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Insofar as tests take place during the construction phase, these do not replace the acceptance test. Test criteria are identical see Chap. The execution of the tests can take place through the qualified customer himself or through a third party who has the appropriate specialist knowledge. With pipeline trenches in traffic areas the carrying out of plate bearing tests are additionally recommended. The employment off "light hammer test equipment" or "dynamic plates" for the monitoring of compaction during construction allows testing in different compaction levels.
The correlation between the measured values and the soil specific Proctor density is to be determined. The separation of test points with pipeline trenches should not exceed 25 m and there should not be less than three checks per construction measure.
The test points for compaction monitoring are laid down by the customer. Backfilling consists of the side backfill, covering within the pipeline zone and the main backfill Fig. The most frequent causes of damage to the pipes are pipe bedding and side backfilling, which deviate from the planning. Simultaneous faulty installation of backfill material and insufficient compacting lead inevitably to settling. The structural analysis is relevant from which even higher values can result.
Fill height, material and the compacting equipment used are to be matched to each other. Fill height and number of passes are to be taken from Table 4. Depending on the condition of the soil they may be exceeded or undercut.
Exact values can only be established by a sample compacting. Trench widths given in DIN EN in Tables 1 and 2 are minimum values which must, under certain conditions, be correspondingly increased, depending on the equipment. With the fabrication of concrete bearing supports and concrete jacketing as well as structures made from concrete or brickwork, a start may be made with the side backfilling only if the concrete or jointing mortar has achieved a satisfactory strength.
For flexible pipes attention is drawn to the comments in Chap. In special cases, for example with narrow trench conditions, which allow no satisfactory compacting of the bedding and side filling or if no suitable material for the pipeline zone is available, the pipeline can be embedded partially or completely, using hydraulically bonded material e. Horizontal or vertical positional changes are, through suitable measures, to be avoided.
The thickness of the covering over the pipeline should, as a rule, be mm, but at least mm over the pipe shaft or mm over the pipe connection. Compacting in this area may be carried out using hand rammers only. To avoid settling the main backfill is so to be carried out in layers, that a sufficient compacting is ensured. Higher values than required in the static calculation can result in accordance with other regulations, e.
Sudden dumping of large masses or earth is not permitted. The abrupt placement of large masses of earth is not permitted. A mechanical compacting of the main backfill over the pipes may take place first after incorporation of a layer thickness of at least mm. For this light compacting equipment is suitable. The minimum covering height of the pipeline here results from the greatest fill height for the planned compacting equipment see Table 4 plus mm.
Medium and heavy compacting equipment may first be used after a minimum covering height of 1. The employment of drop weights as well as a compacting of the main backfill by banging or pressing using the excavator bucket are not permitted. Driving over the covered pipeline with small covering using heavy construction equipment and vehicles as well as the storage of excavated soil above the pipeline are not permitted.
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