Foundation and Backfilling of Corrugated Pipe Culvert

Jun. 14, 2023

Structure Plate Corrugated Pipe Culvert has both rigidity and flexibility. It must rely on the interaction between soil and structure to exert its bearing capacity. The weight of the backfill and the pressure generated by the live load will be transmitted to the filler on the side of the structure and the soil layer below. The supporting soil layer (generally referred to as the foundation) below the structure must be sufficient to provide longitudinal and lateral support.

Construction technical requirements

1. Basic and backfill material requirements

The corrugated steel plate culvert is made of steel plate material and has strong adaptability to deformation. The base material can be replaced with gravel, gravel soil or sandy soil. Try to use granular materials with good structural characteristics and not contain giant pebbles or rocks. There shall be no stones with a particle size exceeding 75mm within 300mm around the structure.

2. Compaction requirements

The foundation should be compacted in layers with a vibratory compaction machine, with a compaction degree of not less than 93%; the wedge-shaped part of the bottom of the pipe can be compacted obliquely with a small compaction machine or compacted with artificial wooden rods; backfilling on both sides should be constructed symmetrically and backfilled in layers , The thickness of each layer shall not exceed 750px; the compaction requirements on both sides and top of the culvert pipe are the same as that of the subgrade at the same elevation; above the culvert pipe, when the thickness of the backfill exceeds 750px, the static pressure of the roller shall be adopted, and the vibration pressure of the roller shall be adopted when the thickness exceeds 1250px.

 Corrugated Steel Pipe

Corrugated Steel Pipe

3. Backfill range and thickness requirements

In frozen soil areas, the range on both sides of the culvert pipe is ≥0.5 times the aperture (minimum 0.5m), and the thickness above the top of the culvert pipe is ≥0.5m (0.8m when the pipe diameter is greater than 3m), and gravel is filled in this rectangular area.

In the non-frozen soil area, the culvert pipe shall be filled with sand and gravel below half of the pipe diameter on both sides, and the filling range on both sides shall be ≥0.5 times the hole diameter (minimum 0.5 m); the same material as the subgrade filling can be filled with more than half of the pipe diameter on both sides and the top.

Construction technology flow

Pre-construction preparation → construction setting out → setting up cofferdam → drainage and dredging → leveling the site → foundation layer backfilling → testing compaction, moisture content, etc. → leveling → leveling the site → construction setting out → installing culvert → testing Culvert bottom longitudinal slope→check culvert pipe sealing and spray anticorrosive coating→culvert pipe in place→wedge backfill and compaction→layer backfill on both sides→check compaction, water content, etc.→pipe top layer backfill→check compaction, content Water volume, etc. → Import and export treatment.

Special reminder: During the construction of the corrugated steel structure, the owner should assign a supervisor with relevant knowledge to supervise the construction process, and assign an inspector to ensure that the installation work fully meets the specifications or design requirements.

(1) For small corrugated steel pipe culverts (150-~1600mm), inspections should be carried out at the construction stage such as foundation, pipe foundation, arch haunch, arch line and minimum filling thickness. Generally speaking, construction records are not required for small structures.

(2) For larger corrugated steel pipes (1800-3000mm) and structural plate corrugated pipes, inspections should be carried out at all stages of assembly and installation.

(3) For large-span structures with a span of more than 3m, on-site inspectors with relevant knowledge should be dispatched to conduct continuous inspections. They are authorized to accept or reject construction procedures or equipment. Long-span structure construction inspection should be recorded, and its inspection and control efforts should be the same as traditional bridge construction.

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