In this paper, various characteristics of the Biot waves in fluid-saturated porous media are examined numerically and analytically based on the relations in the previous paper (Kitsunezaki, 2004a), whose notation is also kept here. The Biot waves mean elastic waves in the Biot theory (Biot, 1956), which consist of two longitudinal waves (I-and II-waves) and a transverse wave. The main aim of this study is to reveal general variation tendency of characteristics of the longitudinal waves in wide range of sediments, typically from consolidated stiff sandstone to unconsolidated loose sand, mainly in connection with variation of skeleton-stiffness, which is represented by the velocity ratio in P-wave of skeleton to sound wave in fluid, V_Pb/V_ƒ. In the wave characteristics, special attention is paid to displacement ratios and stress ratios in fluid to solid, as well as velocities and attenuation (logarithmic decrements). The both ratios are key factors to understand propagation mechanism of the two longitudinal waves. Main points of this study are as follows. First, general feature of the above properties is viewed as functions of frequency and skeleton-stiffness. The frequency characteristics are examined for typical two models of media with hard and soft skeletons. The properties in the low and high frequency limits are remarked to examine the effects of skeleton-stiffness. Second, approximate expressions of the characteristics are derived for media with very low skeleton-stiffness (V_Pb/V_ƒ<<1), which almost corresponds to loose alluvial sand, in order to clarify factors controlling wave properties. Third, dynamic process in the media with very low skeleton-stiffness is analyzed. Then the results are represented as schematic models of stress-strain relations which demonstrate clearly the contrastive properties of I-and II-waves. In all examinations mentioned above, such a reciprocal relation between the two longitudinal waves is remarked as a useful general law, that the displacement ratio of I-wave in fluid/solid is equal to the opposite value of stress ratio of II-wave in solid/fluid, where I and II are mutually exchangeable.

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In fluid-saturated porous media, contrastive characteristics of two longitudinal waves (I- and II-waves) are usually remarked, based on the Biot theory (Biot, 1956). These characteristics are connected by some relations, or controlled by common factors. A little attention has been paid to such properties, although they are keys to promote our understanding for various aspects of the wave phenomena. In such a point of view, we take up the following three properties, which were remarked in the previous papers by the author (Kitsunezaki, 2004, 2005a), but not fully discussed. The first is the reciprocal relation between displacement ratio and stress ratio of two longitudinal waves. The reciprocal relation in this case means that displacement ratio of fluid/solid in I-wave is equal to the opposite value of stress ratio of solid/fluid in II-wave. This relation was found in numerical calculations in the previous paper (Kitsunezaki, 2005a). We prove it analytically in this paper. This relation has wide applicability, and is used in discussion of the following items. The second is energy transmission ratio between solid and fluid in two longitudinal waves. A reciprocal relation is also confirmed in energy transmission ratio. It is held strictly in low- and high- frequency limits, but only approximately in the whole frequency range because of the phase differences between stress and particle velocities. The reciprocal relation in this case means that energy transmission ratio of fluid/solid in I-wave is equal to that of solid/fluid in II-wave. The third is the dynamic compatibility, which means that the relative motion between solid and fluid in I-wave disappears in the medium that satisfies a certain condition. The significance of this condition is discussed based on a relation between phase velocities and the relative motion of fluid and solid. Practical condition for dynamic compatibility is demonstrated in a graph, according to which the corresponding skeleton stiffness is increased with the decrease in porosity.

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It is important to understand the detailed 3-D subsurface structure to estimate the strong ground motions. For this purpose, we will confirm the usability of the gravity survey and propose a process from modeling the ground structure to estimate of the strong ground motions.
The gravity survey has been carried out to estimate the 3-D subsurface structure around the damaged area due to the 1909 Anegawa earthquake. Steep slopes of the bedrock are located around the severely damaged area. On the basis of the estimated 3-D subsurface structure, the strong motions are numerically simulated by using the finite-difference method (FDM). From the results of the simulations, it is shown that the peak ground velocity correspond to the collapse ratio of the wooden structures except for some cases.

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Two-dimensional electrical surveys were conducted on four lines at the Hamaichi site and one line at the Ushiami site, Naruse, Miyagi Prefecture, where large-scale liquefaction of ground was caused by the Miyagi-ken Oki and the Miyagi-ken Hokubu Earthquakes of 2003. The purpose of the surveys was to investigate the resistivity structures and define the depth to the boundary between a reclaimed layer and natural sediments on which liquefaction mainly occurred. The electrical data were collected using the dipole-dipole and Wenner arrays and were applied to two-dimensional inversion for each line. The analyzed resistivity structures were consistent with the geologic structures estimated from geology data and nearby investigation well data. Because the reclaimed layer consists of clay-rich pit sands and its resistivity is low as compared with the resistivity of natural sediments below it, the depth to the boundary, that is the liquefaction region, can be recognized clearly in the resistivity structures. The boundary is shallow at sand boils and deep in collapse zones formed by liquefaction.

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Among the various countermeasures for rolling stock, tracks and structures that have been discussed to prevent the ground vibration along railway lines, burying a wall in the ground is expected to be a comparatively effective solution to cut off vibration. Since the effect of vibration isolation wall depends on the ground conditions and the materials, size and other conditions of wall-in-ground, however, there are no quantitative designing methods established to isolate vibration. Therefore, we reviewed the results of model experiments and field tests in the past from a new viewpoint and developed a method to quantitatively evaluate the effect of vibration isolation wall. In planning and designing vibration isolation wall, it is desirable to have a simple and convenient method to evaluate its effect. Thus, we composed a moderately simple theoretical model to evaluate the effect of vibration isolation wall in quantitative terms. This model features the following:
(1) Assumes that a surface wave (Rayleigh wave) is generated from the railway and that the vibration energy behind the wall-in-ground is the sum of the energy of the transmitted wave through the wall and the energy of the diffracted wave originated from its side and bottom.
(2) Applies Kirchhoff's diffraction theory, which is introduced in the fields of optics and acoustics, to the evaluation of the diffracted wave.
(3) Applies the one-dimensional wave transmission theory that is normally used and the beam deformation theory by regarding the wall-in-ground as a beam to calculate the transmission rate of the wave transmitted through it.
Since it is far simpler than the numerical analysis by the finite element method (FEM), the newly developed evaluation method will be useful for planning and designing vibration isolation wall along railway lines.

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We are developing a three-dimensional simulation tool for wave field induced by running trains in the wayside, in order to support design of measures to reduce the vibrations for environmental preservation. This paper shows some remarks on source modeling in the simulation, which may be important independently of numerical schemes of simulation. If excitation loads are modeled as ones driven with synchronization with vehicle arrival and a propagating system is homogeneous, responses are found out negligibly small in far field. Realistic responses are obtained by assuming vibratory loads that are not synchronized with vehicle arrival. However, it is not a unique model to obtain realistic responses. If the propagating system is inhomogeneous near the moving route, realistic responses are generated even by assuming the vehicle-synchronized loads. In addition, if the vehicle-synchronized loads are modeled with a finite length of the route, responses show realistic amplitudes even in a homogeneous propagating system. They are, however, simply contributions due to waves induced by loads suddenly risen up at starting and ending points of the route, not ones to be expected. The contributions might lead to a serious misunderstanding of the numerical result, since the effect is not easily identified particularly in a frequency-domain simulation.

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This paper describes the field measurements with a vibration exciter to examine the vibration reduction effect of PC Wall-Piles. Three dimensional simulation results are also presented to clarify the basic characteristics of vibration reduction. A PC Wall-Pile, which is widely used for retaining walls, has a hollow part in the square section in order to excavate the natural ground. This wall has an advantage to be made safely adjacent to the important structures, such as a Shinkansen viaduct, because it can prevent loosening the nearby ground. In the field test and the simulation, special attention is devoted to the influence of hollow size on the vibration reduction effect, so that the hollow size varies in three steps from maximum (620 mm of inner hollow diameter) to zero. From the field results, it becomes clear that 1) Apparent vibration reduction effect shows when the wall depth is over approximately one wave length of surface wave, and that 2) Vibration reduction effect of hollow size seems complex, because the pile weight and stiffness may have an impact as well as the hollow size. Then the 3-D numerical simulation is conducted to discuss the field results. It becomes clear that 1) Numerical model of this study is a powerful tool to discuss the vibration effect of the PC Wall-Piles, and that 2) According to the simulation results, PC Wall-Piles with larger hollow has an vibration reduction effect especially in higher frequencies, such as 15 to 25 Hz.

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This paper presents the result of the effectiveness of used tire wall barriers for controlling ground vibrations.
About 90% volume of used tire are recycled effectively, however, almost of them are used to the purpose of thermal recycle as fuel. The pollution of CO₂ by fuelling, therefore, is the source of global warming in the world.
By the way, vibration arising from road and railway traffics, construction works, and factory machines propagates through soil resulting in a ground vibration in their neighborhood. Such ground vibration as well as psychologically adverse effects on the inhabitants around its source.
Field measurements were performed for a few cases having different types of used tire walls. Vibration level as registered on the off-side of the used tire wall barrier was found to be 5-12 dB lower than that recorded at the site with no such barrier.

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