On building the model of the granite body including the faults, inverse analysis carried out to estimate three-dimensional hydraulic properties distribution. To estimate heterogeneous hydraulic properties, it is necessary that the model reflects the shape of the faults, and to discreate ill-posed problem caused by a number of unknown parameters. The authors developed inversion program using the finite element method to easily build fault model. In addition, we used least norm method to discreate ill-posed problem. The results of inverse analysis using in-situ pumping test data show the effectiveness of the least norm method with finite element method.

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Random property associated with a bonded CFRP plate is theoretically analyzed by the use of a spatially random differential equation. An ordinary differential equation describing an axial force of steel plate as well as a shear force of the CFRP plate is extended to a spatially random differential equation by introducing a random field for describing spatially random behavior of a thickness of adhesive. Its solution is formulated by applying the so-called transfer-matrix method. By applying computer simulations, it is shown that, under the conditions assumed in this study, (i) when the thickness of steel plate is relatively small, the maximum principal stress of bonded part becomes almost certainly maximum at the CFRP plate end, i.e., debonding alomost certainly occurs at the CFRP plate end, (ii) when the thickness of steel plate is relatively small, the scatter of the principal stress becomes maximum at the CFRP plate end and its probability distribution is approximated by Weibull distribution or log-normal distribution and (iii) when the thickness of steel plate is not so small, the probability that debonding occurs at the butt end can not be neglected.

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A number of shear correction factors have been proposed for a century. In addition to the classical elasticity, the numerical methods for the computation of the shear correction factor for general complex shape cross-sections are also developed recently based on the discretization of stress field of the cross-section. However, the method for the estimation of the shear stiffness of the heterogeneous beam has not been reported so far. In this paper, exploiting the averaged method of heterogeneous beams by the authors, a computational method for the shear stiffness of the beam with the heterogeneous cross-section is proposed.

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Connectivity reliability is one of the indices to measure the functionality of a road network. This is a probability of a connectivity between an OD pair based on a network geometry and passability of its links. If Dijkstra's algorithm is employed to check the passability, the amount of calculations will increase with the order of the square of number of nodes, therefore the applicability to a large road network will be a problem. In this study, an aggregation of a road network with the use of a network Laplacian and adjacent matrix is discussed. “Partitioning” of a road network and “centrality” of partitioned areas are a key point of the proposed method to make a mesoscale network data. Trial calculations on the emergency transportation road system in Shiga prefecture are conducted to check the applicability of the proposed method. The results shows the proposed method shows good approximation of the original network and always provide a lower bound of connectivity reliability.

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It is important to identify soil hydraulic parameters, in order to simulate rainwater infiltration process adequately. Recently, due to the development of sensing technology, field monitoring systems have been spread. In the systems, the volumetric water contents are measured, and large number of data are accumulated. The authors tried to identify soil hydraulic parameters based on the field measurement data, by using the Particle Filter method, which was one of the sequential data assimilation methods. In this study, the authors focused on the Merging Particle Filter, which was one of the Particle Filter algorisms, and the availavility of three algorisms of Particle Filter method was compared. As a result, it was found that the Merging Particle Filter was most available algorisms to identify soil hydraulic parameters based on field measurements.

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A methodology to utilize lots of accumulated observation data is one of the important topics. The concept of sparse modeling attracts much attention from various fields. It can be interpreted to be one of regularization method in inverse problem. It is reported that it is successfully used in many problems like medical MRI. After illustrating the concept and formulation of sparse modeling with a simple example, the authors shows a inverse problem in which earth pressure is estimated by observed displacement of retaining wall as an example of application in civil engineering. The distribution of earth pressuer is estimated depending on the assumued sparsity. Though more study on the applicability to civil engineering problems is required, the concept of sparse modeling seems useful for various problems.

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Credibility evaluation index of the inverse analysis for heterogeneous hydraulic property was extended for pressure change rate matching. Numerical case study (1-d and 2-d model) and 2-d model laboratory test data were used to check the validity of the credibility evaluation index for the pressure change rate matching method. The results show that pressure change rate matching is effective when the coefficient of the pressure change rate term is adequate, and the method can be applied to the inversion for the laboratory test data which may have some model errors.

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The heterogeneous characteristic of crystal structures in a rock is well known that their size distribution can be expressed by the power law. In this paper we study the inherent stochastic feature hidden in the wave propagating through a granite rock specimen in order to make clear the power law defining the size distribution characteristics of crystal structure and the uncertainty of fissure size distribution in the rock. We develop a system to measure the ultrasonic wave propagation in a rock specimen and a method to analyze the phase characteristic of the wave propagating through the rock specimen. Decomposing the phase into the linear delay part and the fluctuation part from it, we investigate the stochastic characteristics of the phase difference in the fluctuation part. The probability density function of the approximated group delay time is expressed by a unique Levy-flight distribution for any arbitrary small circular frequency intervals. For obtaining the further unique distribution characteristics of phase we investigate the probability distribution characteristics of the second derivative of phase with respect to the circular frequency. Through this study the fractal feature of phase becomes very clear.

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Intermediate-scale laboratory solute transport experiments are conducted in heterogeneous porous formations comprised by 24 × 16 sand cells in a 100 × 80 × 3 cm sandbox. The spatial distributions of hydraulic conductivity having different values of the correlation length are geostatistically generated. Visualization of dye solute is applied to transitional estimates in longitudinal and transverse macrodispersivities caused by the presence of heterogeneities. Experimental results reveal that the longitudinal and transverse macrodispersivities show the dependence and non-dependence nature on the correlation length, respectively. Laboratory study is extended by a random walk particle tracking approach to reconstruct the estimated macrodispersivity transition, demonstrating a good agreement between the experimental and numerical results. A highlight of our experimental approach is that the variations of the ratio of the longitudinal macrodispersivity to the correlation length exhibit almost the same evolution despite of the correlation length. Quantification imaging methodology is proposed to investigate the relation between the apparent heterogeneity and the macrodispersivities based on solute distributions.

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We developed “Geo-environment and root growth prediction model” to forecast time-space changing of soil water and chemical environment under existence of plant root in ground. The developed model will be contributed to optimize geo-environment for phytoremediation. Phytoremediation is purification of ground contaminated by toxic heavy metals using absorption of plants. However, it depends on water holding capacity of soil, holding capacity of chemical substance of soil, growth of plant and climate conditions. This model can clarify relationships between transfer of soil water and water soluble substance in unsaturated-ground and absorption of them by root uptake. This two-dimensional analysis consisted of equation of water movement and advection-diffusion equation considering absorption of soil water and water soluble substance by root with finite-difference method. This paper shows effectiveness of the developed model by calculating several SWCC conditions of soils. In addition, contribution degrees of remediation by single root uptake was clarified. The conclusions are as follows; 1) Absorption of water and water soluble substace were depended on matrix potential of soils. The higher water retention capacity the soil had, the lower root uptake occurred under same effective saturation degree. 2) In case available moisture of soil was lower, contribution of root uptake was higher.

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It is important to simulate accurately a rainwater infiltration process into slopes, in order to predict landslides caused by heavy rains. The accurate simulations of rainwater infiltration process into slopes require elucidating the soil moisture characteristics of soils. The authors have tried to estimate soil moisture parameters based on the field measurements of volumetric water contents by using the Particle Filter method, which is one of the sequential data assimilation methods. In this study, the discussion on determining the soil moisture parameters was carried out from the viewpoint of practical applications of the Particle Filter method. Firstly, discussion about appropriate value of standard deviation of observation noise, which is inherent to the Particle Filter method, was carried out. 60% of variation of measured volume water contents was recommended to an appropriate value of standard deviation of observation noise, in order to determine the adequate parameters of the soil moisture characteristics. Then, another discussion about adequate algorithm of the Particle Filter method was carried out, in comparison between SIR and MPF, which are representative algorithms, respectively, in the Particle Filter method. The appropriate soil moisture parameters could be determined even if either algorithm is applied. However, it was elucidated that the MPF is more effective algorithm than SIR.

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Carbon fiber reinforced plastic (CFRP) is made of stacks of plies, each of which is reinforced by carbon fibers. Since the anisotropy due to the fiber orientation and lay-up of plies shows directional dependency of wave velocity, it is important to know the acoustic property in CFRP in advance of ultrasonic testing. The elastic stiffness constants are fundamental input parameters for simulation of ultrasonic wave propagation in CFRP. In this paper, the elastic constants are determined using wavefield data of ultrasonic propagation on surfaces of CFRP. First the ultrasonic wave propagation is experimentally visualized by a non-contact ultrasonic generation method using scanning laser source. Then phase velocities are extracted from the wavefield data processed by the time-space Fourier transform. By optimizing the elastic constants in the Christoffel equation using the measured phase velocities, five independent components of the elastic constants in the unidirectional CFRP are determined. The accuracy of the estimated elastic constants is validated by a static compression test. Furthermore, the group velocities calculated in the finite element analysis using the estimated elastic constants are compared with the measured ones in the experiment.

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In this study, tsunami drifts analyses considering effects of the structures such as buildings and tsunami barriers are carried out. The model of drift simulation can consider the interaction between tsunami drifts and tsunami propagation. This model is based on 2-dimensional tsunami simulation model, and can also be considered behavier of the tsunami drifts at a wide variety of situation. As for the numelical example, this simulation model is applied for a analysis of tsunami drifts around a building which is to estimate the validity of model. This model is also applied to the drift simulation which has a variety of tsunami drifts and structures such as buildings and tsunami barrtiers. From the results of numerica example, it is shown thate the model can estimate a wide variety tsunami drifts behavior by using extended tsunami simulation model.

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An efficient dispersion analysis method is developed for periodic composite materials with a defect array. In the method scattering waves from the defects are represented by equivalent forces. The dispersion analysis is then reduced to a nonlinear eigenvalue problem. Application of Floquet transform to the dynamic excitation makes it possible to solve this with a small unit cell of the periodic composite having no defects. Since, in the present problem, the inverse Floquet transform is given by a sum of solutions at discrete wavenumber vectors, the numerical effort can be reduced effectively. The nonlinear eigenvalue problem is solved by the Block SS method. The parallel computation in this approach enables to accelerate the dispersion analysis. Performance of the developed method is investigated based on a numerical example.

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In this paper, a computational method was proposed for thermal interactions between compressible fluids and moving solids with different physical properties based on the mixture model. In the present method, physical properties of solids are considered in computational stages for heat conduction and velocities of multiphase fields. The present method was applied to natural convection in the cavity containing a square solid and obtained averaged Nusselt numbers on the heated wall were in good agreement with reference results. In addition, applicability of the present method was confirmed for compressible high buoyancy flows and heat transfer around a rotating triangular solid.

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In this paper, we propose a full Eulerian solid-fluid interaction analysis method using the building cube method, which is capable of achieving high parallel efficiency and generating meshes easily for complex geometry with local mesh refinement. Basic equations of solid and fluid are spatially averaged using volume fractions of each material on the assumption that both solid and fluid are incompressible. The averaged equations are solved using a fractional step method, where the equations are discretized in space using a collocated finite volume method. The VOF method is applied to capture material interfaces and the advection equation of VOF function is computed with the fifth-order WENO scheme. To validate the present approach, we simulate fluid-structure interaction problems, e.g. a deformable disk in a lid-driven cavity, deformation of Stanford bunny in fluid.

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Many scientific and engineering problems, including soil dynamics problems with elasto-plasticity, are involved in solving partial differential equations numerically. The correctness and accuracy of the solutions have to be checked in a rigorous way, i.e., the code used to solve the problems has to be verified. In the field of fluid dynamics, the method of manufactured solutions (MMS) has been proposed and accepted as a de facto standard for code verification. However, we show in this paper that MMS procedures cannot be used directly for soil dynamics problems considering elasto-plasticity. The main difficulty is due to the soil elasto-plasticity which is generally formulated in a rate form coupled by an algebraic constraint (the yield surface). Instead, we propose the method of numerically manufactured solutions (MNMS) for verifying elasto-plastic problems. The concepts and the workflows of MNMS are explained in detail and two simple demonstrations are presented. Though the numerical demonstrations in the present paper are primitive, the capability of the proposed MNMS, as a general and systematic way for developers and users of numerical simulations to verify their codes being used, should not be underestimated.

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In the finite element analysis, a structural element is efficient to represent the overall behavior of simulation models. On the other hand, a solid element is used to evaluate local behavior, such as stress concentration for stepped structures. For the purpose of developing a more flexible modeling for the finite element analysis, it is necessary to propose a numerical procedure for connecting shell and solid elements.
In conventional procedures to connect shell and solid elements, a continuity condition for only displacements is imposed at connecting surface. For applying the continuity condition for displacement fields on the interface between shell and solid elements, unreasonable deformation of solid elements near the interface may be observed.
This paper presents a numerical procedure for connecting shell and solid elements by using Nitsche's method, which imposes the continuity conditions for both displacement and stress vectors on the interface. From this approach, shell and solid elements can be connected with reasonable deformation and stress distribution.

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This paper verifies the influence of pseudo impulse waveform and mesh resolution on auralization. For the pseudo impulse, we employed the pseudo impulse derived from the equation of Lubich's Convolution Quadrature Method and Gussian pulse. In order to investigate the accuracy and frequency characteristics, a 3D wave propagation analysis is performed. We verified the sound data obtained by convolution of sound source and impulse response obtained by the different pseudo impulse and mesh resolution. As a results, the pseudo impulse obtained by Lubich's CQM is suitable for the noise simulation based on the impulse response analysis.

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For the evaluation of mechanical behavior of masonry structures, application of discontinuum-based numerical methods is gaining its imporatance in recent years. However, to investigate the stability of the masonry structures constructed on the soil, it is necessary to consider the deformation and hydraulic behaviors of the foundation ground as well as the discrete behavior of the stones. For example, in the Angkor ruins of Cambodia, there are many structures damaged due to ground instability induced by rainfall infiltration, and the rational stability evaluation method is required for future conservations. In this study, the coupled code of Numerical Manifold Method and Discontinous Deformation Analysis (NMM-DDA), a discontinuum-based numerical method, was extended with simplified three-phase mixture theory for the unsaturated soil, and an analysis method for mechanical interaction between unsaturated soil and masonry structure was newly developed. After the validation study through the simulation of model test and analytical solutions, a seepage problem of a masonry structure foundation was also carried out as an example problem.

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This paper tries to verificate the practicality of large-scale finite element method analysis using constitutive relations of concrete, which is reformed by a previous study considering calculation cost, with the objective of scalability. Since in the previous study they aimed to use the constitutive relation model with fracture analysis,we needt to extend the constitutive relation model to consider the effect of tension crack. This paper first shows the implemented algorithm. In the next step, seismic response analysis of a virtual nuclear power plant building is tried. At last, the practicality of large-sale finite element method analysis of RC structures is shown by the study on scalability of calculation.

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The meta-modeling theory seeks modeling that is consistent of continuum mechanics, and derives governing equations of structural mechanics. In this paper, we extend the theory to modeling of connecting structural components. A relatively massive solid element model of the component of bridge structures is converted to a non-linear spring and dashpot which is consistent to the model. The conversion method is regarded as model reduction, and applicable to linear and non-linear components of any configuration and materials. The limitation in applying the reduced model can be clariid by comparing the target solid element model.

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Nagoya Port is eminent trade port in Japan. In order to maintain the function of Nagoya Port, many dredged soils must be currently filled every year at Nagoya Port Island (hereinafter, PI) as a temporary disposal area. However, a huge earthquake would damage a revetment of PI to flow large volumes of dredged soils into the harbor. This would lead directly to a functional depression of Nagoya Port. For this reason, seismic assessment of PI and improvements to their earthquake resistance are urgent issues. In this study, we conducted a numerical simulation to grasp not only the damage of PI during and after the largest envisioned Nankai Trough earthquake but also the effect of height of reclaimed land on the deformation of PI due to the earthquake. The main conclusions are as follows. 1) If the current situation remains unchanged, a large deformation would occur on the PI by the earthquake, but the damage extent would not be such that dredged soils would flow into the harbor. 2) If the existing height were raised by 4 m, it would be impossible to prevent the lateral displacement of dredged soils, and there would be a high risk of dredged soils flowing into the harbor. 3) If the height were 4m lower than existing height, the lateral desplasement of dredged soils and revetment is reduced. These results indicated that it is dangerous that the height of the reclaimed land was raised more and it is important that the height of reclaimed land is reduced as much as possible for PI earthquake resistance.

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In this research, we deal with nonlinear continuum mechanics including uncertainty in material properties. Here, nonlinearity means material nonlinearity and geometrical nonlinearity. The author proposed NISP-Stochastic Finite Element Method (NISP-SFEM) that uses the approach called NISP (Non-Intrusive Stochastic Projection) method locally when calculating the tangent stiffness matrix, and we have shown the effectiveness of this method through numerical analysis. In that numerical analysis, a one-dimensional random variable problem such that Young's modulus changes stochastically according to a normal distribution has been dealt with. In this paper, we first deal with two-dimensional random variable problems such that the Young's modulus and the yield stress simultaneously change as independent random variables under the assumption of small strain theory. And next, we deal with the finite deformation elasticity problem including one-dimensional random variable such that the Young's modulus varies according to normal distribution. For this purpose, NISP-SFEM is extended to verify its effectiveness through these numerical analyses.

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A determination of cracks using topology optimization in 2-D time domain acoustics is considered. We introduce the cost function which is the misfit function between the obserbed data and the numerical data on the boundary of the domain having the cracks. We determin the cracks as the minimizer of the cost function using the topological derivative. The determination of the branched crack and the determination of the cracks having the less forecast information are shown in this paper.

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This paper presents a large scale fracture simulation method of RC members. In order to simulate the meso-scale fracture behavior of actual RC members, we applied the parallel processing to numerical analysis method of RC members. First, we show the formulation of the constitutive models for steel and concrete. Then, we explain the parallel processing based on domain decomposition method. The calculation efficiency of the proposed analysis method was verified. Finally, we verified the dependence of mesh size on the fracture behavior of RC beams. The numerical results demonstrated that the proposed analysis method makes possible fracture simulation of RC beams independently of mesh size.

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This paper presents the discontinuous Galerkin method for advection equation of free-surface flow analysis based on interface capturing approach. The discontinuous Galerkin method applied to the advection equation that the governing equation of the interface function of VOF method. Results obtained by linear DG method was compared with the result of continuous Galerkin method based on stabilized finite element method. As for the numerical example to verify the present method, the rotating square hill problem and broken-dam problem was carried out. It was concluded that the present method can obtain good mass conservation.

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We propose a new method of multi-scale analysis for plate-like devices such as a flat plate cell of solid oxide fuel cell (SOFC), which is classified into a composite plate composed of in-plane periodic structures. To characterize the macroscopic nonlinear mechanical behavior of the in-plane periodic structure, the method of numerical plate testing is employed. Since the obtained relationships between macroscopic generalized strains and stress cannot be represented by an equivalent homogeneous plate with a single material, we introduce a surrogate model composed of homogeneous layers that is expected to exhibit the same macroscopic responses. After the material parameters of these layers are identified, the macroscopic analysis becomes possible by use of a laminated structure with continuum solid shell elements available in a general-purpose finite element program. Representative numerical examples are presented to demonstrate the capability of the proposed multi-scale analysis method.

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The huge tsunami induced by the 2011 off the Pacific coast of Tohoku Earthquake caused very serious damages to the port structures, particularly the coastal seawalls. Damage mechanism of breakwater has been studied in the past, and there are mainly three causes; (I.) horizontal force due to the water level difference between the front and rear part of breakwater, (II.) soil scour and erosion behind the seawall during overflow and (III.) piping destruction associated with the decline of the soil durability by seepage flow. In this study, an analysis method to represent (III.) piping destruction is developed. A Lagrangian particle method based on the incompressible Smoothed Particle Hydrodynamics (ISPH) is selected as the simulation tool for fluid dynamics of free surface flows and seepage flows, and the movement of soil after the piping destruction is modeled by the Distinct Element Method (DEM). A Darcy-Brinkman type governing equation is utilized for a fluid governing equation, and it is modified to apply a high porosity domain. ISPH method and DEM are coupled by utilizing an interaction force derived from a fluid governing equation. In a piping analysis, a macro-scopic empirical piping judgement is adopted to reduce an analysis cost. In this paper, the comparison between experiment and analysis for the seepage flow of a breakwater is conducted as a validation, and a piping destruction analysis is conducted.

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This paper presents a numerical method for Fluid-Structure analysis based on Finite Cover Method using shallow water flow. With the help of the two-dimensional finite cover method (FCM) as a tool for interface capturing, the effect of debris is taken into account in fluid-structure interaction (FSI) analyses with the standard shallow water equation. The discontinuous interface boundary between the debris and the fluid is expressed by the Finite Cover Method. The motion of the debris is analyzed by Discrete Element Method (DEM) and the rigid body motion is calculated by using the fluid force action on the debris. For the fundamental resarch, several numerical examples are presented to demonstrate for the proposed fluid-structure interaction method.

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In design, the earth pressure of retaining wall is generally estimated by the Coulomb's earth pressure theory based on the limit equilibrium method. However, it is difficult to assess the earth pressure in case of pure three dimensional problem and inhomogeneous ground such as the improved ground. On the contrary, the rigid plastic finite element method is applicable to earth pressure assessment for general three dimensional and inhomogeneous problem. However, it is difficult to assess the active and passive earth pressures without providing a specific velocity admissible field since they are defined in tha same boundary value problem. This paper proposes a new analysis method to estimate active and passive earth pressures by rigid plastic finite element method (RPFEM) without any condition on the admissible velocity field. Moreover, it is applicable to the seismic active earth pressure based on the pseudo-static method. The applicability of proposed method has been examined through some case studies.

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Microtremer survey has played important roles in regional disaster prevention. However, in the survey, because observation data inevitably contains nonstationary noise, time-series data blocks appropriate for analysis are detected manually. It is highly expected that automation of this manual process promotes high-densely and long-time observation which have been major concern currently. In this research, we developed a method for auto detection of analysis blocks in microtremer records. The problem is formulized as binary classification problem, and it was solved using deep learning. Multilayer perceptron and convolutional neural network were applied and they showed about 95% accuracy in maximum.

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In this paper, a rigid plastic finite element analysis of a modified Cam-clay model for the initial plastic yielding under a drained condition is proposed. As a failure criterion of Modified Cam-clay model can be written as a second order cone constraint, the formulation of rigid plastic FEM is based on a second order cone optimization. To check the validity of a formulation, a series of numerical simulations of a cubic specimen with two type of meshes, a coarse mesh (5 elements) and a fine mesh (24 elements), under a drained condition subject to tri-axial compression loading were conducted. Numerical results show good coincidence with the theoretical solutions. In addition, numerical stability and good convergence can been observed. Consequently, it can be concluded that the proposed formulation is reasonable and appropriate.

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This paper presents a time-domain boundary element method for antiplane wave analysis of frozen porous media. Frozen porous media is the three phase model which consists of solid skeleton, pore fluid, and ice matrix, and is adequate to describe the dynamic behavior of seabed layer involving Methane Hydrate. The proposed boundary element method employs a convolution quadrature method based on implicit Runge-Kutta method for temporal discretization. Wave scattering by an inclusion in the frozen porous media has been solved and the results provide that S2-wave plays an important role for the evaluation of the volume ratio of Methane Hydrate in the seabed layer.

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In this paper a coupled elasto-plastic and damage model is presented and applied to predict the ductile damage accumulation under non-proportional loading conditions. The ductile damage constitutive equations, within the framework of the continuum damage mechanics, were coupled with the unconventional plasticity model Extended Subloading Surface¹⁾ in order to investigate the degradation of the mechanical performance of metals under the development of plastic deformation. Moreover, the tangential inelastic contribution²⁾ was introduced to simulate the acceleration of the damage evolution observed during experiments carried out under non-proportional loading paths.

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This paper presents an improved loading criterion in the elastic predictor/plastic corrector (return-mapping) algorithm for the extended subloading surface model for cyclic plasticity. Stress increments pointing inward of the subloading surface do not always lead to purely elastic unloading. More specifically, when a large stress increment in such direction is imposed, the subloading surface model can exhibit elastic unloading, followed by plastic reverse loading. During this transitional process, the subloading surface shrinks and degenerates to a stress point, and then expands toward the normal-yield surface. However, the standard loading criterion merely based on the elastic trial state may give an incorrect loading/unloading judgment, leading to serious error in numerical stress calculation. We thus develop a novel algorithm for the subloading surface model equipped with an improved loading criterion, together with a sub-step scheme, which can properly judge and track a process involving elastic unloading and plastic loading within an incremental step even in the above-mentioned cases. Numerical examples demonstrate that the proposed algorithm enables highly accurate stress calculation even in cyclic loadings with arbitrarily large strain increments.

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A parallel computation method with a multiphase model was applied to the local scour and deposition of a gravel bed, consisting of about 16,700 gravel particles with a diameter of around 7 mm, caused by falling overflows over a rectangular-notch weir. In the computations, representative 26 shapes of gravel particles were modeled with tetrahedron elements and contact-detection spheres. The fluid forces acting on a gravel particle were estimated with the volume integral of the pressure and viscosity terms included in momentum equations for the multiphase field. Through the comparisons with experiments, the applicability of the present computational method was confirmed.

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This paper presents investigation of accuracy and promotion of large-scale for the 2D-3D hybrid method based on the arbitrary domain. The Phase-Field Model (PFM) is applied to capture the free surface which is aimed to increase the accuracy for the 2D-3D hybrid method. The MPI method is used as the parallel computing method. Several numerical examples are examined to show the validity and the effectiveness of the presented method. Finally, the present model is applied to simulate the 2011 Tohoku tsunami.

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After the great east Japan earthquake tsunami 2011, disaster prevention and mitigation techniques are actively developing and establishing prediction method for the next millennium tsunami like the Nankai Trough earthquake. We has been developed a three-dimensional tsunami run-up analysis tool using the stabilized ISPH²⁾ which is one of the semi-implicit Lagrangian particle method. Tsunami run-up simulation in the urban area requires high resolution at least 2m in order to resolve the complicated tsunami flow. It leads to the large scale problem, and the tsunami run-up simulation at Kochi city needs to at least 1 billion particles. It is difficult to simulate the conventional ISPH method even on the premise of using supercomputer. Then, a new particle method ‘Explicit Incompressible SPH’ is developed that takes into consideration both calculation efficiency and accuracy.

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In this paper, the author proposes a finite element procedure based on a mixed variational formulation for incompressible and nearly incompressible hyperelasticity. The displacement field is approximated by the linear tetrahedral element and the pressure is assumed to be constant for each element. The inf-sup condition is circumvented by the stabilization technique using jump on element interface. The numerical properties of the proposed procedure are evaluated by an extended variant of the method of manufactured solution (MMS), which is developed by the author and can be applied to large deformation problems of hyperelasticity.

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External strengthening of Reinforcement Concrete (RC) structures using epoxy-bonded Fiber Reinforced Polymer (FRP) sheets has some negative aspects, such as interfacial debonding and poor resistance ability of epoxy resin for fire and ultraviolet (UV), in addition to the working environment restrictions. To overcome some of those negative aspects, FRP grid bonded with Polymer Cement Mortar (PCM) to strengthen RC structures is developed and proposed in this study. The main objective of this paper is to study the efficiency between Basalt FRP grids and PCM in the flexural strengthening of RC beams. A tensile test was first conducted to determine the static longitudinal tensile strength and maximum elongation properties of the different BFRP grids. Then, the well-known double shear test was conducted to determine the bond mechanism between BFRP grids and concrete. Finally, the flexural behavior of the RC beam externally strengthened with BFRP grids was investigated through a four-point bending test. The results showed the efficiency of using BFRP grids as external strengthening method, as well as the stress-strain relationship of RC beams cross-section shows the compatibility with flexural theory.

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A 3D particle-fluid coupled model was applied to concentrated leak erosion, which one of the mechanisms to trigger internal soil erosion. The method is based on a coupling the Discrete element method (DEM) and the Lattice Boltzmann method (LBM). The motion and collision of solid particles were calculated by the DEM, and the fluid flow of the pore fluid was directly solved at a lower particle scale by the LBM. By coupling these methods, the interaction between the particle and the fluid could be also calculated. In order to verify the particle-fluid coupled method, small 3D models were simulated based on the Hole Erosion Test (HET). Soil erosion parameters (such as critical shear stress and erosion rate) are calculated and compared with the results available in the literature. Consequently, this study facilitates more realistic simulations, compared with the available tests and 2D numerical simulations in the literature.

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We propose a test specimen and its test method for measuring and visualizing internal cracks in reinforced concrete, and demonstrate the validity. The proposed test specimen is a RC beam with steel bars exposed partially, which enables us to measure the internal cracks formed around deformed bars. We first show a numerical example to demonstrate the validity of the proposed test method for measuring internal cracks, using the finite element analysis with a damage model based on fracture mechanics for concrete. Then, the propagation of internal cracks in 4-point bend test of the proposed test specimen is measured and visualized by the digital image correlation. The comparison between the numerical and experimental results shows that the proposed test method is effective for measuring and visualizing internal cracks in the process of loading test.

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We examine the performance of an image analysis based on the digital image correlation for measuring and visualizing the crack propagation of concrete test specimen under compressive load. The image analysis method used in this study is an original approach we have developed to measure the crack propagation in concrete with a general digital camera and lighting equipments. After explaining the summary of the image analysis method, we first examine the relationship between the measuring condition and accuracy of strain in the compressive test of concrete specimen by varying the size and arrangement of subset in which the image corralation is evaluated. Then, an effective size and arrangement of subset is investigated to clearly visualize the crack propagation in concrete.

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Resilience and recoverability play important roles in controlling the structural performance of reinforced concrete (RC) structures after seismic actions. The main objective of this paper was to propose a new earthquake resistant method using a near surface mounted basalt fiber reinforced polymer rods (BFRPR-NSM) to minimize residual displacements, and to execute a fiber model based simulation evaluating the structural performance of the proposed BFRPR-NSM method reinforced RC columns. Based on the experimental results on both existing RC bridge columns and newly constructed columns, the beneficial effects of the BFRPR-NSM method were discussed. Moreover, the analytical studies on post-yield stiffness and residual deformations of BFRPR-NSM reinforced columns were conducted. Finally, suitable FRP design assumptions and concepts certifying the reality of post-yield stiffness are given.

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An optimal design method for rockfall countermeasures based on the discrete element method (DEM) is proposed. In this method, firstly, the path and the kinetic energy of rockfalls are simulated using the 3-dimensional DEM. Secondly, optimal design conditions that maximize the performance of rockfall countermeasures are selected based on the DEM results. In order to quantitatively evaluate the performance of countermeasures under a given set of conditions, we introduce a multi-objective function with three separate objectives. A response surface model for the function is determined by using the maximum likelihood estimation, which is based on the data collected from the DEM simulations, and optimal design conditions can be found by maximizing the response surface model. During the course of the explanation, a simple numerical example is presented to demonstrate the capability and the advantage of the proposed method.

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In order to describe the behavior of cyclic loading of unsaturated soils under various boundary conditions, the governing equations for cyclic loading tests were developed, and the cyclic triaxial test and the hollow torsional shear test were performed for the specimens in different initial conditions and under various boundary conditions for pore water and air. From the tests, the cyclic behavior varied depending on the initial and boundary conditions. The developed numerical technique reproduced the cyclic behaviors obtained in the experiments well. Furthermore, the numerical study showed that the influence of the smaller value of the net stress caused decrease of the skeleton stress more easily, and that the liquefaction resistance obtained from the triaxial test and the hollow torsional shear test varied largely.

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Drainage measures for embankments against rainfall are different during construction and after commencement of use, and the effects are sustained intermittently from the start of construction to after the commencement of use. Of the rainfall over this span of time, it is considered that embankments are undermined internally by the effects of the rainfall during construction. However, as the dates of construction of embankments cannot be determined and the amounts of rainfall sustained during construction are varied, the effects of rainfall on the initial stress conditions upon the completion of embankments have not been clarified. In this study, soil/water/air-coupled F.E. analysis was used to perform analyses of embankments which take into account compaction and the history of rainfall/evaporation, and a comparative study is made of the effects of differences in the amount of rainfall during construction on the initial stresses inside embankment.

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In the 2016 Kumamoto Earthquake, numerous serious structural damages occurred along the active faults. Many of these damages are caused by the fault movement and the deformation of surface ground. This suggests the importance of deformation prediction of the surface ground around the active fault. In this study, employing finite element method with a finite-strain damage model, we conduct a series of case studies on numerical models with ideal topography as a basis examination for predicting the surface ground deformation. After confirming the applicability of the employed material models and analysis conditions, we investigate the effects of the inclination of the fault and the topography on the surface rupture due to fault movement.

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This study presents a numerical study on effects of spatial characteristics of slopes in rockfall simulations using DEM. A series of DEM simulations of a model experiment were performed under the different calcu- lation conditions and different spatial characteristics of slope, and effects of these factors were quantified. Based on the obtained results, it was found the accuracy of the mean values of input parameters is much more important than considering the spatial characteristics. However the conclusion is limited to simulated results obtained in this study, hence more detailed verification is necessary.

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