Model Test On Vacuum Penetration And Pullout Of Low Skirted Suction Caissons

In order to improve the bearing capacity of the skirted suction caisson,make it easier to penetrate and better protect the soils around the barrel from the ocean current,this paper proposes a new model of the low skirted suction caisson.In order to verify the rationality of the new model of the low skirted suction caisson,respectively make the traditional single suction caisson model,ordinary skirted suction caisson model and the low skirted suction caisson model to do the contrast experiment.In order to simulate ocean soil,a method of underneath vacuum preloading put forward in this paper,can quickly consolidate soft soil and save time.Using this method,the foundation soil can be well simulated and its strength increases along the depth.Through the SEM image and permeability analysis,it is concluded that the soil’s physical property indexes and seepage stability is good.Penetrated the suction caisson models of different specification by vacuum method into the soil,and then studied the low skirted suction caisson’s feasibility by the comparative way.Penetrating the caisson with double barrel of vacuum pressure can effectively reduce the height of “soil plug”.The penetration resistance was analyzed,and a formula was put forward by fitting the experimental data.It is concluded that the formula is more suitable for the test condition.Then,combined with practical engineering of suction caisson,by 45 ° pullout test and the finite element analysis,the bearing capacity of the suction caisson was studied,and the rationality of the low skirted suction caisson was verified.Finally,get the following main conclusions:(1)During the penetrating course of the suction caisson model by vacuum method,“soil plug” phenomenon is inevitable;(2)The penetration depth of low skirted suction caisson is deeper than ordinary skirted suction caisson;(3)The low skirted suction caisson put forward in this paper can effectively reduce the height of “soil plug”;(4)The formula obtained from fitting the experimental data is suitable for the soil whose strength increase along the depth.So it is more closer to the actual engineering;(5)The bearing capacity of the low skirted suction caisson is superior to the ordinary skirted suction caisson according to the 45° pullout test;(6)The two bearing capacity—oblique displacement curves respectively obtained from the model test and PLAXIS 3D are highly consistent.So the rationality of the pullout bearing capacity is verified.