11.10. MISCELLANEOUS DETAILS
The exit gradient of the seepage water at the downstream end of the culvert floor must be within permissible limits. Some nominal protection in the form of loose stone may also be provided on the upstream as well as the downstream of the impervious floor.
The foundation of any cross- drainage structure should meet the requirement of the bearing capacity of the soil under optimum loads, seismic effects, anticipated scour, and settlement.
To facilitate drainage of the backfills due to rise in water table or otherwise, small openings are provided in abutments, wing walls, and return walls. These openings are called weep holes.
In big siphons, stop log grooves on the sides of the upstream entrance and downstream outfalls should be provided so as to isolate one or more barrels for periodic inspections, repairs, and maintenance.
Trash racks are desirable at the entrance of the siphon where large quantity of floating material is expected in the channel water. These racks are generally made in panels for convenient handling. These trash racks are usually inclined at a slope of 1(H) : 4(V).
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