Interaction Between Soil And Underwater Excavator

Underwater excavator refers to excavating apparatus that installed in a variety ofunderwater equipment, widely used in the field of water transportation, dredgingproject used for port channel construction, sampling used for seabed geologicalexploration and research, underwater archeology, etc. The interaction betweenunderwater excavator and underwater soil is one of key issues need to be consideredin the design of underwater excavator, meanwhile, the performance and efficiency ofequipment will be affected by the digging resistance. The interaction betweenexcavator and soil will be analyzed by using explicit dynamic software ANSYS/LS-DYNA.Two kind of underwater excavators will be selected, one with dredging grab, andthe other one with columnar sediment sampler. The research is based on two differentexcavating method, as well as different material properties between excavator and soil.Specific contents are as follows:Firstly, impact kinetic theory of soil excavation is analyzed, and then finiteelement calculation equations of their interaction are concluded. General physical andmechanical properties with underwater soil are summarized. According to stress-strainproperties for soil, constitutive relation of two kind of ideal elastoplastic models arecomparative analyzed, and one will be selected for appropriate model of followingfinite element analysis.Secondly, dredging grab for the study. As a reference to the onshore disband grab,the structure design of grab jaw and solid modeling are needed. The force situation forits excavating will be taken into consideration, and the situation of all each resistancewith the change of excavation depth for designed grab can be calculated by usinggeneral experience formulas. The finite element model is built in softwareANSYS/LS-DYNA, and then initial angular velocity is imposed. The resultscalculated by LS-DYNA are imported into post processing software LS-PREPOST, sothat the distribution of von-mises stress with grab and soil, contact force of system, energy consumption can be obtained.Thirdly, columnar sediment sampler for the study. Considering its workingmanner, its resistances against soil are concluded. The finite element model is built insoftware ANSYS/LS-DYNA, and then time-displacement load is imposed so that thesampler is able to insert vertically into underwater soil for sampling. Similarly, theresults calculated by LS-DYNA, and the distribution of von-mises stress, contactforce of system, energy consumption can be achieved.Lastly, my work is summing up, as well as its feasibility of the analytical methodis verified, and conclusion maybe provided for optimal design for material parameterswith underwater excavator. Meanwhile, both the limitations of my study and futurework will be pointed.