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Against the background of strengthening the marine industry, China’s marine resource development activities have gradually extended to the deep sea. However, due to harsh geological conditions, major submarine geological hazards pose constraints on marine resource evelopment and engineering. It is necessary to comprehensively understand the typical characteristics and causallaws of submarine geological hazards and summarize the monitoring techniques and methods for typical submarine geological hazards. This study provides an overview of the research history of submarine geological hazards and their monitoring. It summarizes the common types and characteristics of submarine geological hazards, and reviews the research on the mechanisms of submarine geological hazard evolution as well as the progress in monitoring techniques and networks for submarine geological hazards. The study suggests that it is important to improve the evaluation theory and methods of submarine geological hazards in circumcontinental shelf basins, strengthen the study of disaster mechanisms and prediction for these hazards, and conduct research on detection and monitoring methods and precursory identification of submarine geological hazards to enhance our understanding of key scientific issues. Furthermore, the study emphasizes the need to establish a comprehensive database of submarine geological hazards in the circumcontinental shelf basins, create a detailed information repository of submarine resource distribution and engineering facilities in the South China Sea’s circumcontinental shelf area, develop visualization and simulation techniques for the dynamic evolution process of submarine geological hazards, and construct a multi-level and multi-hazard cooperative monitoring system and early warning network for submarine geological hazards, aiming to overcome key technological bottlenecks.

As a new severe plastic deformation processing technology, friction stir processing (FSP) has a very broad application prospect in microstructure modification of materials, preparation of fine - grained superplastic materials and improvement of comprehensive properties of materials. Compared with the specimens processed by normal friction stir processing (NFSPed), the grain sizes of the specimens treated by submerged fiction stir processing (SFSPed) were smaller, the microstructure was compact and uniform, and the microhardness, tensile rate and wear resistance were all greatly improved. Moreover, the specimens treated with double - pass submerged friction stir processing had smaller grain sizes, more compact and uniform microstructures and higher tensile rates than that treated with single - pass submerged friction stir processing. In this paper, the technical characteristics of submerged fiction stir processing were reviewed and the evolution of microstructure and mechanical properties of magnesium based alloys after FSP under different processing conditions were compared. At the same time, the research progress and deformation mechanism of superplasticity of magnesium alloys processed by submerged fiction stir processing were introduced, and furthermore, its industrial application was prospected.

Bioclogging is a commonly encountered operational issue that lowers hydraulic conductivity and the overall performance of the infiltration systems. In this paper, a novel processing for alleviating bioclogging by filter media surface hydrophobic modification was presented. Two-dimensional porous media cells were used to observe the influence of hydrophobic modification on biofilm growth in the pore structure. Moreover, two continuous-flow columns packed with gravel, one of which half gravel was hydrophobically modified, were operated with artificial wastewater to verify the effect of hydrophobic modification on bioclogging alleviation. The results showed that the biofilm growth in the cell with hydrophobic modification was slow, and the biomass was less and liable to wipe off after hydrophobic treatment. Meanwhile, the hydraulic efficiency of the flow seepage field was also improved after hydrophobic treatment. The column tests results showed that the hydraulic conductivity of the filter bed with hydrophobic modification (Column B) decreased more slowly than that of another without hydrophobic modification (Column A). Column B had the hydraulic conductivity (k) of 0.66 cm/s in the final stage of the experiment, while the k of Column A was 0.14 cm/s. It verified that hydrophobic modification of partial filter media can alleviate the bioclogging problem of the infiltration systems to some extent. The results provide a new idea and potential technical support for solving bioclogging problem. [ABSTRACT FROM AUTHOR]