| 摘要 |
PROBLEM TO BE SOLVED: To absorb and disperse the vibration of ground by a base isolation layer due to an earthquake, and prevent the breakage of a tunnel by covering the whole outer peripheral face of the tunnel constructed underground by the base isolation layer. SOLUTION: A base isolation layer 10 is formed between the whole outer peripheral face of the tunnel 2 of concrete structure constructed in the excavated hole 6 of ground 4 and the excavated hole 6 to be made base isolation structure 8. The base isolation layer 10 has a dynamic shearing elastic coefficient of 3 kgf/cm2 and a Poisson's ratio of 0.3-0.5, hydroxyl containing liquid-like polybutadiene is made a main material, polyisocyanate is made a hardener, and the base isolation layer 10 is formed by mixing and injecting asphalt, oil and the other additive at need. The viscosity of the main material is 100 poise or less, and the NCO component of the hardener is within 0.4-1.6 to the OH component of the main material. Thereby the vibration of the ground 4 is absorbed and dispersed by the base isolation layer 10 during an earthquake to be transmitted to a tunnel 2, and the breakage of the tunnel 2 can be effectively prevented.
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