STABILISATION OF OFFSHORE MARINE PIPELINES BY DUMPED STONE

Tests were carried out on a scale model of a rock berm in a wave-current flume to determine the resistance of the berm to damage from combined wave and current action. The range of tests covered many of the situations possible in the field and serves to aid in the design of pipeline protection systems. Two distinct mechanisms of berm damage were observed. The first was damage on the downstream face of the berm caused by the formation of a vortex and the second was damage due to excessive bed shear stress causing rocks to dislodge from the berm. These mechanisms can occur individually or simultaneously to cause unacceptable damage to the berm. The results are presented as a design chart, indicating under what conditions damage to a rock berm can be expected to occur and the extent of the expected damage where it does occur.