Dynamic seepage flows have been mainly estimated by static parameters at the maximum amplitude. The estimation consider neither underground cavities in the practical ground nor various compoments of the seepage frequency. This study revealed the influence of frequency of seepage in a porous medium containing the area of regular flows by numerical analysis which took account for Beavers-Joseph conditions at the boundary of the different flow phases. The calculated results suggested that the fluctuation of seepage force and velocity disappered with increase of frequency of subjected hydraulic gradient at the surface. On the other hand, the high water pressure remained in wider area of the ground and the cavity with higher frequency, because of the limitation of pressure reduction. Consequently, this study proposed a new index for evaluating effect of frequency and revealed that high freqnency component of the seepage could not be negligible.

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An overhanging failure is one of major problems in river engineering affecting the riverbank geometry. Unfortunately, the previous studies had limitation on the coupling fluvial erosion and overhanging failure. Therefore, the aim of this paper is to introduce new coupled processes for simulating the fluvial erosion and overhanging failure of the experimental banks as well as the real riverbanks at U-Tapao River in Thailand.
For fluvial erosion, the actual shear stresses of the experimental banks are between 0.68 and 1.23 Pa, while at the U-Tapao River, they are within the range of 18.51 to 22.52 Pa. Moreover, the critical shear stresses estimated by the percentage of silt-clay content of the experimental banks are within the range of 0.38 to 0.57 Pa, while at the U-Tapao River, they are between 9.44 and 12.99 Pa. Additionally, the previous relationship between the critical shear stress and the erodibility coefficient indicate that they do not follow the present values of the experimental results and the U-Tapao River. Furthermore, the critical shear stress and the erodibility coefficient showed that these parameters varied significantly from one site to another site. Therefore, relationship between the critical shear stress and the erodibility coefficient are needed to be measured locally. For overhanging block stability, the results revealed that the dominant overhanging failure of the experimental study is the beam-type failure while the shear-type failure is the dominant failure mechanism in the U-Tapao River.
Finally, the overhanging failure was simulated by the present numerical model within the frameworks of the fluvial erosion and overhanging failure. The numerical results were validated with the temporal variations of spatially averaged bank width. Moreover, this validation results showed a good agreement between the numerical results and the experimental results.

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Numerical simulations, which include spacial descretization, difine the controlling domain of descrete elements, according to each characteristics of methods. Finite Element Method uses nodes and elements to define their controlling domains, whereas particle based methods use the interpolation functions. Particles based methods usually updates its geometric position, while they continue to use the same interpolation function through the whole simulation process. In particle based methods, separations due to numerical algorithms often occur when the intensive streches act on the materials, not because materials reaches its criteria of separation but because the distance from neigbor particles exceeds the interpolation radius.
The same difficulty has been discussed over the Material Point Method. Although original MPM, which generates numerical noise when crossing numerical grids, does not consider a controlling domain, GIMP method, which considers the change of controlling domain in axial direction, has been proposed to overcome the problems. More recentry, CPDI method, which considers the whole change of controlling domain, has been proposed. In this paper the author focuses on CPDI method and newly propeses the three dimensional formulation of CPDI method and applies it to the large deformation problem of geomaterials.

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Cushioning materials, such as sand cushion and granular mats placed on rock sheds, can effectively disperse and reduce rock fall energy before rocks collide with protection works. Although the construction costs for sedimentary layers are low, these layers are attracting attention as construction devices that can substantially improve the margin of safety ratio. To elucidate the formation mechanism that governs the impact force waveform of falling mass, this study examines the loading rate dependency of sand cushion by 2D-DEM simulation. In the simulation, particular attention is paid to the velocity of stress waves that propagate in sand cushion. The results are summarized as follows: (1) The impact force of falling mass depends only on loading velocity and penetration depth, not on loading history. (2) The larger the loading velocity, the smaller the area wherein volume strain is borne only by the loaded surface, rather than shared by the penetration of falling mass. This imbalance in support explains the loading rate dependency of sand cushion. (3) The relationships between the compressive strain of a particle group and mean principal stress are determined over dynamic and static loading. These relationships are almost the same between the loadings. (4) Using σ=ρcv to estimate the impact force waveform of falling mass produces large-scale experimental and 2D-DEM simulation results.

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The failure of earth dams is mainly caused due to internal erosion and piping phenomena. Concentrated leak erosion, one of the mechanisms to trigger internal erosion, is driven by flow in the cracks or other openings. In the present study, an effort has been made to investigate the microscopic coupled behavior of soil skeleton and water by employing the Discrete Element and Lattice Boltzmann coupled method. Many simulations were conducted under different constant pressure conditions with 2-D small model based on Hole Erosion Test presented by Wan and Fell (2004). Soil erosion parameters (such as, hole diameter φ_t, shear stress τ_t, erosion rate ε) are calculated and compared with the results available in the literature. Consequently, this study facilitates more realistic simulations compare to the available tests and simulations in the literature.

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In the 2011 off the Pacific coast of Tohoku Earthquake, caisson breakwaters in several ports were damaged by the tsunami. According to the acutual damage examples of the breakwater after the tsunami, it is considered that these failures were caused by not only horizontal large tsunami force, but also scouring destruction of foundation mound due to the tsunami overflow. In this paper, SPH-DEM coupling analysis method which is based on drag model is employed in order to analyze scouring and seepage flow phenomena at caisson breakwater during tsunami. Firstly, basic numerical tests are conducted to verify the coupling analysis method to calculate the interaction force between SPH and DEM. Secondly, parametric studies of the simulation on the tsunami overflow experiment are carried out to check the effect of the numerical parameter to express pore water flow influenced by rubble shape.

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In order to investigate effects of particle size and particle shape in DEM simulations, a series of simulations of a model test using dry sand were carried out. By analyzing the simulated results, following findings were obtained. Non-spherical particles can describe flow behavior of sand much better than spherical particles, and it is possible to describe the flow behavior even if some bigger non-spherical particles are used in the simulation. It is also found that considering particle shape is important to describe the flow behavior but degree of the shape is not sensitive factor.

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In this study, the apparent thermal conductivity of unsaturated sand is simulated numerically modeling the sand as a periodic porous medium having immobile solid, fluid and gas phases. By varying the amount and location of the pore water, the thermal conductivity is obtained as a function of S_r (the degree of saturation) for three different sand particle packing structures. The numerical results show that the three typical relationships between the thermal conductivity and S_r, which are well known, but have been modeled poorly, can be well reconstructed by the present numerical approach.

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Smectite to illite transformation is assumed to be one of the factors that causes earthquakes. Interpretation of the mechanical behavior considering smectite to illite transformation is needed in the study of earthquake. It has been reported that asperity which is a slight projection from surface of the plates existed in decollement zone, and the area existing asperity is known as an earthquake occurrence area. However, the mechanism of decollement formation and mechanical behavior has not been studied rigorously.
Therefore, the purpose of this study is to challenge to this unsolved problem from the point of view of geotechnology. As the first step, the influence of dehydrating action due to smectite to illite transformation and mechanical characteristic change is modeled. Consequently, it is found that smectite to illite transformation causes increasing in share strength and hence, it is thought that this mechanism would be a major factor to cause gigantic earthquake because the energy release of deformation is estimated to be a quite large volume.

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A tsunami caused by an earthquake off the Pacific coast of Tohoku seriously damaged many coastal structures. It is important to reinforce these structures with the concrete blocks and to give the function of tenacious structures. In case of coastal dikes, the stability of concrete blocks and the damage of coastal dikes are affected by the fluid forces and turning moments acting on concrete blocks armoring on slope just near the crest of dikes in the side of land for overflow in tsunami. In this study, we measured the fluid forces and turning moments acting on the armor concrete block covering coastal dikes for steady overflow. We also looked into the applicability of CADMAS-SURF/3D to estimate these force and moments.

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In this study, seepage/seismic behavior of a large river levee on alternately layered ground of sandy and clayey soil was evaluated by a soil-water-air coupled finite deformation analysis code. The main findings are as follows: 1) Focusing on the river level, the analysis during seepage and during/after an earthquake was performed. The higher the river level, the larger the deformation in a direction toward the landside. 2) If the water permeability of the sandy soil layer is as high as “gravel”, 8 hours after the river level rose, ground heaving which will lead to piping occurred near the landside toe. This is because the permeability of covering clayey soil layer is low and much water was supplied from the river to the sandy soil layer. 3) In the case of high permeability in the sandy soil layer as 2), during an earthquake, even when the river level is low, pore water is able to migrate in the sandy soil layer underlying clayey soil layer with low permeability. This results in liquefaction of the top of the sandy soil layer though the permeability is as high as gravel.

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This paper presents a multi-agent based evacuation simulation software capable of simulating mass mixed mode evacuations of large areas including sub meter details of the environment. A mathematical framework is introduced in order to provide a framework for the specification and description of the software, enabling to compare the developed multi-agent system with other existing evacuation simulation tools and identify underlying differences and areas of improvement. Details of the high resolutions environment, including the modelling of dynamic changes like earthquake induced damages, etc. are briefly explained. Furthermore, the basic constituent functions of autonomous agents, which enable them to perceive their visible surrounding and interact with it and neighbouring agents, are also briefly explained. The mixed mode interactions are briefly presented along with its validation results. Demonstrative mass urban area mixed mode evacuation scenarios are presented in order to highlight the need of incorporating detailed models of environment and the complex agent functions and interactions. Most of these scenarios cannot be simulated with the simplified models without sacrificing accuracy or making broad assumptions.

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“Integrated Earthquake Simulator” (IES) is developed by the Earthquake Research Institute of the University of Tokyo. In this study, first, the structure response to an observed earthquake wave for the city model of Takamatsu constructed by GIS data is analyzed by the IES. Secondary, the city model in which building damages can be considered is prepared and the evacuation simulations for the city model are carried on. The numerical results show that the evacuation time and way depend on the city structure, the existence or non-existence of building damages, and the kind of input earthquake wave.

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In this paper, the numerical analysis focused on the liquefaction of body of embankment was performed with the three-phase (soil, water, and air) coupled analysis based on porous media theory. In this technique, the conventional constitutive model for describing the cyclic behavior of unsaturated soil was employed. From the numerical simulations about the shaking table test, it was revealed that the simulation could reproduce the experimental results well and that the proper consideration of the unsaturated condition is important. Furthermore, the series of simulations indicated that the existing embankment would be deformed beyond the limitation of the settlement required in design.

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The spread foundations are expected to generate restoring forces such that the seismic loads do not significatnly increase for a level of horizontal displacement of the structure after yielding, because of the lifting of the footing edges and the plastic behavior of the ground in contact with the footing. Therefore, those structures with spread foundations are expected to be advantageous in terms of the seismic performance owing to the elongation of the natural period and enhanced damping caused by energy absorption, which are effectively similar to the seismic isolation mechanism. Moreover, those effects can be enhanced with the increase of the seimic ground motion amplitude, making the dynamic performance even more preferable under extreme seismic events. In this paper, the characters of the effective seismic isolation of the spread foundation are evaluated by thoretical assessment using the equivalent linearization method and by nonlinear dynamic analysis. It is successfully shown that the variation of the dynamic amplification factors caused by the nonlinearity of the spread foundations can be represented by the change of th equivalent stiffness and equivalent damping, and that the abrupt change of the dynamic response amplitude of the structure observed in the numerical simulation can be well accounted by the bifurcation of the dynamic amplification curves derived by the nonlinear amplification factors.

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In this study, we carried out static cyclic loading of the rectangular steel bridge piers. Determination criteria in the initial inspection after the earthquake, is intended to collect the basic data for the development of inspection focused site and inspection methods. We checked the basic seismic performance of retrofitted steel bridge pier, and investigated the relationship of damage and residual strength by measuring the damage occurrence site and the amount of deformation.

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In this study, smoothed particle hydrodynamics (SPH) method is applied to simulate gravity granular flow past forward-facing and rearward-facing pyramids (tetrahedral) wedge. These types of obstacles used as a typical defense structure to divert the flow and guide the avalanches to pass the protected buildings and areas. The elastic-perfectly plastic model with the implementation of Mohr-Coulomb failure criterion is applied to simulate the material behavior. The numerical results are then compared with experimental data, and numerical results obtained from quasi-two-dimensional flows model. The results obtained from these comparisons show that the SPH method is capable to describe the behavior of the flow around such obstacles and can capture the formation of shock waves, dead zones, and granular vacuum.

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Intermediate-scale laboratory solute transport experiments were conducted in heterogeneous porous formations comprised by 144 sand cells. Visualization of dye solute was applied to transitional estimates in longitudinal and transverse macrodispersivities caused by the presence of heterogeneities. Results showed that a distinct transition of the longitudinal macrodispersivity was confirmed due to the local heterogeneity while a continuous decrease in transverse dispersivity was shown despite of the initial source location. Quantification methodologies were proposed to achieve the ensemble estimation of five distinct transitions of macrodispersivities and the local heterogeneity quantification based on solute pathways, leading to appropriate outcomes relevant to not only the variation and distribution of estimates but the degree of the longitudinal macrodispersivity.

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The drag-force model has a bottleneck in choosing the model drag coefficient C_D. An appropriate C_D profile is estimated by a numerical simulation where fluid motions around each canopy element are fully resolved in a minimal unit of the target flow. While Yokojima and Kawahara (J. JSCE B1 71(4) 2015) computed C_D (C_D;global) based on the bulk-mean velocity as the velocity scale , the present study obtains a C_D profile (C_D;local) taking into account the approaching velocity to each element. Application to vegetated open-channel flows reveals that neighter C_D;local nor C_D;global gives satisfactory results. Including the unsteady effects and/or reformulating the model expression might be required for better performance.

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An estimation model for planktonic capture rate in turbulent environment has been developed. The planktonic encounter and capture rates are obtained in a numerical experiment where the Reynolds number and the predator's motility and ingestion capabilities are varied systematically. The present model is based on several scaling laws obtained from the experimental results and consists of elementary algebraic equations. Its applicability is examined against another numerical experiment of Baba et al. (J. JSCE B1 69(4) 2013). It is demonstrated that the prediction results are in good agreement with the experimental data.

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The effects of particle shape on settling behavior of a sand particle cluster in an ambient water environment have been studied by a two-dimensional numerical experiment. The particle is ellipse of size about 1mm, and the aspect ratio α is varied without changing the volume. Due to the shape invariance under the rotation around its centroid, the circular particle shows distinct behavior from the elliptic particle in the initial stage of the sedimentation process. It is also revealed that the terminal velocity is decreased with increasing α and that the terminal velocity averaged over the particles in a cluster is slightly slower than that of an isolated particle.

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This paper describes the water waves generated by the elevation of the bed. The effect of time-depepndent bottom deformation on water waves is investigated, based on Boussinesq equation. Linearized solutions are derived, using one-dimensional Boussinesq equation in both cases of constat speed elevation and of non-linear time-dependent change. They are divided into hydrostatic solution and the other parts relative with vertical acceralations terms of Boussinesq equation. Findings are verified by the comparison with two dimensional numerical simulations. Finally, it is found that the effect of the time-depepndent bottom deformation terms in Boussinesq equation appears in the case of non-linear bed elevation and that it becomes larger, as the bed elevation speed is higher.

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During the flood, high-velocity flow sometimes generates large surface waves called " triangular wave train", which look like the jagged plates on the back of a dinosaur. These waves cause local erosion of riverbed and may have great destructive effects on revetment blocks. Although the wave train is thought as one of the surface waves on antidunes, study on their occurrence condition have not been sufficiently conducted. In this paper, we made the flume experiment to understand the occurrence condition of triangular wave. The experimental results showed that the triangular waves were generated when Shield number is larger than 0.15 and Frude number is in the range of 1.0 to 1.7. The number of waves train increased with the increase in the ratio of width and depth.

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The purposes of this study are to examine clearly the hydraulics functions of groins and the characteristic of fish behavior around the groins. To complete them, the hydraulics experiments and to observe the movements of fish were done.
As the results, 1) curved flow was formed by the groin, 2) low velocity areas were formed in the downstream of the groin and 3) The relativity of the riverbed scour, gravel deposit, and vorticity is low. Moreover, fish stayed in the low velocity areas and big vorticity areas. On the other hand, fish run up in the high velocity and small vorticity areas. Therefore, fish behavior depends on the vorticity.
In Addition, numerical analyses were done. As the results, the formation situation of a curved flow and vorticity reproduced roughly. However, scare of velocity or vorticity were not able to reproduce.

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This paper examines dissipation of tsunami due to overflow over different shapes of dike by hydraulic experiments. The experimental results were compared and validated against the classical theory of weir. Experimental results showed that a dike with slope on upstream side and vertical back side is the most effective to reduce the tsunami energy. A numerical model was used to simulate a series of experimental results. Most of test results were successfully simulated; however, for the condition that nappe flow appears, the numerical model should be improved for the accurate estimation of energy dissipation.

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Direct numerical simulations of the secondary flow and the gas transfer in an open-channel flow with the sidewalls are carried out to investigate the effects of Prandtl's second kind of secondary flow on the turbulence dynamics and the gas transfer at the water surface. Turbulent characteristics on the secondary flow such as the velocity-dip phenomena and counter-rotating vortex pairs near the upper and lower corners are verified to be reproducible in comparisons with existing experimental and numerical results. Turbulent structures visualized based on the second invariant of the velocity gradient tensor make it clear that swirling vortex tubes generate near not only the bed but also the sidewalls of the channel. The turbulence dynamics due to such vortex structures may play important roles in driving the surface velocity divergence. The numerical results don't agree quantitatively with the gas transfer velocity by a surface divergence model. It is concluded from the present results that the secondary flow in open channel influences significantly the gas transfer at the water surface.

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For examining characteristics of residual stress generated by patch welding on a steel member under the tensile loading, a series of experiments and numerical simulation were carried out. The difference of residual stress around the weld metal between the case under the constant tensile loading and that without loading was almost the same as the stress applied by loading. On the other hand, the difference of residual stress in the base metal was larger than that around the weld metal due to the effects by not only the loading but also the restraint. Furthermore, the residual stress was released by annealing under the loading with using a portable ceramic heater. Although the residual stress was released without being affected by the loading, the stress was re-generated during the cooling process in annealing. However, the tensile residual stress became around 30% of the welding residual stress by annealing.

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Bridge accessories such as parapets, duct, slab deck are commonly used in bridge structures, but their real effects on the structural behavior of the bridges are still unknown. In this study, experiments were performed on a railway bridge to confirm the contribution of the bridge accessories and their design details. Both displacements on key sections and sectional strains were measured in the test, and the theoretical results on the basis of the classical mechanics were provided to compare with the test results. In order to evaluate actual stiffness of the bridge, numerical studies were conducted, and the stress concentration on the concrete slab near the expansion joints was confirmed. The results obtained in this study can be used for improving the design method of new railway bridges and maintenance of old railway bridge structures.

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Carbon fiber reinforced polymer, CFRP, plate bonding method is one of the new crack repair methods. The effect of fatigue life extension by bonding CFRP plate can be estimated by using stress intensity factor, SIF. In this study, to clarify the effect fatigue life extension of edge crack by bonding CFRP plate under axial load, tensile fatigue tests were carried out. Furthermore, to evaluate the effect of fatigue life extension by bonding CFRP plate, stress intensity factor, SIF, of a cracked steel plate with CFRP plates was calculated by finite element analysis and simple calculation procedure based on linear fracture mechanics. Finally, crack propagation analysis were carried out and analysis results compared with test results.

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Many numerical and experimental studies have been conducted to predict the fatigue life of RC slabs under moving load. Most of these works study the modeling of fatigue behaviors of RC slabs reinforced with deformed bars. The current study presents an experimentally verified numerical method to simulate the fatigue behaviors of RC slabs reinforced with plain bars under moving load. This numerical method is based on the bridging stress degradation concept. The bond-slip effect between a reinforcing bar and surrounding concrete is taken into consideration under repetitive load. The fatigue behaviors of RC slabs under moving load can be simulated through this numerical method. This method is also able to capture the cracking pattern, displacement evolution and rebar strain. The numerical method shows a good agreement with the experiments under static and moving load.

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Guided wave has already been introduced to a wide variety of nondestructive testing especially for plate and pipe components. The shape of the cross section of the infrastructure is different in every portion, and the components consist of heterogeneous materials such as concrete and reinforced steel bar. Therefore it is useful to know the property of the guided wave in the target material prior to the testing. In this research, we adopted two numerical tools to assist the guided wave testing. One is the semi-analytical finite element method (SAFE), and the other is the elastodynamic finite integration technique (EFIT). The SAFE and EFIT were used to obtain the dispersion curve and the transient wave propagation, respectively. These methods were validated with the experimental measurement using an I-beam metal specimen. In the measurement, we used a wireless experimental system to receive signals of the guided wave. The guided wave was excited with an impact hammer, and then received with wireless accelerometers at multiple points. The simulation results and measurements showed good agreement with respect to the velocity dispersion curve, and the polarization shape in the propagation.

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Crack percentage is established as an index for quantitatively assessing asphalt pavement crack damage. Currently, calculating the crack percentage involves sketching cracks on the road surface and then counting the number of cracks within a partition, and this manual labor further requires significant amounts of work and time and does not collect important information such as crack opening width. This study combines machine learning with decision tree and image analysis to establish a method for automatically detecting cracks from digital images. We verified the high crack detection performance of the developed method by analyzing the images of dense graded asphalt and porous asphalt pavement.

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Although hot dip galvanizing is a method of giving long-term corrosion protection to steel structures, steel materials may suffer cracks and/or distortion during hot dip galvanizing due to abrupt changes in temperature. As measures against cracks, beam-to-column welded connection with non-scallop methods having draining holes may be applied. However, there are some cases that cracks occurred in spite of taking such measures.
Therefore, in this study, we carry out immersion tests into molten zinc using specimens which changed the diameter and the position of draining holes for the partial model that assumed beam-to-column welded connection. Furthermore, the diameter and the position of draining holes can reduce possibility of cracks are examined by using the three-dimensional thermal conductivity and elastic- plasticity thermal stress analysis.

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This paper aims to investigate dynamic characteristics of an FRP truss pedestrian bridge in service by means of field vibration test and eigenvalue analysis. Pedestrian-induced vibrations are also measured and utilized to identify dynamic parameters of the bridge. A multivariate autoregressive model combined with stabilization diagram was utilized to identify modal properties of the bridge. Every node of the bridge is reinforced by stainless steel plate, and FE models considering the reinforcement by increasing Youg's modulus led to comparable frequencies and mode shapes to those from observed in the test. Moreover as a boundary condition at both ends fix model resulted in a comparable modal properties to experimental ones. This study also demonstrated that the effect of reinforcement and boundary conditions have to be properly considered in an FE model to analyaze real behaviour of the FRP bridge.

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For strengthening of steel members suffering deterioration and/or insufficiency of load carrying capacity, externally bonding patch plate have been used. Furthermore, pretensioned patch plate have also been used in several strengthening cases. Although the pretensioned patch plate can improve stress in steel member not only by live load but also dead load, the shear and normal stress tend to be introduced in adhesive layer. The stresses may cause the reduction of debonding load of patch plate. To improve the debonding load of pretensioned patch plate, applying non-pretensioned region at the end of patch plate was proposed. In this study, prestress introduced into steel plate by partially pre-tensioned patch plate was observed. In addition, the improvement of debonding load due to the non-pretentioned region is confirmed from debonding tests. The improvement effect in the debonding load is evaluated from the view of principal stress in adhesive.

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This paper presents an FE-based elastic wave transmission analysis method for composite layers consisting of different periodicities. In particular, problems in which the ratio of lattice constants of both composite arrays is given by a rational number are considered. Under this condition, by the aid of the Floquet transform, the present problem is reduced to a dynamic response of a unit cell representing each periodic layer. The developed method is applied to wave transmission through composite layers formed by circular inclusions. Numerical results showed that a combination of composites having different stop bands contributes to the vibration attenuation.

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A deformation behavior of a buried flexible pipe used as an irrigational pipeline is not substantially clear during earthquake. In this study, in order to clarify an influence of a deformation of ground on the dynamic behavior of the buried flexible pipe, cyclic shear tests for buried flexible pipes having an outside diameter of 140 mm and 150 mm in the laminar box and DEM analyses were conducted. As the results, it was found that the 45-225 and 135-315 degrees deflection of the buried flexible pipe were larger than the 0-180 deg. (vertical) and 90-270 deg. (horizontal) deflection. This tendency became remarkable as the relative density of the backfill material increased. It was indicated that the relationships between the deflection of the pipe and the shear strain obtained from the analyses results could be in good agreement with the test results. In addition, the buried flexible pipe was deformed due to the contact force acted on the oblique direction of the pipe during earthquake.

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