One of the key strengths of the UPP® pipework system is in the choice of materials which bring the ideal balance between robust design and flexibility. The following will detail the effects of deformation translated into strain caused by ground movement.
GROUND MOVEMENT EFFECTS
Two types of deformation can be caused by ground movement, these are bending and linear tensile deformation that comes from two fixed points being moved away from each other.
- As even the larger diameters of UPP® pipe can be formed into a coil, the bending caused by ground movement would not be sufficient to damage the pipe.
- Linear tensile deformation can however be translated into strain on the pipe, the worst case for this can be demonstrated by the following equation:
- Ɛ = Strain caused by deformation
- δ = Design Stress of Polyethylene, (PE80 = 8Mpa divided by safety factor 1.25 = 6.4Mpa)
- E = Creep Modulus, (Assuming the worst case is 3 minutes after exerted load = 700Mpa)
Therefore, the admissible ground movement for Polyethylene pipe is 0.9% which equates too 9mm for each 1metre of pipe or 9cm for each 10 meter run of pipe. Due to the way that Polyethylene relaxes over time following deformation these figures would increase to 16mm for each 1 meter or 16cm for each 10 meters after approximately 100 hours
- UPP® pipework is capable of withstanding the bending caused by general ground movement.
- Even from very conservative calculations a ground movement causing linear tensile deformation of around 1% is well within the capability of the construction of UPP® pipework.