Kyoto University · Engineering
Professor Naotoshi Yasuda's research lab specializes in geomechanics, structural health monitoring, and advanced materials processing. The lab investigates the dynamic mechanical behavior of natural soils—particularly gravel foundations—using large-scale triaxial testing and in-situ measurements, aiming to evaluate the stiffness and damping characteristics of undisturbed ground. It also pioneers non-contact, laser-based inspection techniques for concrete structures, enabling precise detection and quantification of internal defects through vibration-based modal analysis. Additionally, the lab explores ultrafast laser-induced material modifications in glass, including optical waveguide writing and spatially controlled crystal precipitation for integrated nonlinear optics.
Figures are computed from collected data and may differ slightly.
The strength and deformation characteristics of undisturbed specimens measured by large-scale triaxial tests were compared with those of reconstituted specimens to evaluate the stiffness of natural ground. The undisturbed specimens were sampled from the riverbed gravel foundation of an embankment dam using the freezing sampling method with liquid nitrogen. The validity of the results from the undisturbed specimens was evaluated by comparing the stiffness of the natural ground using P- and S-wave
Cet article examine la resistance dynamique des materiaux grâce a des essais cycliques de chargement triaxial et des essais de cisailement simple en torsion. On a etudie l'influence du nombre de cycles, de la deformation de cisaillement, de l'indice de densite, de la pression de confinement et de la contrainte de cisaillement initiale sur la resistance dynamique. On compare les valeurs obtenues dans les essais de chargement cyclique avec la resistance statique developpee dans des essais monotoni
Les caracteristiques de puissance des specimens inchanges mesures par un essai triaxial a grande echelle ont ete comparees a celles des specimens reconstitutes afin d'evaluer la puissance du sol naturel. Les specimens inchanges ont ete echantillonnes a partir du fond en graviers du lit de la riviere d'un barrage en remblai, en employant une methode de congelation des specimens par nitrogene liquide. On a constate que les caracteristiques de puissance dynamique des specimens inchanges sont plus i
加振用および計測用の2つのレーザーを用いた非接触検査法を利用し,コンクリート構造物の健全性評価を試みた.内部欠陥を有するコンクリート供試体を用いた室内実験から,次のことが明らかとなった.欠陥の有無は減衰振動の有無を調べることで推定できる.計測結果をインパルス応答とみなし,これに対してモード特性同定法の一種であるLSCF法を適用することで,ノイズが重畳された環境下でも高精度で欠陥の有無を安定的に判定でき,欠陥が有る場合はその振動特性を物理的に有意な指標で定量化できる.続いて,新幹線トンネル内で実験を実施し,提案手法の有用性を実証するとともに,欠陥部の振動特性からその健性度を評価する際は,最低次モードの固有振動数が有用な指標の1つとなることを明らかにした.
We report on the fabrication of optical waveguides and the precipitation of nonlinear optical crystals inside glass caused by local element migration with high-repetition femtosecond laser irradiation. Elements that contribute to the high refractive index migrated to the center of the focal region because of the femtosecond laser irradiation in phosphate and borate glasses. Based on this result, we successfully wrote optical waveguides in these glasses, where element distributions were continuou
山岳トンネルの地震被害メカニズムを理解するための基礎として，調和振動の平面波がトンネル軸に対して斜めに入射した場合の円形トンネルの変形挙動を3次元弾性波動論に基づいて解析した．地震波で想定される周波数範囲では，トンネル横断方向の挙動は地盤と覆工の相対的な剛性の比で決まり，入射波の波長の影響をほとんど受けないが，トンネル縦断方向の挙動は剛性比に加え，入射波のトンネル軸方向に生じる見かけの波長の影響を受ける．そのため，トンネル横断面内に変位成分を持つS波だけでなく，トンネル軸を含む縦断面内に変位成分を持つS波でも被害が生じる可能性があることが明らかとなった．また，実際の被害においてもトンネル軸を含む縦断面内に変位成分を持つS波が被害要因の一つと考えられる事例のあることが確認された．
Abstract Bolts have been used under various geological conditions as reinforcement to support underground openings. However, quantitative evaluations of the impacts of reinforcement bolts remain controversial. When a bolt is modeled explicitly, one challenge is determining the parameter that represents the interaction between the bolt and surrounding medium. This study aims to derive a simplified Winkler model for the ground support provided by a bolt, with the mutual interaction between the bol
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