| 摘要 |
PROBLEM TO BE SOLVED: To reduce labor for maintenance by increasing service life more than that of a publicly known structure, reducing the sink of a ballast by the intentional use of a specified elasticity particularly through a laminated layer, reducing a load on the ballast, and improving the slidable movement of a roadbed to the side. SOLUTION: A solid layer 6 formed of a material with high durability against breakage and disabled to compress or slightly enabled to compress is disposed between an upper side layer 4 having a high returning force and formed of a volumetrically compressible porous material and a lower side layer 5 formed of a plastically elastic material. COPYRIGHT: (C)2006,JPO&NCIPI
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