Maintenance of railway structures in Japan has a wide sphere to cover, because the railway structures have various structural forms of various eras, ranging from the old fashioned style, for example, a structure of over 100 years old, to the latest style, and they have a large variety of types, such as embankment, tunnel, bridge, etc. In around 1965, together with an increase in the disaster prevention investment, the maintenance of railway structures turned from the corrective maintenance system to the efficient maintenance system, combining corrective and preventive maintenance methods. As a result of the turning, accidents were reduced.
However, a large quantity of railway structures, constructed in the period of high economic growth between 1955 and 1973, has been over forty years of age, and a quantity of structures to be taken care of attentively, increased rapidly. This paper presents the history of maintenance, current problems to be solved, and the maintenance standard of railway structure in Japan enacted by the Ministry of Land, Infrastructure and Transport in 2007. Further the present activities for solving the current problems by Railway Technical Research Institute and the railway companies in Japan are introduced, and lastly a prospect of future research and development is described.

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The accuracy of displacement measurements using GPS depends on the environment surrounding the receiver set on the measurement point. Overhead obstacles of the receiver cause a disturbance to the signals transmitted from the satellites and a degradation of the measurement accuracy. In this paper, it is shown that the influence of overhead obstacles can be found by the double-difference phase, and a method for improving the measurement accuracy is proposed. In order to verify the method, it is applied to long-term measurement results. In addition, field experiments are conducted to detect small displacements. It is proven that the proposed method can be effective not only for improving the measurement accuracy, but also for shortening the time required to detect displacements.

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Owners in the public sector and contractors in the private sector have traditionally conducted the diverse management tasks for executing public works in Japan.
Construction management (CM) system, where partial commissions of such management tasks are conducted by third sector, has introduced into some public works on a trial basis in recent years. Its effectiveness and possibility for substantial introduction of CM system are now under investigation.
The application of CM system requires well-defined needs and merits for construction management, well-defined scopes of services and duties of the CM service providers, and estimates of appropriate costs for management tasks.
This paper especially has suggested construction cost reduction and success reward of construction management system introduced to public works.

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Magnetic anisotropy sensor is used for nondestructive measurement of stresses of a nut which is part of the head part of a PS anchor usually used for stabilizing rock mass in large scale underground caverns. Since the stresses in the nut reflect the level of axial force in the anchor, the results of the stress measurement can be used indirectly to estimate the current axial forces of PS anchors. By knowing distribution or changes in PS anchor forces, one can establish a fundamental safety assessment routine for large-scale underground caverns.

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This paper focuses on applicability of risk assessment method regarding cost variation for countermeasure due to unexpected water inrush into the underground facility constructed in fractured rock masses. In this study, the risk assessment method has been applied to the construction of the Mizunami Underground Research Laboratory, which is now under construction by the Japan Atomic Energy Agency. And, the relationship between the amount of information due to the progress of the investigations and the risk regarding cost variation for the countermeasure has been discussed from the viewpoint of the ex-post-facto assessment.

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Downsizings have been done in a lot of civil engineering governments in Japan. Especially, the downsizing is often focused on the maintenance staffs who are employed in some local offices. Though we cannot avoid carrying out administrative reform in the future, it is necessary for each civil engineering government to reform its organization reasonably, especially on some road maintenance offices.
In this paper, a personnel allocation method for road maintenance offices is presented as numerical counting processes. In the processes, we make use of public management principles, statistical techniques, and the risk management. Furthermore, we also report on the application experience of Yamaguchi prefecture for considering it.

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The pipe roofing method has been used to minimize the surface settlement of ground, in cases of the tunnel construction close to the existing structures. However, an ordinary design method established based on allowable stress design method, so that it can not consider the effects of minimizing settlement of the ground.
In this paper, the authors analyzed the mechanism of the pipe roofing method by using three dimensional numerical simulations. Taking into account those results, the authors propose a new design method of pipe roof by using the model of simple beam on the elastic foundation.

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The estimation of consolidation processes is an important subject for the asset management of airport facilities. In the planning and design stage, there exist many uncertainties in geotechnical conditions, it is impossible to estimate the ground consolidation process by deterministic methods. In this paper, the sets of sample paths designating ground consolidation processes are generated by use of a one-directional consolidation model incorporating uneven ground settlement. Given the sample paths, the mixed consolidation model is presented to describe the probabilistic structure behind the sample paths. The mixed model can be updated by the Bayesian methods based upon the monitoring data. Through a case study, this paper veriaed the validity of the proposed method and illustrated its possible appllication and future works.

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The shear force between the rings occurs due to the splice effect for the shield tunnel assembled in a staggered pattern. When the width of segment is enlarged, the additional moment due to the shear force increases accordingly. The distribution of moment in transverse direction of segment is non-uniform and concentrated at the side of segment.
In this paper, the flat-type reinforced concrete segments with full-scale size were directly loaded on the circumferential joints to failure. Meanwhile the segment rings were analyzed based on the beam-spring model and shell-spring model, respectively. From the results of experiment and numerical analysis, the moment concentration degree along the width of segment was investigated and the rational design method for the segment with enlarged width was suggested.

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Artificial Neural Network is used as a key technique for back analysis in a nonlinear tunneling problem. Database is created by performing series of nonlinear finite element analysis while varying parameter values within reasonable ranges determined from experience. Neural networks created from this database are found to be able to identify parameters concerned with both linear and nonlinear deformation behaviors of shallow tunnel. The exercises conducted here show that the proposed method has reasonable stability in all aspect of data preparation and computation and could be a new engineering tool for modern tunnel engineers.

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