Hdpe Pipe Construction Technology

Construction process: measurement→layout→ditch excavation→foundation treatment→connection, pipe running, pipe adjustment→pipe slot backfilling→inspection well masonry, backing→acceptance. In addition to the construction of HDPE pipes according to the construction specifications, the characteristics of HDPE pipes should pay attention to the following points:

(1) HDPE pipes have severe thermal expansion and contraction, so HDPE pipes should be constructed and used in an environment with little temperature difference.

(2) When the buried depth of the HDPE pipe is lower than the bottom surface of the foundation of the structure, the pipeline shall not be located within the compression range of the foundation diffusion angle under the foundation of the structure.

(3) In areas where the groundwater level is higher than the elevation of the excavated trench bottom, the groundwater level drops to 0.3 m～0.5m below the nearest point on the trench bottom.

(4) When excavating the pipe trench, strictly control the digging depth and not disturb the undisturbed soil at the bottom of the basement. In case of over-excavation and disturbance, replace the natural graded sand and gravel material with a particle size of 0.1 m～0.5 m, and level and ram it.

(5) The HDPE pipeline foundation adopts sand gravel foundation instead of concrete foundation, with a thickness of 0.05 m to 20 m, depending on the geological conditions.

(6) During the pipeline laying process, the lowering of the pipe shall be carried out manually or by a crane. When the lowering of the pipe by the crane, the two ends of the pipe shall be fastened 1/4 away from the pipe mouth with non-metallic ropes. It is strictly forbidden to hoist.

(7) The backfill requires stricter requirements for the backfill. Some of the backfill uses a certain specification of medium (coarse) sand (locally called asbestos sand). The hard edges and corners of the gravel (soil) are easy to damage the PE pipe and the backfill is not easy to compact. Asbestos sand It has an automatic compaction function when the moisture content is optimal, and compaction with a small compaction machine can meet the compactness requirements.

(8) Backfill the part above 0.7 m from the top of the pipe, using mechanical backfill. Backfilling below the top of the pipe must be backfilled from both sides of the pipe at the same time and tamped, otherwise the HDPE pipe will be easily compressed unevenly, resulting in deformation and displacement of the HDPE pipe. Other backfills are performed according to the specifications.

(9) The pipeline is connected to the inspection well. In the original construction plan, the nozzle was retracted into the inner wall of the inspection well by 0.3 m～0.5 m, painted with mortar to form a "trumpet shape", and the surrounding area was filled with mortar to be dense, and then bricks were built, but the closed water test could not meet the requirements. The following problems exist in the inspection: ①The thermal expansion and contraction of HDPE pipe will break the inspection well, causing water leakage in the inspection well. ②The inspection well was not split, but the joints between the pipeline and the inspection well did not meet the sealing requirements, resulting in water seepage and leakage.

To solve the above two problems, the following solutions are proposed: ①Increase the burying depth of the HDPE pipe so that the HDPE pipe is in an environment where the relative temperature does not change much. At the same time, the HDPE pipe is immediately backfilled after the laying, and completed in a relatively short time. The construction length is controlled within a certain range. ②After the HDPE pipeline is laid, the inspection well shall be built. ③In response to the second problem, the connection method is re-adopted, and the joint between the inspection well and the HDPE pipe is sealed with hot-melt fiber, instead of the original mortar packing and sealing