Since tracks deteriorate due to repeated loading by passing vehicles, much work is required for track maintenance. To make railways sustainable, it is thus necessary to clarify track deterioration mechanisms and develop effective countermeasures. Furthermore, to reduce cost and labor, new technologies for maintenance must be introduced.
This report introduces recently conducted basic track technology research. The research covers areas such as running safety, clarification and detection of rail and ballast deterioration, and in particular includes methods to reduce rail crack initiation, clarification of crack growth mechanisms and behavior aged ballast.

Environmental problems along railway lines caused by passing trains include the following: noise, low-frequency sound, micro-pressure waves radiating from tunnel portals, ground vibrations. To make railways more environment-friendly, it is necessary to mitigate the impact of these phenomena. This paper outlines some recent studies carried out by the Railway Technical Research Institute to address these issues, with a focus on work related to plans to increase Shinkansen running speeds. This paper also introduces specifications and plans for the use of newly constructed experimental facilities by RTRI for research on high-speed railways.

In order to increase the earthquake resilience of railways, it is important to simultaneously improve "strength" and "recovery" in a well-balanced way. "Strength" is defined as the performance to prevent the decrease in railway functionality during earthquakes and "recovery" is the capacity to rapidly restore functionality after earthquakes.
This paper first introduces recent research and development for improving the strength and capacity to recover of railways after earthquakes with common core technologies. The paper then summarizes recent essential trends in research, focusing particularly on recovery, which "utilize external information," "merge estimation and observational information," and "combine of strength and recovery."

For railway infrastructure management, railway companies carry out inspections and manage inspection data with ledger data, by 'field', such as track, civil engineering, electric power, and signal. If we can browse and analyze these data comprehensively, the quality of infrastructure management can be improved, eventually increasing running safety. Therefore, we are developing a system that integrates inspection data and ledger data from each field. In this paper, we show elemental technologies required for developing the system, after organizing merits of integrated data management. In addition, we show some examples of using the integrated management system for infrastructure management across fields.

In the development of slab track, in Japan concrete track components were designed using an allowable stress design method. Currently, they are designed using a performance-based design method according to "Design Standards for Railway Structures and Commentary (track structure)" established in 2012. In this design method, the required performances of safety and serviceability are verified by a limit state design method. This paper gives an outline of the structure of slab track and introduces the method of performance verification of the slab track using a performance-based design method.

Unsupported sleepers on a ballasted track would bring about rapid track subsidence and decrease the safety margin for lateral stability of the track. However, to date no high-precision method for detecting unsupported sleepers on railway tracks has been proposed, and the actual distribution of unsupported sleepers along the track is unknown. Therefore, we developed a new high-precision detection method for unsupported sleepers, and confirmed its effectiveness by using actual data of sleeper distribution on commercial lines. Finally, we applied the method to develop a system for detecting unsupported sleepers on actual tracks by using measured track irregularity data, which can be useful for railway operators in order to improve track conditions.

Tunnel hoods are one of the countermeasures adopted for reducing micro-pressure waves emitted from high-speed railway tunnels. Experimental studies were conducted using axisymmetric models to investigate the effect of the cross-sectional area of hoods. The results show that the effective cross-sectional area of the hood with a uniform cross-section is larger than that of existing hoods installed in Shinkansen tunnels in the high-speed range with faster speed than 260 km/h. Furthermore, tunnel hoods with multi-step cross-sections are more effective than those with a uniform cross-section. Adoption of the proposed hood specifications based on these findings enables the required hood length to be shorter than existing hoods.

Aerodynamic forces acting on railway vehicles depend not only on the shape of the vehicles but also on types of infrastructure. In this study, the leading car of a train is simplified as a finite-length square cylinder; and the middle car is simplified as an infinite-length square cylinder. We conducted large-eddy simulations (LES) of the flow around the simplified vehicle model on flat ground, an embankment and viaducts. The LES results confirm that the side force coefficients of the vehicle models change depending on the type of infrastructure. We investigated the reasons why the type of infrastructures affected the side force acting on the vehicle in terms of the flow field.

Curve squeal noise is one of the major sources of railway noise which, because of strong public opinion, needs to be reduced. Therefore, it is important to understand the mechanisms underlying the generation of squeal noise and develop methods to reduce this noise. In this study, field tests at the Railway Technical Research Institute were carried out to understand the mechanisms underlying this noise in running trains. It was found that curve squeal noise is generated at frequencies closely related to wheel resonance, and that a dominant noise source is the leading wheel on the inner rail of curved sections.

This paper proposes a method for estimating earthquake motion at the engineering bedrock level using surface seismic observation records, by employing nonlinear time domain analysis. In addition to general optimization methods, the perturbation waveform incorporated in a forward analysis was used to drastically improve the convergence of calculations. Furthermore, the equivalent single-degree-of-freedom model of the ground was incorporated when performing the nonlinear analysis in the time domain. As a result, the calculation time decreased sufficiently to be able to estimate seismic motion more economically in terms of cost, while still considering complex soil nonlinearity.

Centrifuge shaking table tests were conducted to evaluate damage level of embankments before sliding failure. In the test series, high-resolution digital images of the model embankments were obtained and strain distributions inside the embankments were calculated using a PIV technique. Results showed that the level of damage in embankment before sliding failure can be evaluated from the level of damage in embankment material near its toe using a stress-strain relationship of embankment material. Finally, we propose a performance verification method for embankments based on the level of damage in embankment material.

In order to resume operations after a large earthquake, it is necessary to investigate the degree of damage to railway structures. The inspection of bearings is labor-intensive, particularly when the bearings are located on the high piers or in narrow places. This study proposes a method for detecting seismic damage to bearings using a displacement sensor. The relationship between the degree of damage and running safety of train is investigated for a rubber bearing and a line bearing. In addition, we developed a displacement sensor that detects the seismic damage of bearings and enables remote monitoring by wireless communication.