Review and Analysis of Key Techniques in Marine Sediment Sampling

Deep-sea sediment is extremely important in marine scientific research,such as that concerning marine geology and microbial communities.The research findings are closely related to the in-situ information of the sediment.One prerequisite for investigations of deep-sea sediment is providing sampling techniques capable of preventing distortion during recovery.As the fruit of such sampling techniques,samplers designed for obtaining sediment have become indispensable equipment,owing to their low cost,light weight,compactness,easy operation,and high adaptability to sea conditions.This paper introduces the research and application of typical deep-sea sediment samplers.Then,a representative sampler recently developed in China is analyzed.On this basis,a review and analysis is conducted regarding the key techniques of various deep-sea sediment samplers,including sealing,pressure and temperature retaining,low-disturbance sampling,and no-pressure drop transfer.Then,the shortcomings in the key techniques for deep-sea sediment sampling are identified.Finally,prospects for the future development of key techniques for deep-sea sediment sampling are proposed,from the perspectives of structural diversification,functional integration,intelligent operation,and high-fidelity samples.This paper summarizes the existing samplers in the context of the key techniques mentioned above,and can provide reference for the optimized design of samplers and development of key sampling techniques.

Design and Experimental Study of Pressure Compensation System for Full-Ocean-Depth Gas-Tight Sediment Sampler

Aiming at the requirement of the full-ocean-depth(operating water depth 11000 m)manned submersible to carry out the gas-tight sampling operation of the abyss seabed sediment,a kind of full-ocean-depth carrier submersible mechanical hand-held,full-ocean-depth gas-tight sediment sampler(GTSS)with the function of pressure-retaining and coring is designed.Firstly,the volume change model of pressure compensator is established,and it is pointed out that the volume of pressure compensator is about 16.14%equal to the volume of gas-tight sediment sampler(GTSS).Secondly,the pressure compensator is analyzed and calculated,and the relationship between the precharge pressure of the pressure compensator,the nominal volume of the pressure compensator and the pressure holding effect of the gas-tight sediment sampler(GTSS)is studied.The results show that with the increase of gas precharge pressure in the pressure compensator,the final pressure of the sampler also increases.Under the same precharge pressure condition,the larger the nominal volume of the pressure compensator,the greater the final pressure of the sampler.Finally,the air tightness test method is designed by using the developed gas tightness sampler of the full-ocean-depth product,and the change of the final pressure in the gas tight sampler under different precharge pressure is observed.The test results are consistent with the simulation results,indicating the correctness of the pressure compensation system(PCS)model.

Simulated and Experimental Study of Seabed Sediments Sampling Parameters Based on the VOF Method

Sediments in the seabed hold vital clues to the study of marine geology,microbial communities and history of ocean life,and the remote operated vehicle(ROV)mounted tubular sampling is an important way to obtain sediments.However,sampling in the seabed is a particularly difficult and complicated task due to the difficulty accessing deep water layers.The sampling is affected by the sampler’s structural parameters,operation parameters and the interaction between the sampling tube and sediments,which usually results in low volume and coring rate of sediments obtained.This paper simulated the soft viscous seabed sediments as non-Newtonian Herschel-Bulkley viscoplastic fluids and established a numerical model for the tubular sampling based on the volume of fluid(VOF)method.The influence rules of the sampling tube diameter,drainage area rate,penetration velocity,and sediments dynamic viscosity on coring rate and volume were studied.The results showed that coring volume was negatively correlated with all the parameters except the sampling tube diameter.Furthermore,coring rate decreased with increases in penetration velocity,drainage area rate,and sediments dynamic viscosity.The coring rate first increased and then decreased with increasing of the sampling tube diameter,and the peak value was also influenced by penetration velocity.Then,based on the numerical simulation results,an experimental sampling platform was set up and real-world sampling experiments were conducted.The simulation results tallied with the experimental results,with a maximum absolute error of only 4.6%,which verified that the numerical simulation model accurately reflected real-world sampling.The findings in this paper can provide a theoretical basis for facilitating the optimal design of the geometric structure of the seabed sediments samplers and the parameters in the sampling process.