Application of GFRP for Unburied Submarine Pipeline in Shallow Water of Coral Islands

Flexible pipelines such as high density polyethylene pipes (HDPE) and bonded pipes for seawater intake systems are often subjected to oscillations, due to the combined action of the wave and current in a shallow water region. Rigid pipe materials like aluminum or stainless steel are not economically viable for a seawater desalination project and steel pipes are susceptible to corrosion. This paper focuses on the application of glass fiber reinforced polymers (GFRP), considering their various merits for submarine pipelines in lieu of other pipe materials. The proposed GFRP pipe cannot be buried because of the coral seabed in the shallow water region and exposed to high marine environmental loads. A new methodology was developed to design the GFRP pipe drawing inference from various standards. A suitable winding angle of 30° and a 18.46-mm wall thickness of GFRP pipe were achieved. Pipe specimens were manufactured and tested to validate the design parameters. This paper mainly focuses on the design process for the GFRP pipeline in complex marine environment conditions, where direct methods and standards are not available for unburied submarine pipelines and qualification of GFRP pipe by conducting laboratory and prototype tests.