Surface Load Mitigation Measures - Best Practice

METHOD	ADVANTAGE	DISADVANTAGE
Reduce the operating pressure of the pipeline.	Provides a direct reduction of the hoop stress due to internal pressure. This reduction allows for additional circumferential stress due to equipment loads	Reduces the beneficial effect of internal pressure on the pipe circumferential bending stresses due to fill and traffic loads. Could reduce the overall capacity of the pipeline and therefore should not be considered as a long term fix.
Limit surface pressures under vehicles (e.g., using floatation tires or caterpillar tracks)	Spreads the surface load over a larger area and reduces the overall load to the pipe.	Depends on equipment. May not be possible or too costly to implement
Consider the beneficial effect of lateral soil restraint on circumferential stress	Has effect similar to pressure stiffening	Requires estimates of soil stiffness parameter, E’
Provide additional soil fill over the pipeline in the vicinity of the crossing	Reduces circumferential stresses due to traffic loads.	Increases circumferential stresses due to fill loads.
Deploy steel plates over the crossing	Easy to install.	Flexibility of steel plates can result in bending of the plate with a corresponding reduction in loaded footprint. Need to consider required thickness.
Deploy timber mats over the crossing area	Provides large loading footprint. Relatively easy to deploy.	Flexibility of timber mats can result in bending of the mats with a corresponding reduction in loaded footprint.
Construct a concrete slab with steel reinforcement over the crossing area	Provides large loading footprint. Slab can provide high bending stiffness	Relatively expensive. Usually reserved for permanent crossings. Slab limits access to pipeline for inspections and repairs.
Construct a short bridge crossing over the pipeline	Completely uncouples the traffic loading from the buried pipeline.	Requires construction of foundation structures. Expensive to construct. Usually reserved for permanent crossings. Bridge structure may limit access to pipeline for inspections and repairs.
Relocate the pipeline	Removes pipeline from loaded area.	Expensive to construct. Usually considered only as a last resort.
Lower pipeline	Reduces circumferential stresses due to traffic loads.	Expensive to perform. Usually considered only as a last resort.