Designing Of Large Diameter, Long Distance And Assembled Corrugated Steel Culverts

As per Technical Specifications for Corrugated Metal Culverts in Highway Engineering (TCECSG:D66-01-2019), the internal forces acting on corrugated metal culverts must account for wall pressures induced by three primary factors:

Permanent loads (e.g., overburden soil),Variable loads (e.g., traffic or live loads),Seismic effectsWhile Project-Specific Conditions are Overburden depth: 11 m of compacted backfill above the culvert.No live loads: The culvert is not subjected to vehicular traffic or transient forces.Seismic exclusion: Located in a seismic intensity VI zone,and the seismic effect is not considered. The design pressure of the pipe top only considers the permanent effect, that is, the pipeline pressure generated by the upper filling soil.

Project Overview:Culvert length: Single pipeline spans 2.16 km.Foundation type: Engineered trench with manually leveled and compacted subgrade.Challenge: Despite the inherent deformation adaptability of corrugated steel culverts (6-12% axial strain tolerance), uneven compaction during backfilling risks differential settlement and structural distortion.

Engineered Settlement Control Measure:Subgrade Reinforcement:Trench preparation: Post-excavation compaction to ensure uniform load distribution.

Layered cushion system:Base layer: 0.7 m 3:7 lime-soil cushion (calcium oxide to soil ratio), compacted in 150 mm lifts to ≥95% density.

Intermediate layer: 0.3 m coarse sand bedding (max. particle size 12 mm) for drainage and stress dispersion.

Backfill: Native excavated soil recompacted at optimal moisture content.Expansion Joint Deployment,Installed at critical interfaces to absorb differential movement:Junctions: Connections to concrete structures (reservoirs, stilling basins).Geotechnical transitions: Boundaries between differing foundation lithologies.Cut-fill interfaces: Zones separating excavated and backfilled areas.

While current practices align with TCECSG:D66-01-2019, two areas require prioritized study.Performance validation: Quantifying the efficacy of expansion joints in corrugated steel culverts under long-term settlement.Material optimization: Testing hybrid joint designs

Expansion devices have been installed at the connection points between steel corrugated pipes and large concrete structures such as reservoirs and dissipation pools, as well as at locations where the rock types of the foundation strata are inconsistent, and at excavation and backfilling boundaries. However, due to the limited use of expansion devices in similar projects, there is a lack of research on the effectiveness of steel corrugated pipe expansion devices. The next step will be to further study the anti settlement performance of different expansion devices.ubber-bitumen composites, HDPE sleeves) to enhance deformation compatibility.

The waterproofing of assembled corrugated metal culverts primarily relies on segment installation methods and sealing materials. In previous applications, the waterproof structure of these culverts adopted a lap-joint design. The assembly involves overlapping two corrugated steel plates and connecting them with bolts. During this process, gaps between plates, bolt holes penetrating the plates, and spaces between bolts and holes become potential leakage points.

The main leakage occurs at circumferential lap joints. This is primarily caused by uneven settlement in flexible foundations within months after backfilling. Such settlement stretches or compresses the lap joints, displacing bolts from their original positions and misaligning sealing materials, ultimately creating leakage paths.

The outward-flanged flange process integrates the flange with corrugated steel culvert plates as a single unit, featuring a 70mm-high flange. Plates are bolted without penetrating the inner/outer walls of the corrugated structure, transforming circumferential connections into a single linear leakage path (eliminating point leaks). Even under compression or tension, bolts remain fixed within holes, preventing displacement.

In this project, outward-flanged flanges connect corrugated steel culvert sections. Additional sealing measures are applied:

Seal strips and adhesive at joints between sections, couplings, flanges, and overlapping plates. An external waterproof layer using self-adhesive metalized aluminum foil membrane.

corrugated metal culvert segments are not pre-fabricated. For diameter changes, branches, or transitions, custom parts like reducers or tees are required. In design:

The bend radius is determined based on the effective length of each segment (typically under 1.15m).Multiple segments are connected via bolts through flange plates to form a complete pipeline. To prevent water flow from deforming flange joints at bends, anchor blocks are installed to limit horizontal displacement

Corrugated steel culverts are currently underutilized in hydraulic engineering, with no standardized industry design guidelines. However, their practical advantages—such as cost efficiency and rapid installation—will drive broader adoption in water management projects.

This project represents the first urban flood control application of large-diameter, long-span assembled corrugated metal culverts. By using this system, construction costs and timelines were significantly reduced. The success of corrugated steel culverts in this hydraulic project highlights their potential for future infrastructure solutions.