A Novel Autonomous Inspection System of USV for Submarine Buried Pipeline

The conventional method of surveying utilizing manned vessels requires a large investment of labor-intensive and time-consuming efforts. With the phenomenal progress of unmanned surface vessels (USVs), they have become a useful tool for surveyors and engineers who have been seeking a more productive and low-cost method as an alternative. This paper depicts a novel design of USVs for autonomous detection and recognition of buried submarine pipeline. The design adopted a parametric subbottom profiling system with embedded algorithms for path planning, autonomous obstacle avoidance, and autonomous pipeline recognition and navigation. The pipeline detection is based on the analysis of quadratic functions generated by the subbottom data set. Compared to the conventional method, the use of USVs equipped with subbottom profiling system turns out to be more useful and efficient for accurate detections of submarine pipeline.

Pore pressure on a submarine pipeline in a cross-anisotropic nonhomogeneous seabed under water-wave loading

Conventional investigations for the wave–seabed–pipe interaction problem have dealt with a uniform and isotropic seabed, despite the influences of anisotropic soil behaviour and variable soil characteristics. This paper proposes a finite-element model to investigate the effects of cross-anisotropic soil behaviour and variable soil characteristics (permeability and shear modulus) on the wave-induced oscillatory pore pressures on a submarine buried pipeline. The present model is verified with previous experimental data for the case of a uniform and isotropic seabed. The numerical results indicate that the effects of cross-anisotropic soil behaviour and variable soil characteristics on the pore pressure around the pipe surface cannot always be ignored. The maximum relative difference of pore pressure may reach 10% of the amplitude of the wave pressure at the seabed surface.Key words:pore pressure, pipeline, cross-anisotropic, nonhomogeneous