1. Construction principles
1) Pipeline construction: dry first and then branch, and branch and branch line construction after structural construction is completed.
2) The pipe trench is excavated by mechanical excavation (manual cooperation, artificial trench clearing 200 meters thick). The slope of the trench is 1: 1. When the trench depth exceeds 4 m, a reserved horse track with a width of 1.2 m should be excavated in layers. Small pipe trenches are excavated manually. When the machine cannot dig, manual digging is used.
3) Visual inspection and type inspection shall be carried out before the inspection well is installed.
4) Double wall corrugated pipe equipment adopts socket interface. When a single socket connection cannot be adopted, a double socket connection and a two-way socket elastic sealing ring connection can be adopted.
5) Before construction of the double-wall corrugated pipe equipment , a 200 mm thick sand cushion layer should be laid on the trench, and the compactness should reach 85% -90%. In the double-wall corrugated pipe backfill construction, medium coarse sand backfill must be used. The range of backfill soil should not be less than the design support angle of 2a + 30 degrees (180 degrees), and the compaction degree of backfill soil should be greater than 95%.
6) The connection of the double wall bellows equipment to the inspection well can be rigid or flexible.
Rigid connection: When inspecting the well body masonry, insert the pipe fittings or short pipes into the wall, with the sockets facing outwards to facilitate the connection of the sockets. When using this connection method, the cement mortar should be full.
Flexible connection: A precast concrete ring beam with a socket is placed on the inspection well. The inner diameter of the ring beam and the outside of the pipe seat have a certain gap, so that the rubber ring at the end of the pipe is connected to the ring beam, and a certain angle meets the requirements. Check the uneven settlement between the well and the pipeline.
2. Foundation treatment and laying
1) After excavation, find special conditions such as soft soil foundation and bottom sills, and jointly determine the treatment measures with the supervision unit and design unit, and sign the design modification and transfer records. The foundation is strictly prohibited from over-digging, and sand can be backfilled if necessary. When the foundation needs to be replaced, it should be thoroughly cleaned, and backfill materials, operating methods and quality standards should be determined according to specific conditions. After ramming the basement according to the design requirements, the pipeline foundation construction is carried out according to the design requirements.
2) After the basement is compacted, a 200mm thick sand cushion is directly laid on the bottom of the trench to stabilize the pipeline after compaction. For ordinary soil, when the characteristic value of the bearing capacity of the foundation is greater than 80 kPa, medium coarse sand can be laid on the foundation; when the characteristic value of the bearing capacity of the local foundation is lower than FAK <80 kPa or the bottom of the tank is below the groundwater level, It is recommended to lay a gravel base layer of thickness N. OT is less than 200 mm, or laid in two layers. The lower layer is crushed stone with a diameter of 5 to 40mm, and the upper layer is not less than 50mm thick. For the soft soil foundation, when the characteristic value of the bearing capacity of the foundation is less than 55 kPa, or due to construction reasons, the original soil of the foundation is disturbed and the bearing capacity of the foundation is affected. The foundation must be strengthened first, and then the medium and coarse sand foundation is the foundation. . Lay after reaching the required foundation bearing capacity.
3, down tube
According to the proficiency of the construction staff, the weight of the pipeline, the length, the construction environment, the depth of the trough, the supply of lifting equipment, and in accordance with the principles of safe construction and easy operation, determine the method of pipe down. The key to management is safety, which must be guided by experienced workers. Use a reliable lifting device to level the trench. Do not collide violently with the trench wall and trench bottom. Two lifting points shall be provided during lifting. Do not lift from the center. It is strictly forbidden to stand under the riser. When manually lowering, personnel inside the tank must avoid the position of the pipeline. The trench must be thoroughly inspected when it is lowered, including the soil quality of the base, impurities in the base, and stability of the trench.
HDPE double-wall corrugated pipe construction: After the sand mat is compacted, installation can begin. Double wall bellows shall be installed along the flow direction of the socket, and opposite to the flow direction of the socket, they shall be installed from the low point to the high point in turn. Pipes can be installed manually. During the installation, workers lifted both ends of the pipeline to the bottom of the trench. For pipes larger than 3m or more than 400mm in diameter, non-metallic cables can be used to slide the pipes smoothly on the slots. It is forbidden to use metal rope to hook the nozzles at both ends or roll the pipe from the groove side into the groove. The length of the pipe can be adjusted with a hand saw, but the cross section should be vertical and flat. When the interface is operated, the socket should be cleaned, put on a rubber ring to check whether the rubber ring is well matched, and apply lubricant. The center of the socket end should be aligned with the central axis of the socket for slow docking. Do not use construction machinery to push the pipe into the socket. If the pipeline is severely damaged during construction, it can only be used after passing professional inspection. If the pipeline is not severely damaged, it can be repaired and reused.