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Ductile iron pipe can be laid on normal slopes without any special construction techniques. Once the pipeline exceeds a certain angle, the pipe and/or the slope itself will tend to slide. As a general rule, the designer should consider potential problems when the slope exceeds 25% for underground pipelines and 20% for aboveground pipelines.
Once the slope of the pipeline approaches these values, the designer should pay particular attention to the need for special restraint or anchor requirements for the slope and the pipeline. For pipelines on piers above ground, suitable restraint can be obtained by strapping each pipe length behind the bell to a secure anchor block and laying the pipe with the sockets pointing uphill. A slight gap between the spigot and bottom of the socket may be provided to allow for expansion and contraction. In underground pipelines with steep slopes, it is normal for the pipe to also be specified with restrained joints and also laid uphill. |
