Preparations for laying pipelines: road demolition and restoration. During urban pipeline construction, a certain number of existing pavements will be destroyed. In order to ensure the safety of construction and the quality of the roadbed, when the pipeline is to be excavated on the road during construction, the opening width should be calculated according to the design requirements of the construction drawings, and the excavation line should be marked with white paint, and the road surface should be cut off with a cutting machine. The surface layer and the subgrade slag layer are excavated by excavators, the stable subgrade sand layer is reasonably stacked for reuse, and the remaining soil is transported to the spoil field by dump trucks. After the pipeline construction is completed, the quality of trench backfill will directly affect the quality and function of the road. When excavating the foundations of buildings, structures, utility poles, and light poles, measures to prevent them from sinking or deforming, and reinforcement engineering calculations and drawings shall be reported. Some sites require drainage to keep excavators working in dry conditions. The drainage process shall not cause excessive settlement of the ground, affecting the normal use and safety of buildings, structures and other public facilities around the site. Pipeline construction: trench excavation. First, prevent over-digging at the bottom of the groove. When digging the trench, a special person should check the elevation of the bottom of the trench. When using mechanical trenching, reserve 20cm soil layer above the designed trench bottom elevation for manual excavation. In case of over-excavation, gravel (or pebbles) shall be used to fill up to the design elevation, or the soil shall be compacted, and its compactness shall not be lower than that of the original natural foundation. Second, the groove section should meet the requirements. The width of the groove bottom should be the width of the pipe structure plus the working width on both sides. Therefore, when determining the excavation section, the production and engineering quality should be considered, so that the grooved section is reasonable. Concrete foundation with vertical formwork. According to the center line of the road, the technicians and construction workers jointly determine the center line of the pipe position and then set up the formwork on both sides. The template adopts the new template. The wooden formwork is required to be stable and the elevation is accurate, and a 100mm gravel cushion is required. The cushion requires that the surface of the graded gravel has no weathering and is basically flat. The bottom plate is poured with C20 concrete. After the bottom plate concrete is vibrated twice with a flat plate vibration tamper, it is smoothed and brushed, and covered with straw bags in time for maintenance. Pipeline installation: First, the selection and inspection of pipes. The pipes and main accessories are provided by the selected qualified manufacturers. After the pipes enter the site, the material engineer of the construction party will verify the quality of the products. When the visual inspection cannot ensure the quality of the pipe, carry out the internal and external pressure test. The pipes entering the field must be products that have passed the batch inspection of professional laboratories and obtained the inspection report. The second is downpipe. According to the center line of the measuring and placing, use the string to control the side line of the pipe. The tire-type crane is used to lower the tube, and the crane runs along the groove to a distance of 1m from the edge of the groove to avoid the collapse of the groove wall and affect the stability of the groove slope. When lowering the pipe, use a special hook or flexible sling, and it is strictly forbidden to use a steel wire rope to pass through the pipe for lifting. At the same time, there is a special person instructing, the tie (sleeve) pipes should find the center of gravity, and they should be placed horizontally and gently to avoid disturbing the collision of the base pipes. When the pipe section is lowered into the groove, avoid collision with the groove wall support and the pipe under the groove, and strictly control the level and direction. The installation of pipes must meet the quality requirements.
