Osaka, Japan
Osaka, Japan

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Mizutani H.,Kyoto University | Nakagawa H.,NEWJEC Inc. | Yoden T.,Kyoto University | Kawaike K.,Kyoto University | Zhang H.,Kyoto University
Journal of Hydraulic Research | Year: 2013

This paper reports laboratory experiments and numerical simulations of river embankment failure due to overtopping flow for different sediment sizes and different saturation conditions of embankment body. The effects of saturation and sediment size of embankment materials on the erosion process are discussed based on the results of the laboratory experiments. A numerical model is proposed to simulate the erosion process of embankments by overtopping flows. The proposed model considered the effects of infiltration process and resisting shear stress due to suction of unsaturated sediment. To simulate the embankment erosion phenomenon, the numerical model consists of four modules: two-dimensional (2D) shallow-water flow, seepage flow, sediment transport using a non-equilibrium model framework, and 2D slope stability. The validity of the developed model is tested using experimental data on embankment erosion. The numerical results on progressive embankment erosion agree well with the results of the sandy river embankment experiments. © 2013 © 2013 International Association for Hydro-Environment Engineering and Research.

Yamasaki M.,Tokyo University of Agriculture | Terao T.,NEWJEC Inc.
Civil-Comp Proceedings | Year: 2013

This paper describes a mechanism for creating 3D highway shapes and producing drawings with the data input and creation function in OHPASS. The functions developed include a method for creating 3D terrain and control points that are input using Civil 3D, and a function for incorporating the calculated results back into Civil 3D. In addition the system is linked with UC-win/Road Ver.9.0 (produced by FORUM8 Co., Ltd.), 3D VR (Virtual reality) system designed especially for creating a variety of 3D models and running many types of realistic simulations within the 3D VR environment built by the software itself. UC-win/Road is capable of providing various real-time presentations with CG after generating a three-dimensional VR space, and is being utilized extensively in landscape examination, design consultation, and for presentations at project briefings. The authors have developed a function that loads the results of the road alignment examination obtained in OHPASS, and displays them as horizontal and vertical drawings within the UC-win/Road 3D VR environment. As a feature of OHPASS, it is possible to examine two or more alignments by changing design conditions. Now a function for selecting and loading each and every alignment has been added so that the multiple results of the road alignment examination can be loaded. In the study, described in this paper, the authors have attempted to link OHPASS, an optimal road alignment search program, with three-dimensional CAD. In addition, by enabling the optimal design calculation results to be loaded into 3D CAD, graphical representations of the design the results can be linked with a 3D VR system. As the design results can be linked with a 3D VR system, they can used to create an integrated 3D VR system. The 3D VR system enables the realistic surrounding landscape of the designed project to be viewed. Within the 3D VR system, dynamic 3D space can be controlled in real time, for example, it is possible to "drive" on the designed road in virtual space as if we are actually driving .These driving experiences and the visualization in the 3D VR system allows us to examine and evaluate the designed project effectively. © Civil-Comp Press, 2013.

Goto H.,Kyoto University | Sawada S.,Kyoto University | Hirai T.,NEWJEC Inc.
Wave Motion | Year: 2011

We introduce a new conserved quantity, Normalized Energy Density (NED), alternative to the conventional definition of energy for a layered structure in a 2D SH problem. NED is defined by the average of power of a half transfer function multiplied by the impedance, and the conservation across the material interface is analytically proved for a two-layered case. For three, four, and ten-layered cases, the conservation is examined by applying the Monte Carlo simulation method, and then NED is supposed to be conserved through the layers. © 2011 Elsevier B.V.

Kabir M.A.,The Bureau of Meteorology | Kabir M.A.,Monash University | Dutta D.,CSIRO | Dutta D.,Monash University | Hironaka S.,NEWJEC Inc.
Water Resources Management | Year: 2014

The paper presents a process-based distributed modelling approach for estimating sediment budget at a river basin scale with partitions of suspended and bed loads by simulating sediment loads and their interactions. In this approach, a river basin is represented by hillslopes and a network of channels. Hillslopes are divided into an array of homogeneous grid cells for modelling surface runoff and suspended sediments. Channels are defined by incorporating flow hydraulic properties into the respective hillslope grids as sub-grid attributes for modelling both suspended and bed loads. Suspended sediment transport is modelled using one dimensional kinematic wave approximation of Saint-Venant's principles of conservation of mass and momentum. Transport capacity of runoff or streamflow is used to set the limit of suspended sediment transport rate. Bed load in channels is estimated based on the instantaneous water and hydraulic parameters. Fractional interchange between suspended load and bed load is then back calculated. The performance of the model was evaluated through a case study application in a large river basin in Japan. The model satisfactorily calculated the sediment transport and total sediment budget in the basin. The simulated bed load was found to be reasonable and consistent with the water flow and suspended sediment flux. The results showed the bed load can be expressed as a linear function of the suspended load. The fractions of different sediment loads also exhibit linear relationships with water discharge for the rising and recession limbs of the flood hydrographs. The case study has demonstrated that the process-based distributed modelling approach can efficiently describe the basin-scale sediment budgets with due consideration of the suspended and bed loads and their interactions in the hillslopes and channels. © 2014 Springer Science+Business Media Dordrecht.

Fukuda T.,NEWJEC Inc.
Journal of Geosciences | Year: 2011

In Japan, slope failures frequently occur during heavy rain, and there have been large-scale disasters.Techniques to reduce the damage due to slope failures can be characterized as hard or soft measures. For instance, a hard measure would be setting up a retaining wall,and a soft measure would be making a hazard map. Although hard measures proved to be effective, their construction is often difficult to justify in terms of economic efficiency; the cost of management is also expensive. Therefore, the making of hazard maps to reduce the effects of the disaster is very important. However, present hazard maps do not provide sufficient information on hazard risks. In this study the author investigated making hazard maps of the Shirasu slope failure, oriented to the prediction of the time of occurrence and probability of the debris flow area, called "real-time hazard map." The proposed real-time hazard map is a map to represent the product of the probability of slope failure occurring and the probability of debris flow area. In order to organize the timeline of the probability of slope failure, the setting of Fragility Curve to relate the rainfall pattern to the probability of slope failure occurrence is needed. Fragility Curve on the Shirasu slope failure becomes a relational expression of the effective rainfall and the probability of slope failure occurrence if a supposed instability by the prime factor of the Shirasu slope is uniformity because early rainfall greatly influences the moisture state in the Shirasu slope from the continuous measurement result of the resistivity etc. The probability method mainly utilizes the angle of elevation formed by slope height and distance between end margin of debris and slope head crown, 6. Using the above 6 distributions, they developed a stochastic simulation system for predicting the hazard areas of shallow slope failure debris, and this simulation called SLSS (Shallow Landside Simulation System). SLSS simulation is applied for the calculation of probability of debris flow area. To use the real-time hazard map drawn up in the results of this study, the methodology of this study is available for making hazard maps of slope disaster risks.

Kabir M.A.,Monash University | Dutta D.,Monash University | Dutta D.,CSIRO | Hironaka S.,NEWJEC Inc. | Pang A.,Monash University
Water Resources Management | Year: 2012

Bed load transport is a key process in maintaining the dynamically stable channel geometry for restoring the form and function of river ecosystems. Bed load consists of relatively large sediment particles that are moved along the streambed by rolling, sliding or saltation. Currently, various empirical correlations are used to estimate bed load transport rates since no single procedure, whether theoretical or empirical, has yet to be universally accepted as completely satisfactory in this aspect. Bed load particles are primarily sourced from river bed materials or banks. The amount of bed load and its spatial distribution contributes significantly to river bed level changes. Hillslope sediment contribution, mostly available to the river in the form of suspended load, also plays an important role in river bed level changes. This study aims to analyse different bed load equations and the resultant computations of river bed level variations using a process-based sediment dynamic model. Analyses have revealed that different bed load equations were mainly deduced from the concept of relating bed shear stresses to their critical values which are highly factored by the slope gradient, water discharge and particle sizes. In this study, river bed level variations are calculated by estimating total surplus or deficit sediment loads (suspended loads and bed loads) in a channel section. This paper describes the application of different widely used bed load equations, and evaluation of their various parameters and relative performances for a case study area (Abukuma River Basin, Japan) using a basin-scale process-based modelling approach. Relative performances of river bed level simulations obtained by using different bed load equations are also presented. This paper elaborates on the modelling approaches for river bed load and bed level simulations. Although verifications were not done due to unavailability of field data for bed load, qualitative evaluations were conducted vis-à-vis field data on flow and suspended sediment loads as well as the bed loads presented in different past studies. © 2011 Springer Science+Business Media B.V.

Nakamura N.,Takenaka Corporation | Akita S.,Kansai Electric Power Co. | Suzuki T.,Takenaka Corporation | Koba M.,Kansai Electric Power Co. | And 2 more authors.
Nuclear Engineering and Design | Year: 2010

The probabilistic safety assessment (PSA) is important for nuclear power buildings in Japan because the risk of the occurrence of seismic ground motions beyond the design assumption cannot be denied. In this paper, the building fragility of the seismic PSA was evaluated using a high accuracy analysis model (three-dimensional nonlinear FEM building model considering soil-structure interaction and basemat uplift behavior). First, the response analyses were conducted increasing the input acceleration up to 3500 Gal, until the damage of the building reached the ultimate condition. The damage of the building was estimated from the shear strain, the axial stress, and the consumed strain energy of the shear walls. Then, the influence on the response given by the vertical ground motion and the basemat uplift was evaluated. In addition, considering the shear destruction of the web wall and compressive crash of the flange wall as the fracture modes, the building fragility was evaluated. As a result, it was shown that the investigated method is efficient for more accurate seismic PSA estimation. © 2009 Elsevier B.V. All rights reserved.

Egashira S.,NEWJEC Inc.
Journal of Disaster Research | Year: 2011

The author thinks keys to debris flow studies lie in 1) sediment sorting in debris flow body, 2) phase shifting to or from fluid to solid, 3) difference between sediment concentration and flux sediment concentration, 4) constitutive relations and 5) governing equations employed in numerical simulation. In discussing 3)- 5), the author stresses that 1) Eq. (1) predicts the spatial average sediment concentration of the flow body well from debris flow to bed load, and thus it should be prized, 2) researchers must be careful for the difference between sediment concentration and flux sediment concentration and for different flow structures over erodible and rigid beds, and realizes that 3) many problems associated with governing equations such as bed shear stress, erosion and deposition rates and correction parameters for sediment transport still remain to be solved.

Kabir M.A.,Monash University | Dutta D.,Monash University | Dutta D.,CSIRO | Hironaka S.,NEWJEC Inc.
Hydrology and Earth System Sciences | Year: 2011

Modeling of sediment dynamics for developing best management practices of reducing soil erosion and of sediment control has become essential for sustainable management of watersheds. Precise estimation of sediment dynamics is very important since soils are a major component of enormous environmental processes and sediment transport controls lake and river pollution extensively. Different hydrological processes govern sediment dynamics in a river basin, which are highly variable in spatial and temporal scales. This paper presents a process-based distributed modeling approach for analysis of sediment dynamics at river basin scale by integrating sediment processes (soil erosion, sediment transport and deposition) with an existing process-based distributed hydrological model. In this modeling approach, the watershed is divided into an array of homogeneous grids to capture the catchment spatial heterogeneity. Hillslope and river sediment dynamic processes have been modeled separately and linked to each other consistently. Water flow and sediment transport at different land grids and river nodes are modeled using one dimensional kinematic wave approximation of Saint-Venant equations. The mechanics of sediment dynamics are integrated into the model using representative physical equations after a comprehensive review. The model has been tested on river basins in two different hydro climatic areas, the Abukuma River Basin, Japan and Latrobe River Basin, Australia. Sediment transport and deposition are modeled using Govers transport capacity equation. All spatial datasets, such as, Digital Elevation Model (DEM), land use and soil classification data, etc., have been prepared using raster "Geographic Information System (GIS)" tools. The results of relevant statistical checks (Nash-Sutcliffe efficiency and R-squared value) indicate that the model simulates basin hydrology and its associated sediment dynamics reasonably well. This paper presents the model including descriptions of the various components and the results of its application on two case study areas. © 2011 Author(s).

Hebig K.H.,TU Berlin | Ito N.,NEWJEC Inc. | Scheytt T.,TU Berlin | Marui A.,Geological Survey of Japan
Hydrogeology Journal | Year: 2012

While research focuses mainly on the intensively used shallower aquifers, only a little research has addressed groundwater movement in deeper aquifers. This is mainly because of the negligible relevance of deep groundwater for daily usage and the great efforts and high costs associated with its access. In the last few decades, the discussion about deep geological final repositories for radioactive waste has generated strong demand for the investigation and characterization of deep-lying aquifers. Other utilizations of the deeper underground have been added to the discussion: the use of geothermal energy, potential CO 2 storage, and sources of potable water as an alternative to the geogenic or anthropogenic contaminated shallow aquifers. As a consequence, the fast growing requirement for knowledge and understanding of these dynamic systems has spurred the research on deep groundwater systems and accordingly the development of suitable test methods, which currently show considerable limitations. This review provides an overview of the history of deep groundwater research. Deep groundwater flow and research in the main hydrogeological units is presented based on six projects and the methods used. The study focuses on Germany and two other locations in Europe. © 2011 Springer-Verlag.

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