MORIKAWA Yukihiro

写真a

Affiliation Department etc.

Department of Architecture, Civil Engineering and Industrial Management Engineering
Department of Architecture, Civil Engineering and Industrial Management Engineering
Advanced Disaster Prevention Engineering Center

Title

Assistant Professor

Mail Address

E-mail address

Graduate School

  • 2010.04
    -
    2013.03

    Nagoya Institute of Technology  Graduate School, Division of Engineering  Department of Scientific and Engineering SimulationDoctor's Course  Completed

  • 2003.04
    -
    2005.03

    Nagoya Institute of Technology  Graduate School, Division of Engineering  Department of Architecture, Civil Engineering and Industrial Management EngineeringMaster's Course  Completed

 

Papers

  • STUDY ON CONVERTER SLAG AS GROUND IMPROVEMENT MATERIAL

        2021.03  [Refereed]

    Research paper (scientific journal)   Multiple Authorship

    In this study, converter slag, which has problems with expandability and pretreatment to prevent it, was studied. The advantages of converter slag as a ground improvement material were studied, focusing on its frictional properties, grain size characteristics, and hydraulic properties. The present study showed that mixing fine grained soil with gravel and sand-rich converter slag improved the particle size distribu-tion of the soil mixture. As a result, the compaction characteristics of the mixtures were greatly improved and the lack of compaction was less likely to occur regardless of the compaction method. It was also found that the ground strength of the soil mixture increased with the mixing rate of the converter slag, and that the fine-grained soil acted as a cushion to reduce the expansion of the converter slag. Further-more, the effect of mixing slag into the soil was found to increase the improvement of the cement by improving the particle size distribution, alkalization, and decreasing the unit water volume for mixing of tar-get soil.

  • Liquefaction Damage Suppression Effects of Existing Small Scale Structure Receiving Eccentric Load Using Floating Grid-type Improvement

        2020.12  [Refereed]

    Research paper (scientific journal)   Multiple Authorship

    In recent years, liquefaction damage of detached houses due to large-scale earthquake has become se-rious all over the world. If the existing small-scale structures such as houses are tilted due to liquefaction, they suffer more serious damage than they are subsided. In this paper, the effect of countermeasure against tilting damage due to liquefaction using floating grid-type improvement was investigated by 2D model tests under 1g condition using eccentric model structure, and non-linear FEM analyses. From the results, it was found that the floating grid-type improvement can significantly suppress the settlement damage of structure by suppressing the lateral flow of the liquefied ground even if the dead load of struc-ture is eccentric. It was also found that lateral flow of the liquefied soil hardly occurs when the structure inclines due to liquefaction, and the effect of countermeasure against tilting damage due to liquefaction using floating grid-type improvement was not as high as the effect of suppressing subsidence damage. Therefore, it was found that desirable to use a floating grid-type improvement and drainage method to prevent tilting damage of structure.

  • Numerical Analysis on Mechanism of Dewatering as a mitigation method Against Liquefaction

    Y. Morikawa, H. Cho

    International Journal of GEOMATE   18 ( 66 ) 68 - 75   2020.02  [Refereed]

    Research paper (scientific journal)   Multiple Authorship

    In recent years, liquefaction due to major earthquake caused serious damages to many infrastructures and houses around the world. In order to protect people’s daily life and infrastructure from the disaster, development of effective and economical countermeasure against liquefaction that can be applied to existing houses is becoming increasingly important. Although many liquefaction countermeasures have been developed by many researchers, most of them require large construction machines and are costly, which limits their application to existing structures. For this reason, a liquefaction countermeasure, called as groundwater-level decreasing method, has been proposed in Japan. This method has already been put into practice and the construction of the countermeasure has finished several years ago. The purpose of this method is to change a liquefied layer to a non-liquefied layer by lowering the groundwater level. Yet the performance of this method has not been fully evaluated quantitatively. Therefore, in this paper, numerical analysis using FEM method was carried out to evaluate the liquefaction damage before and after the lowering of groundwater level. The calculation is conducted with 2D soil-water coupling finite element-finite difference (FE-FD) analysis based on a rotating-hardening elastoplastic constitutive model. From the analyses, it is found that the effective stress of the ground below under-groundwater level increases significantly because of the lowering of groundwater-level, resulting in an increase in resistance to liquefaction and mitigating the settlement damage of ground.

  • New Chemical Grouting Method Using Ultrasonic Vibration

    Journal of the Society of Materials Science, Japan   69 ( 1 ) 63 - 68   2020.01  [Refereed]

    Research paper (scientific journal)   Multiple Authorship

    Injecting the improvement material into the ground by the chemical solution injection method, the permeability of the ground decreases due to the occurrence of clogging in void of ground. The permeability of the ground greatly affects the penetration range of the chemical solution and the quality of the improved body. In other words, it is very important to prevent the decrease of the permeability of the ground in the chemical injection method. Therefore, in this research, a new chemical grouting method that prevents the decrease of the permeability of the ground is developed by applying ultrasonic vibration when grouting the chemical solution. Consequently, in our previous laboratory and the field verification, it was found that the decrease of the permeability of the ground can be prevented, also the diameter and the quality of the improved body were improved by applying ultrasonic vibration when grouting the chemical solution.

  • Reduction Effects of Liquefaction Damage Using Small Scale Floating Grid-Type Improvement for Existing Small Scale Structure

      75 ( 2 ) 329 - 339   2019.12  [Refereed]

    Research paper (scientific journal)   Multiple Authorship

    Earthquake resistance of important structure have benn promoted based on the lessons learned from the big Earthquake in Japan. However, liquefaction still causes serious damages to many detached hous-es in the world. Also, most soil improvement methods apply to original ground without structure, and countermeasure against liquefaction for existing small structure has not been sufficiently investigated. Therefore, we investigated reduction effects of liquefaction damage using small grid-type improvement as countermeasure against liquefaction for existing small structure. To this end, 2D model tests under 1g condition and non-linear FEM analyses have been carried out. From the model tests results, it was found that if the interval of improved wall is within 1.2 times of the base width, some degree of counter meas-ure effect agaisnrt subsidence due to liquefaction can be obtained with a small grid-type improvement where the improvement depth is about twice the base width. The numerical simulation has shown a simi-lar result as found in the observations.

  • Liquefaction-Induced Buckling Failure of Group-Pile Foundation and Countermeasure by Partial Ground Improvement

    K. Hamayoon, Y. Morikawa, Guanlin Ye and Feng Zhang

    International Journal of Geomechanics ( American Society of Civil Engineers )  19 ( 5 ) 04019020-1 - 04019020-16   2019.02  [Refereed]

    Research paper (scientific journal)   Multiple Authorship

    Pile foundations may lose their lateral resistance in earthquake-induced liquefaction and may fail not only by bending and shear forces but also buckling. Although research has been done on the buckling of pile foundations, it is still necessary to investigate further the buckling of pile foundations during an earthquake and a corresponding efficient countermeasure. Some existing pile foundations may not meet the requirement of present seismic design standards and are vulnerable to buckling failure. In the present study, numerical analyses and model tests were conducted. The validity of the proposed numerical method was first verified through a 1-g shaking table test. Then, the buckling risk of a group-pile foundation and its strengthening with partial ground improvement (PGI) were carefully estimated. Meanwhile, the effectiveness of the proposed countermeasure with PGI against the buckling of the group-pile foundation was confirmed by a static model test. The purpose of the study was to investigate the effectiveness of ground improvement for the retrofitting of vulnerable pile foundations against buckling due to seismic loading.

  • Effective method to increase ground stiffness and bearing capacity in 2D and 3D flat foundations

    Y. Morikawa, H. M. Shahin and T. Nakai

    Proc. of the 7th China-Japan Geotechnical Symposium     215 - 219   2018.03  [Refereed]

    Research paper (international conference proceedings)   Multiple Authorship

    To increase bearing capacity of ground, geosynthetic is laid below the foundation. In the present study, for increasing bearing capacity, reinforcing effect in the case where each edge of the reinforcement is fixed with the soil has been investigated. For this purpose, 2D model tests under 1g condition model tests was carried out. According to the 2D model test, it is revealed that the appropriate depth of the reinforcement is not too deep. The 3D centrifuge model test was also conducted in order to verify the reinforcing effect which was observed by 2D model tests in actual stress condition. According to the 3D centrifuge model test, almost same tendency is seen between 2D model test and 3D centrifuge model test. From the results of the 3D centrifuge model test and 2D model tests, it is revealed that the fixity condition of reinforcement plays an important role in increase of the bearing capacity. The bearing capacity increases significantly when reinforcing the ground in the same length or a little larger than the width of the foundation with an appropriate depth.

  • Numerical Analysis on Mechanism of Liquefaction not only in Main Earthquake but also in After Shock

    Y. Morikawa, H. Sakaguchi, A. Taira and H. Cho

    International Journal of GEOMATE   14 ( 45 ) 58 - 65   2018.03  [Refereed]

    Research paper (scientific journal)   Multiple Authorship

    During the 2011 Great East Japan Earthquake, liquefaction occurred in the reclaimed ground in the wide area of east Japan. In some areas, liquefaction happened in the aftershock was even more serious than what happened in the main shock. For this reason, the liquefaction that happened a long time after the earthquake caused not only by the main shock but also the multiple aftershocks within a short period of time, is intensively investigated in recent years. In this paper, particular attention is paid to the characteristic features of the liquefaction and its consequent consolidation-induced settlement. Based on the observed data, a series of dynamic-static analyses, considering not only the earthquake loading but also static loading during the consolidation after the earthquake shocks, are conducted in a sequential way just the same as the scenario of the earthquake. The calculation is conducted with 3D soil-water coupling finite element-finite difference (FE-FD) analyses based on a rotating-hardening elastoplastic constitutive model. From the analyses, it is recognized that small sequential earthquakes, which cannot cause liquefaction of a ground in an independent earthquake vibration, cannot be neglected when the ground has already experienced the liquefaction after a major shock. In addition, the aftershocks have great influence on the long-term settlement of the soil layers with low permeability. It is confirmed that the numerical method used in this study can describe the ground behavior correctly under repeated earthquake shocks.

  • Effective use of geosynthetics to increase the bearing capacity of shallow foundations

    H. M. Shahin, T. Nakai, Y. Morikawa, S. Masuda, S. Mio

    Canadian Geotechnical Journal   54   1647 - 1658   2017.05  [Refereed]

    Research paper (scientific journal)   Multiple Authorship

    In this research, a reinforcement mechanism for shallow foundations is determined through laboratory model tests and numerical analyses. The numerical analyses are performed with the finite element program FEMtij-2D using the elastoplastic subloading tij model. The frictional behavior between the reinforcement and the ground is simulated using an elastoplastic joint element. Several tests were performed whereby the installation depth, length, roughness, and fixity conditions at the edges of the reinforcement were varied. Results show that the effectiveness of the reinforcement and the bearing capacity of the reinforced ground depend on the position, length, roughness, and fixity condition of the reinforcement. A significant increase in the bearing capacity can be achieved if the geosynthetics are properly placed at an optimum length with the boundary fixed to the ground. The effect of the loading position is also investigated because in reality the load on a foundation does not always act at the center of the foundation. The numerical results accurately describe the experimental results; the simulations accurately account for the mechanical behaviors of both the soil and reinforcement and the frictional behavior between them. Therefore, the simulation technique can be used to predict the bearing capacity of reinforced ground.

  • Reinforcing effects of geosynthetics whose edges are fixed with soil in bearing capacity problems of foundations

    Yukihiro MORIKAWA, Ryo SUZUKI, Saki MASUDA, H. M. SHAHIN, Teruo NAKAI

    Japanese Geotechnical Journal ( Japanese Geotechnical Society )  12 ( 2 ) 277 - 287   2017.03  [Refereed]

    Research paper (scientific journal)   Multiple Authorship

    In practice, geosynthetic laid beneath the foundation is a common reinforcement technique to increase the bearing capacity of foundation. In this study, the geosynthetic with both ends are fixed with the soil has been investigated in order that the bearing capacity is improved and at the same time the settlement can be reduced. For this purpose, 2D model tests under 1g condition and 3D centrifuge model tests have been carried out as well as the corresponding non-linear FEM analyses. In the 2D model tests, several depths of the reinforcement have been tested under both concentric and eccentric loads. According to the 2D model test and simulation, we found that the appropriate depth of the reinforcement is not too deep. The 3D centrifuge model test and simulation were also conducted in order to confirm the reinforcing effect under actual stress condition. The results under the 3D model test also revealed that the bearing capacity increased significantly when reinforcing the ground in the same length or a little larger than the width of the foundation with an appropriate depth. The numerical simulation has shown a similar result as found in the observations.

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Presentations

  • Applicability of crushed roof tile as ground material

    Y. Morikawa, K. Maeda, T. Sato, H. Kamiya

    IWS MAURITIUS 2019  (Mauritius)  2019.11  -  2019.11 

  • EFFECTIVENESS OF CRASHED TILE IN COUNTERMEASURE AGAINST LIQUEFACTION

    Y.Morikawa

    3rd International Conference on Geotechnique, Construction Materials and Environment  (Nagoya, Japan)  2013.11  -  2013.11