Creep is defined as the time-dependent strain and deflection of a material under persistent stress. During creep, deformation of the material (e.g. a buried pipe), progress gradually under a constant load to either equilibrium or fracture. The applied stress in buried pipes that may give rise to creep in buried pipes may come in the form of the weight of soil above the pipe or internal hydrostatic pressure.
Trenchlesspedia Explains Creep
The rate of creep of a material depends on several factors including:
- The material properties
- The applied load (stress)
- Exposure temperature, and
- Exposure time
Creep is usually a concern for engineers during the trenchless installation of pipes, especially when evaluating components under high pressure or temperature. As most pipes are under constant loads, creep can be troubling (especially in plastic pipes) as the time-dependent increase in length can be detrimental to the pipe while in service.
Long-term creep can eventually lead to the formation of cracks due to the exposure of the material to continuous stresses and increased strain.