The pollution of ground water caused by the inflow of drainage water from mudstone excavation sites is a serious issue. It has been recognized that the problem results from the discharge of sulfate generated by the decomposition of pyrite contained in the mudstone. Urban natural ground commonly contains mud sediments, and when the underground environment is altered by underground openings, pollution by acid water originating from these mud sediments may occur. The prediction of pollution is therefore important in constructing underground openings. We used numerical simulation to attempt prediction of the spatial extent of pollution caused by the drainage of acid water with heavy metals from mud sediment.

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Railway structures are often built near active faults in the Japanese Archipelago. In order to improve the safety of trains running on railway structures, therefore, it is important to predict earthquake ground motion taking into account the effect of such faults. We first investigated the characteristics of earthquake motion propagation over wide areas with active faults using the stiffness matrix method, and then developed a technique to predict near-fault ground motion by coupling the results of the stiffness matrix method with 2D FEM analysis.

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Embankment collapse due to heavy rainfall along railway lines takes a variety of shapes and scales, which need to be predicted to determine effective measures for prevention. The results of such prediction also give information that is useful in estimating the amount of damage that will be caused to railway lines. Accordingly, we carried out statistical analysis of many past collapse examples and developed a method to predict the shape and scale of embankment failure. This report gives an outline of the method.

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The train-detecting track circuit currently used is dependable and has the characteristics required of a railway signalling system in terms of economy, continuous detection, etc. However, when rails become rusty, the shunt resistance becomes higher, making it difficult for the track circuit to detect trains precisely. We have therefore researched shunting malfunction to enable the proposal of a new countermeasure against the phenomenon. In this paper, we describe the measurement and analysis of environmental conditions and resistance. We then show the results of these experiments, and propose that shunting malfunction is a problem of railway systems as a whole that should be addressed through the adjustment of the various conditions involved.

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On commuter lines, trains are often forced to decelerate or stop between stations as a result of delays of the preceding train. Once a train stops between stations, both the headway and the travel time increase. To solve these problems, we propose a train control method based on the prediction of train movement. We estimated the effects of this method on the time taken to recover from train delays using a model of the recovery mechanism, and evaluated its effect on train traffic by computer simulation. The results confirmed that the proposed method was effective in reducing the amount of time trains stopped between stations as well as recovery time.

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Benefits can be expected from the use of formal methods in increasing the reliability of software. In preparing the formal specifications of complicated systems from a preliminary draft text, stepwise revisions are very useful in creating specifications that are easily understandable and in producing verified code that satisfies the specifications. In this report, we first explain the concept of gradual revision, which involves initially writing abstract specifications with minimal conditions and then refining them until they are serviceable. Next, we present an example in which the permissive speed of a train is calculated from a given stop distance.

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We conducted research on the derailment and overturning of railway vehicles as a result of earthquakes. Previous numerical simulation helped to clarify the dynamic behavior and running safety limits of vehicles on a vibrating track, and the results of this simulation are currently adopted in the design of railway structures.
We carried out an experiment using a full-scale half carbody mounted on a Shinkansen bogie placed on a triaxial structural vibration test rig. The simulation analyzed the experimental conditions, and its results were consistent with those obtained from the experiment, thus confirming its validity.
In this paper, we describe the results of analysis and performance improvement for safe running by modifying the parameters of the bogie using our numerical simulation. Our concept exchanged the lateral damper between the carbody and bogie for a High Speed Large Force damper (known as a HSLF damper). This damper performs to generate a larger damping force than that of ordinary dampers only at higher piston speeds. When the HSLF damper is used, a safety effect is gained for vibration over a large frequency range. No adverse effects on ride comfort were found from its operation as an ordinaryperformance damper.

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This paper introduces the non-contact vibration measuring system known as U-Doppler that has recently been developed by the RTRI. In the field of railway structure monitoring, dynamic characteristics estimated by vibration measurements are applied to evaluate structural integrity. Adopting a long-distance remote measurement method with U-Doppler enables improvement of the efficiency and safety of measurement, since it is unnecessary to install sensors and cables at locations high above structures and remove them later. This report first gives an outline of U-Doppler and its measuring method. It then goes on to verify the accuracy of U-Doppler using the results of laboratory experiments, microtremor measurement of a rigid-frame viaduct, impact vibration measurement of a bridge pier, and deflection measurement of a bridge girder.

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The reduction of aeroacoustic noise generated by pantographs has been an important subject of discussion in increasing the speed of Shinkansen trains. As the panhead significantly influences the aeroacoustic characteristics of the pantograph, reduction of its aeroacoustic noise is strongly demanded. This paper describes a method of evaluating the contributions of low-frequency aeroacoustic noise sources around the panhead. Visualization of these contributions can indicate the structure of such noise sources.

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