| 摘要 |
The concrete manhole chamber (1) consists of a base (2) and side walls (3a, 3b, 3c, 3d) with holes (4) for connecting pipes. Each hole has a supple seal ring (5) which is embedded in the concrete during casting and is fitted with a rigid circular plug (6). The axial dimension of each seal ring corresponds to the thickness of the side wall and it has two inner seal lips, with at least one lip making contact with a plug. The outer annular surface of each ring has collars to anchor it in the concrete.
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