Clay Pipe Installation Handbook

Chapter 7, Final Backfilling

Final Backfilling

Final backfilling is normally done in layers. Usually a front end loader or a bulldozer is used to push the spoil bank into the trench at an angle so that impact on the pipe zone is minimized. (Figure 24) This material should not contain large boulders or lumps that might damage the pipe or disturb pipe alignment.

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Compaction

The engineering specifications may call for compaction of the backfill material. The degree and method will be specified to minimize settlement of the pavement subgrade. All methods of compaction used to achieve the specified density should be done under the direction of the engineer. (Figures 25 & 26)

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If the soil permits, adequate compaction may be obtamed by careful water flooding.

When native materials cannot be satisfactorily cornpacted by any normal method, suitable materials might have to be imported for the backfill operation.

There should be a minimum of 5 feet of cover over th! top of the pipe before any mechanical compaction e quipment is employed. This will tend to reduce dangerous impact loads on the pipeline.

Extreme care should be taken when using heav mechanical equipment. (Figure 26)

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Compaction Abuse

The selection and use of suitable compaction equip ment must be made with care so that the pipe will no be disturbed or damaged.

A pavement breaking type of falling weight "stomper" or drop hammer, should never be used for compacting even with a substantial cover over the pipe. These im pact devices can damage the pipe and/or force it out of alignment.

NCPI - Clay Pipe Installation Handbook

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