Construction Process Of Hdpe Pipe

Construction process: measurement → setting out → trench excavation → foundation treatment → connection, pipe laying, calibration → pipe trench backfilling → inspection well masonry, backfilling → acceptance. In addition to following the construction specifications, the construction of HDPE pipes should also pay attention to the following points due to their own characteristics:
(1) HDPE pipes are subject to severe thermal expansion, so HDPE pipes should be constructed and used in an environment where the temperature difference changes little.
(2) When the burial depth of HDPE pipes is lower than the bottom surface of the building foundation, the pipes shall not be located within the range of the diffusion angle compression of the foundation under the building foundation.
(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 to 0.5 m below the nearest point of the trench bottom.
(4) When excavating the pipe trench, the excavation depth shall be strictly controlled and the undisturbed soil at the bottom layer of the foundation shall not be disturbed. In case of over excavation and disturbance, natural graded sand and stone materials with a particle size of 0.1 m to 0.5 m shall be replaced and leveled and compacted.
(5) HDPE pipeline foundation adopts gravel foundation instead of concrete foundation, with a thickness of 0.05 m to 20 m, depending on geological conditions.
(6) During the pipeline laying process, manual or crane operation is used to lower the pipe. When the crane is used to lower the pipe, non-metallic ropes are used to tie the two ends of the pipe at a distance of 1/4 from the pipe mouth. It is strictly prohibited to lift through the center.
(7) In backfilling, there are strict requirements for backfill soil. Some backfill soil uses a certain specification of medium (coarse) sand (locally known as asbestos sand). The hard edges and corners of crushed stone (soil) can easily damage the PE pipe and the backfill is not easy to compact. Asbestos sand has an automatic compaction function at the optimal moisture content, and small compaction machines can be used to compact it to meet the compaction requirements.
(8) Mechanical backfilling shall be used for backfilling above 0.7 meters above the pipe top. Backfilling below the top of the pipe must be done simultaneously from both sides of the pipe and compacted, otherwise it may cause uneven pressure on the HDPE pipe, resulting in deformation and displacement of the HDPE pipe. Other backfilling shall be carried out according to the specifications.
(9) Connect the pipeline to the inspection well. In the original construction scheme, the pipe orifice was retracted 0.3 m~0.5 m into the inner wall of the inspection well, painted with mortar to be "trumpet shaped", and the surrounding area was filled with mortar. After that, bricks were built, but the closed water test could not meet the requirements. The following problems were found after inspection: ① The inspection well was cracked by thermal expansion of HDPE pipe, resulting in water leakage of the inspection well. ② The inspection well was not cracked, but the sealing at the connection between the pipeline and the inspection well did not meet the requirements, resulting in water seepage and leakage.
In response to the above two issues, the following solutions are proposed: ① Increase the burial depth of HDPE pipes to keep them in an environment with relatively little temperature change, and at the same time, backfill immediately after laying the HDPE pipes, which should be completed in a relatively short period of time. Control the construction length within a certain range. ② After the HDPE pipeline is laid, the construction of the inspection well can be carried out. ③ In response to the second issue, the connection method was adopted again, and the connection between the inspection well and the HDPE pipe was sealed with hot melt fiber, replacing the original mortar filling seal.