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Structural Design & Durability...
The calculation for determining the structural performance of Atlantic CSP is based on the programme “Design of Buried Corrugated Metal Structures” which defines the minimum steel thickness required for a given installation. The programme takes into account the requirements of the Highways Agency BD12/01 specification, relating to depth of cover to the pipe, static and dynamic loads, the I value of the pipe corrugation profile, durability of the coating (allowing for sacrificial steel), soil constraint modulus and the required design life, which is typically 120 years for H.A. projects; however a more valued engineered approach can be applied if a lower design life is acceptable, e.g. 60 years. Atlantic will be pleased to advise on specific installations and supply you with structural calculations to validate our products performance.
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Bedding & Backfill Requirements...
CSP is designed as a flexible structure; the structural calculation therefore takes into account the relationship of the pipe to the surrounding backfill material. As static and dynamic loads are imposed the pipe will attempt to deflect, the compacted backfill will limit this deflection by giving lateral support. Most granular materials, with sufficient compaction, will afford the required values to ensure the pipe is operating within the deflection limits. A typical detail should be 20mm granular bedding material to the required depth (bed depth is generally 10% of the pipe diameter) and a backfill of 75mm down, granular material (6M or similar) to 650mm above the pipe crown. The minimum cover depth from finished surface level to the pipe / tank crown will vary, depending on pipe diameter, type of live load and required design life. The use of an R.C. Slab will greatly reduce the depth of cover required, for a given installation. In a non-trafficked, soft landscaped location, the use of selected, non-cohesive as-dug materials may be possible; however consideration should be given to dynamic loading from construction traffic. The minimum distance between multiple rows of pipes and the pipe and existing excavation wall should be sufficient to achieve the necessary compaction.
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