Local scour beneath pipeline with shell-sand mixture seabed
The stability of submarine pipelines is a significant guarantee for the safe operation of marine engineering,and is a key challenge that urgently needs to be addressed in the marine energy and island development.However,the geological environment of the seabed is usually complex,for instance,shell-sand seabed is commonly seen in the coastal area which has an important impact on the safety of submarine pipelines.Therefore,gaining an in-depth understanding of the local scour mechanism of pipelines beneath non-uniform shell-sand seabed is of vital significance for the installation and maintenance of submarine pipelines.Based on two-dimensional flume,equilibrium scour depth beneath submarine pipelines with shell-sand mixture seabed was studied.The results show that mixing of shell and sand will cause the bed surface to the so-called"coarsen"phenomenon,which enhances the stability of the bed surface.Compared to uniform sandy seabed,the shell-sand mixture seabed can reduce the equilibrium scour depth beneath pipeline to a maximum 33%.