Construction Scheme of Rainwater Collection in PVC Double Wall Corrugated Pipe Residential Area: Slope Design and Drainage Optimization

With the acceleration of urbanization process, the rainwater collection system in residential areas has become an important part of sponge city construction. PVC double-wall corrugated pipes are widely used in rainwater pipe network projects due to their advantages of high ring stiffness, corrosion resistance and convenient construction. This paper combines engineering practice, from the two aspects of slope design and drainage optimization, elaborates the construction technical points of the rainwater collection system in residential areas.

First, Engineering Design Basis

The rainwater collection system in residential areas needs to be hydraulically calculated according to the catchment area, rainstorm intensity formula and local rainfall data. PVC double-wall corrugated pipes (DN200-DN600) are used as the main pipeline, and the design flow needs to meet the requirements of rainstorm discharge in 50 years. The pipeline material is made of SN8-level or higher ring stiffness products to ensure the structural stability under ground load.

Second, the key technology of slope design

1. Slope value specification

According to the "Building Water Supply and Drainage Design Standard" GB50015, the minimum slope of rainwater pipes should meet: DN200 pipe 0.003 (0.3%), DN300 pipe 0.002 (0.2%). The actual construction needs to be combined with topographic adjustment, 0.5% -1% slope should be used in flat areas, and the mountain area can be raised to 1.5% -2%, but the flow rate needs to be controlled 5m/s to prevent initialization.

2. Slope control measures

- Use a level for elevation measurement, and set a slope control pile every 50 meters to ensure that the pipeline is laid with a linear deviation of 20mm

- The bottom of the trench adopts a 150mm thick graded sand and gravel cushion, and the compaction coefficient is 0.93 to avoid the slope abrupt change caused by pipeline settlement

- 200mm200mm concrete piers need to be set at nodes such as elbows and tee to enhance pipeline stability

III. Drainage optimization implementation plan

1. Pipe network system layout

- using the combined form of branch pipe network and ring pipe network, the main road is laid along the green belt of the community road, and the branch pipe spacing is controlled at 25-30m

- the distance between the rain nozzles is set: 30-40m/piece of motor vehicle road, 40-50m/piece of sidewalk, using anti-theft cast iron grate (load-bearing 30kN)

- 3 times the curvature radius of the pipe turning, avoiding 90 right-angle elbows

2. Hydraulic performance improvement

- The water inlet is equipped with a sinking manhole (depth 800mm), with a built-in 60-mesh stainless steel filter screen to reduce the risk of sediment blockage

- The exhaust valve is set at the highest point of the system, and a maintenance well (diameter 1200mm) is set every 300m. The well adopts a flow channel design to reduce water head loss

- The pipeline backfill adopts a layered compaction method: plain soil (90% compaction) + medium coarse sand (95% compaction) to avoid pipeline compression deformation

3. Quality inspection standard

- closed water test: test head 2m, water permeability 0.05L/(m · min)

- slope retest: the use of total station for pipeline axis measurement, allowing deviation of 1% design slope

- interface quality: rubber ring socket connection to ensure that the interface gap 3mm, no water seepage phenomenon

4, construction precautions

1. Rainy season construction needs to set up temporary drainage ditches, trench excavation depth > 1.5m need to slope 1:0.75 and set slope support

2. Pipeline installation needs to check the smoothness of the inner wall of the bellows, no cracks, depressions and other defects

3. Set up a check valve at the connection with the municipal pipe network to prevent rainwater backflow

Through scientific slope design and drainage optimization measures, the rainwater collection system of PVC double-wall corrugated pipe can effectively improve the efficiency of rainwater discharge in the community and reduce the risk of waterlogging. During construction, it is necessary to strictly follow the design specifications and dynamically adjust the parameters according to the actual working conditions on site to ensure the long-term stable operation of the system. It is recommended to establish a smart monitoring platform synchronously to monitor the drainage status in real time through flow sensors to realize intelligent operation and maintenance management.