| Bucket foundations have been widely used in ocean engineering due to their advantages of saving cost,shortening installation time and better bearing capacity.A series of problems in the production,installation,working and reutilization of bucket foundations have also become the focus in the academic and engineering fields.Among them,the installation and post-installtion stability of bucket foundation are the key and difficult problems in the design and construction.On one hand,the penetration resistance,which is influenced by factors such as end bearing capacity factor,soil properties and soil flow mechanism,affects the behavior of penetration directly.At the same time,due to the effect of squeezing with the penetration of wall in the soil,soil heave in the bucket will happen and affect the depth of installation.On the other hand,the stability of the foundation affects the safety of structures,but in most previous numerical studies of bearing capacity,the penetration effect after installation was neglected.In fact,the phenomena of soil heave and soil softening around bucket wall during installation may affect the bearing capacity of foundation.Based on this background,this paper has carried out a series of researches on the installation of bucket foundations and their stability after installation.The main contents are as follows:(1)A user subroutine VUSDFLD was used in the Couple EulerianLagrangian(CEL)finite element method and was verified by comparing the CEL result with theoretical result,which implemented the linear distribution of soil strength and the flow of soil strength considering strain softening and rate model.The introduction of free surface boundary and soil strength profile from Euler model to small strain Lagrange model was realized by graphical interface processing and interpolation in order to calculate the post-installation bearing capacity.(2)The installation of the bucket foundation in centrifuge test was simulated by CEL method,and the exactness of the simulation was also verified.The penetration resistance of the foundation and soil heave were investigated under different parameters.Base on the CEL results,the calculation formulae of end bearing capacity coefficient and resistance from bucket walls were modified under different parameters.The corrected formulae for total penetration resistance of foundation penetration was given.The formulae for predicting the volume and the height of soil heave was established.(3)The penetration effects in the installation of bucket foundation were analyzed.Then the influence of the penetration effects on the bearing capacities of the bucket foundation post installation were studied by comparing with that of wish-in-place foundation.The mechanism of interaction between structure and soil was observed,and the result of penetration effects on bearing capacity of foundation was explained.(4)The penetration effects on the bearing capacity of foundation under different parameters were studied systematically.The influence of penetration effect on both uniaxial bearing capacities and the HM failure envelops of foundation were analyzed.According to the analysis results,the formulae for calculating post-installation uniaxial bearing capacity and HM failure envelopes of bucket foundations were fitted. |
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