Railway Technical Research Institute

集水地形など降雨や浸透水により間隙水圧の上昇が懸念される鉄道盛土には建設時に排水ブランケットの敷設が行われるが，その仕様は経験的に定められており，降雨浸透に対する効果は定量化されていない。本研究では，排水ブランケットによる鉄道盛土の耐降雨性の向上効果を評価することを目的に降雨実験を実施した。実験結果より，排水ブランケットは盛土法尻部の水位上昇の抑制に寄与し，通常の盛土が崩壊に至った累積降雨量の9倍程度の累積降雨量に対しても法面の崩壊は確認されなかった。また，解析的に評価した盛土内水位を考慮した安定解析により，実験で確認された崩壊形状と良い整合を示すすべり面を表現できることが示唆された。

A data-efficient analytical approach was developed to quantitatively predict and control the joint resistivity in sonic-welded REBCO coated conductors. By employing the proposed Acoustic Energy Activation Bonding (AEAB) model, which describes an exponential dependence of bonding probability on the input acoustic energy, the AEAB model successfully reproduced the experimental data within approximately ±22% relative deviation. Even when only five distinct process conditions were used, the model achieved reasonably accurate prediction of joint resistivity (12.1 ± 2.1 nΩcm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>) and identified optimal conditions realizing 9.8 nΩcm2 without degradation. This suggests that, unlike conventional empirical methods requiring extensive trials, the present approach provides a data-efficient framework for controlling joint resistivity from a limited dataset. The model was further applied to MOCVD-processed tapes, confirming its consistency and general applicability across different types.

With a declining birthrate, aging population, and shrinking working population, the cost of train operations must be reduced to maintain the railway network. A solution for overcoming this problem is to introduce automatic train operation (ATO). ATO systems, which are equipment for automated driving control under the protection of an automatic train control (ATC), a continuous type of automatic train protection (ATP), are introduced in specific types of rail lines, such as automated guideway transit (AGT) systems or subway systems in Japan. A new type of ATO systems operated by staff who are not required to have a driver's license is required to reduce operating costs further. The authors have developed an ATO system based on automatic train stop (ATS)-DK which is an intermittent ATP and equipped with continuous speed check. This system has achieved the first automatic operation in the ATS line, which conventionally has required ATC, and also the first GOA2.5 in which an attendant other than the driver performs emergency stop operations at the front of the train. This paper describes the details of the study, the progress of the demonstration operation, and the effects of the introduction of the GOA2.5 system.

水平力に対する杭基礎の設計においては，群杭効果による影響を考慮して水平地盤反力係数を評価する。群杭効果の影響は群杭効率と呼ばれる低減係数で表されるが，基本的に群杭効率の検討は杭頭が地表から突出していない条件で行われている。一方で，線路上空建築物やパイルベント構造等の1柱1杭形式の杭基礎は，地中梁やフーチングがないため，杭と地上部の柱をあわせて突出杭の挙動を示すと考えられる。そこで，本研究では突出の有無が群杭効果に与える影響を調べることを目的に，遠心載荷実験および3次元弾塑性有限要素法解析を行った。その結果，突出によって群杭効果が小さくなることを示し，杭の変形モードと地盤の応力分布の観点からそのメカニズムを明らかにした。

Both amplitude modulation and frequency modulation occur in a sound field radiated from moving sound sources. However, the amplitude modulation for different source types has not been clarified experimentally. In this study, the directivities of sound radiated from an ultrasonic transducer attached to a moving scaled train model and used as a simplified vibrational sound source were measured. The surface of the vibrational source was parallel to the movement direction of the source. The directivities of an aeolian tone sound generated using a cylinder attached to the train model were also measured; the cylinder was used as an aerodynamic sound source for a simplified dipole component of aerodynamic sound, which is dominant at low Mach numbers, generated from pressure fluctuation. The experimental results show that the acoustic intensity of sound radiated from a vibrational source increases roughly in proportion to the fourth power of the Doppler factor, whereas that of the dipole component of aerodynamic sound increases roughly in proportion to the eighth power of the Doppler factor. Sound radiated from an aerodynamic source moving at low Mach numbers leads to a greater amplitude modulation due to source movement compared with sound radiated from a vibrational source.

Under the "Belt and Road" and other related policies, the political, economic and cultural interactions between China and Europe have increased greatly, which has led to the growth of common interests and stimulated the rapid development of the transportation industry between the two sides. This has also made international container shipping using sea and rail transport the main mode of international logistics. In the sea part of container shipping between China and Europe, there are problems such as transportation time, transportation cost, transportation safety and environmental costs. Conducting an in-depth analysis of these problems is of great practical significance.

This study proposes a technique to temporarily improve the friction force by jetting dry air with less than 30% humidity on the contact surface. The tangential contact force was first measured under the condition that a very small amount of water was on the contact surface and the velocity was 30 km/h to confirm that the proposed technique is effective even in rainy weather. The findings revealed that the adhesive force increased by reducing the amount of water on the contact surface. These experimental results indicate that the dry-air jetting technique effectively increases the friction coefficient, even under rainy conditions, because dry-air jetting can remove water droplets on the surface. Subsequently, an experiment was conducted on the tangential contact force using a twin-disc sliding-frictional rolling machine to verify our proposed technique under different dry conditions. The tangential contact force coefficient increased simultaneously with dry-air jetting and remained stable during dry-air jetting under dry and high-humidity environmental conditions. Furthermore, the findings clarified that the tangential contact force improvement effect of dry-air jetting depends on the combination of the contact patch and its surface properties. Finally, based on these experimental results, we compared the same rail vehicles with and without considering the braking distance as an example of a dry-air jetting system application, using a vehicle dynamics analysis constructed using the SIMPACK commercial software. Consequently, the validity of the proposed technique was confirmed for actual rail vehicles.

This paper presents an algorithm for the re-adhesion control of electric rolling stocks. Generally, an engineer manually adjusts parameters used in any re-adhesion control algorithm before a commercial operation. However, it depends heavily on the experience of the engineer. Therefore, developing an automatic adjustment system for re-adhesion control is imperative. To this end, we apply the particle swarm optimization (PSO) algorithm to re-adhesion control. In our approach, a cost function based on the averaged tangential force of an electric bogie is optimized by the PSO algorithm, and the parameters for re-adhesion control are automatically adjusted. In addition, experiments using a scale model railway vehicle are carried out to validate the proposed method.

This paper presents the results of a validation study assessing the adequacy of a method proposed in a previous study, which continuously measures the lateral contact position between the wheels and rails of a railway vehicle. A series of tests were conducted at speeds of up to 30 km/h using a railway vehicle equipped with an instrumented wheelset specifically designed to measure the contact position. This wheelset had been fabricated as part of the earlier study. Consequently, it was confirmed that the proposed method is capable of continuously measuring the contact position, even during wheel climb events. However, there were instances in which the contact position could not be determined. Periodic fluctuations caused by computational errors were also observed; however, these were effectively mitigated through a moving average processing. The inability to determine the contact position was primarily attributed to high-frequency fluctuations (approximately 300 Hz) in the bridge output and computational errors inherent in the proposed method. The former is considered to have minimal impact when the contact position is measured at approximately 100 Hz. The latter affects the filtered contact position at 100 Hz, but its influence can be reduced through moving average processing. To further verify the adequacy of the proposed method, the authors conducted a direct measurement of the contact position using paint. This was achieved by photographing the areas of the wheel tread where the paint had been removed due to contact with the rail. A comparison with the moving-averaged contact positions revealed a discrepancy of approximately ±2 mm, thereby confirming the sufficient accuracy of the proposed method.

We propose a method to evaluate the restorability of railway structures. In the proposed method, all earthquake motions expected within a structure's design service life are used as the design earthquake motions. In addition, the recovery time after an earthquake, which is directly related to early recovery, is used as the verification index. We also propose a more practical method of representing structural conditions that correspond to the same recovery time using a nomogram by performing calculations under various conditions in advance. The proposed method allows us to design structures that can be restored more easily, following the same procedure as conventional seismic design, and it is expected to shorten the recovery time after an earthquake.