Recently, it is required to assess the safety of old fill-dams considering the risk of strong earthquake motion and optimize the methods of earthquake-proof reinforcement based on the conception of LCC (Life cycle cost). In this study, the deformation analysis using Monte Carlo Simulation Method is conducted for the model fill-dams at the level-2-earthquake motion to consider the variety of fill materials. Moreover, both the seismic hazard evaluation and the failure probability of embankments after the aseismic reinforcement as well as in the present condition are performed. Furthermore, the amount of the damage by the collapse of them is assumed, and the measures for the earthquake-proof reinforcement are investigated from the view point of LCC. In addition, in this study the amount of damage is figured out on the assumption that model fill-dams are failed, but in the future it must be necessary to set the existing fill-dams of certain areas and to estimate the real cost of damage in order to consider LCC.

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A medium-scale earthquake happened to cause severe damages on the asphalt facing zone of an earth-dam; many cracks appeared on the slope surface especially near the crest and on the bottom surface of the reservoir, though the dam body itself was scarcely damaged. Due to viscous natures of bitumen, asphalt mixtures are in general highly flexible, accompanying much stress relaxation, and can follow large deformation without serious damages, as compared with cement mixtures. It is well known, however, that under low temperature in winter season and under high rate of cyclic loading during earthquake, asphalt mixtures are often to be damaged by reducing flexibility due to their temperature and strain rate dependencies. In this paper, new asphalt bitumen is developed, from view points of visco-elasticity and sensitivity to temperature, in order to improve flexibility under low temperature, and also to have sufficient resistance against flow under high temperature. Several laboratory tests are carried out to investigate mechanical properties of the asphalt mixtures made with this new bitumen, and the results are compared with those of usual straight asphalt mixtures to verify improvement of high flexibility and stress relaxation, and of high ductility under low temperature and cyclic loading conditions.

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An appropriate measurement of physical properties of the foundation and the embankment materials improves the accuracy of a dynamic analysis of an earth fill dam. A series of physical property tests of the embankment material are implemented to carry out a dynamic analysis for a verification of an earth fill dam's seismic performance. This article reports the cases of the investigation and test implemented for the dam completed in the 40s of the Showa period (around 1970) and the one now under construction.

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