Cut and cover tunnels for railways in Japan are designed according to the Design Standards for Railway Structures and Commentary (Cut and Cover Tunnels). The standard was published about 15 years ago. Subsequently, the design of railway structures, except tunnels, shifted to a performance-based design system. Therefore, a committee was established to revise the Design Standards for Railway Structures and Commentary (Cut and Cover Tunnels) in 2014. The committee completed a draft new set of standards in 2017. This paper discusses recent trends in the design technology of cut and cover tunnels for railways, with a focus on the contents of the committee's revised draft.

In order to ensure reliability and stability of the electric railway systems, adequate maintenance operation for the electric power supply system is an essential matter. On the other hands, its maintenance operation involves high cost, because this system has a huge spatial scale. Furthermore, working population in Japan has been decreasing today, resulting in high demands on improving efficiency of the maintenance operation. RTRI has therefore been tackling the issue of improving in quality, efficiency and cost of the maintenance operation for the electric power supply system. This paper describes recent RTRI's research and development activities on the maintenance technologies for the power supply system in order to overcome these issues.

RTRI is advancing basic research into superconducting maglev. The topics covered in this field include experimental evaluation of REBCO high-temperature superconducting coils, the development of a system for collecting sensor data from ground coils, inter alia. RTRI is also conducting research for the application of maglev technology to conventional railway systems. The areas covered in this field are wireless power transfer systems and flywheel energy storage systems.

This research investigates the mechanical behavior of segmental linings of shield tunnels based on 1/3 scale model loading tests. The test results show that the location of joints influences mechanical behavior. The bolt axial force decreases with the occurrence of compressive failure and the deformation capacity is large compared to cast-in-place RC linings. This research also carried out numerical calculations using 3D FEM, taking into account joint sections such as segmental joint bolts and joint plates. It was found that the calculation results corresponded to results obtained through model tests.

It is considered that the best way to calculate the earthquake response of sheds on viaducts, is to use an integral model of the shed and the viaduct. Calculations based on integral models require a vast amount of work because of the need to understand the structural design of both the shed and the viaduct. This report describes the factors affecting the earthquake response of sheds. A method is proposed for estimating the maximum response displacement of sheds considering the coupled vibration behavior between the shed and the viaduct based on structural design information obtained for the shed and the viaduct. The applicability of this method was verified under the earthquake conditions that appear in the seismic design standards for railway structures.

This study aims to reveal the characteristics of and factors influencing uplift forces acting on bridge bearings during earthquakes. Firstly, three different analysis models were compared through seismic response analyses in order to select a suitable model for parametric analysis. Secondly, factors influencing the uplift force were investigated by examining the seismic response analyses of six different bridge models of normal Japanese steel railway bridges. Finally, a nonlinear hysteresis model of a bridge bearing was proposed and the influence of using this model was investigated. As a result, it was confirmed that the response displacement does not exceed the limit displacement even during large-scale earthquakes.

One of the critical points in the DC feeding system is the insulated overlap. In the insulated overlap, the contact wire breakage accident during standstill sometimes occurred. It is caused by joule heat due to the current flowing between the contact wire and the contact strip, through the arc due to poor contact condition. To understand the phenomenon of this kind of accident and to take countermeasures against it, it is important to evaluate the current that flows through breakage point. However, since the current is affected by the other train load current, it is difficult to estimate it based on the recorded data of the substation.

Once the contact wire is softened, its mechanical strength decreases resulting in breakage due to tension force. The authors conducted wire break tests focusing on the arc. As a result, it has been found that the necking of the contact wire at the point of the breakage caused by the arc depends on the arc current and tension of the contact wire. In this study, the relationship between the arc current, the tension of the contact wire, and the necking length of the contact wire was investigated through the tests conducted under the condition where the arc current was set from about 30 A to 300 A under the tension of 9.8 kN or 19.6 kN. Then we proposed a method of estimating the current of the contact wire at the time of its breakage accident during standstill in the insulated overlap section based on the necking length of the contact wire.

This paper describes new inspection equipment and a new circuit structure used for evaluating the lightning protection performance of earthing systems in railway substations. The new inspection equipment consists of an impulse generator and a measurement unit, and allows the inspector to measure the earth resistance, the high frequency earth impedance and the voltage difference of an earthing system without specialist knowledge. The new measurement circuit for the inspection of the earthing system only makes use of existing infrastructure components, i.e. independent earthing for a remote terminal unit, the earthing system of an adjacent substation and an overhead contact line. Therefore, the proposed circuit requires no temporary test earth electrodes for measurement.

Compound catenary systems on Shinkansen lines will soon enter a period where they will have to be replaced on a large-scale. In order to facilitate replacement and reduce maintenance costs, compound catenary systems can be replaced with simple catenary systems. This study explores new types of simple catenary systems developed for running speeds of about 320 km/h, which is the maximum Shinkansen commercial operating speed. In addition, a simple catenary system for operation up to 360 km/h is also being developed.

Application of the flywheel energy storage system (FESS) using high temperature superconducting magnetic bearings (SMB) has been demonstrated at the Komekurayama photovoltaic power plant located in Yamanashi Prefecture. In order for the FESS to be applied to railways as a system able to prevent cancellation of regenerative braking its storage capacity must be increased. Therefore, levitation force tests up to 158 kN and tests to determine the creep characteristics of the levitation force were carried out to verify the margin in SMB levitation force. Furthermore, to evaluate long-term reliability and durability of the levitation and rotation characteristics of the SMB against repeated change in rotation speed, new SMB test apparatus capable of simultaneously testing both the levitating and rotating states of the SMB is being developed.

REBCO (Rare-Earth Barium Copper Oxide) is a high temperature superconducting material and is suitable for use in on-board maglev train magnets because of its high current density in a high magnetic field. A real-scale REBCO coil was fabricated and its basic performance confirmed. As a next step in this research, electromagnetic vibration tests on ground coils using real-scale REBCO coils are planned. Since electromagnetic vibration tests usually take several weeks to complete, a monitoring and protection system for the REBCO magnet is required. A high-sensitive coil voltage detection method was evaluated.

Maglev train systems require a high number of ground coils which are installed in the open over extended periods of time. Efficiency is therefore crucial for the maintenance of these ground coils in operation. When Maglev vehicles are running, a high voltage is applied to propulsion coils. Insulation diagnosis methods have been designed to detect partial discharge, which is a predictor of insulation failure in the propulsion coils [1], [2]. This paper describes the development of a partial discharge generation test specimen to evaluate insulation performance, and examination of electromagnetic wave propagation involved in partial discharges.