Numerical Study On The Characteristics Of The Seepage And Penetration Resistance Of Bucket Foundation During Suction Installation

Suction bucket foundation is a new type for offshore platform which has a goodprospect of application and extension. Because of its advantages such as convenientconstruction, stablity, environmental protection and low cost, the bucket foundation iswidely used as the base of offshore platform, offshore wind turbine, anchor bankprotection, etc. Suction-assisted penetration is the outstanding characteristic of bucketfoundation, and the quantity and process of applied suction directly concern whetherthe foundation can be installed smoothly and meet the load capacity or not. This thesisstudies the seepage field around the bucket during installation and the penetrationresistance in methods of theoretical analysis and numerical simulation, concentrationboth on steel thin-walled and concrete thick-walled bucket foundations. The maincontents are as following:(1) The characteristics of the seepage fields in varieties of penetration depths arestudied and the seepage path length and critical suction are calculated in use of thefinite element method. The calculating formula of critical suction for both steelthin-walled and concrete thick-walled cases is established respectively under thecontrol of exit hydraulic gradient, which can be used to guide the installation andconfirm the critical suction.(2) The installation process of bucket foundation is actually a flow-soil couplingprocess and therefore the seepage field is influenced by multiple factors. This thesisalso studies the effects of the variation of permeability coefficient and layered soil,which widens the practice range of the result of the study.(3) According to the features of large soil deformation and nonlinearity oflarge-scale concrete bucket foundation penetration process, an axial symmetricalflow-soil coupling model is established based on the CBF-3-150Complex BucketFoundation using finite element method, in order to analyse the variations ofpenetration resistance in both jacked-in case and suction-assisted case. Thepenetration resistance characteristics of thick-wall bucket bucket foundation areattained through comparision with those of the thick-wall. Then two work conditionsare set up in which the effect of suction are analysed.