Journal of JSCE
Online ISSN : 2187-5103
ISSN-L : 2187-5103
Current issue
Displaying 1-28 of 28 articles from this issue
Special Topic (SPECIAL ISSUE ON THE STORM AND FLOOD DAMAGE 2019 IN JAPAN)
Preface
  • Hiromune YOKOKI, Tatsuhiko UCHIDA, Yoshihisa AKAMATSU, Shinta SETO, Sh ...
    2022 Volume 10 Issue 1 Pages 1-7
    Published: 2022
    Released on J-STAGE: January 20, 2022
    JOURNAL FREE ACCESS

     In 2019, the Kanto-Koshin area and the Tohoku area suffered devastating damage from floods and sediment disasters caused by the record-breaking heavy rainfall that came with Typhoon No. 19 (Hagibis). In the same year, the heavy rainfall caused severe damage in the northern part of Kyushu area, such as Saga Prefecture, as well as the wind and rain disaster caused by Typhoon No. 15 (Faxai) in Chiba Prefecture. These disasters also highlighted the danger posed by a series of disasters that could cause extensive damage in large areas due to combinations of multiple factors. It is one of the missions of JSCE to compile and disseminate lessons learned from disasters in Japan for solving future challenging issues in managing infrastructures and mitigating disaster damage. This special issue on the storm and flood damage in 2019 in Japan includes valuable information on the disasters in 2019 from different disciplinary points of view, aiming to contribute to the growth and development of interdisciplinary academic fields of civil and environmental engineering.

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Paper
  • Kensaku MATSUMOTO, Shoichi TAKADA, Kyoya NAKAJIMA, Kazuya TSUJI, Hiron ...
    2022 Volume 10 Issue 1 Pages 8-18
    Published: 2022
    Released on J-STAGE: January 20, 2022
    JOURNAL FREE ACCESS

     Flooded areas along the Akiyama River were investigated after Typhoon Hagibis in 2019. The areas that experienced severe flood damage and the two levee failures that occurred were all areas where the river became narrower, and both levee failures occurred upstream of the foot of a bridge. The particularly severe damage to the levee on the right bank of the Kairiku Bridge in Akasaka-cho might have been the result of multiple compounding factors, including its location on the outer bank of a curve and risks, such as the angle at which the girders were built relative to the downstream current. The times when the levee failures occurred were determined through interviews with residents of the damaged areas, and a numerical analysis that took each of the relevant conditions into account indicated that the severe damage to downtown Sano City might have been caused not only by the flooding that resulted from the overflow from the Akiyama River and failures of the levees, but also by multiple compounding factors including the effects of the flooding from nearby rivers, such as the Kikusawa River.

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  • Norio TANAKA, Yoshiya IGARASHI, Hiroshi SUENAGA
    2022 Volume 10 Issue 1 Pages 19-29
    Published: 2022
    Released on J-STAGE: January 20, 2022
    JOURNAL FREE ACCESS

     During the flood event caused by Typhoon Hagibis, a large number of trees on the forested gravel bars were destructed in Kumagaya, on the alluvial fan in the Arakawa River. Parts of the trees were trapped in the downstream bars and formed debris dams. The change in the resistance by a debris dam could affect not only the formation of repelling current, but also the flood propagation downstream. A two-dimensional flood simulation model of the destruction and trapped driftwoods was applied to the site, to clarify the changes in flow pattern due to the destructive flood. The maximum velocity was decreased on the gravel bar where debris dams were formed although the velocity was increased by the destruction in the low channel. The tree destruction situation itself was mitigated in the sheltered area of the forest by the debris dam formation. From the point of the maximum water depth at the embankment, the trapping effect was low in the case of Arakawa River, which has a wide cross-section, but it also reduced the peak discharge by around 10m3/s.

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  • Masato KITA, Chaochao QIAN, Takehiko KONOSHIMA, Masaaki NAKAYASU, Tets ...
    2022 Volume 10 Issue 1 Pages 30-44
    Published: 2022
    Released on J-STAGE: January 20, 2022
    JOURNAL FREE ACCESS

     The 2019 Typhoon Hagibis brought heavy rainfall to eastern Japan. In the downstream basin of the Arakawa River, which is located in the Metropolitan area, the water level rose close to the inundation risk level. As flooding is likely to occur in the downstream basin in the event of still heavier rainfall, it is necessary to obtain data on increased rainfall as basic information for the planning of evacuation activities. This paper reports the results of a reproducibility study together with an analysis of changes in rainfall due to manipulation of sea water temperature using a Weather and Research Forecasting (WRF) model and of their impact. The overall shape of hyetograph was reproduced in the study, albeit with differences in peak time and amount of rainfall. In addition, it was verified that the amount of rainfall fluctuates in correspondence with fluctuations in sea surface temperature. The study revealed that this is caused by the effect of the topography of the Arakawa upstream basin, in addition to changes in the course of the typhoon resulting from changes in the atmospheric pressure field and fluctuation of the water vapor flux.

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  • Naoya SHIBATA, Yuma MASUDA, Hiroyoshi MORITA, Shinichiro NAKAMURA
    2022 Volume 10 Issue 1 Pages 45-55
    Published: 2022
    Released on J-STAGE: January 20, 2022
    JOURNAL FREE ACCESS

     Land use regulation is a fundamental measure of flood mitigation and climate change adaptation for reducing the amount of exposure in floodplains. In Japan, land use regulation for flood mitigation has been considered in the classification area under the City Planning Act and the Location Normalization Plan under the Act on Special Measures Concerning Urban Reconstruction. However, mitigation effects and operational challenges have not been fully elucidated. In this study, we analyzed the characteristics of flood damage in the urbanization control area in Naganuma District of Nagano City, which was severely damaged by the Chikuma River levee break triggered by Typhoon Hagibis in 2019. The analysis, which adopted building point data, determined that land use regulation by area classification played a role in reducing damage in the area. However, at the community level, it was confirmed that more buildings were located in areas with high flood hazards owing to the development of new houses and businesses associated with the development of infrastructure.

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  • Fuko NAKAI, Shinichiro NAKAMURA, Kensuke TAKENOUCHI
    2022 Volume 10 Issue 1 Pages 56-69
    Published: 2022
    Released on J-STAGE: January 20, 2022
    JOURNAL FREE ACCESS

     This study examined the evacuation behavior of two communities—Naganuma and Toyono—in Nagano City, Japan, during typhoon Hagibis. Only two casualties were reported, despite the large size of the inundated area and significant building damage. We analyzed the relationship between (1) the numerical statement of aggregated evacuation behavior, (2) social and hazard circumstances, and (3) the social background, including disaster preparedness plans formulated by the community. The study focused on “the details” of evacuation promotion factors revealed by previous research, rather than “the existence or absence” of such factors. Data were collected from newspaper articles, a post-interview survey conducted by Kansai Television Co. Ltd., minutes from the flood control meetings in the flooded area, and district disaster management plans. The results revealed that the main factors promoting evacuation action differed for the two communities due to their disaster preparedness styles. While Naganuma established a specific (a particular measurement of the water level of the Chikuma River) and socially agreed-upon criterion for evacuation, Toyono had experienced several inland flooding events. It was found that both communities participated in the flood control meetings, formed organizations for voluntary disaster mitigation action, and cultivated common awareness regarding “the sign of a dangerous situation” and “what information is important for evacuation.”

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  • Nozomu ONAKA, Yoshihisa AKAMATSU, Shinji HIRATA, Takahiro SAYAMA
    2022 Volume 10 Issue 1 Pages 70-81
    Published: 2022
    Released on J-STAGE: January 20, 2022
    JOURNAL FREE ACCESS

     Typhoon Hagibis caused the serious flood damage on the Naka River, which is one of the major class A rivers in the Kanto region since the flood damage in 1986. In this study, we recorded the disaster situation and conducted field survey in the damage concentrated segment of the bank breakage and overflow. In addition, we conducted the runoff analysis for the Naka River Basin and the flood analysis for some regions near the Nakagawa River. As a result, it is clarified that 1) the large-scale inundation (average inundation depth: 1.9m) occurred near the Fujii and Tano rivers that are tributaries of the Naka River and 2) the inundation continued for a while (four days) because the drainage capacity was not sufficient. In addition, based on the water level changes of the Naka and Fujii rivers and the traces of the flood flow, it was inferred that the Fujii River was affected by the backwater. Furthermore, the reproduction simulation, which combined the runoff analysis and the flood analysis, reproduced 1) the inundation depth obtained by the field survey and 2) the backwater in the Fuji River.

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  • Fumiya YAGI, Tatsuhiko UCHIDA, Yoshihisa KAWAHARA
    2022 Volume 10 Issue 1 Pages 136-144
    Published: 2022
    Released on J-STAGE: February 20, 2022
    JOURNAL FREE ACCESS

     In October 2019, a typhoon caused major damage along the Chikuma River, including the structural failure of major roads along the river and of bridge piers. To mitigate flood damage, it is useful to develop a flow pattern evaluation method for detecting high-risk river reaches against bank erosion during a flood. This study focuses on the turbulent energy distribution along the riverbank, which was increased by several flow patterns, such as secondary flows in curved channels, high velocity downstream from a weir, three-dimensional flow around a pier, and water surface fluctuations along the bank — all of which induced bank erosion. The three-dimensional flow structures were investigated using the bottom velocity computation (BVC) method for several instances of bank erosion in three rivers: the Chikuma River, which suffered riverbank erosion damage due to the heavy rainfall brought by Typhoon 19 in October 2019, and the Misasa and Seno Rivers, where massive riverbank erosion occurred due to heavy rain in July 2018. All bank erosions in the reaches in this study are found where the turbulent energy takes a local maximum.

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  • Daisuke KOMORI, Vempi Satriya Adi HENDRAWAN, Akihiro ICHIBA, Keitaro Y ...
    2022 Volume 10 Issue 1 Pages 195-205
    Published: 2022
    Released on J-STAGE: March 20, 2022
    JOURNAL FREE ACCESS

     This study aims to clarify the mechanism of rainfall inundation caused by the 2019 Typhoon Hagibis in Iwate prefecture coastal zone, Japan, using probable one-hour rainfalls estimated for the 2 periods of 1976-2005 and 1989-2018. The differences between rainfalls by the 2019 Typhoon Hagibis and the ten-year return level of one-hour rainfall (P10) of 1976-2005, which is generally assumed as the discharge standard of drainage system in Japan, at Fudai village, Iwaizumi town, Miyako city, and Yamada town were in the ranged of 40.7 mm–106.6 mm for maximum three-hour rainfall during the 2019 Typhoon Hagibis, and the estimated massive rainfall inundations. On the other hand, massive rainfall inundations were also observed at Kamaishi city, although the amount of water overflow from the existing drainage system was only 3.5 mm for a maximum of three-hour rainfall during the 2019 Typhoon Hagibis. These were caused by water overflow at narrow sections in the streams and drainage systems by huge sediment and large wood and debris from landslides dammed up, and by damming up rainfall inundation at coastal levees for tsunami. In addition, P10 at all study areas were increased by 8–24% from 1976-2005 to 1989-2018, which corresponded with increasing frequency of P10 of 1976-2005 by 1.4-2.1 times. Thus, increasing frequency of rainfall inundations in the Iwate prefecture coastal zone is expected in the future.

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  • Yoshiya IGARASHI, Norio TANAKA
    2022 Volume 10 Issue 1 Pages 213-227
    Published: 2022
    Released on J-STAGE: April 20, 2022
    JOURNAL FREE ACCESS

     Typhoon Hagibis 2019 recorded the highest precipitation in history, in several areas of East Japan. Levee breaching occurred at 7 places in the Arakawa River system. The risk of downstream migration should be discussed when conducting river channel management. For this purpose, it is necessary to understand the inundation between the river and the flood plain. Therefore, the effects of the levee breaching of the Tokigawa River and the timing on flood volume were considered as a first step.

     It was suggested that the levee at the junction section of the Tokigawa River and the Oppegawa River gradually scoured, considering the change in water-level hydrograph by changing the levee breaching timing. In addition, it can be considered that the left levee breaching at the Tokigawa River at 6.5 KP occurred after 10:00 PM on October 12th, noting the change in flood volume by changing the levee breaching timing. The inundation on the right side of the Tokigawa River in the section managed by Saitama Prefecture was caused by the inundation from the Kasumi-tei (open levee); therefore, the levee breaching at the 1.4 KP right levee had little effect on the inundation level.

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  • Daisuke NOHARA, Tetsuya SUMI
    2022 Volume 10 Issue 1 Pages 275-287
    Published: 2022
    Released on J-STAGE: May 20, 2022
    JOURNAL FREE ACCESS

     Recordable-high rainfall hit and caused severe floods in wide areas in the eastern Japan due to Typhoon Hagibis in October, 2019. This paper aims to clarify an effective way for reservoirs to manage large-scale floods by analyzing reservoir flood control practices during this flood event. The paper firstly reviews flood control of reservoirs in this event to discuss the effectiveness of, and issues in current reservoir operation practices. A detailed analysis is then carried out to estimate effects of flood control by two reservoirs in the Sagami River basin, where one of the reservoirs conducted the emergency spillway gate release operation due to extremely large-scale rainfall. The paper also investigates the applicability of a medium-term operational ensemble rainfall forecast to preliminary release of reservoirs for enhanced management of large-scale floods.

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Technical Report
  • Tadao ENOMOTO, Yuuki SATO
    2022 Volume 10 Issue 1 Pages 82-95
    Published: 2022
    Released on J-STAGE: January 20, 2022
    JOURNAL FREE ACCESS

     The 2019 typhoon No. 19 hit Japan on October 12. It caused severe damage to Kanto-koshin and Tohoku areas upon landing. The authors conducted damage investigations on all the breached sections of river dikes in Ibaraki prefecture in total five times after the disaster occurred. The survey results showed that: 1) the breach of river dikes in Ibaraki prefecture might be attributed to the erosion of levee slopes caused by the overflow; 2) no signs of soil ejection and piping were found around the breached sections of river dikes; 3) some river dikes with the crest pavements and revetment blocks for both side surfaces demonstrated that they could occasionally be collapsed by the overflow.

     At the time of the above-mentioned survey, geomaterials were retrieved from both slope surfaces of each undamaged dike section, which was adjacent to the damaged area, for laboratory tests. The test results revealed that most of the retrieved materials were non-/low-plastic sandy or gravelly soils with fines content less than 20%.

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  • Kosuke IIMURA, Hirokazu IKEDA
    2022 Volume 10 Issue 1 Pages 96-101
    Published: 2022
    Released on J-STAGE: January 20, 2022
    JOURNAL FREE ACCESS

     The heavy rainfall from 10th to 13th October 2019, due to Typhoon Hagibis, caused numerous disasters in various parts of eastern Japan. In Tochigi Prefecture, the maximum one-hour rainfall was 58mm and 52.5mm, and total rainfall for three days was 423mm and 512.5mm at the Shioya and Okunikkou weather station, respectively. Consequently, 27 levee breaches occurred in 13 rivers. In the present study, field survey and numerical simulation were performed to clarify the complicated behavior of inundation flow in Arakawa river in the Nakagawa river system, where the levee breach occurred due to the inundation overflow from the landside to the riverside. Moreover, this flow influenced the opposite-side levee breach.

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  • Mirei SHIGE-EDA, Juichiro AKIYAMA, Adelaida Castillo DURAN, Ryo KANAYA ...
    2022 Volume 10 Issue 1 Pages 102-110
    Published: 2022
    Released on J-STAGE: January 20, 2022
    JOURNAL FREE ACCESS

     This report investigates the characteristics of heavy rainfall and flood inundation area due to heavy rain caused by Typhoon No. 19 in 2019. We obtained data on rainfall, inundated areas, and topographic characteristics of the affected area. We also examined the relationship among them. This study confirmed the following: (1) In prefecture-managed rivers, inundation occurred due to insufficient flow capacity within areas of heavy rainfall. Furthermore, reduced flow capacity was caused by rising water levels in the main river at the confluence. (2) In rivers under the jurisdiction of the Ministry of Land, Infrastructure, Transport and Tourism (MLIT), rainwater due to heavy rain upstream flowed into the river channel and downstream. It caused the water level in the river channel to rise in the downstream area where rainfall was relatively low. The rise of the water level caused inundation with levee failure. (3) Depending on the topographical characteristics, there were two types of floodplains: one that attempted to divert floodwater back into the river channel, and the other that acted as a retarding basin. (4) The area where the levee breach occurred in the Kanto region, where most of the land was used as a field and where the inundation flows were stored, may have served as a flood-retarding basin.

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Technical Note
  • Tomoya MATSUDA, Shunzo KAWAJIRI, Yasuharu WATANABE, Kenji WATANABE
    2022 Volume 10 Issue 1 Pages 206-212
    Published: 2022
    Released on J-STAGE: April 20, 2022
    JOURNAL FREE ACCESS

     Typhoon 19, which landed on the Japanese Islands on October 12, 2019, brought record-breaking heavy rain to the Kanto-Koshin and Tohoku regions. In the Chikuma River basin of the Shinano River system, severe damage to bridges and large-scale inundation occured due to a levee breach occurred. On October 23 and 24, 2019, about 10 days after the disaster, we carried out a field survey at the damaged sites of river structures in the Chikuma River. The investigation techniques used field exploration and aerial photography by Unmanned Aerial Vehicle (UAV). This paper reports the damage situations obtained from the field survey at the sites where the abutment backfills were washed away and the levee breach occurred. It also cites issues for future consideration.

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Division A: Structural Engineering & Earthquake Engineering / Applied Mechanics
Paper
  • Toru IGARASHI, Sumio SAWADA, Hiroyuki GOTO
    2022 Volume 10 Issue 1 Pages 111-123
    Published: 2022
    Released on J-STAGE: January 20, 2022
    JOURNAL FREE ACCESS

     Semi-underground structures are often constructed for storing water. Most parts of their bodies are placed underground and the roofs are covered with thin or no soil layers. The current earthquake design standard for semi-underground structures mainly considers the earth pressure, which is proportional to ground acceleration and displacement. Detailed mechanisms of active and passive earth pressures are not considered in the current design method. In this paper, we study the dynamic interaction mechanism between ground and side wall of semi-underground structures during earthquakes based on FEM analysis. Earth pressures during and after the earthquake, which result from shear-failures in the surrounding soil, are especially examined. The results show that effects of soil failure enlarge the earth pressure. Passive earth pressure only acts on the shallow part of the wall, whereas active earth pressure acts on the deeper part as well, during earthquake. The residual earth pressure acts after earthquake, which is intermediate between the maximum and minimum values during earthquake.

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  • Tatsuya DOI, Yoshitaka MURONO, Ho CHO
    2022 Volume 10 Issue 1 Pages 162-181
    Published: 2022
    Released on J-STAGE: March 20, 2022
    JOURNAL FREE ACCESS

     In this paper, a new type of foundation composed of micropiles and soilbags is proposed. The foundation is characterized by laying soilbags between the pile head and footing on which a superstructure stands. The expected effects of the foundation are: (1) eliminating the fixed junction between the piles and the footing, (2) reducing the diameter of piles, and (3) reducing the response acceleration of structures. In this study, a seismic response evaluation method for the proposed structure in real-scale is also proposed, and the seismic responses of the proposed structure and pile foundation are compared with different conditions of input acceleration and height of pier. From the calculation results, except for the case where the pier height was low, it was found that, compared to a pile foundation, the prolonged period due to the uplifting of footing during rotation may cut off peak response acceleration of the pier and suppress the bending moment at the base of the pier. It was also found that the response displacement of the proposed structure was almost the same as that of the pile foundation, and that the residual displacement of the proposed structure was smaller than that of the pile foundation. Moreover, it became clear that laying the soilbags could suppresses the bending moment of piles.

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Division B: Hydraulic Engineering / Coastal Engineering / Ocean Engineering
Paper
  • Takashi IZUMIYA
    2022 Volume 10 Issue 1 Pages 124-135
    Published: 2022
    Released on J-STAGE: January 20, 2022
    JOURNAL FREE ACCESS

     Temporal and spatial variations in tsunami coda waves in medium- to long-term decay processes were investigated based on theoretical analysis and observations. In this paper, medium- and long-term were defined as approximately τt ≤ 2τ and t ≥ 2τ, respectively, where t is elapsed time from the earthquake origin time, and τ is the coda energy e-folding decay time. In the medium- to long-term decay processes, the energy and amplitude of tsunami coda waves may become small so that the energy dissipation due to turbulent friction can be negligible compared to the directional spectrum of coda waves. It was found that the energy balance equation without dissipation for the directional spectrum, D(f,θ), should be approximately satisfied in a quasi-steady state, and the quantity CCgD(f,θ) should hold for any two points, where C and Cg are the wave phase speed and group velocity, respectively. The latter relationship indicates the inverse proportion of the tsunami coda energy to the water depth, and the similarity of the frequency spectrum of coda waves between any two points. The water depth dependency of tsunami coda was confirmed over a wide frequency range by using the 2011 Tohoku Earthquake Tsunami data. However, the tsunami coda energy with periods of 30–70 min did not follow the h-1 law, because continental seiche and edge waves were generated at Kochi, and the amplitude of tsunami coda waves at other stations did not show exponential decay in time. The estimated frequency spectra of coda waves at depths larger than 100 m were found to be inversely proportional to frequency squared, f2, for a wide frequency range. The f-2 law of frequency spectrum was theoretically derived by using linear shallow water equations with linear friction and dispersion terms. The effects of linear friction and dispersion on the frequency spectrum were deduced from the spectral solutions.

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  • Yusuke NAKATANI, Yoshiaki IWAOKA, Motoki OKUMURA, Shuzo NISHIDA
    2022 Volume 10 Issue 1 Pages 228-234
    Published: 2022
    Released on J-STAGE: April 20, 2022
    JOURNAL FREE ACCESS

     In urban rivers where combined sewer overflows occur, scum appears several days after rainfall, causing bad odor and adverse effects on the landscape and ecosystem. To clarify the generation and floating behavior of scum, we conducted a detailed observations of scum using multiple fixed-point cameras and sediment surveys in the Hirano River, an urban tidal river in Osaka, Japan. Organic mud derived from sewage was deposited in two separate areas, of which the upstream was the main source of scum in the river. The floating behavior of scum was mainly dominated by tide, and scum accumulated at the stagnant point at rising tide. Scum was frequently observed at the bend of the river channel, suggesting that the local flow structure had a considerable influence on the behavior of scum over a wide area of the river.

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  • Masahiro ISHIZAKI, Yusuke NAKATANI, Shuzo NISHIDA
    2022 Volume 10 Issue 1 Pages 288-306
    Published: 2022
    Released on J-STAGE: May 20, 2022
    JOURNAL FREE ACCESS

     This study developed an autoregression-driven deep neural network model using deep learning techniques and nonlinear time-series analysis to estimate water quality variations in coastal areas. This local prediction model analyzes the autoregression characteristics of the nonlinear water quality system combined with an extrinsic deep learning model to express the relationship between water quality items and external factors such as tides and weather.

     By combining both models, two water quality items were estimated: the electrical conductivity in a tidal river and the dissolved oxygen concentration in the bottom layer of an enclosed bay. Both models showed high accuracy in estimating the two water quality items. However, the autoregression-driven deep learning model was superior, particularly for water quality items affected by several internal state variables, such as physical, biological, and chemical processes.

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  • Takehiko ITO, Jin KASHIWADA, Nodoka HARAYAMA, Ryo KANEKO, Tomoya KATAO ...
    2022 Volume 10 Issue 1 Pages 307-314
    Published: 2022
    Released on J-STAGE: May 20, 2022
    JOURNAL FREE ACCESS

     We improved the fundamental equation and the data assimilation algorithm of the DIEX-Flood, which can estimate the longitudinal profile of the water level in the current and future situation in order to reduce the computational cost and maintain the robustness of the model. As a result of applying the improved DIEX-Flood to some flood events of the Kinu River, we can simulate the longitudinal profile of the water level in the current situation with high accuracy, good stability and low computational cost. Furthermore, we proposed a new flood forecasting method combining the DIEX-Flood and deep learning. This prediction method can calculate the longitudinal profile of the water level in the future, so it makes the evaluation of the spatial and temporal distribution of flood risk possible. As a result of the flood forecast simulation using this system, we can predict water level profiles 6 hours ahead with high accuracy.

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  • Hajime MASE, Sooyoul KIM, Masatoshi YUHI, Masahide TAKEDA, Shinya UMED ...
    2022 Volume 10 Issue 1 Pages 315-327
    Published: 2022
    Released on J-STAGE: May 20, 2022
    JOURNAL FREE ACCESS

     This study carried out a transient wave overtopping and overflow modeling to improve the accuracy of simulated inundation due to extremely large storm surges, like in the worst-case scenario of a tsunami. Preparing an inundation hazard map for such extreme storm surges is essential for risk management and evacuation plan. Since existing studies considering the transient phenomena of wave overtopping and overflow are scarce, the present study proposes such modeling using two kinds of wave overtopping models that integrate wave runup and overtopping. The present model can be applied to seawalls from vertical and gentle slopes installed at deep water to very shallow water, even on land. The combined wave overtopping and overflow model was implemented into a wave-surge coupling simulation model to show the importance of the transient phenomena in inundation for simple cases of typical bathymetry and typhoon conditions.

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  • Kohji MICHIOKU
    2022 Volume 10 Issue 1 Pages 328-347
    Published: 2022
    Released on J-STAGE: June 20, 2022
    JOURNAL FREE ACCESS

     A one-dimensional two-layer model was developed in order to examine the hydrodynamics of rubble mound weirs. First, depending on the water depth relative to the weir height, the flow was classified into three regimes: (a) “Regime-S, ” in which the weir was submerged along the whole reach, (b) “Regime-P, ” in which the weir was submerged only in the upstream reach, and (c) “Regime-E, ” where the weir was emerged in the whole reach. Second, each regime was further grouped under two sub-categories: (i) “B-flow” that is controlled by backwater from downstream of the weir, and (ii) “C-flow” that is controlled by a critical hydraulic depth appearing at the weir exit. Theoretical solutions for water surface profile and discharge rating curve were obtained for the six flow regimes and were validated in comparison with experimental data.

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Division E: Pavement Engineering / Materials and Concrete Structures
Paper
  • Addisu Desalegne BONGER, Akira HOSODA, Hamed SALEM, Takahisa FUKAYA
    2022 Volume 10 Issue 1 Pages 145-161
    Published: 2022
    Released on J-STAGE: February 20, 2022
    JOURNAL FREE ACCESS

     Corrosion due to insufficient grout filling can result in a sudden fracture of PC steel tendons. When a vertically tightened PC tendon in PC girders is ruptured, all the accumulated strain energy is suddenly released. The ruptured PC bar will severely damage cover concrete and asphalt pavement, and PC bars may protrude out of the structure, which may cause severe accidents. In the current study, the effects of 15 mm cover concrete and two-layered asphalt pavement system on preventing protrusion of PC bars were investigated. Numerical simulation of rupture and protrusion of PC bars were studied using the Applied Element Method. The numerical simulations were verified based on the experimental results. In the process of verification, many influential parameters, such as the effects of contact stiffness between elements, fracture energy of concrete, mesh sensitivity, time interval sensitivity, material properties, and strain rate effect, were investigated. This study found that AEM numerical simulation with appropriate modeling showed good agreement with the experimental results, which exhibited the effectiveness of the asphalt pavement system with appropriate material and thickness preventing protrusion of the PC bar tendon.

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  • Dang Quoc THUYET, Masakazu JOMOTO, Kazunari HIRAKAWA, Yin Lei LEI SWE
    2022 Volume 10 Issue 1 Pages 235-246
    Published: 2022
    Released on J-STAGE: April 20, 2022
    JOURNAL FREE ACCESS

     This study presents the development and application of an autonomous program for road surface inspection using Laser Crack Measurement System (LCMS) images acquired by a road surface property measurement vehicle. The program automatically detects road lane line marks and makes grid mesh of analyzed parts. It applies a robust color space transformation and Hough transformation algorithms for the detection of analysis area between two lane lines. The program utilizes a deep convolutional neural network (CNN) to automatically detect crack, non-crack, and patch parts on a high-resolution road surface image. Transfer learning and fine-tuning parameters were employed during CNN model training for the image classification. The model accuracy for the classification of three classes was 97.9%. The precision for each class, crack, non-crack and patch classes were 99.7%, 97.9%, and 95.5%, respectively. The study reveals the novelty of transfer learning application, and the importance of data preparation in CNN model training for road surface image inspection. The program is automated for image importation, detection of the analysis area, analysis visualization, and summary of the crack and patch parts. It significantly improves road inspection efficiency. Compared to the inspection time of a professional engineer in 1-km road surface images with a crack ratio of 20%, the program shortens inspection time by 98% for lane line detection and marking grid mesh, and road damage judgment by 82%. Total inspection time of 1-km road is shortened by 50%. This study opens the potential application of AI on road inspection.

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Division F: Construction Engineering and Management
Paper
  • Haihua ZHANG, Akihiko OGATA, Hitoshi TEZUKA, Seiji KANAMORI, Shun SHIM ...
    2022 Volume 10 Issue 1 Pages 247-259
    Published: 2022
    Released on J-STAGE: April 20, 2022
    JOURNAL FREE ACCESS

     In the New Austrian Tunneling Method (NATM) of tunnel design and construction, it is important to know the actual compressive strength of lining concrete at early ages, which determines the time of demolding and its future durability. The degree of hydration reaction of in-place concrete is regarded as a useful reference to estimate the development of the strength of concrete. Based on the concept of On-Site Visualization, this paper presents a new approach to monitoring the hardening progress of fresh concrete/mortar using plastic optical fiber (POF) sensors. The principle of sensing is illustrated conceptually. The fundamental experiments were carried out to investigate the change in the visible light intensity reflected from the sensing plane of POF sensor during the hydration of concrete/mortar at early ages. The typical influence factors were also studied. The hydration process of concrete/mortar at early ages was well observed by the POF sensors. The direction of POF sensor installation had a significant effect on the pattern of light intensity change. When the sensor was installed pointing downwards, the light intensity dropped at first but increased rapidly in a few hours, which indicated the phase evolution when the free water disappeared in the hardening concrete/mortar. While the sensor was set up pointing upwards, the light intensity dropped in the first stage and then grew up slowly with time. Furthermore, the hydration process of concrete was characterized by introducing the nominal refractive index (NRI), which could be calculated from the measured light intensity. Thus, the hydration of concrete could be divided into three stages approximately according to the curve of NRI of concrete (when the sensor was installed pointing upwards), which coincided with the common knowledge of the concrete hydration process. Finally, the future work is discussed briefly.

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  • Koji HATA
    2022 Volume 10 Issue 1 Pages 260-274
    Published: 2022
    Released on J-STAGE: April 20, 2022
    JOURNAL FREE ACCESS

     The design of support structures for Japanese mountain tunnels is difficult owing to the limitations in investigating techniques and the complexity of the geological structures involved. In general, during excavation, the size of a support structure is modified to best suit the geological conditions. As such, engineers must carefully observe the rock mass conditions to understand their mechanical and hydraulic properties as accurately as possible, and to predict their deformation behavior and hydraulic structure. In recent years, artificial intelligence (AI) has been adopted in various fields. In this study, a deep neural network (DNN) was applied to evaluate a mountain tunnel’s rock mass. The input was a photo of the excavation surface (face) of the mountain tunnel, and the output was the rock mass properties such as degree of weathering, alteration, and fracture. Based on past excavation records, the DNN was tested using supervised learning, and the results showed that the AI judgments were consistent with the engineers’ judgments, having a 73%–97% accurate answer rate. Therefore, practically applying the method of rock mass evaluation using AI was determined as being feasible. Furthermore, to allow ease in its field-based application, a cloud computer system using a tablet computer device was used to enable evaluations, creating a system that contributed to increased productivity.

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Division G: Environmental Systems and Engineering
Paper
  • Kazuhiko MIURA, Hiroshi TSUJIMOTO, Eishi KUSAKA
    2022 Volume 10 Issue 1 Pages 182-194
    Published: 2022
    Released on J-STAGE: March 20, 2022
    JOURNAL FREE ACCESS

     The volume of radioactive cesium-contaminated soil being removed during the cleanup process after the explosion of Fukushima nuclear power plant 1 is estimated to be 13 million m3. Soil contaminated with more than 20,000 Bq/kg of radioactivity is targeted for decontamination by the particle-size separation method to pass the criteria for reuse in Japan. Because more than 80% of the targeted soil is composed of fine silt and clay derived from farmland, a system was developed to increase the amount of recyclable soil by a combination of mud crushing and fine-particle separation with the classification point set lower than about 20 μm. Mud crushing is one of the key technologies for effective decontamination because clay forms aggregates due to the presence of organics such as humus. Four types of mud-crushing equipment were examined on site, followed by pebble milling or ultrasonic dispersion, both of which showed promising results. Using the selected equipment, the proposed soil-size separation was carried out. Overall, the proposed system was proven effective by the results of radioactivity reduction ratio and volume of soil for recycling. Furthermore, lab-scale pebble mill tests using a pot-type wet mill were carried out to confirm the basic characteristics of mud crushing for organic aggregates.

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