Keywords: GIS, maintenance, seismic evaluation, railway embankment, Tokaido Shinkansen, liquefaction, circular slip.

Three large-scale earthquakes in the Pacific Coast of Japan are predicted to occur with high possibility. Because the railway structure has a significant defect that the damage at one site stops totally the function, sites potentially to cause a damage are not allowed. Therefore, seismic reinforcement of the railway structure should be performed in all necessary sites. This paper focuses on the seismic reinforcement management of the railway embankments. It is necessary to evaluate the seismic performance of embankments considering the ground condition of each site. As a result, it is imperative to perform the geologic reconnaissance in all embankments, and a great amount of cost, time, and effort is required with respect to the conventional methods.

In this research an information support system has been established to select seismic reinforcement sites from the embankments on the soft subsoil and on the ground having the possibility of the liquefaction and to suggest seismic reinforcement methods [1]. A GIS application of the information support system has been newly developed in the railway embankment to maintain Tokaido Shinkansen. The potential users of the developed system are expected to be engineers who perform seismic evaluation and determine an appropriate seismic reinforcement method, budget managers who judge whether seismic reinforcement should be carried out in time, and furthermore field engineers who actually maintain and manage the embankment.

This system contains following seven kinds of information: (1) Ground type and relevant properties, (2) Embankment dimensions and properties, (3) Potential seismic wave data, (4) Topographical information, (5) Existing information by municipalities, (6) Seismic evaluation results, and (7) Drawings and specifications of reinforcement methods. Information types (1), (2), and (3) are indispensable for selecting the seismic reinforcement sites, and a seismic evaluation is performed by referring to these information resources from the system. It is useful that the topographical information illustrates the seismic evaluation results on the map. Moreover, existing information by municipalities is added to enable a comparison with the prediction performed by this research. The reality is that these data resources have been managed separately. Therefore before selecting the seismic reinforcement sites and determining the reinforcement methods, it used to be necessary to search information types one by one from among resources covering the whole Tokaido Shinkansen line that exist separately thus finding the data concerned with a selected site took a long time. The developed information system can manage the information unitarily, treat information collectively, and display it on the map visibly. In the system, it is also possible to display the seismic evaluation results in the form of capacity obtained by the stability calculation taking into account circular slip of an embankment and the subsidence by liquefaction with a given seismic wave input. It also shows possible reinforcement methods to be applied.

As an example, in this paper, the selection of sites in the Tokaido Shinkansen is performed with use of existing data such as soil pillar-shaped charts from the investigations done by Central Japan Railway Company and other agencies. The seismic reinforcement sites which a design earthquake is assumed to influence are able to be selected efficiently.

As a result, the following findings were obtained.

1. The total time required for the selection of the seismic reinforcement sites has been greatly decreased.
2. The system has reduced the downtime after an earthquake by selecting the seismic reinforcement sites appropriately.
3. The uncertain factors have been reduced by installing the detailed information such as physical properties of the embankment into this information system resulting in the improvement of the analytical accuracy.
4. Since there used to be only limited information at particular points such as soil pillar-shaped charts, the accuracy of presuming values for factors whose value was unknown was very low. But information on the line such as the geologic profile has been obtained and built into this information system, resulting in easier and more accurate presumption.

In the future, the measures against other large-scale earthquakes that are claimed to occur will be treated. Since the system already has the basic data, seismic evaluations with seismic waves of various characteristics at a given site can be performed by only changing the input seismic wave. In addition, this system can be further improved as the synthetic maintenance management system in the Tokaido Shinkansen embankments by the supplement and expansion of further information such as rainfall, snowfall, and ground vibration near the railway-tracks without being limited to seismic measures.

1

Sakamoto, Y., Seki, M., Nagao, T. and Itoh, Y., "Development of an information system for the selection of seismic reinforcement sites of railway embankments", Journal of Structural Engineering, JSCE, Vol.51A, II, 1093-1102, March 2005 (in Japanese).

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