Offshore underwater artificial structures (e.g., sea transmit pipeline) are susceptible to instability due to long-term hydrodynamic impacts, biological attachment or blockage, which requires regular detection and precise inspection. Grounded in the concept of multi-source data fusion, this study proposes an acoustic-optical multimodal joint diagnostic methodology. By integrating three underwater monitoring technologies—multibeam bathymetry, dual-frequency imaging sonar, and optical imaging from remote operated vehicle (ROV)—an acoustic-optical-topographic comprehensive data evaluation framework is established, with spatiotemporal registration and dynamic quantitative analysis methods for multi-sensor. Field tests demonstrate that this approach enables accurate defect identification in certain complex marine conditions, significantly improves detection efficiency compared to conventional methods, and effectively mitigates reconstruction errors induced by scouring. The findings provide valuable insights for the intelligent operation and maintenance of marine engineering structures such as offshore wind turbine foundations and cross-sea tunnels.

To address the limitation of traditional cross-sectional scanning methods for submarine pipelines, which only capture localized cross-sectional information and hard to detect continuous axial deformation features, this paper proposes a data fusion method based on acoustic sub-bottom profiling that integrates both cross-sectional and longitudinal scanning. By deploying survey lines both perpendicular and parallel to the pipeline axis, and utilizing a parametric sub-bottom profiler combined with a high-precision positioning system, this method enables the simultaneous extraction and comprehensive analysis of multiple parameters, including pipeline inclination, cross-sectional ellipticity, longitudinal elevation deviation, joint misalignment, and external environmental anomalies. Field tests conducted on a water pipeline in the South China Sea successfully identified five types of typical anomalies, including pipeline tilt, depressions, obstacles, and upheavals. The results verify the effectiveness and engineering applicability of the proposed method for diagnosing submarine pipeline stability, providing a reliable technical approach for continuous deformation monitoring and safety maintenance of long-distance submarine pipelines.

Pore structure significantly governs the seepage characteristics of porous media. This study investigates this influence by comparing the infiltration behavior of homogeneous and heterogeneous porous structures through microfluidic experiments and numerical simulations. It constructed one heterogeneous structure derived from real rock cores and four homogeneous structures with regular particle arrangements, all with identical porosity. Heterogeneous structure and homogeneous structure exhibit similar finger-like flow patterns and minimal differences in water saturation. Air displacement in dead-end pores is driven by internal-external pressure differences, with water replacing air only when internal pressure surpasses external pressure. In homogeneous models, water pressure shows pulse-like fluctuations; pressure peaks due to interfacial resistance decrease from approximately 88 Pa to approximately 38 Pa as pore size increases. Meniscus evolution, linked to pore width variations, presents three states: Stretching, equilibrium, and expansion. This study clarifies the dominant role of pore morphology in fluid transport, providing a theoretical basis for optimizing structural design and efficiently regulating seepage processes in engineering applications such as resource extraction and CO₂ sequestration.