Manhole box-frame construction null of protecting tube for subterranean buried cable

摘要

PROBLEM TO BE SOLVED: To prevent a protective tube from coming out of a manhole wall or protruding into the manhole to damage cables even if the protective tube is horizontally shifted by lateral vibration due to severe earthquake or the like. ;SOLUTION: A sheath tube 10 extending from the inside surface toward the outside surface of manhole walls 1, 2 is penetrated through the manhole walls 1, 2. The length of the sheath tube 10 is larger than the distance of horizontal shift of a buried protective tube P₁ that may occur due to severe earthquake or the like. The opening of the protective tube P₁ is inserted into the sheath tube 10 from outside the manhole walls 1, 2 with rubber water stops 11, 12 in-between. The insertion end is positioned in the middle of the sheath tube 10 so that it will not come out of the sheath tube 10 even if the protective tube is displaced. A series of rings 13 the inside diameter of which is equal to that of the protective tube P₁ are continuously fitted in the protective tube P₁ between the inner end of the manhole walls and the insertion end of the protective tube P₁ with the rubber water stop 14 in between.;COPYRIGHT: (C)1998,JPO