論文 - 京川 裕之
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Constitutive model describing the hydro-mechanical behaviors of compacted bentonite clay based on the crystal surface phenomena 査読あり
Hiroyuki Kyokawa
E3S Web Conf. (2nd International Conference on Energy Geotechnics (ICEGT 2020)) ( 205 ) 2020年11月
担当区分：筆頭著者 記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
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Experimental study on the mechanical behaviour of bounded geomaterials under creep and cyclic loading considering effects of instantaneous strain rates 査読あり
Zain Maqsood, Junichi Koseki, Yukika Miyashita, Jiren Xie, Hiroyuki Kyokawa
Engineering Geology 276 2020年10月
掲載種別：研究論文（学術雑誌）
© 2020 Elsevier B.V. Rational evaluation of the long-term performance of large-scale foundations, tunnels and natural slopes located in seismically active areas necessitates accurate assessment of the strength and deformation characteristics of bounded geomaterials, such as natural rocks and cemented soils, under creep and cyclic loading conditions. In the present study, a unique approach for examining the induced instantaneous loading/strain rates during unconfined creep and cyclic loading was adopted to unveil the effects of creep and cyclic loading on the mechanical behaviour of laboratory-produced bounded geomaterial, namely Gypsum Mixed Sand (GMS). At first, a series of unconfined monotonic tests at six different strain rates ranging from 5.3E+0 to 2.1E-5%/min were conducted on GMS. Subsequently, the mechanical behaviour of the GMS was examined under unconfined creep/sustained loading at four different stress levels. Further, these results were compared with a number of unconfined cyclic loading tests performed at different stress amplitudes. Identical patterns of the variations of axial strain accumulation and instantaneous strain rates were observed during the creep and cyclic loading. Based on the relationships between the failure stress/strain and the corresponding instantaneous strain rate, the mechanical behaviour of the GMS specimens subjected to creep and cyclic loading was found to be similar to each other, and was distinctively different than those under monotonic loading condition.
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A method for extending a general constitutive model to consider the electro‐chemo‐mechanical phenomena of mineral crystals in expansive soils 査読あり
Hiroyuki Kyokawa, Shintaro Ohno, Ichizou Kobayashi
International Journal for Numerical and Analytical Methods in Geomechanics 44 ( 6 ) 749 - 771 2020年04月
担当区分：筆頭著者 掲載種別：研究論文（学術雑誌） 出版者・発行元：Wiley
© 2020 John Wiley & Sons, Ltd. The mechanical behavior of expansive soils varies according to the chemical composition of the pore fluid. It is well known that electrochemical phenomena on the surface of clay mineral crystals considerably affect their macrostructural behavior. In particular, a change in the pore fluid composition causes osmotic consolidation or swelling. In this study, a model is constructed to describe the characteristic behavior of expansive soils by coupling the interlaminar behavior of clay mineral crystals and the soil skeleton behavior. The interlaminar behavior is derived from the electro-chemo-mechanical coupling equilibrium of mineral crystals, and the soil skeleton behavior is given by a general elastoplastic constitutive model for soils. This modeling approach extends a general model to consider the electro-chemo-mechanical phenomena of mineral crystals. Oedometer tests with the replacement of the cell fluid and the swelling pressure and deformation tests on expansive clays are simulated with the proposed model. The simulation results indicate that the proposed method can reasonably represent the typical behavior of expansive soils.
DOI： 10.1002/nag.3026
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発泡ポリプロピレンブロックの強度・変形特性に及ぼすひずみ履歴とその後のクリープ期間の影響
京川 裕之, 古関 潤一
ジオシンセティックス論文集 35 103 - 108 2020年
記述言語：日本語 出版者・発行元：国際ジオシンセティックス学会 日本支部
地震などの過去に受けた荷重履歴によってEPS盛土が潜在的なダメージを受けても，そのまま供用継続できたり，あるいは少なくとも本復旧までの期間は暫定供用できることが望ましい．そのため，EPS等軽量化材料の荷重・変状履歴に対する復元性能を把握することは重要である．本研究では，緩衝特性および復元特性に優れているとされる発泡ポリプロピレン（EPP）ブロックについて，載荷ひずみ速度，ひずみ履歴，除荷後のクリープ期間を変えた一軸圧縮試験によりその強度・変形特性の検証を行った．実験結果より，EPPブロックの応力ひずみ関係は弾粘塑性挙動を示し，除荷後の残留ひずみは時間とともに減少，つまりクリープ膨張し，同時に再載荷剛性も増加することが確認された．
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Effects of loading rate on strength and deformation characteristics of gypsum mixed sand 査読あり
Zain Maqsood, Junichi Koseki, Hiroyuki Kyokawa
E3S Web of Conferences 92 2019年06月
掲載種別：研究論文（国際会議プロシーディングス）
© The Authors, published by EDP Sciences. It has been unanimously acknowledged that the strength and deformation characteristics of bounded geomaterials, viz. cemented soils and natural rocks, are predominantly governed by the rate of loading/deformation. Rational evaluation of these time-dependent characteristics due to viscosity and ageing are vital for the reliable constitutive modelling. In order to study the effects of ageing and loading/strain rate (viscosity) on the behaviour of bounded geomaterials, a number of unconfined monotonic loading tests were performed on Gypsum Mixed Sand (GMS) specimens at a wide range of axial strain rates; ranging from 1.9E-05 to 5.3E+00 %/min (27,000 folds), and at different curing periods. The results indicate shifts in the viscous behaviour of GMS at critical strain rates of 2.0E-03 and 5.0E-01 %/min. In the light of this finding, the results are categorized into three discrete zones of strain rates, and the behaviour of GMS in each of these zones is discussed. A significant dependency of peak strength and stress-strain responses on strain rate was witnessed for specimens subjected to strain rates lesser than 2.0E-03 %/min, and the effects of viscosity/strain rate was found to be insignificant at strain rate higher than 5.0E-01%/min.
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Experimental and analytical investigations of volume change behaviour of saturated expansive soils in oedometer test 査読あり
Misa Hiraga, Hiroyuki Kyokawa, Junichi Koseki
E3S Web of Conferences 92 2019年06月
掲載種別：研究論文（国際会議プロシーディングス）
© The Authors, published by EDP Sciences. The chemical and mechanical behaviours of saturated bentonite were experimentally and analytically investigated. A series of oedometer tests on saturated bentonite was conducted. By replacing the cell fluid during the oedometer test, one-dimensional osmotic consolidation and swelling behaviour were observed. The experimental results were simulated numerically using a constitutive model by considering the influence of electrochemical phenomena of clay mineral crystals on the macrostructural behaviour. It was concluded that the typical mechanical swellability of water-saturated bentonite in oedometer test is affected by a positive dilatancy behaviour due to the lower shear strength. After the osmotic consolidation test, a lateral contraction of the specimen in the oedometer was observed; this affected the compressibility during the subsequent mechanical consolidation. It was also concluded that the concentration of Na+ in the pore fluid affects the specific mechanical properties of bentonite.
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A system to measure permeability of unsaturated soils using local pin-type sensors in triaxial apparatus 査読あり
Jaylord U.Tan Tian, Junichi Koseki, Hailong Wang, Hiroyuki Kyokawa, Takeshi Sato
7th Asia-Pacific Conference on Unsaturated Soils, AP-UNSAT 2019 7 ( 2 ) 305 - 309 2019年
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス） 出版者・発行元：The Japanese Geotechnical Society
© 2019 7th Asia-Pacific Conference on Unsaturated Soils, AP-UNSAT 2019. All rights reserved. This paper describes development of a triaxial permeameter apparatus for measuring coefficient of permeability of unsaturated soils by directly measuring the head difference between two points in a specimen using local pin-type sensors. The local pin-type sensors are made of stainless steel wrapped with membrane filter to measure suction. The apparatus includes the measurement of inflow rate by Mariotte's bottle and a weighing scale, while outflow rate is measured by burettes and a differential pressure transducer (DPT). Typical results show that the steady state flow condition can be achieved by using membrane filters to allow passage of water but prevent flow of free air. At steady state flow condition and reasonably stable measured head by the local pin-type sensors, permeability values were obtained by simple average.
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EPS盛土の実大振動台実験による新型緊結金具の効果とロッキング対策の評価 査読あり
西 剛整, 谷 美宏, 林 夏希, 窪田 達郎, 京川 裕之, 古関 潤一, 小浪 岳治
ジオシンセティックス論文集 34 ( 0 ) 153 - 160 2019年
記述言語：日本語 出版者・発行元：国際ジオシンセティックス学会 日本支部
本論文は，発泡スチロールを用いた土木工法（EDO-EPS工法）について，2011年東北地方太平洋沖地震のような継続時間の長い地震動や，2016年熊本地震に見られた震度7クラスの地震動が連続するような地震を想定して，耐震性能を強化した新型緊結金具の効果確認のための実大振動台実験を行った結果を示したものである．また，同時にトップヘビーな構造体であるEPS盛土のロッキングの影響を考慮し，これによる変状を軽減するための対策工の検討を行っている．実験の結果，従来用いられている緊結金具に比較して新型金具は変状を抑制できることが確認された．また，緊結金具の配置条件に対する工夫と，変状が生じやすい床版部において滑動を抑止するずれ止め鋼板を設けることで，ロッキングによる変状は軽減できることがわかった．
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EPSブロックとジオグリッドを併用した橋台の耐震対策に関する振動台実験 査読あり
京川 裕之, 川崎 広樹, 古関 潤一, 小浪 岳治, 西 剛整, 窪田 達郎
ジオシンセティックス論文集 34 ( 0 ) 161 - 168 2019年
記述言語：日本語 出版者・発行元：国際ジオシンセティックス学会 日本支部
本研究では，既往研究で効果が確認されているジオグリッド補強土とEPSブロックの併用に加え，ネイリングを考慮した補強土工法による橋台および背面地盤の耐震対策を模型振動台実験で検証した．実験では，ジオグリッド，EPSブロック，ネイリングを様々に組み合わせた計６ケースの橋台背面補強土に対して，正弦波を段階的に与えた．実験結果から，ジオグリッド補強土とEPSブロックを併用した場合，裏込め地盤の上段にジオグリッド，中段にEPSブロックをそれぞれ配置することで，地震時における擁壁の変位・傾斜ならびに背面地盤の沈下を抑制できることが示された．また，これらジオグリッド補強土とEPSブロックに加えて，ネイリングを設置することでその耐震性が向上することを確認した．
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Reconnaissance of the 2017 Puebla, Mexico earthquake 査読あり
Yolanda Alberto, Masahide Otsubo, Hiroyuki Kyokawa, Takashi Kiyota, Ikuo Towhata
Soils and Foundations 58 ( 5 ) 1073 - 1092 2018年10月
掲載種別：研究論文（学術雑誌）
© 2018 A normal-fault earthquake (Mw = 7.1) occurred in the state limit of Puebla and Morelos on September 19, 2017, exactly 32 years after the 1985 Michoacan Earthquake. A total of 5765 buildings suffered damage in Mexico City and about 300 in Puebla City. The authors carried out a reconnaissance of Mexico City, and some locations in the states of Puebla and Morelos, to identify the affected areas and the extent of damage. This report is a summary of the damage characteristics observed during the survey for both structural and geotechnical aspects. A series of microtremor measurements were taken to understand the ground motion characteristics in three key areas of the Mexico City Basin. The results are presented and compared to the data gathered from the accelerograph network available in Mexico, and the damage characteristics are discussed. Whenever relevant, the conditions before the earthquake are compared with the damage encountered by the inclusion of photographs. In order to understand the extent of the damage incurred by the 2017 earthquake, an overview is provided of the geological and geotechnical conditions of Mexico City, which is renowned for its soft soils and problems associated with those soils. Given that the 1985 Michoacan Earthquake established the standards for seismic design in Mexico City, this report provides background on the effects of the 1985 earthquake and comparisons are made with the Puebla earthquake.
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緊結金具を用いたEPS構造体の地震時挙動 査読あり
西 剛整, 塚本 英樹, 谷 美宏, 林 夏希, 小浪 岳治, 林 豪人, 古関 潤一, 京川 裕之, 安原 一哉, 窪田 達郎
ジオシンセティックス論文集 33 ( 0 ) 191 - 196 2018年
記述言語：日本語 出版者・発行元：国際ジオシンセティックス学会 日本支部
EDO-EPS盛土は所定の緊結金具を所要数用いることにより大規模地震においても耐震性能が確保できることが実大規模の耐震実験で確認されている．一方で近年，2011年東北地方太平洋沖地震のような継続時間の長い地震動や，2016年熊本地震のように震度7クラスの地震動が連続するなど，これまで想定されていない地震の発生が続いている．このような中で，EPS盛土の耐震性をさらに向上させ，複数回の大規模地震に対してもより高い健全性を確保することが期待されている．本論文では新しい緊結金具の現場での作業性，静的なせん断抵抗を検証した結果を示し，従来の緊結金具より効果が高いこと報告する．また緊結金具を用いたEPS盛土の小型振動台実験の結果，所定数の緊結金具を用いて，中間床版上のロッキング対策を施すことで耐震性が高まることを明らかにする．
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EPSブロックとジオグリッドを併用した擁壁の耐震対策に関する振動台実験 査読あり
京川 裕之, 山崎 佑太朗, 古関 潤一, 小浪 岳治, 西 剛整, 窪田 達郎
ジオシンセティックス論文集 33 ( 0 ) 197 - 204 2018年
記述言語：日本語 出版者・発行元：国際ジオシンセティックス学会 日本支部
本研究では，ジオグリッド補強土擁壁の高い耐震性に加えて，擁壁躯体とその裏込め土の境界部にEPSブロ ックを配することで,擁壁と背面地盤一体の耐震性を高める工法の効果を1g場での模型振動実験により検証した．実験では，無補強の片持ち梁式擁壁，条件が異なるジオグリッド補強土擁壁とEPSブロック・ジオグリッ ド併用補強擁壁をぞれぞれ2ケースに対して，正弦波を段階的に与えた．実験結果から，ジオグリッド補強士 と唾Sブロックを併用した場合，裏込め土のより上層にEPSブロックを配置することで,擁壁の変位・傾斜お よび背面地盤の沈下麓が大きく抑制された．そして， これらの補強効果は，上方にEPSブロックがあることで 擁壁に作用する地震時土圧およびモーメントが低減されたためであることが示された．
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Isogeometric analysis of THM coupled processes in ground freezing 査読あり
Yared W. Bekele, Hiroyuki Kyokawa, Arne M. Kvarving, Trond Kvamsdal, Steinar Nordal
Computers and Geotechnics 88 129 - 145 2017年08月
掲載種別：研究論文（学術雑誌）
© 2017 Elsevier Ltd An isogeometric analysis (IGA) based numerical model is presented for simulation of thermo-hydro-mechanically (THM) coupled processes in ground freezing. The momentum, mass and energy conservation equations are derived based on porous media theory. The governing equations are supplemented by a saturation curve, a hydraulic conductivity model and constitutive equations. Variational and Galerkin formulation results in a highly nonlinear system of equations, which are solved using Newton-Raphson iteration. Numerical examples on isothermal consolidation in plane strain, one-dimensional freezing and heave due to a chilled pipeline are presented. Reasonably good agreements were observed between the IGA based heave simulations and experimental results.
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Effect of slaking on direct shear behaviour of crushed mudstones 査読あり
Keshab Sharma, Takashi Kiyota, Hiroyuki Kyokawa
Soils and Foundations 57 ( 2 ) 288 - 300 2017年04月
掲載種別：研究論文（学術雑誌）
© 2017 This study investigates the effects of wetting and drying cycles, known as slaking, on the strength-displacement characteristics of crushed mudstone. A series of direct shear tests was conducted by simulating cyclic wetting and drying under different stress conditions using a modified direct shear apparatus. The effects of the stress ratio, the density of specimen, the initial water content before wetting, the slaking index, and the number of wetting and drying cycles on the test results was investigated. Experiments were also performed on less-slakable materials, including crushed sand stone, silica sand and glass beads, to compare the results with the crushed mudstone. Considerable creep displacement on the crushed mudstones was observed during both drying and wetting phases under the constant shear stress conditions. The creep displacement during the drying was more significant than during the wetting phase. The creep displacement accumulated with progressive wetting and drying cycles. The drying-induced displacement was observed when the water content became smaller than the amount of water absorption of the mudstone specimens. Correspondingly, a gradual decrease of the peak stress ratio was observed with the number of wetting and drying cycles. In contrast to the mudstones, the influence of cyclic wetting and drying on the crushed sand stone, silica sand and glass beads is almost negligible. A higher slaking index, a lower water content before wetting, and lower initial density accelerate the slaking of mudstones.
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ＴＲＵ廃棄物地層処分施設の化学的変遷を考慮した長期力学挙動解析コードの開発 査読あり
三原 守弘, 平野 史生, 高山 裕介, 京川 裕之, 大野 進太郎
原子力バックエンド研究 24 ( 1 ) 15 - 26 2017年
記述言語：日本語 出版者・発行元：一般社団法人 日本原子力学会 バックエンド部会
<p> TRU廃棄物地層処分施設の長期力学挙動を評価するための解析コードMACBECEを開発した．解析コードには，セメント系材料からのカルシウムの溶出やベントナイト系材料のカルシウム型化およびスメクタイトの溶解などの化学的変遷に伴う力学特性変化および処分施設と周辺岩盤との力学的な相互作用を考慮した．開発した解析コードを用いてクリープ変形が生じやすいと考えられる軟岩サイトを想定し，TRU廃棄物地層処分施設の建設段階から，処分施設閉鎖後10万年までの力学挙動解析を行った．緩衝材の力学挙動モデルとして，ECモデルを用いることで応力が降伏曲面の特異点付近に陥ることを解消し，数値解析上，安定な解を得ることができた．さらに，周辺岩盤と処分施設の力学的相互作用を同時に解析することにより，周辺岩盤と処分施設の力学挙動を別々に解析した第2次TRUレポートの結果と比較して処分坑道の内径変位量が半分程度となることが示された．</p>
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Ultimate Lateral Resistance of Piles in Soils Based on Active Pile Length 査読あり
Mary Roxanne Aglipay, Kazuo Konagai, Takashi Kiyota, Hiroyuki Kyokawa
Geotechnical Hazards from Large Earthquakes and Heavy Rainfalls 525 2016年09月
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Effect of in-situ sample quality on undrained cyclic strength and liquefaction assessment 査読あり
T. Kiyota, T. Ikeda, Y. Yokoyama, H. Kyokawa
Soils and Foundations 56 ( 4 ) 691 - 703 2016年08月
掲載種別：研究論文（学術雑誌）
© 2016 Japanese Geotechnical Society This study investigates the effects of quality of in-situ sandy samples, which were taken by a conventional tube sampling (TS) method, on liquefaction assessment. The sandy samples were retrieved from a loose fill layer and medium-dense Holocene deposit in young reclaimed land in Urayasu City where significant liquefaction occurred during the 2011 off the Pacific Coast of Tohoku Earthquake. First, a series of small strain measurements and undrained cyclic triaxial tests was conducted on the TS and reconstituted samples. Second, in order to investigate an applicability of the tested samples for the liquefaction assessment, an effective stress analysis was performed by use of soil parameters obtained from the examined samples. Input earthquake motions of the analysis are the 2011 off the Pacific Coast of Tohoku Earthquake and the 1987 Chiba Toho-oki Earthquake, the first and the second largest earthquakes the investigation site has experienced. The result of a sample quality assessment with the small strain shear moduli indicates that the TS sample retrieved from the Holocene deposit remains of high quality. In addition, for the reconstituted sample of the fill layer, since the small strain shear moduli of the sample are found to be nearly equal to those obtained at the field, it can be considered that the in-situ soil structure condition is reproduced in the reconstituted sample. According to an official report, the liquefaction resistance of the TS sample of the loose fill layer is RL20=0.38, which is much larger than that of medium-dense Holocene deposit (RL20=0.29) measured in this study. This is because the fill layer is so loose that the TS sample could have been strengthened due to disturbance during the sampling. On the other hand, the test result for the reconstituted sample of fill layer shows an appropriate level of liquefaction resistance (RL20=0.14). The results of the effective stress analysis using the soil parameters obtained from the TS sample of Holocene deposit and the reconstituted sample of fill layer show the most probable behaviors of the ground at the investigation site for both the 2011 off the Pacific Coast of Tohoku Earthquake and the 1987 Chiba Toho-oki Earthquake, which are consistent with the evidence reported after the earthquakes. The results indicate that the sample quality assessment by using a small strain shear moduli is applicable for the rational liquefaction assessment, and it would be possible to employ the reconstituted sample, which the small strain shear moduli are the same with the in-situ value, in substitution for a high quality sample.
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破砕泥岩のスレーキング現象と変形挙動 査読あり
菊本 統, 福田 拓海, 京川 裕之
土木学会論文集C（地圏工学） 72 ( 2 ) 126 - 135 2016年
記述言語：日本語 出版者・発行元：公益社団法人 土木学会
乾湿繰り返しに伴う風化現象であるスレーキングを，従来型の促進スレーキング試験と一次元圧縮条件下で湿乾履歴を与える圧縮スレーキング試験により検討した．促進スレーキング試験では，試料によるスレーキング特性の違いや，細粒化に伴う土の力学特性の不可逆な変化について考察した．圧縮スレーキング試験では，圧縮過程での粒子破砕が圧縮性の増加に寄与すること，拘束応力下のスレーキングは土の大圧縮を引き起こすことを示した．最後に，湿乾履歴を考慮した粒度指標<i>I<sub>G</sub></i>の発展則により記述し，粒度指標<i>I<sub>G</sub></i>と最大・最小間隙比や限界間隙比を関係付けることでスレーキング現象を構成則の範疇で考慮できるとの考えを示した．
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航空レーザ測量に基づく浦安市の液状化による道路沈下分析 査読あり
須山 翔太, 清田 隆, 小長井 一男, 京川 裕之, 上村 健太, 濱中 亮
土木学会論文集C（地圏工学） 72 ( 1 ) 38 - 47 2016年
記述言語：日本語 出版者・発行元：公益社団法人 土木学会
2011年東北地方太平洋沖地震により，関東地方では東京湾沿岸部に代表される若年埋立地盤を中心に顕著な液状化が発生し，それに伴う構造物の様々な被害が発生した．本稿では，特に甚大な液状化被害が生じた千葉県浦安市を対象に，著者らが整備した液状化地盤沈下マップを用いて，液状化に起因する道路等の沈下量を抽出した．これらのデータ分析により，道路の舗装・路盤層厚が厚いほど液状化による沈下量は小さくなる傾向が確認された．また，液状化の程度を示すPL値と道路沈下量の関係においても上記の影響が認められ，液状化による地盤沈下予測やPL値に基づくハザードマップの高度化に資する結果を得た．更に，液状化対策として地盤改良が施されていた地区を対象とした沈下分析も行い，液状化後の沈下量に及ぼす地盤改良工法の効果を定量的に示した．
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TRU廃棄物処分システムの性能評価の観点からの人工バリアの透水性に対するセメント系材料のひび割れの影響に関する検討 査読あり
平野 史生, 大谷 芳輝, 京川 裕之, 三原 守弘, 清水 浩之, 本田 明
日本原子力学会和文論文誌 15 ( 2 ) 97 - 114 2016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：一般社団法人 日本原子力学会
The mechanical analysis code MACBECE2014 has been developed at the Japan Atomic Energy Agency (JAEA) to make realistic simulations of the physical integrity of the near field for performance assessment of the geological disposal of TRU waste in Japan. The MACBECE2014 code can be used to evaluate long-term changes in the mechanical behavior of the near field and any subsequent changes in the permeability of engineering barrier components, including crack formation in cementitious materials caused by expansion due to metal corrosion. Cracks in cementitious materials are likely to channel the flow of groundwater and so the represent preferred flow paths of any released radionuclides. Mechanical analysis was conducted using the MACBECE2014 code to investigate the concept of the TRU waste disposal system described in JAEA's Second Progress TRU Report. Simulated results of a disposal system with a bentonite buffer demonstrated that the low permeability of the engineering barrier system could be maintained for long time periods because the physical integrity of the bentonite buffer remained intact even if cracks in the cementitious components had formed locally. Simulated results of the disposal system with a concrete backfill instead of a bentonite buffer showed that crack formation leads to a significant increase in the permeability of the engineering barrier system.
