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Figure 4.2
Manhole used in the Faisalabad Area Upgrading Project |
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cover and welded to the reinforcement. This was considerably cheaper than the angle iron design and lent itself to use with circular covers. |
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A weakness of the standard OPP design is that no surround is provided to contain the cover in place. The experience in the early projects in Faisalabad is that this allows the cover to move laterally so that part of it can extend beyond the manhole walls and be subjected to large stresses when a load passses over it. To prevent this, a mass concrete surround will be provided to contain the cover on future projects. It is probably advisable that, the vertical face in contact with the cover should be provided with a steel edge strip as for the cover itself. |
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The larger circular manholes used in North-east Lahore have single brick walls on a plain concrete base. The cover is a standard Lahore Water and Sanitation Agency (WASA) design: circular in plan and cast in concrete inside a cast-iron frame. The cover is set over a circular access hole in a flat reinforced concrete roof slab, thus conforming with standard sewerage prac- |
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