The unprecedented heavy rainfall that occurred in western Japan in 2018 caused flooding, inundation, and sediment disasters extending over a wide area, resulting in various types of damage to lifelines, transport systems, diverse structures and so on, and exposing problems that extend across many sectors. One of the major roles of the Japan Society of Civil Engineers is to compile disaster survey data regarding the frequent occurrence of increasingly severe disasters in recent years and then share this information widely with the public. In order to contribute to the development of disaster prevention technologies and academic fields, this special issue is devoted to a collection of reports and preliminary research papers regarding the 2018 heavy rain event in western Japan. Some of the Japanese papers have been translated into English and posted on the Journal of JSCE.
In this study, we detect the detours of commercial vehicles during heavy rains in western Japan using machine learning technology and then analyze the cause of these detours. Due to heavy rains in 2018 in western Japan, road regulation was implemented over a wide area. GPS-generated probe trajectories revealed the detour routes taken. The necessity of taking detours is one of the traffic failures caused by disasters. To identify these detours, a road administrator must visually check and analyze the probe vehicle trajectory, which requires considerable labor. Therefore, in this study, we detected detours during a disaster by learning the probe vehicle trajectory under normal circumstances using a one-class support vector machine (OCSVM). Results of detour detection for Shikoku revealed that vehicles were using distant detour routes even when nearer detour routes were accessible. An analysis of the cause of these detours showed that the “risk” of the traffic failure was one factor.
This paper explores the variation properties of trip generation, trip attraction, intrazonal trips, and travel time under transport network disruption in Tenno district in July 2018 due to landslides. The empirical results obtained by using multiple passive transport data show that (1) traffic volume per hour on the National Route 31 went down to around 300 vehicles at maximum due to a large number of short-distance trips traveling between the affected area and a disaster response base, (2) recovery of the train line did not really reduce the travel time on the National Route 31, and the average travel time had been 1.5 times longer compared to that before the disaster for more than two months after the disaster, and (3) travel time variability, which could not be explained by day of week and time of day, had been dominant for the first one month after the disaster.
This study presents the characteristics of disaster-related meteorological information and evacuation protocol based on a case study of the heavy-rain event of July 2018. By clarifying their characteristics, this enables us to obtain policy implications for municipalities and residents to respond appropriately to imminent heavy-rain hazards. As a result, it was found that many municipalities did not issue the evacuation preparation protocol. In addition, the proportion of residents who received the evacuation protocol in the order of the evacuation preparation, the advisory, and the order, was less than 50% of the residents targeted by the order. Moreover, the national government recommends that municipalities should associate their issuance of evacuation protocol with the meteorological information; however, there were differences in the utilization of the meteorological information between the municipalities.
This paper presents an analysis of reflection and transmission coefficients as boundary element solutions of guided Lamb wave scattering in a two-dimensional, isotropic, and linear elastic layered plate. A scatterer, defined as a debonding, is located on the interface between layers. The numerical model is formulated based on the boundary element method with elastodynamic traction and displacement fundamental solutions in frequency domain, where the boundary integral equations, including artificial boundaries, are discretized with constant elements. Lamb wave modal functions in each layer can be calculated by using the partial wave technique. Wave fields on the artificial boundaries, which are set long enough from the debonding to neglect near-field evanescent scattering modes, are treated as the superposition of incident wave and possible scattered waves. Then, the traction boundary condition on the artificial boundary can be expressed by unknown total displacement fields. In addition to the artificial boundary condition, the continuity condition of layer interface and the traction-free boundary conditions yield a system of linear equations that can be solved by the efficient indirect solver. The reflection and transmission coefficients are obtained from the total displacement fields after solving the system of linear equations. Various configurations of problems, including materials and length of the debonding are considered. Furthermore, the mode conversion and resonance phenomena of scattering coefficients can be seen directly related to the length of the debonding.
The authors intend to clarify the swimming ability of the natural sweetfish (Plecoglossus altivelis altivelis) fingerlings during the initial period of its upstream river migration in the field. The critical swimming speed (CSS) of the natural sweetfish was measured in a small channel with a rectangular cross section under an average cross-sectional water flow velocity of 9–75 cm/s. The body length of the natural sweetfish fingerlings ranged from 5.9cm to 9.9 cm (the mean body length was 7.5 cm, and the number of fishes was 50). The following results were obtained: (1) The CSS, measured for a duration of 60 min, ranged from 19 to 61 cm/s, and a positive correlation was observed between the CSS and the body length. A regression formula between the 60-min CSS and body length was obtained. (2) The ratio of the CSS and the body length was 3.1–8.0 (that is, the distance travelled per second based on the body length), and the mean ratio of the CSS and the body length was 4.7 times (the standard deviation was 1.1).
The fender is part of the ancillary equipment of mooring facilities and plays an important role in safe vessel berthing and smooth cargo handling. If fenders are damaged, economic loss will occur due to the suspension of service or restriction of operation of the mooring facility, and the operation and maintenance of the entire facility may be affected. Since fenders are used for a long time, it is necessary to ensure their durability. In 2002, the International Navigation Association (PIANC) published the “Guidelines for the Design of Fender System” and proposed a new method for confirming the durability of rubber fenders. In Japan, in 2010, consistent with the PIANC guidelines, a description of the durability of rubber fenders was added to the Standard Specifications for Port and Harbour Works of the Ports and Harbours Bureau of the Ministry of Land, Infrastructure, Transport and Tourism. In this study, the data of durability tests conducted by rubber fender manufacturers were statistically analyzed. From the results of the durability tests, a longterm performance criterion for rubber fenders was proposed.
Two types of transformants with different drug resistance were developed from the phenol-oxidizing bacterium, Cupriavidus sp. KN1. The first transformant is Cupriavidus sp. KN1-TGF that has green fluorescence and tetracycline resistance. The second transformant is Cupriavidus sp. KN1-KRF that has red fluorescence and kanamycin resistance. These two strains can be selectively colonized with antibioticcontaining media, and they can be also distinguished by fluorescent color. First, Cupriavidus sp. KN1-TGF cells remaining after predation with the flagellate, Spumella sp. TGKK2, were mixed with Cupriavidus sp. KN1-KRF that did not contact with the flagellate TGKK2 to investigate the change in characteristics for the protistan predation. As a result, Cupriavidus sp. KN1-KRF was preferentially predated. On the other hand, Cupriavidus sp. KN1-TGF in the same tube was relatively resistant to predation. Similar phenomena were observed when the conditions of these two strains were reversed. Next, two complete mixing reactors connected in series were operated. Bacteria were cultured in the first reactor, and the protistan predation was made in the second reactor. Two runs were operated, one with Cupriavidus sp. KN1-TGF and the other with Cupriavidus sp. KN1-KRF. Then the first reactor effluent that contains Cupriavidus sp. KN1-KRF was mixed with the second reactor effluent that contains residual Cupriavidus sp. KN1-TGF and the flagellate TGKK2 in a tube. The cells of Cupriavidus sp. KN1-KRF not in contact with the protist were preferentially predated. This phenomenon was similarly confirmed by combinatorial inversion that Cupriavidus sp. KN1-TGF from the first reactor was mixed with Cupriavidus sp. KN1-KRF from the second reactor.