Pipe Classification

Selection of Grandpipe GRP pipes is based on stiffness and pressure class requirements.

Stiffness of GRANDPIPE GRP pipes is selected from one of three stiffness classes listed below. Stiffness class represents pipe's minimum initial specific stiffness as EI/D³ in N/m² (Pa).

Stiffness is defined according to two parameters. These are: (1) burial conditions, which include native soil, type of backfill and cover depth and (2) negative pressure, if it exist. Native soil characteristics are rated according to ASTM D1586 standard penetration test. Some typical soil blow count values relative to soil types and density are given following table.

A wide range of backfill soil types are offered in tables to allow each installation to be customized providing the most economical installation. In many instances, native trench soils can be used as pipe zone backfill. Maximum allowable cover depths for threee different stiffness classes in six native soils groups are illustrated in following table - assuming standard trench construction, an allowable long term deflection 5 % ( DN 300 – 4000 mm) – 4 % (DN 100 – 250 mm), with consideration of traffic loads.

The second parameter for pipe stiffness class selection is negative pressure. If it exists, following tables show which stiffness to select for various amounts of negative pressure and burial depths for average native and backfill soil conditions.

Stiffness selected should be higher than determined value to suit negative pressure and burial Long life and good performance of Grandpipe GRP pipes can only be achieved by proper handling and installation of the pipes. For owners, engineers and contractors, it's important that GRP pipes can be obtained excellent performance when recommended installation procedures are applied by using suitable bedding and pipe backfill support. Engineers have found through considerable experience that compacted granular materials are ideal for backfilling GRP pipes. Together pipe and embedment material form a high performance pipe-soil system. For complete installation instructions, consult to Grandpipe Field Department.

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