element and a transmitting boundary are developed for a water‐saturated layered half‐space using a paraxial boundary condition. The exact dynamic stiffness of a half‐space in plane strain is derived and a second‐order paraxial approximation of the stiffness is obtained. A half‐space finite element and a transmitting boundary are then formulated. The development is verified by comparison of the dynamic stiffness of impermeable and permeable rigid strip foundations with other published results. The advantage of using the paraxial boundary condition in comparison with the rigid boundary condition is examined. It is shown that the paraxial boundary condition offers significant gain and the resulting half‐space finite element and transmitting boundary can represent the effects of a water‐saturated layered half‐space with good accuracy and efficiency. In addition, the numerical method described herein maintains the strengths and advantages of the finite element method and can be easily applied to demanding problems of soil–structure interaction in a water‐saturated layered half‐space. Copyright © 2010 John Wiley & Sons, Ltd.     

Numerical instabilities of a local transmitting boundary

A local transmitting boundary is presented in a compact form, which can be directly incorporated into finite elements. The accuracy of the boundary is studied thoroughly for a one-dimensional model in order to clarify numerical instabilities introduced by the boundary. Discretization of the model and reflection from the boundary are rigorously considered in the study, and the mechanism of the instability is then illuminated in the frequency domain by the amplification of reflection from the boundary and the multi-reflection of wave motion in a finite computational region. Typical characteristics of the instability in the time domain are illustrated by numerical results of the simple model and explained completely by the mechanism. On the basis of this understanding of the mechanism, a modified transmitting boundary is devised and its stability criterion is given for the one-dimensional model.     

Doubly asymptotic multi-directional transmitting boundary for dynamic unbounded medium-structure-interaction analysis

The novel doubly asymptotic multi-directional transmitting boundary combines the advantages of the doubly asymptotic and multi-directional formulations. It is rigorous for the low-frequency limit (static case) and the high-frequency limit in the wave-propagation direction perpendicular to the artificial boundary and at all the preselected angles corresponding to various apparent velocities. It is implemented straightforwardly in the finite-element method. The doubly asymptotic multi-directional transmitting boundary is temporally local and spatially either global or local depending on the implementation of the static-stiffness matrix. It leads to much higher accuracy than other transmitting boundaries with the same finite-element mesh.     

基于混合边界条件的有限单元法GPR正演模拟

从Maxwell方程组出发,推导了探地雷达(GPR)有限元波动方程.阐述了透射边界条件和Sarma边界条件的原理,推导了这两种边界条件的理论公式;通过在衰减层内加入过渡带优化了Sarma边界条件的加载方法,压制了介质区和衰减层交界面处的人为反射.考虑到透射边界条件与Sarma边界条件不同的理论机制,提出了一种结合透射边界条件和Sarma边界条件的混合边界条件,它利用Sarma边界条件对到达边界区域的GPR波能量衰减功能和透射边界对GPR波能量的透射功能,使GPR波经过Sarma边界条件的衰减吸收后,再通过透射边界条件将剩余能量透射出去,集成了二者的优势.并以二维均匀模型中的中心脉冲激励源方式为例,通过Matlab程序实现,以GPR的全波场快照的直观方式,对比了有、无边界条件及不同边界条件对人工截断边界的处理效果,说明了该混合边界条件对到达截断边界处的GPR波的处理优于单一边界条件.最后,以基于混合边界条件的有限单元法对两个典型的GPR地电模型进行了正演模拟,指导了GPR数据处理与工程实践.     

Simulation of near-fault bedrock strong ground-motion field by explicit finite element method

Based on presumed active fault and corresponding model, this paper predicted the near-fault ground motion filed of a scenario earthquake （Mw=6 3/4 ） in an active fault by the explicit finite element method in combination with the source time function with improved transmitting artificial boundary and with high-frequency vibration contained. The results indicate that the improved artificial boundary is stable in numerical computation and the predicted strong ground motion has a consistent characteristic with the observed motion.