Research On No-disturbing Sampling And Truth-preserving Technique Of Deep-sea Seafloor Sediment

The seafloor sediment may maintain gases(especially CH₄,H₂S,H₂) and high concentration of high pressure-hobby microbe.It is essential that sealing the sediment core at in-situ pressure in order to collect the microbe and gases,which would otherwise die or escape from the sediment due to decreasing pressure while the depth becomes small and small.Also,the temperature cannot be held during the process.Besides,the sediment will be disturbed badly while sampling with former traditional deep-sea sediment sample equipment.All of these will lead to the result that the truth and reliability of sediment sample is doubtful.It will form a false judgement for the following process and research of sediment.In this paper,through analysis of disturbances that may be occur in the process of sampling and before sampling,a truth-preserving sediment equipment is proved to be applicable,which is under control of monitor and can achieve to obtain in-situ sediment.The thesis includes six chapters.Chapter 1 introduces the application of the seafloor sediment sampling technology and the concept of truth-preserving sampling. In addition, the development actuality of the deep-sea sediment truth-preserving sampling technique and equipment is mentioned.Finally,the main research contents of this thesis are put forward.In chapter 2,Firstly this chapter analysis the driving method of cylinder liner. On the basis of this,a new hydraulic driving way with pressure-compensation is proposed. Finally,the model of the oil pressure-compensation is established and analyzed in order to reduce pressure variation during the process of sampling.Chapter 3 study the structure of cylinder liner which get rid of petal structure and can reduce the disturbance on sediment firstly. And then mainly research the technique of sample transfer and truth-sealing during the process of sampling. Through illuminating the relationship between the quantities of compensatory seawater and the pressure variation during the process of sampler is raised up, a design rule of the pressure-compensator was put forward to achieve the half-automatic pressure compensation.In chapter 4, the disturbing effects of sampler's mechanical structures are mainly analized and researched. The truth-preserving sample cylinder consists of four parts: the multistage hydraulic cylinder,the thick-wall cylinder,the sediment core and the double-spherical valve. The thick-wall cylinder contains the sediment core and keeps its original pressure. The reliability of sealing structure and the stability of withstanding voltage are most important. In this chapter, the structures of key parts of the truth-preserving sample cylinder are designed, especially the multistage hydraulic cylinder and the double-spherical valve's design.Also, it can be through stress analysis simulation to study the potential plastic deformation of the thick-wall cylinder under high pressure, and then to verify the rationality of thick-wall cylinder.In chapter 5, The global optimum design of overall structure of the no-disturbing and truth-preserving sediment sampling equipment is discussed. In order to reduce the effects of pressure-wave while the simple equipment down to the seafloor, it is must that the cross section of the equipment and every part decrease as much as impossible. This chapter arranges the equipments reasonably and checks the strength of the frame structure.In last chapter, there is a conclusion of the research fruits of this thesis and the further study direction is brought forward.Also the innovation during the thesis is stated again.