To provide a double impervious sheet which is lightweight, easily transported and laid, prevented from the shift of a water stop material downward between the double sheets even in the hanging or the laying on an inclined or a vertical surface and capable of having an apparent specific gravity corresponding to the laying location and a laying method of sinking the double impervious sheet below sea or water surface and laying.
The double impervious sheet X is structured so that the water stop material 2 formed by charging granular bentonite 2a in a bag-like part 1b tightly closed by sealing the whole edge part of the four peripheries of a pair of opposed rectangular impervious sheets 1, 1 to insert between the upper cloth 2b and the lower cloth 2c and connecting by needle-punching the upper and the lower clothes with a prescribed interval is inserted in a water permeable non-woven fabric 3 in which a tube 3a for water permeation is inserted and which is laid on the upper cloth 2 through the whole surface in the nearly longitudinal direction and an injection means 4 for injecting water and a suction means for sucking air in the bag-like part 1b are provided in the impervious sheet 1 in the upper cloth 2b side.
YOSHII HIROTAKA
KAWAGUCHI TAKESHI
TOSOH NIKKEMI CORP
TAIYO KOGYO CO LTD
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