Papers - TAKEUCHI Yasushi
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路盤の圧縮ひずみに着目したアスファルト舗装の健全度評価手法の検討 Reviewed
山本 尚毅, 竹内 康, 若林 由弥, 渡邉 一弘
土木学会論文集 79 ( 21 ) 1 - 8 2024.03
Authorship：Corresponding author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：土木学会
2016年に策定された「舗装点検要領」では，舗装の長寿命化やライフサイクルコストの削減に向けて，表層や基層の適時修繕により，路盤以下の層を保護することの重要性を示している．また，舗装の早期劣化区間では，詳細調査を実施することが示されており，主な詳細調査として，FWDたわみ量調査が広く活用されている．FWDたわみ量を用いた健全度評価手法は，D0たわみ量により舗装全体の支持力を評価する方法や，多層弾性理論に基づく逆解析により弾性係数を評価する方法が一般的である．本稿では，アメリカのNCHRP（全米共同道路研究プログラム）で報告されている粒状路盤層上面の圧縮ひずみの評価式に着目し，実道で取得したFWDデータを用いてアスファルト舗装の評価手法への適用に向けた検討を行ったので，その結果を報告する．
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アスファルト舗装の路床における小型FWD試験の多層弾性理論による順解析
齋藤 賢人, 山本 尚毅, 山中 光一, 川名 太, 竹内 康
土木学会論文集 79 ( 21 ) 23-21012 2024.03
Authorship：Last author Publisher：土木学会
路床のレジリエントモデュラス試験（以下Mr試験）の結果は，米国の力学的・経験的舗装設計ガイドなどの舗装の理論的構造設計に用いられている．ただし，Mr試験の実施には多くの時間と費用がかかることから，現場試験である小型FWD試験などを用いて，Mrを推定することが望ましい．そこで，車道として供用されている舗装の路床において，小型FWD試験の計測結果とMrの関係を把握できれば，舗装の理論的構造設計の普及と高度化に貢献できると考えられる．本研究では，アスファルト舗装の路床を対象として，Mrを入力パラメータとした多層弾性理論による小型FWD試験の順解析を行った．その結果，動的効果を考慮した順解析から得られる載荷中心のたわみは，小型FWDで計測されたたわみとよく一致することが明らかとなった．
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RELATIONSHIP BETWEEN HEAVILY TRAFFICKED ASPHALT PAVEMENT SOUNDNESS EVALUATION INDEX AND GRANULAR BASE COMPRESSIVE STRAIN USING FWD DATA
TAKEUCHI Yasushi, YAMAMOTO Naoki, KAWANA Futoshi, YABU Masayuki, WATANABE Kazuhiro
Japanese Journal of JSCE 81 ( 2 ) n/a 2025
Language：Japanese Publisher：Japan Society of Civil Engineers
<p> In order to evaluate the soundness of the granular base course by FWD for heavily trafficked asphalt pavement, the authors proposed a simple compressive strain prediction model using the base damage index (BDI) obtained directly from the FWD deflection curve which based on the relationship between BDI and the compressive strain on the surface of the granular base obtained from the multi-layered elastic analysis. In this study, we added data to improve the reliability of the compressive strain prediction model and its temperature-correct equation and examined about the relationship between compressive strain and various FWD based soundness evaluation indices of asphalt pavement shown in existing technical books. As the results, a soundness evaluation method for asphalt pavement by combining compressive strain with existing evaluation indices was proposed in this study.</p>
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RELATIONSHIP BETWEEN DAMAGE OF ASPHALT MIXTURE LAYER AND COMPRESSIVE STRAIN OF GRANULAR BASE ON HEAVY TRAFFIC ROUTES
YAMAMOTO Naoki, TAKEUCHI Yasushi, TAKADA Koki, WAKABAYASHI Yuya, KUWABARA Masaaki, WATANABE Kazuhiro
Infrastructure Maintenance Practices 4 ( 1 ) 182 - 190 2025
Language：Japanese Publisher：Japan Society of Civil Engineers
<p> Road managers are required to manage pavements efficiently under budget constraints. One of the management strategies for asphalt pavements is to use the granular base layer semi-permanently and to replace the asphalt layer repeatedly. In order to realize such management, it is important to keep the load on the granular base layer below a certain level, and the vertical compressive strain on the top surface of the granular base layer is considered as an indicator to grasp this load. In this study, we conducted excavation surveys at three different locations along the same national highway, and verified the relationship between the compressive strain of the base and the degree of damage to the asphalt and granular base layers. The results showed that the degree of damage to the asphalt layer tended to be greater at locations where the compressive strain was greater. On the other hand, there was no difference in the density of the granular base layer, but the bearing capacity below the granular base layer tended to be smaller at locations where the compressive strain was greater.</p>
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COMPRESSIVE STRAIN ESTIMATION METHOD OF GRANULAR BASE OF ASPHALT PAVEMENT USING FWD DEFLECTION CURVETURE
TAKEUCHI Yasushi, YAMAMOTO Naoki, KAWANA Futoshi, YABU Masayuki, WATANABE Kazuhiro
Infrastructure Maintenance Practices 3 ( 1 ) 40 - 47 2024
Language：Japanese Publisher：Japan Society of Civil Engineers
<p> In this study, as a method for evaluating the soundness of the granular base directly from the FWD deflection shape, we focused on the granular base compressive strain prediction equation shown in the NCHRP report. Then, the accuracy of the NCHRP’s prediction formula was using the FWD survey results on the national highway was verified, and based on the FWD operating conditions in Japan, a new prediction equation establish method was examined. As a result, it was found that the prediction equation of NCHRP tends to deviate from analytical results of FWD using the multilayered elasticity theory (MLET). In addition, the MLET analysis results based on the FWD operating conditions in Japan were used to formulate the compressive strain prediction equation and the temperature correction equation, and the threshold for the compressive strain soundness evaluation was shown.</p>
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Evaluation of the Effect of Interlayer Bonding Condition on the Deterioration of Asphalt Pavement
Wakabayashi Yuya, Takeuchi Yasushi, Kawana Futoshi, Watanabe Kazuhiro
Transportation Research Record: Journal of the Transportation Research Board 2677 ( 7 ) 500 - 508 2023.02
Publisher：SAGE Publications
<jats:p> In this study, to investigate the effect of interlayer bonding condition on the deterioration of asphalt pavement, we conducted numerical analysis based on multi-layer elastic theory, verification of numerical analysis results by experiments on a full-scale test track, and comparison of the progress of deterioration based on accelerated loading tests conducted on the test pavement. Firstly, the analysis indicated that stronger tensile strain could occur on the upper side of the interlayer when the interlayer bonding weakens. Furthermore, the test pavement simulating interlayer debonding showed the same strain tendency as the analysis. These results suggest that if the interlayer debonding continues, the pavement may suffer early fatigue failure. On the other hand, there are some results that are not consistent with those of the analysis, such as the magnitude of deflection in the test pavement; thus, further investigation is required. Furthermore, because of the accelerated loading on the test pavement, the sections where the layers were debonded immediately after construction became bonded. Since the deflection of the test pavement did not change significantly from that immediately after construction, and no conspicuous damage such as cracks was observed on the road surface, it is considered necessary to continue follow-up surveys. </jats:p>
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EVALUATION OF PROBABILITY CHARACTERISTIC OF THE STRAIN OCCUREED IN THE ASPHALT PAVEMENT USING THE MONTE CARLO SIMULATION
KAWANA Futoshi, KOUNO Asako, TAKEUCHI Yasushi
Journal of Japan Society of Civil Engineers, Ser. E1 (Pavement Engineering) 78 ( 2 ) I_100 - I_108 2023
Language：Japanese Publisher：Japan Society of Civil Engineers
<p> In this study, to evaluate the influence of variability of the design variable on calculated strain for asphalt pavement, Monte Carlo simulation was demonstrated. The results are summarized as follows. (1) The design parameters having the greatest influence on the horizontal strain variability at the bottom of the asphalt layer are asphalt elastic modulus, base elastic modulus and asphalt thickness. (2) The design parameters having the greatest influence on the vertical strain variability at the top of the subgrade are layer thickness, subgrade elastic modulus and subgrade Poisson’s ratio. (3) In the case of thick asphalt layer, it was confirmed that the coefficient of variation of the strain became the constant value without depending on pavement structure and elastic modulus if coefficient of variation of each design variable was given. (4) On the other hand, when thickness of asphalt layer was thin, coefficient of variation of the strain greatly changed depending on pavement structure and elastic modulus.</p>
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STUDY ON THE RELATIVE EQUATION BETWEEN SUBGRADE CBR AND ELASTIC MODULUS
IKEDA Akane, YMANAKA Kohichi, TAKEUCHI Yasushi, KAWABATA Shinichiro, SEKINE Etsuo
Journal of Japan Society of Civil Engineers, Ser. E1 (Pavement Engineering) 78 ( 2 ) I_240 - I_247 2023
Language：Japanese Publisher：Japan Society of Civil Engineers
<p> The Subcommittee on Pavement Materials of the Committee on Pavement Engineering of the Japan Society of Civil Engineers conducted CBR testing and resilient modulus testing using sandy soil as simultaneous tests to study the strength and deformation characteristics of subgrade soils. The results showed that not only the moisture ratio but also the dry density had a significant effect on <i>CBR</i>, since its variation at the same dry density was great. Resilient modulus was also found to be greatly affected by dry density and moisture ratio as in the case of <i>CBR</i>. The relationship between <i>CBR</i> and elastic modulus was examined in domestic and foreign studies, including the results of this study, and it was found that the elastic modulus was widely distributed within the regression line of 5×<i>CBR</i> to 20×<i>CBR</i> for the same <i>CBR</i>.</p>
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Development of green infrastructure construction method applying plastic rainwater storage structure suitable for load resistance to planting base.
TAZAKI Kazuhiro, WATANABE Sachiko, IRIE Teruaki, FURUHATA Taiga, TAKEDA Kazuaki, TAKEUCHI Yasushi, SUZUKI Ayumu, HAMANO Masayuki, OSAWA Ayuko
Technical Reports of Landscape Architecture 2 ( 0 ) 20 - 25 2023
Language：Japanese Publisher：Japanese Institute of Landscape Architecture
<p>This study reports development of green infrastructure construction method applying plastic rainwater storage structure suitable for load resistance to planting base. Observation items in this study are water level, moisture content, soil temperature, and heat index, and test surveys are soil hardness test, permeability test, and root elongation. As a result of this research, the planting base has a pF value within the range of 1.5 to 2.7, which is an effective value for plant growth. In the control plot, there was a tendency for excessive humidity (pF value: 1.2 to 1.4), and a value outside the effective value for growth was observed. Under the shade of greenery, the daytime temperature is about 3°C lower than the surface of the pavement. In the one year after green infrastructure construction method applying plastic rainwater storage structure to planting base, it was confirmed that Zelkova serrata and Liquidambar styraciflua showed elongation of the root and vigorous rooting of fine roots in both 100% and 50% filling of the planting base soil. This study showed the effectiveness of the green infrastructure construction method that applied rainwater storage structure to the planting base for roadside trees.</p>
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RE-EVALUATION OF STRUCTURAL DEGRADATION IN CONCRETE PAVEMENT WITH FWD DYNAMIC BACK-ANALYSIS
NISHIZAWA Tatsuo, TERADA Masaru, YABU Masayuki, KOYANAGAWA Masashi, TAKEUCHI Yasushi
Japanese Journal of JSCE 79 ( 4 ) n/a 2023
Language：Japanese Publisher：Japan Society of Civil Engineers
<p> In this study, a dynamic back-analysis method that estimates degradation stage as well as layer modulus from FWD deflection basin was developed. Using the developed method, effects of dynamic loading of FWD test on structural evaluation of back-analysis for concrete pavement was investigated. FWD test data measured on the concrete test pavement on the circular accelerating pavement testing (ATP) facility was analyzed with static and dynamic back-analysis. As a whole, although dynamic back-analysis evaluates slightly more serious degradation stage and higher bending stress than static one, it was found that the evaluated results with both analysis methods are not so much different with each other.</p>
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YAMAMOTO Naoki, TAKEUCHI Yasushi, WAKABAYASHI Yuya, WATANABE Kazuhiro
Japanese Journal of JSCE 79 ( 21 ) n/a 2023
Language：Japanese Publisher：Japan Society of Civil Engineers
<p> The Pavement Inspection Procedure, developed in 2016, indicates the importance of protecting the layers below the base by timely repair of the surface and base layers to extend the life of the pavement and reduce life cycle costs. It also indicates that a detailed investigation should be conducted in early deteriorated sections because damage to the layers below the base layer is suspected. As the main detailed investigation, the FWD deflection survey is widely utilized, and the method to evaluate the bearing capacity of the entire pavement by D<sub>0</sub> deflection or the method to evaluate the elastic modulus by inverse analysis based on the multi-layer elasticity theory are commonly used. In this paper, we focus on the compressive strain on the top surface of granular base layer, which is reported by NCHRP (National Cooperative Highway Research Program) in the U.S., and discuss its application to the evaluation method of asphalt pavements.</p>
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博物館でのインクルーシブ展示の試み ー地域創成科学科展を事例としてー Reviewed
町田 怜子, 竹内 康, 藤川 智紀, 下嶋 聖
日本視覚障害理科教育研究会、ＪＡＳＥＢ ＮＥＷＳ ＬＥＴＴＥＲ 43 2023
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小型FWDを用いた路床のレジリエントモデュラスの材料定数推定手法の提案 Reviewed
竹内 康・川名 太・山中 光一・木幡 行宏・関根 悦夫
土木学会論文集E1（舗装工学） 78 ( 1 ) 40 - 51 2022.05
Language：Japanese Publishing type：Research paper (scientific journal)
舗装の理論的構造設計において適切な路床剛性評価を行えるようにすることを目的とし，現場において迅速に測定可能な小型FWD 試験結果から，多層弾性理論を用いてMr の算出に用いる材料定数の推定方法について検討を行った．その結果，多層弾性理論による順解析より計算着目点が設定できること，計算着目点における載荷時の応力状態からMr の回帰式を用いて材料定数を求められることがわかった．また，過去のMr 試験結果を用いた算定結果より，路床面からの計算着目点の深さと路床の弾性係数は1 次関数で近似できることがわかった．
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Changes in Growth of <i>Egeria densa</i> in Shading Conditions
ASAI Toshimitsu, FUJIKAWA Tomonori, TAKEUCHI Yasushi, SUZUKI Shinichi, NAKAMURA Yoshio
Transactions of The Japanese Society of Irrigation, Drainage and Rural Engineering 90 ( 1 ) I_209 - I_216 2022
Language：Japanese Publisher：The Japanese Society of Irrigation, Drainage and Rural Engineering
<p>This study aimed to develop a new method to control <i>Egeria densa</i>, which overgrows in agricultural irrigation canals. We conducted two experiments (one in the laboratory and one in the field), focused on changes in light conditions and the growth of <i>E. densa</i>. In the laboratory experiment, the maximum tensile load of the stems was significantly reduced when the light was shaded to about 20 μmol·m<sup>-2</sup>·s<sup>-1 </sup>(1,400 lx). We discovered that shading exerted a significant negative effect on the number of roots. Furthermore, in the field experiment, which was conducted in an actual agricultural canal, the maximum tensile load on stems was reduced in both the 85-90% and 95-98% shade plots. In particular, in the 95-98% shade plot, the tensile load was reduced to about half of that in the control plot (non-shade) during the high grow season from August to October.</p>
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路床のレジリエントモデュラス を用いた小型FWD 試験の順解析 Reviewed
山中 光一・竹内 康・川名 太・峯岸 邦夫
土木学会論文集E1（舗装工学） 77 ( 2 ) I_225 - I_231 2021.12
Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)
本研究では，既往の研究では整合性が確認されていなかった小型FWD試験とMr試験の関係を検証するために，関東ローム地盤を対称にこれらの試験を実施するとともに多層弾性理論による順解析を行い理論的検討を行った．その結果，載荷時間および接地圧分布の影響を考慮することで両試験結果は良く一致することが確認できた．
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円形走行路載荷試験におけるコンクリート舗装の長期的な荷重支持性能のFWDによる評価 Reviewed
西澤 辰男, 寺田 剛, 藪 雅行, 小梁川 雅, 竹内 康
土木学会論文集E1（舗装工学） 77 ( 1 ) 39 - 52 2021.12
Language：English Publishing type：Research paper (scientific journal)
土木研究所円形走行路に施工したコンクリート舗装に49kN換算の輪荷重を520万回作用させた後の構造評価を3DFEMにより行った。その結果，コンクリート版中央部での劣化は殆ど進行していないが，ひび割れ部での劣化進行は非常に早いことが示唆された。
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FWDによる円形⾛⾏路載荷試験におけるコンクリート舗装の構造的変化の評価 Reviewed
⻄澤 ⾠男・⼩梁川 雅・⽵内 康・寺⽥ 剛・藪 雅⾏
土木学会論文集E1（舗装工学） 76巻 ( 2号 ) I_45 - I_52 2020.12
Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)
コンクリート舗装の長期的な耐久性を確認するために，土木研究所円形走行路に建設した試験舗装に49kN 換算輪数120 万輪を走行させて構造評価を行った結果，中央部での劣化は
ほとんど進行していないが，ひび割れ部での劣化の進行は非常に早いことがわかった． -
車両重量調査結果のコンクリート舗装設計への適用に関する検討 Reviewed
竹内 康・西澤辰男・川名太・桑原正明・小梁川雅
土木学会論文集E1（舗装工学） 76巻 ( 2号 ) I_21 - I_28 2020.12
Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)
国土交通省による車両重量調査結果のコンクリート舗装の版厚設計への適用方法について検討した。その結果，12時間毎に集計される輪荷重群は，版厚設計に直接的に使用できること，現行の設計法で求められるコンクリート版の疲労度は，12時間の輪荷重群を用いた場合に比べて大きく算定されることがわかった．
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遮光ネットによる農業用水路のオオカナダモ駆除効果の検討 Reviewed
浅井俊光，藤川智紀，竹内 康，中村好男，鈴木伸一*
水土の知（農業農村工学会誌） 88 ( 11 ) 893 - 897 2020.11
Language：Japanese Publishing type：Research paper (scientific journal)
オオカナダモ（Egeria densa Planch.）は南米原産の沈水植物で，近年，在来種への影響や農業用水路内での通水阻害などが問題視されている。神奈川県小田原市の鬼柳堰において，実際に農業用水路内に繁茂したオオカナダモに対して，遮光率が85～90%，95～98%の2つの遮光ネットを展張し遮光実験を行った。その結果，茎部引張強度の著しい低下や葉色の変化，枯損，株の消失など，高い駆除効果が認められた。
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STRUCTURAL CHANGES OF CONCRETE PAVEMENT ON CIRCULAR ACCELERRATED PEVENENT TESTING FACILITY
NISHIZAWA Tatsuo, KOYANAGAWA Masashi, TAKEUCHI Yasushi, TERADA Masaru, YABU Masayuki
Journal of Japan Society of Civil Engineers, Ser. E1 (Pavement Engineering) 76 ( 2 ) I_45 - I_52 2020
Language：Japanese Publisher：Japan Society of Civil Engineers
<p> In this study, test sections of concrete pavement were constructed on the circular accelerated pavement testing (APT) facility and subjected to 1.2 million of 49kN equivalent standard wheel loads. The test pavement has sections with and without steel mesh in concrete slab and asphalt interlayer under the slab to investigate the effect of these devices. During the loading, FWD tests were conducted periodically and the sturactural changes were evaluated with FWD backanalysis, which considered the degradation process with 3DFEM models. The analysis revealed that interior parts of the slabs did not significantly degrade, while transverse cracks exibited severe degradation. Also, it was estimated that no void formed at the transverse joint, except for two joints on the asphalt interlayer.</p>