Analysis On The Penetration Resistance During Self-weight Penetration And The Characteristics Of Seepage During Suction Installation For Bucket Foundation

A smooth installation of a bucket foundation is the prerequisite to implement its engineeringapplications. The process of installation for bucket foundation consists of two stages: sinkingunder self-weight and then continue sinking by negative pressure. Using the finite element methodas well as the model test data, this thesis firstly studies the squeezing effect and penetrationresistance for bucket foundation during self-weight penetration ether in sand or in clay. And thenthis thesis studies the seepage field around the bucket and the critical negative pressure duringsuction. The main contents are as following:(1)At first, we study the jacked penetration process in sand for bucket foundation. Aiming atthe grid distortions during penetration, this thesis implemented a dynamic simulation of the wholeprocess for bucket foundation installation using an arbitrary Lagrangian–Eulerian method. Thismethod was confirmed to be reliable as the numerical analysis results are in good agreement withthe model test data. The mechanism of the soil squeezing effect of soil inside and outside thecylinder and the―soil arch‖effect were elucidated by analyzing the soil squeezingdisplacement,stress distribution and the max principal stress vector both inside and outside thecylinder.Then sensitivity analysis for parameters such as dilation angle, internal friction anglewere performed to offer reference for penetration simulation. At last, a penetration resistanceformula for bucket foundation considering the effect of soil squeezing was proposed and sidefriction resistance and tip resistance calculated by the formula were analyzed.(2)A dynamic continuous sinking process for bucket foundation installed in clay wasestablished referring to a model test of single cylinder penetration. The mechanism of the soilsqueezing effect was elucidated by analyzing the soil squeezing displacement and stressdistribution inside and outside the cylinder.The proportion of side friction resistance and tipresistance were obtained from the numerical analyze results. Finally, a finite element model wasestablished based on the complex bucket foundation in order to study the characters of penetrationresistance.(3) The installation process of bucket foundation is actually a flow-soil coupling process andtherefore a seepage-stress coupling transient analysis is needed. A series of finite element modelwith different permeable coefficients using seepage-stress coupling transient method wereestablished to analyze the pore pressure distribution of soils whose permeable performance variesfrom relative impervious to medium permeable. The pore pressure distribution and criticalnegative pressure of steady analysis and transient analysis were compared then and showed thecritical negative pressure was higher using steady method. At last, a series of finite elementmodels were established for the bucket foundation with bulkheads in it.Then a comparison waspresented between the critical negative pressure of bucket foundation with and without bulkheadsand the results showed that the critical negative pressure reduced with the bulkheads. Additionallythe analysis of seepage during the suction leveling shows that the critical negative droppedrapidly with increasing dip angle. Suggestions for leveling construction were proposed bycompare the critical negative pressure of suction leveling using single bulkhead and using threebulkheads.