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Characteristics of the trench for buried plastic pipes

80a

  • Realization of the trench

It will be excavated up to the line of the soil provided that the soil is uniform; if the rigid elements are not covered such as stones, rocks, old bricks, etc., it will be necessary to excavate below the soil to perform the following filling.

The material coming from the excavation will be stacked are enough from the edge of the trenches to avoid their collapse or that the landslide of it could endanger the workers.

The filling of the complementary excavations performed below the soil will be regularised leaving a uniform soil. The filling will be performed preferably with loose sand, gravel or crushed stone, provided that the maximum size of them doesn’t exceed 2 cm. It will be avoided the use of unsuitable lands. These fillings will be carefully tamped down and the surface will be regulated.

  • Types of trench

80b

  • Filling of the trench

Once the pipe is placed, the filling of the trench will be compacted by successive layers. The first layers up to some 30 cm above the superior generatrix of the pipe will be performed avoiding placing stones or gravel with diameters higher than 2 cm and with a grade of compaction not lower than 95% of Proctor Test. The rest will be able to have thicker material, however, we advise not to use elements superior to 20 cm and with a grade of compaction of 100% of Proctor Test.

Special care will be taken in the procedure used to level trenches and consolidate fillings, in the way that there won’t be movements of the pipes. The trench will not be filled in periods of big frosts or with icy material.

The long term behaviour of any pipe is directly related with the quality of the assembly and of the materials used in the installation of the product. It is necessary to follow scrupulously the steps indicated and perform a competent supervision in all the phases of the assembly.

80c

  • Depth of the trench

The minimum depth of the trench will determine the form that the pipes result protected from the transit effects and exterior loads, just like preserving them from the variations of temperature of the environment. For that, it will be taken into account the situation of the pipe (if it is under the ground or below the street or a place with more or less transit, or under pavements or a place without transit), the type of filling, if there is paving, the form and quality of the base of support, nature of the soil, etc.

Like a general rule, below the streets or in possible transit fields, the minimum depth will be such that the superior generatrix of the pipe be at least at 0.8 m from the surface; in pavements or places without transit the covering can be reduced to a 0.6 m. If the covering indicated like minimum could not be respected for topographic reasons, for other canalizations, etc., it will be taken the necessary measures of protection.

The conductions of the sewerage will be placed in an inferior level than the supply ones, with vertical and horizontal distances between one and the other must not be lower than 1 m. If these conditions couldn’t be kept justifiably or if it is needed crossings with other canalizations, especial precautions will must be adopted.

  • Width of the trench

The width of the trench depends on the size of the pipes, depth of the trench, slopes of the lateral walls, nature of the soil and the need or not of piping, etc.; like a general rule the minimum width can’t be lower than 0.7 m and it must be left a space of 0.25 m at both sides of the pipe, to be able to compact the kidneys of the pipes.

>>>The Rigidity of the pipe acquires its higher importance during the installation and compacting period, where it can occur light deviations of the codes of good practice. Leave a comment, please.

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