| Popis: |
Sediment disasters from concentrated heavy rains severely damage to civil life. Concrete check dams are widely used to mitigate disasters, however, sometimes such structures are damaged due to collision of boulders or fluid force of debris flow. Placing buffer material in front of concrete structure can be an effective solution. On the other hand, there exist abundantly unused natural resources such as volcanic ash, scoria and pumice in the mountain regions. They sometimes have become risks of debris flow. Utilization of these materials is hence useful for resource circulation as well as disaster prevention. In this study, shock-absorbing capability of lightweight concrete utilizing volcanic pumice as coarse aggregate was experimentally investigated, for application to buffer material. In the impact test, a falling weight impact tester was employed, with placing buffer layer concrete on base layer concrete. Type of coarse aggregate, water-to-cement ratio, thickness of buffer layer and impact velocity were considered as experimental factors, and the experiments were designed with the Taguchi method. Sizes of specimens and levels of experimental factors were selected based on actual phenomena observed in sediment disasters. As a result, the lightweight concrete is proved to have a superior shock-absorbing capability than control concrete using crushed limestone as coarse aggregate. Statistical analysis results indicated that the lightweight concrete is by averages of 28% and 41% more effective in reducing the maximum impact load than the control concrete, under the impact velocities of 1.5 m/s and 4.5 m/s, respectively. |
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