研究者詳細 - 野田　利弘

論文 - 野田　利弘

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Influence of development/diminishing of anisotropy on the mechanical behavior of clayey specimen 国際誌

Khan, I., Nakai, K., Noda, T. and Mizukami, K.

4th International Conference on Science, Engineering and Environment (SEE) 頁： 593-598 2018年11月

記述言語：英語

Anisotropy refers to the directional dependence of material properties. In order to know the true behavior of naturally deposited soil, the knowledge of development/diminishing of anisotropy are very important. The anisotropy of clays and silty clay intimately connected with their structure, which depends on the environmental conditions during which the soil is deposited as well as the stress changes subsequent to deposition. In this paper, triaxial tests were carried out using the vertical and the horizontal extraction specimen of the reconstituted clay and silty clay, for accumulating experimental facts of development of anisotropy during the preliminary consolidation process and the influence of the anisotropy on the shear behavior. Pre-consolidation pressure of 200kPa applied to induced initial anisotropy. Undrained shear triaxial test was performed with different isotropic stresses on clay and silty clay, isotopically consolidated for 24 hours and undrained shearing was carried out under constant axial strain rate of 0.0056(mm/min). Vertical sample shows larger peak strength as compared to horizontal, because of the development of anisotropy on the compression side. As the confining pressure increases, the difference between peak strength of vertical and horizontal becomes smaller and smaller which indicate that the anisotropy diminished and intensity ratio decreases. By comparing clay and silty clay, silty clay materials lose their anisotropy at lower confining pressure as compared to clay materials. Therefore, the grain sizes have significant effect on the developing and diminishing of anisotropy. Another important fact observed was critical state index is decreasing and become constant as confining pressure increases.

堤体基礎の地震動脆弱性が津波氾濫解析に与える影響に関する検討査読有り

今井健太郎, 中井健太郎, 野田利弘, 新井伸夫, 岩間俊二, 馬場俊孝

土木学会論文集B2（海岸工学） 74 巻 ( 2 ) 頁： I_247 - I_252 2018年11月

記述言語：日本語掲載種別：研究論文（学術雑誌）

本研究では，愛知県の巨大産業を支えるサプライチェーンを擁する地域のひとつである碧南市を対象として，南海トラフ巨大地震による地震動に対する堤体基礎の沈下量を数値解析によって評価した．この解析結果を津波氾濫解析に組み込むことで，堤体基礎の脆弱性が氾濫過程や浸水域に与える影響について検討を行った．堤体基礎の沈下や直立堤の崩壊を考慮することにより津波浸水域は大きく拡大することを定量的に示すことができた．このことは，沿岸構造物の耐震化の重要性を示していることはもちろんのこと，強震動による海岸・河岸構造物や堤体基礎部の脆弱性が津波ハザード評価に与える影響を無視できないことを示している．

DOI： 10.2208/kaigan.74.I_247

Deformation-failure mechanism of saturated fill slopes due to resonance phenomena based on 1g shaking-table tests 査読有り国際誌

Murao Hidehiko, Nakai Kentaro, Noda Toshihiro, Yoshikawa Takahiro

CANADIAN GEOTECHNICAL JOURNAL 55 巻 ( 11 ) 頁： 1668 - 1681 2018年11月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Canadian Geotechnical Journal

Earthquake motions include waves of various frequency bands ranging from low to high frequency. Notably, the dominant frequency affects the seismic stability of fill slopes. Hence, to analyze the deformation–failure mechanism during an earthquake, 1g shaking-table tests were conducted in this study on saturated fill slopes considering the resonance phenomenon. Results show that the deformation–failure mechanism of a fill slope cannot be defined by only one sliding surface. Multiple sliding surfaces are formed progressively depending on the ground and external conditions. Moreover, evaluating the seismic stability of fill slopes depends not only on the magnitude of the acceleration, but also on the relationship between the natural frequency of the fill slope and the input frequency. These phenomena cannot be considered in the seismic-intensity method nor in the Newmark’s method used in conventional design. When implementing seismic countermeasures, it is important to determine the frequency characteristics of fill slopes and design the countermeasures considering the predominant frequency of the seismic wave anticipated at the site.

DOI： 10.1139/cgj-2017-0385

Web of Science

Scopus

MONITORING THE TRIGGERING OF LIQUEFACTION USING IMAGE PROCESSING 査読有り国際誌

Uy Erica Elice Saloma, Noda Toshihiro, Nakai Kentaro, Dungca Jonathan Rivera

INTERNATIONAL JOURNAL OF GEOMATE 15 巻 ( 51 ) 頁： 180 - 187 2018年11月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：International Journal of GEOMATE

Inrecent studies triggering or initiation of liquefaction is usually performed to characterize the potential of the soil to liquefy. Its behavior before, during and after liquefaction in a laboratory test needs to be understood. Image processing was implemented to monitor the triggering of liquefaction and estimate the cyclic shear strain that would trigger liquefaction. Lucas and Kanade pyramidal optical flow algorithm were used to track the movement of the soil. A mirrorless camera was the instrument used. The strain-controlled consolidated undrained cyclic triaxial test was performed. The loose condition was tested at 2.4, 1.6 and 0.8 mm strain amplitudes. The confining pressures used were 50, 100 and 200 kPa. Based on the results, the estimated values for the cyclic shear strain that would trigger liquefaction had a range of values due to the occurrence of non-homogeneous deformation. The minimum values were in agreement with the typical values while the maximum values were larger. For the behavior of the soil before, during and after liquefaction had occurred, the deformation behavior was different. More deformations were observed after the triggering of liquefaction.

DOI： 10.21660/2018.51.02150

Web of Science

Scopus

Seismic Response Analysis of Ground/Geo-structures using Geo-Analysis Integration Code 招待有り

Asaoka, A., Noda, T.

International Press-in Association Newsletter 3 巻 ( 3 ) 頁： 3-10 2018年9月

Full-field estimation of cyclic threshold shear strain 国際誌

Uy, E. E. S., Noda, T., Nakai, K. and Dungca, J. R.

Proceedings of the 20th International Conference on Soil Mechanics and Geotechnical Engineering, Osaka 頁： 3062-3066 2018年3月

記述言語：英語

Cyclic threshold shear strain is the cyclic shear strain amplitude that serves as the indicator of the development of pore water pressure. The parameter can be obtained by performing either cyclic triaxial test, shaking table test, cyclic simple shear or resonant column. In a cyclic triaxial test, other researchers install measuring devices in close proximity of the soil to measure the parameter. This method can cause sample disturbance which can affect the result of the experiment. Although there are already existing methods for determining the parameter, the movement and behavior of the soil before and after reaching this parameter needs to be understood. A method that can be used is by applying full-field measurement technique. The technique uses a camera to monitor and measure the movement of the soil. This study is an attempt to estimate the cyclic threshold shear strain parameter. The applied technique has the capacity to monitor the behavior of the particles at cyclic loading. For this study, the technique was incorporated in a strain-controlled consolidated undrained cyclic triaxial test. Two-dimensional image processing was implemented. Lucas and Kanade optical flow algorithm were applied to track the movement of the soil particles. Results from the full-field measurement technique were compared with the results from the linear variable displacement transducer. A range of values were determined from the estimation. The minimum values were in the order of 10-2% in some areas of the specimen. Nonhomogeneous movement was also observed.

Non-contact measurement of soil deformation in a cyclic triaxial test 国際誌

Uy, E. E. S., Noda, T., Nakai, K. and Dungca, J. R.

Proceedings of the 20th International Conference on Geotechnical Earthquake Engineering and Dynamic Soil Properties, Singapore 頁： 2318-2327 2018年3月

記述言語：英語

Deformation in a conventional cyclic triaxial test is normally measured by using a point-wise measuring device. In this study, non-contact measurement technique was applied to be able to monitor and measure the occurrence of the non-homogeneous behavior of the soil under cyclic loading. Non-contact measurement is executed through image processing. Two-dimensional measurements were performed using Lucas and Kanade optical flow algorithm and it was implemented Labview. In this technique, the non-homogeneous deformation was monitored using a mirrorless camera. A mirrorless camera was used because it is economical and it has the capacity to take pictures at a fast rate. The camera was first calibrated to remove the distortion brought about the lens and the testing environment as well. Calibration was divided into 2 phases. The first phase was the calibration of the camera parameters and distortion caused by the lens. The second phase was for eliminating the distortion brought about by the triaxial plexiglass. A correction factor was established during this phase. A series of consolidated undrained cyclic triaxial test was performed using a coarse soil. The results from the non-contact measurement technique were compared to the measured deformation from the linear variable displacement transducer. It was observed that deformation was higher in the area where failure occurs.

埋立高さの異なる名古屋港ポートアイランドの南海トラフ巨大地震時の耐震性評価査読有り

酒井崇之, 野田利弘, 中野正樹, 浅岡顕

土木学会論文集 A2(応用力学) 73 巻 ( 2 ) 頁： I_233-I_244 2018年1月

記述言語：日本語掲載種別：研究論文（学術雑誌）

名古屋港ポートアイランド(以下，PI)には，名古屋港の機能維持のため，毎年多くの浚渫土が仮置きされている．地震によりPIの護岸が被害を受けると，浚渫土の流出等により，名古屋港の機能低下に直結する恐れがある．本研究では，PIを対象に南海トラフ巨大地震を想定した地震動を用い，地震応答解析を実施し，浚渫土砂埋立高さがPIの地震時の挙動に及ぼす影響を調べた．結果は以下の通りである．現状の埋立高さであれば，浚渫土が護岸を乗り越えて港湾へ流出するまでには至らない．しかし，現状から4mの嵩上げを行うと，護岸部の変状が大きくなり浚渫土が港湾へ流出する危険性が高くなる．一方，埋立天高さを下げることにより，埋立地盤や護岸の側方流動を軽減できる．つまり，PIの埋立高さを少しでも低くすることが，地震被害を低減する上で重要である．

水～土連成有限変形解析による自然堆積粘土地盤に打設された杭に作用する地盤反力の検討査読有り

中井健太郎, 野田利弘, 河村精一, 白鳥洋平

土木学会論文集 A2(応用力学) 73 巻 ( 2 ) 頁： I_535-I_544 2018年1月

記述言語：日本語掲載種別：研究論文（学術雑誌）

地盤に長尺の杭が打設されている場合，地盤変位が大きく生じる大地震時には，杭の損傷が懸念される．これまでに，地盤の降伏および杭周面地盤の回り込みの影響を確認するために，土層内に配置された杭に強制変位を与える模型実験が実施され，杭に作用する地盤反力と粘性土のせん断強度の関係を把握している．本報では，模型実験のシミュレーションを行い，数値解析コードのValidationを行うとともに，自然堆積粘土地盤を想定した数値実験を実施した．その結果，1）間隙水のマイグレーションの影響で，地盤反力は，ある載荷速度領域内で急変すること，2）鋭敏比が大きく軟弱な自然堆積粘土地盤を想定した場合，再構成地盤に比べて地盤反力が小さくなるとともに，地盤内で局所的なせん断帯が次々と発生し，せん断ひずみの発生領域が広がることを示した．

名古屋大学減災館を活用した振動工学教育査読有り

岡本正吾, 原進, 福和伸夫, 野田利弘, 田代喬, 飛田潤, 長江拓也, 倉田和己, 井上剛志

工学教育（日本工学教育協会） 66 巻 ( 2 ) 頁： 64-68 2018年

Delayed deformation and progressive failure of slopes by soil-water coupled analysis

Asaoka A., Nakano M., Noda T., Mizuno K.

ISRM International Symposium 2000, IS 2000 2018年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：ISRM International Symposium 2000, IS 2000

Delayed deformation and progressive failure of a cut slope in an overconsolidated clays is examined through a series of soil-water coupled finite deformation analysis using the subloading surface Cam-clay model for overconsolidated soils. In this present problem analyzed, the slope exhibits progressive failure after a long time period (90 years), associated with the fluctuation of nodal velocities on the slope. High shear strains occur initially at the toe of slope and subsequently propagate towards the top of slope with time forming a clear “circular slip surface”. The overconsolidation ratio (OCR) in this highly sheared zone is almost equal to 1.0 due to softening with swelling. Time to failure depends on the soil permeability that comes to the soil-water coupled analysis with Darcy's law. For either high initial OCR or low heights of the slope, no failure is observed due to lesser porewater migration within the slope that results low shear strain.

Scopus

Soil-water coupled analysis of pore water pressure dissipation method targeting even the case where excess pore water pressure exceeds the permissible value specified in the current design - examinations of effectiveness in reclaimed ground - 査読有り

Nonaka, T., Yamada, S. and Noda, T.

Geotechnical Engineering Journal of the SEAGS & AGSSEA 48 巻 ( 3 ) 頁： 19-31 2017年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

Japan has a large number of reclaimed regions unimproved against liquefaction and countermeasures in such regions are necessary to prepare for a great earthquake. A new macro-element method has been proposed that involves applying the soil-water-coupled finite deformation analysis code GEOASIA with an inertial term, and a numerical-analysis technique has been designed that quantitatively evaluates the improvement effect of the pore water pressure dissipation method (PWPDM). In this study, PWPDM effectiveness was examined for a reclaimed ground using the proposed method. Detailed examinations were conducted with the intention of developing a more advanced performance design, without being limited to the concept of the current design code. The main findings are as follows: 1) the proposed analysis code enables quantitative evaluation of the improved effectiveness of PWPDM in a reclaimed ground; 2) more advanced PWPDM designs are possible by not only suppressing the maximum excess pore water pressure to the permissible range of the current design code, but also evaluating the ground deformation adequately; and 3) the new macro-element method, capable of reproducing the phenomenon of well resistance, can evaluate the reduction in the improvement effect because of the degradation of drainage capability, thus making it useful for maintenance purposes such as drain clogging.

Soil-Water Coupled Analysis of Pore Water Pressure Dissipation in Performance Design-Examinations of Effectiveness in Reclaimed Ground 査読有り

Nonaka Toshihiro, Yamada Shotaro, Noda Toshihiro

GEOTECHNICAL ENGINEERING 48 巻 ( 4 ) 頁： 19-31 2017年12月

2011年東北地方太平洋沖震の余震時の補強土壁におけるにおける補強材の支圧抵抗と摩擦の動態観測査読有り

武藤裕久，神谷隆，長沼明彦，小高猛司，崔瑛，中野正樹，野田利弘

土木学会論文集C（地圏工学） 73 巻 ( 4 ) 頁： 311-329 2017年10月

記述言語：日本語掲載種別：研究論文（学術雑誌）

補強土壁構造物は，これまでの地震時の実績より抗土圧構造物よりも高い耐震性が示されている．また，多くの機関で実施された実験により，その耐震性能の高さが証明されている．しかしながら，既往の研究はジオテキスタイルを用いた室内実験や模型実験が多く，全体安定などの挙動は示されているが，補強材軸力の効果や挙動については十分に把握されていない．本研究では，支圧抵抗と摩擦抵抗を組み合わせたアンカー式の補強材を用いた補強土壁において，2011年東北地方太平洋沖地震の余震時の補強材軸力を計測することができた．その結果，地震時には支圧補強体と摩擦補強体のそれぞれが抵抗力を発揮し，その抵抗力は補強材の土被りが小さい位置では支圧補強体，土被りが大きい位置では摩擦補強体が効果的に抵抗力を発揮することが示された．

DOI： 10.2208/jscejge.73.311

Seismic assessment of sheet pile reinforcement effect on river embankments constructed on a soft foundation ground including soft estuarine clay

Nakai Kentaro, Noda Toshihiro, Kato Kenta

CANADIAN GEOTECHNICAL JOURNAL 54 巻 ( 10 ) 頁： 1375 - 1396 2017年10月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Canadian Geotechnical Journal

Conventional seismic assessments of river embankments have focused on liquefaction damage of sandy ground. However, following the 2011 earthquake centered off the Pacific Coast of Tohoku, extensive damage of river embankments built on a clayey foundation has garnered greater attention. This paper presents seismic response analyses of river embankments constructed on soft and sensitive estuarine clay, as well as analyses of countermeasures implemented with sheet piles with a succession of penetration depth and placement. River embankments have kept stable if the clayey ground was assumed to be a nonsensitive condition. However, if a strong shake impacts actual sensitive clay, there is a risk of slippage generated from the clayey layer. If the penetration depth of piles is shallow in the clayey layer, the clay is strongly disturbed by the tip of the pile, generating extensive damage; if the penetration depth is sufficiently deep in the supporting layer, significant deformation control may be obtained at the reinforced side, although there is a risk of promoting deformation at the opposite side. These results indicate the importance of the specific inspection of pile penetration depth; otherwise, not only is it not possible to obtain a sufficient countermeasure effect, but also an adverse effect may be generated.

DOI： 10.1139/cgj-2016-0019

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Scopus

A Full Formulation-based Soil-Water Coupled Finite Deformation Analysis on Undrained Compression Tests on Highly Permeable Soil Specimen 査読有り

Toyoda, T. and Noda, T.

Proceedings of the 19th International Conference on Soil Mechanics and Geotechnical Engineering, Seoul 2017 頁： 863-866 2017年9月

記述言語：英語

In the mechanics of saturated soil based on the theory of mixtures, the pore water pressure p and the displacements u and U of the solid and liquid phases, respectively, are assumed to be independent variables that are unknowns of the field when solving the equation of motion of each phase by coupling with the law of conservation of mass. This is called full formulation. In many analysis codes for saturated soil, this strict formulation is modified to reduce the number of equations by assuming that the
acceleration of the liquid phase relative to the solid phase is much smaller than that of the solid phase (u-p formulation). As this assumption neglects the dynamic permeation of pore water, it has not been possible to apply u-p formulation to soils with very high permeability. This paper demonstrates that by utilizing the finite element method, the finite volume method, etc., it is possible to carry out deformation analysis of soils with very high permeability by solving the strict governing equations based on full formulation for finite deformation fields of soil-water coupled systems.

Verification of a macro-element method in the numerical simulation of the pore water pressure dissipation method - A case study on a liquefaction countermeasure with vertical drains under an embankment

Nonaka Toshihiro, Yamada Shotaro, Noda Toshihiro

SOILS AND FOUNDATIONS 57 巻 ( 3 ) 頁： 472 - 487 2017年6月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Soils and Foundations

In the simulation of the vertical drain method using a soil-water coupled finite element analysis, a macro-element method has often been used as an approximate method to introduce the water absorption functions of drains into individual elements. In order to extend the function of this method, the authors modified the formula of the flow coefficient from soil to drains and introduced the discharge function of vertical drains to the method by treating the water pressure in the drains as an unknown and adding a continuity equation for the drains to the governing equations. The first attempt made it possible to divide a finite element mesh independently of the drain arrangement and the drain spacing, and the second attempt enabled the well resistance to be automatically generated by a series of calculations depending on the given conditions. Furthermore, although the macro-element method has been applied to quasi-static problems in most cases, the authors applied the expanded one to dynamic problems by equipping it with the soil-water coupled finite deformation analysis code GEOASIA with the inertial term. In this paper, in order to verify the new macro-element method in a dynamic problem, the results of a 2D approximate model using the new macro-element method were compared with those of a 3D exact model where vertical drains were exactly represented by finely dividing the finite element mesh in the case of a sand ground improved by the pore water pressure dissipation method under the embankment. The findings of this study are as follows: (1) 2D mesh-based analyses under plane strain conditions, using the new macro-element method, can accurately approximate 3D mesh-based analyses with a fine mesh in dynamic problems in terms of changes in the excess pore water pressure and ground deformation; (2) the new macro-element method can adequately evaluate the influence of drain spacing on a countermeasure for liquefaction in the quantitative sense, while using a single mesh; and (3) the new macro-element method improves the calculation efficiency in the simulation of the pore water pressure dissipation method by laborsaving in mesh-dividing and dramatically reducing the calculation time.

DOI： 10.1016/j.sandf.2017.05.012

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Scopus

New developments related to clarification of the mechanisms of ground deformation caused by earthquakes - In the wake of the Great East Japan Earthquake - 招待有り査読有り

Noda, T., Kazama, M. and Asaoka, A.

Journal of JSCE 5 巻 ( 1 ) 頁： 133-144 2017年3月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

The 2011 Great East Japan Earthquake caused massive ground damage, including liquefaction of sandy grounds, collapse of river levees and lands developed for housing, etc., particularly in regions across eastern Japan. Not only damage to 'currently unqualified' structures that did not conform to existing design standards and codes but also ground damage that could not be explained within the framework of conventional geomechanics and geotechnical engineering was observed. Particularly in the latter case, therefore, it has become necessary to develop new techniques in geomechanics without being restrained by the conventional framework. From the above standpoint, this paper reviews the research that has been carried out in the field of geotechnology after the Great East Japan Earthquake. More specifically, new knowledge relating to the mechanism of liquefaction damage at Urayasu City and other ground deformation caused by the earthquake is introduced, together with the results of research carried out on ground strengthening techniques.

DOI： 10.2208/journalofjsce.5.1_133

地盤－煙突構造物相互作用系の耐震性に及ぼす入力地震波の影響査読有り

中井健太郎，野田利弘

土木学会論文集 A2(応用力学) 73 巻 ( 2 ) 頁： I_409-I_418 2017年1月

記述言語：日本語掲載種別：研究論文（学術雑誌）

本論文では，液状化危険度の高い地盤上に実在する煙突を対象に，二次元平面ひずみ条件下での地震応答解析を実施し，地盤－構造物相互作用系における耐震性評価を行った．その結果，地震波が構造物の固有周期帯を多く含んでいると，共振によって構造物の揺れが大きくなることに加えて，液状化によって剛性を失った地盤が煙突を支えることができず傾倒してしまうことを示した．つまり，地盤の上に建つ構造物の地震時挙動は，加速度の大きさのみで評価できるのではなく，構造物の固有周期と入射される地震動の卓越周期との関係性が極めて重要であることを意味する．また，地盤の不整形性および周辺構造物の影響評価を行ったところ，深部地層の傾斜や周辺構造物による引きずり込み沈下によって，上部構造物の地震時安定性が低下することを示した．

DOI： http://doi.org/10.2208/jscejam.72.I_409

講義を行う建物ごと自由振動させる体験型振動工学授業の試み査読有り

原進，福和伸夫，野田利弘，田代喬，飛田潤，長江拓也，倉田和己，井上剛志

計測自動制御学会論文集 53 巻 ( 1 ) 頁： 99-101 2017年1月

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