| 摘要 |
PURPOSE: To make a sheet elongate less under a constant load so as to use the sheet suitably for discharging spring water from inside a tunnel, particularly in cold climates by providing a water barrier layer made of a hydrophobic resin or rubber on one side of a needle punched nonwoven fabric having predetermined values of METSUKE (weight/unit area) and thickness. CONSTITUTION: A water barrier layer 3 made of a hydrophobic resin or rubber is provided on one side of a needle punched nonwoven fabric with a METSUKE of 300g/m<2> or more and a thickness of 3mm or more. The sheet is made to have an elongation ratio of 2% or less after 7 days of application of a constant load of 1.5kg per width of 5cm. The coefficient of permeability in the surface direction of the sheet is 1.0×10<-1> cm/sec or more. Therefore, the sheet 1 is not elongated even by the load of a heat insulating layer 4, and spring water can be efficiently discharged out of the tunnel.
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