1. Precast concrete circular pipes can be formed by centrifugation, roller hanging, vibration or vertical extrusion, and should be manufactured in factories and mobile factories.
2. The inner surface of precast concrete circular pipe should meet the requirements of operating hydraulic conditions for roughness, and its roughness coefficient n should not be greater than 0.0 13.
3. The wall thickness of precast concrete circular pipe should be113 ~1/9 of the inner diameter of the pipe; The length of the pipe joint shall be determined according to the manufacturing, transportation and installation conditions, but it shall not be less than 2m.
4. When the wall thickness of the circular tube is not more than 100mm, a single-layer stress ring rib can be configured, and its position should be placed at 2/5 of the wall thickness of the inner surface of the tube; When the thickness of the pipe wall is greater than 100mm, it is appropriate to configure double-layer stress ring reinforcement.
5. Reinforced concrete circular tube, when the wall thickness is not more than 80mm, the minimum thickness of ring reinforcement protective layer should not be less than 8 mm; When the wall thickness is more than 80mm and not more than 100mm, the minimum thickness of the annular reinforced protective layer should not be less than12 mm; ; When the pipe wall thickness is greater than 100mm, the minimum thickness of the annular reinforced protective layer should not be less than 20 mm. 。
6. The clear distance between the annular reinforcing bars in the reinforced concrete circular tube should not be less than 25mm. Longitudinal reinforcement can usually be configured according to the structure. For slotted pipe joints, the longitudinal reinforcement spacing is 300mm. For the top pipe joint, the longitudinal reinforcement spacing is 200mm. For the top pipe joint, the stirrup spacing of the pressure-bearing surface at the top of the nozzle should not be greater than100 mm.
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