What Does Buoyancy Loads Mean?
Pipe buoyancy can be defined as the tendency of a buried pipe to float. The buoyancy depends on the type and weight of pipe material used, weight of the liquid carried by the pipe, the volume of water that the pipe can displace, and the weight of the backfill material.
Lighter pipe materials such as high density polyethylene (HDPE) and polyvinyl chloride (PVC) have a greater tendency to float than reinforced concrete pipes because of its weight.
Where pipe deflection has damaged the pipe, trenchless rehabilitation methods may not work and trenching may have to be done in the affected area to rectify the problem.
Trenchlesspedia Explains Buoyancy Loads
The tendency of a pipe to float due to buoyancy exists especially in areas where the the pipe is buried under water, water table is high or where the pipe is near stream crossings or in a flood plain.
When the water table reached above the pipe invert level, the pipe will have a tendency to float. When this water is displaced by the pipe, there is a buoyant or upward force acting on the pipe.
This upward acting force is equal to the weight of water displaced. Flotation will occur when the buoyant force is greater than the weight of the pipe displacing the water.
This fact should be considered for choosing the appropriate pipe material where such phenomenon is likely to occur.