Rigid Pipe Mean?
Rigid pipes are usually made of plain concrete, reinforced concrete, vitrified clay, cast iron and asbestos cement. Rigid pipes have sufficient strength to support loads even if no side support, such as backfill, is provided. However; this load carrying capacity can be significantly increased by providing proper bedding and backfill.
Rigid pipes made of plain concrete are considered as failed if a crack or fracture is observed, however; for reinforced concrete pipes, cracks up to 0.01-inch are considered permissible.
Trenchlesspedia Explains Rigid Pipe
The total load that a rigid pipe can support is called its carrying capacity. When a pipe experiences a dead or live load, the rigid pipe's behavior depends on whether proper bedding and backfill have been provided.
An improperly installed rigid pipe will initially bear the imposed load and the trench walls will support the backfill weight. As time passes, more of the trench load will be transferred to the pipe until failure occurs. The resulting cracks can expose the steel in reinforced concrete pipes to the internal contents of the pipe, leading to corrosion.
Unstable bedding can also cause failure of the pipe by causing gasket compression due to the joint movement caused by vertical movement.