Faculty Profiles - NODA, Toshihiro

Papers - NODA, Toshihiro

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Importance of considering unsaturated triaxial tests including ceramic disk as initial and boundary value problems Reviewed International journal Open Access

Yoshikawa, T., Noda, T. and Kodaka, T.

Soils and Foundations 2021.3

Language：English Publishing type：Research paper (scientific journal)

Considering unsaturated triaxial tests including a ceramic disk as initial and boundary value problems, a series of suction change, isotropic consolidation, and drained shearing processes was simulated using a soil-water-air coupled elastoplastic finite deformation analysis code. As a result, it was demonstrated that the delayed behavior of a wetting-induced collapse during the suction change and isotropic consolidation processes, as well as water-absorption behavior during the subsequent drained shearing process, were attributed not to the characteristics of the soil specimen, but to the permeability of the disk. Thus, it is important to take the ceramic disk into account in unsaturated triaxial tests regarded as initial and boundary value problems in order to understand the temporal change behavior of unsaturated soil specimens. Otherwise, there is a risk that the behavior appearing as the solution of an initial and boundary value problem may be modeled as a constitutive relation.

DOI： 10.1016/j.sandf.2020.12.009

Open Access

Scopus

LIQUEFACTION DAMAGE SUPPRESSION EFFECTS OF EXISTING SMALL SCALE STRUCTURE RECEIVING ECCENTRIC LOAD USING FLOATING GRID TYPE IMPROVEMENT Reviewed Open Access

Vol. 76 ( 2 ) page： I_279 - I_288 2021.2

Language：Japanese Publishing type：Research paper (scientific journal)

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 structure 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.

DOI： https://doi.org/10.2208/jscejam.76.2_I_279

Open Access

PROGRESSIVE FAILURE OF UNSATURATED FILL SLOPE CAUSED BY CUMULATIVE DAMAGE UNDER SEEPAGE SURFACE Reviewed International journal Open Access

Murao Hidehiko, Nakai Kentaro, Yoshikawa Takahiro, Noda Toshihiro

INTERNATIONAL JOURNAL OF GEOMATE Vol. 20 ( 78 ) page： 1 - 8 2021.2

Authorship：Last author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：International Journal of GEOMATE

Seepage surface position of fill slope can fluctuate owing to rainfall and groundwater supply from behind the slope. Therefore, in this study, shaking-table tests of an unsaturated fill slope were conducted to examine the influence of the seepage surface position on the fill slope stability by comparing with previous results in the fully saturated condition. An acceleration amplification factor was used to evaluate the stability. If the embankment was in an unsaturated condition, a slip plane was formed along the seepage surface. With ongoing increase of input acceleration, the slip progressed to behind the slope. Comparison of the unsaturated and saturated results showed that although the failure mechanism in which the slip surface was formed by the reduction in rigidity was common, the input acceleration at failure and deformation mode were different. When the slip surface was formed and failure occurred, the input acceleration in the unsaturated fill slope was more massive, and the deformation at the same excitation stage was small. These results imply that the unsaturated fill slope has a higher earthquake resistance than the saturated fill slope. Moreover, it is shown that the progress of plastic deformation inside the embankment and the formation process of the slip plane can be estimated from the change in the acceleration amplification factor regardless of seepage surface position.

DOI： 10.21660/2020.78.j2036

Open Access

Web of Science

Scopus

Triaxial test on water absorption compression of unsaturated soil and its soil-water-air coupled elastoplastic finite deformation analysis International journal Open Access

Yoshikawa Takahiro, Noda Toshihiro

SOILS AND FOUNDATIONS Vol. 60 ( 5 ) page： 1151 - 1170 2020.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Soils and Foundations

Triaxial tests and numerical simulations were conducted to determine the water absorption compression of unsaturated soil. In the triaxial tests, unsaturated silt specimens under the same initial condition were prepared and the processes of different suction reduction, isotropic consolidation, and exhausted-drained shearing were applied to the specimens. The numerical simulations used a soil-water-air coupled finite deformation analysis code with a newly incorporated elastoplastic constitutive model. The degree of saturation was introduced to the internal state variables of the yield function of the SYS Cam-clay model and a soil-water characteristic model with void ratio dependency. Then, the triaxial test was treated as an initial and boundary value problem, and the series of processes in the experiments were simulated using a single set of material constants and initial values. The new findings are as follows:
1)The loading criterion and the classification of loading conditions considering change in saturation degree can be specified in the elastoplastic constitutive model for unsaturated soil.
2)Water absorption compression behavior was observed in the experiments not only under suction reduction but also under constant suction condition. This water absorption compression under constant suction condition was explained as a saturation-increase behavior due to volume compression using the soil-water characteristic model with void ratio dependency.
3)By considering the triaxial test as an initial and boundary value problem, the temporal change in the volume and the amount of water absorption/drainage were able to be reproduced.

DOI： 10.1016/j.sandf.2020.06.010

Open Access

Web of Science

Scopus

Seismic damage of soft clay layer directly under the river levee that becomes prominent by L2 earthquake International journal

Noda, T. and Nakai, K.

Proc. of the 17th World Conference on Earthquake Engineering (17WCEE) page： 4b-0040 2020.9

Localized/enormous seismic damage of subsurface ground induced by the stratum irregularity International journal

Nakai, K. and Noda, T.

Proc. of the 17th World Conference on Earthquake Engineering (17WCEE) page： 1d-0092 2020.9

Numerical analysis on aftershock-induced liquefaction of sandy ground with water-level raised by main shock International journal

Yoshikawa, T. and Noda, T.

Proc. of the 17th World Conference on Earthquake Engineering (17WCEE) page： 4b-0051 2020.9

Validation of the applicability of a drainage method for reducing settlement and inclination of utility poles in liquefied ground Reviewed Open Access

ITO, H., ISHIMARU, M., NAKAI, K. and NODA, T.

Vol. 15 ( 3 ) page： 643 - 652 2020.9

Authorship：Last author Language：Japanese Publishing type：Research paper (scientific journal)

In the 2011 Earthquake off the Pacific coast of Tohoku, extensive liquefaction occurred in the Kanto region. This resulted in the settlement and inclination of thousands of utility poles. In urban areas, utility poles are often installed in narrow easements with limited clearance. Therefore, a simple and inexpensive countermeasure is desired. In this study, we attempted to reduce the settlement and inclination of utility poles in the liquefied ground by providing drain
holes in the utility pole. In the centrifugal model tests conducted using pole models with drain holes at the bottom and sides, settlement and inclination decreased in relation to the amount of drainage. Therefore, it was determined that the drainage method has a definite effect on the reduction of both settlement and inclination of utility poles in the
liquefied ground.

DOI： https://doi.org/10.3208/jgs.15.643

Open Access

Scopus

Deformation-failure mechanism of saturated fill slopes due to resonance phenomena based on lg shaking-table tests (vol 55, pg 1668, 2018)

Murao, H; Nakai, K; Noda, T; Yoshikawa, T

CANADIAN GEOTECHNICAL JOURNAL Vol. 57 ( 8 ) page： 1263 - 1263 2020.8

Soil-water-air coupled finite deformation simulation of model test on seepage failure of levee Reviewed Open Access

Vol. 75 ( 2 ) page： I_379 - I_388 2020.2

Language：Japanese Publishing type：Research paper (scientific journal)

Due to heavy rain in northern Kyushu in July 2012, failure of the Yabe River levee occurred, caused by local piping in highly permeable foundation ground, and it was a great shock when river engineers and researchers realized that levees can collapse without overflow. Regarding the Koyoshi River levee slope slip and the Kakehashi River levee slope failure that occurred in July 2013, it is also considered that the damage was the result of highly permeable foundation ground. In this paper, to clarify the seepage failure mechanism of river levee with highly permeable foundation ground, numerical simulations of model tests were conducted using a soil-water-air coupled finite deformation analysis code. As a result, the simulation was able to reproduce the difference between the case when the seepage failure occurred and the case when the seepage failure did not occur in the experiment. In addition, using this analysis code, case studies were conducted and the influence of introducing suction effect to elastoplastic constitutive model on seepage failure behavior was also discussed.

DOI： 10.2208/jscejam.75.2_I_379

Open Access

Reduction effects of liquefaction damage using small scale floating grid-type improvement for existing small scale structure Reviewed Open Access

Vol. 75 ( 2 ) page： I_329 - I_339 2020.2

Language：Japanese Publishing type：Research paper (scientific journal)

Earthquake resistance of important structure have been promoted based on the lessons learned from the big Earthquake in Japan. However, liquefaction still causes serious damages to many detached houses 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 measure 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 similar result as found in the observations.

DOI： 10.2208/jscejam.75.2_I_329

Open Access

Influence of neighboring houses on liquefaction damage of detached houses Reviewed Open Access

Vol. 75 ( 2 ) page： I_401 - I_410 2020.2

Language：Japanese Publishing type：Research paper (scientific journal)

In the 2011 off the Pacific Coast of Tohoku Earthquake, the liquefaction damage in the residential area of Urayasu City was huge, and many detached houses suffered uneven settlement. In Japan, however, there has not been sufficient knowledge about liquefaction- induced damage of detached houses. Therefore, in this study, with regard to the liquefaction damage form of the detached houses constructed on the liquefiable ground, the following points were clarified focusing on the influence of the neighboring houses using soilwater coupled finite deformation analysis. 1) In the case of single structure evaluation, even if stability is maintained without tilting, tilting damage may occur when considering neighboring houses. 2) The direction of inclination of neighboring houses can be explained by using the computed direction of post-seismic displacement vector in the case of one house alone.

DOI： 10.2208/jscejam.75.2_I_401

Open Access

Undrained cyclic shear behavior of clay under drastically changed loading rate International journal

Khan Imran, Nakai Kentaro, Noda Toshihiro

INTERNATIONAL JOURNAL OF GEOMATE Vol. 18 ( 66 ) page： 16 - 23 2020.2

Language：Japanese Publishing type：Research paper (scientific journal)

The earthquake damage prediction is mainly focused on the seismic instability of sandy foundations although the clayey foundation could also be vulnerable to earthquake damage. Moreover, it is known that clayey soil shows a marked loading rate dependency in monotonic shear behavior due to its low permeability. Therefore, this paper aims to determine the undrained cyclic shear behavior of clayey soil under a drastically changed loading rate. Reconstituted clayey samples were subjected to undrained cyclic triaxial compression/extension tests with loading rate from 1.0Hz to 0.0042Hz by stress control, and 0.01%/min by strain control. The cyclic loading was stopped when the double amplitude exceeded 5%. Then, the specimen was left for a while in an undrained condition, until the value of pore water pressure converged. Results revealed that as the loading rate decreases, the number of cycles that corresponds to DA=2% and 5% also decreased. Therefore, the degree of strain evolution varies depending on the loading rate and the undrained shear strength also varies depending on the cyclic loading rate. This is because when the cyclic loading rate was high; the pore water did not migrate sufficiently, leading to the non-uniform distribution of the excess pore water pressure inside the specimen. However, the final values of excess pore water pressure after the homogenization process was the same regardless of the loading rate. This means that if sufficient time is left after cyclic loading, the final mean effective stress value becomes equal regardless of the loading rate.

DOI： 10.21660/2020.66.07893

Web of Science

Scopus

Experimental research on development/diminishing of anisotropy and its effect on mechanical behavior of clay Reviewed International journal Open Access

Khan Imran, Nakai Kentaro, Noda Toshihiro

INTERNATIONAL JOURNAL OF GEOMATE Vol. 18 ( 65 ) page： 9 - 14 2020.1

An analytical consideration on aftershock-induced expansion of liquefaction damage of sandy ground with groundwater-level rise due to main shock International journal

Proc. of 16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019 2020

Correction: Deformation–failure mechanism of saturated fill slopes due to resonance phenomena based on 1g shaking-table tests (Can. Geotech. J., 55(11), 1668-1681, 2018, 10.1139/cgj-2017-0385) International journal

Murao H., Nakai K., Noda T., Yoshikawa T.

Canadian Geotechnical Journal Vol. 57 ( 8 ) 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Canadian Geotechnical Journal

Replace Fig. 10 with the figure shown herein, where labels “(a)” and “(b)” have been added; and “ch.3 (upper)”, “ch.2 (middle)”, and “ch.1 (lower)” in part (b) of the figure have been replaced with “ch.6 (upper)”, “ch.5 (middle)”, and “ch.4 (lower)”, respectively.(Image presented).

Scopus

Numerical simulation of Riedel shear bands formation considering effects of geometrical barrier on strike-slip fault International journal

Toyoda T., Noda T., Yamada S., Asaoka A.

16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019 2020

Language：English Publishing type：Research paper (scientific journal) Publisher：16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019

Displacements of strike-slip faults generate Riedel shear bands and flower structures at the surface ground above the faults. This paper aims to simulate deformation of strike-slip deformation of the surface ground considering jogs as geometrical imperfections. Analyses are based on the GEOASIA with SYS Cam-clay model that considers overconsolidation, which allows us to simulate softening behavior of brittle materials. Since the analytical results consider the presence of jogs, fractal shear zones (duplexes), P-shear, R/R'-shear, outer shear/splay shear, and tulip/palm-tree structures are successfully simulated. Furthermore, in terms of the scale effect, Riedel shear bands fractally appear when setting same overconsolidation ratio at the bottom of models.

Scopus

Numerical simulation of Riedel shear bands formation considering effects of geometrical barrier on strike-slip fault International journal

Toyoda Tomohiro, Noda Toshihiro

Proc. of the 16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering (16ARC) page： JGS-064 2019.10

Language：English

Soil-water-air coupled elasto-plastic finite deformation simulation of unsaturated silt triaxial test using void ratio-dependent soil water retention model International journal

Yoshikawa Takahiro, Noda Toshihiro

Proc. of the 7th Asia-Pacific Conference on Unsaturated Soils (AP-UNSAT2019) page： EA56 2019.8

Language：English

A soil-water-air coupled finite deformation analysis of unsaturated silt triaxial tests, which were conducted by Kodaka et al. (2006), was performed considering the triaxial test not as an element test but as an initial and boundary value problem. The analysis can deal with suction effect accounting it in the elasto-plastic constitutive equation, SYS Cam-clay model. A series of processes of suction variation, isotropic consolidation, and exhausted-drained shearing were simulated beginning from a single initial condition and using a single set of material constants. The results showed that considering ceramic disc permeability was required to reproduce well both the mechanical and hydraulic behavior. Accordingly, it is suggested that a laboratory test result should be seized as the solution for an initial and boundary value problem. In addition, to experimentally clarify that the ceramic disc permeability is comparatively low, unsaturated silt triaxial tests were conducted using both a ceramic disc and a micro-porous membrane for suction control.

An analytical study on expansion of liquefaction damage during aftershock induced by groundwater-level rise due to main shock International journal

Noda Toshihiro, Yoshikawa Takahiro

Proc. of the 7th Asia-Pacific Conference on Unsaturated Soils (AP-UNSAT2019) page： EA59 2019.8

Authorship：Lead author Language：English

Extensive liquefaction damage was observed in the 2011 off the Pacific coast of Tohoku Earthquake over a wide range of reclaimed coastal land. It is reported that in Chiba Prefecture, the large aftershock that occurred 29 minutes after the main shock extended the liquefaction damage in sandy ground. In this paper, using a soil-water-air coupled finite deformation analysis code incorporating the elasto-plastic constitutive equation SYS Cam-clay model, it is shown that the groundwater level rises due to the main shock and that during the aftershock, this groundwater level rise could cause extended liquefaction damage.

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Papers - NODA, Toshihiro