The elastomer joint gaskets provide ductile iron pipelines with a degree of flexibility which is one of the elements of safety when passing through inconsistent or unstable ground.
A pipeline’s route may pass through inconsistent or unstable ground (marshy regions, subsidence due to pumping underground water, mining areas, consolidation of roadwork backfill, etc.). In each of these cases, it is necessary to assess the potential subsidence and take all precautions to minimize the effect of soil movements on the pipeline. Site measurements are always recommended.
Experience has shown that when soil movements occur, pipes must be able to match the deformation imposed by the mass of moving earth rather than resisting the often considerable mechanical stress (axial and bending stresses). In this respect, PAM socket joints are nil tension and nil bending points, within the range of their joint deflection.
For extensive and uniform subsidence, the joint allows the pipe to function like a flexible chain. Of course, deformation extremes are determined by the maximum admissible deflection and slippage for each joint.
in the event of subsidence causing high extension, one solution may be to anchor the joints and make up for the extension with collars installed at the borders between the stable and unstable areas.