Finite Element Study On Time Effect Of Soil Strength Between Sand Compaction Piles

With the rapid development of China’s national economy,the ground environment of inland projects is constantly deteriorating,gradually showing the characteristics of less soil resources,expensive construction costs,and high construction difficulties,forcing us to turn our attention to the construction of the ocean.As a commonly used foundation treatment technology,sand compaction pile(SCP)has unparalleled advantages in foundation treatment due to its characteristics such as fast construction speed,wide application range and obvious reinforcement effect.Compacted sand piles have been widely used by countries all over the world to strengthen large-scale foundations under offshore water.China’s underwater construction sand pile technology started late,but progressed quickly.China’s underwater construction sand pile technology started late,but progressed quickly.It has been successively in the Lianyungang embankment project,the second phase of the Shantou port Zhuchi port area project,the Tianjin port terminal project,the Yangshan deep water port terminal project,the Hong Kong Zhuhai Macao bridge island tunnel project was successfully used.The construction of SCP in soft clay foundations will generate a large amount of excess pore pressure.As the excess pore pressure dissipates,the effective stress of the soil between the piles gradually recovers and increases,and the strength also recovers and increases substantially,up to twice the initial strength.However,the existing design codes do not take into account the effects of soil strength and timeliness.In this paper,the multistage Euler-Lagrange numerical simulation calculation method(MSEL)is proposed to carry out the finite element analysis of the pile-consolidation process of the underwater SCP,focusing on the analysis of the pile circumference during the pile-consolidation process The change of soil stress state and the strength growth law of soil between piles after consolidation process.Firstly,the numerical simulation study of single SCP is carried out,and the results show that squeezing the clay is the cause of many installation effects.Among them,the surface soil shows uplift on the surface of the soil;the middle clay shows the increase of lateral stress;the deep soil shows the accumulation of excess pore pressure.During the consolidation process,the excess pore pressure of the clay dissipates with the consolidation time.The greater the depth of the soil body and the closer it is to the side of SCP.The more excess pore pressure is generated,the more the effective stress of the clay increases.The undrained shear strength of the clay body increases rapidly after consolidation begins.Then the numerical simulation study of SCP group was conducted,and it was found that the soil strength distribution after the construction of SCP was related to the pile formation sequence,and was affected by the strength superposition effect and the sheltering effect.The reason for the change in the strength of the soil between SCPs mainly comes from two aspects,partly from the flow deformation of the clay during the pile formation process,which decreases exponentially with the depth of the soil.The other part comes from the effective stress growth during the consolidation process,which decreases linearly as the number of piles increases.Important influencing factors that affect the change of soil strength include soil constitutive parameters,diameter,area replacement ratio,and layout of SCP.Finally,the parameter analysis is carried out according to the above influencing factors,and the formula for predicting the postinstallation strength of the clay between SCPs is proposed.