| It has been recognized that offshore wind power is the core of the future nationalenergy strategy, which is favored by the scientists from all over the world. However,its fan base bearing stability analysis under wind loads and wave loads as well as flowloads is a huge challenge for researchers. For the previous fan base, they all have thefollowing three shortcomings: first, the seabed wave erosion around fan base isserious; second, the horizontal load-bearing capacity under the cyclic loading declinesrapidly; third, foundation installation makes enormous disturbance to the marinegeological environment, etc. Focusing on the disadvantages of existing fan bases, anew type fan base-umbrella suction anchor foundation (USAF) was designed anddiscussed in this paper. USAF load-bearing characteristics and dynamic responseproblems were systematically studied through theoretical analysis, model test andnumerical simulation methods. The monitoring and early warning system for USAFwas built using fuzzy mathematics, based on the critical pore pressure ratio principleof soil liquefaction. The main research achievements are as follows:1. In the Yellow River delta area as an example, the design of umbrella suctionanchor foundation was proposed. Then, its design principles, structure advantages,penetration mechanisms, installation methods were illustrated.2. Based on the principle of maximum limit analysis, the damage zones of USAFfoundation were divided into logarithmic spiral slide zone, round table rupture zone,conical rupture zone, branches pressure zone and squeeze failure zone. And on thisbasis, focusing on analysis of soil permission sliding state and licensing velocity field,soil plastic power dissipation and external forces acting power were found byassociating soil strain rate with the motor speed. So that, three-dimensional upperbound method of horizontal bearing capacity for USAF was proposed, which has beenproved to be correct.3. The characteristics of anchor-soil interaction under horizontal static loads/horizontal cyclic loads/vertical drawing loads were researched in soil box testes. Thedisplacement response of USAF was simulated respectively under low frequencyloads and storm surge loads.What’s more, the"segmented phenomenon" in the processof USAF drawing was found and explained. Based on the above phenomenon, a search method for determining USAF ultimate uplift bearing capacity was putforward and verified.4. The dynamic load-bearing characteristics of USAF under wave loads, seismicloads and ice loads were analyzed by using ANSYS. In the process of finite elementsimulation,the different modal vibration mode and vibration regularity of mastercylinder, tube skirt and anchor branches were obtained. Furthermore, the harmonicresponse of USAF structure under the loads of0~130Hz was discussed.In addition,USAF vibration response to wave loads was analyzed based on PSD method.Finally,two kinds of random loads (seismic loads and ice loads) were applied to USAFstructure which vibration characteristics were following researched.5. By using Geo-Studio software the finite element model of USAF wasestablished. Based on numerical simulation results, deformation of foundation, soilfailure mode, the maximum shear stress area and the center of rotation of the anchorbody were analyzed emphatically. The bearing capacity between USAF model andconventional single cylinder suction anchor model was compared, and the resultsshowed that USAF had obvious advantages on horizontal load-bearing characteristics.6. According to advantages of renormalization group theory in critical mutationanalysis, the microbalance unit damage renormalization group model of seabed soilwas built and fracture damage critical probability of structural surface was studied.After that, the relationship of saturated seabed soil macro-liquefaction andmicro-strength was analyzed considering seepage and stress coupling effect.what’smore, the standards of different seabed soils liquefaction and their influencing factorswere found followed by the introduction of a critical pore pressure ratio uw/uf.7. Based on the critical pore pressure ratio principle of seabed soil liquefaction,intelligent monitoring methods and implementation process of early warning systemwere introduced. In monitoring methods, fuzzy mathematics was used to analyze data,and soil liquefaction criterion was established under different disturbance conditionsof USAF. On this basis, the monitoring and early warning system were completed,which has guiding significance for USAF applications. |
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