Study On Sinking-resistance And Compaction Effect Of Jacked Pile In Sand

Among all kinds of foundations,jacked pile is favored for their advantages of high construction efficiency,relatively low cost,low construction noise,low vibration,no mud pollution,high bearing capacity.Jacked piles belong to the dump replacement pile,which can squeeze the soil and result in changes in the stress and displacement fields of the sand during pile driving,and has a negative impact on the surrounding structures.Therefore,it is of great significance for practical engineering to analyze and clarify the change rule of compaction effect of pile driving in the process of pile driving and its influence on the surrounding environment before construction.In addition,it is also very necessary for the design and construction of jacked piles to explore the changes of pile force in the process of pile driving.Based on the indoor model test and finite numerical simulation,the key problems of pile-pressing force,pile-driving resistance,pile-driving compaction effect and continuous penetration numerical simulation of jacked pile driving are analyzed.This paper mainly studies the following contents:(1)Sand dropping device was used to prepare sand samples by sand rain method,and suitable sand samples were provided for calibration test of earth pressure box.The calibration test of the earth pressure box on the model pile is carried out by using the self-developed calibration tank of the earth pressure box.The device combines soil medium calibration and air pressure calibration.It not only considers the effect of stress concentration and soil arching in actual situation,but also avoids the lag of unloading response.The ideal calibration results are obtained,which lays a foundation for jacked pile model test.(2)Indoor jacked pile driving model test is carried out by using self-developed static pile driving model test device.The soil pressure at pile side at different depths is measured,and the variation law of pile driving force,pile tip resistance and pile side friction resistance with pile driving depth is explored.(3)Using ABAQUS numerical simulation software,the numerical simulation of continuous penetration of model piles in sandy soil is realized.A three-dimensional finite element model of model pile penetrating into sandy soil is established.Considering the influence of large deformation,displacement nonlinearity,material nonlinearity and soil dilatancy,the ALE numerical method is used to optimize the mesh generation,and the initial in-situ stress balance is carried out.Under Mohr-Coulomb yield criterion,the whole process of static pressure pile is simulated by displacement penetration method.Comparing the simulation results with the model test results,the change law of the two is basically the same,which proves the feasibility of ABAQUS numerical simulation software in jacked piles engineering.Based on this,the finite element model of large-scale jacked piles driving close to the actual project is established.The changes of pile driving force,pile tip resistance and pile side friction with pile driving depth are analyzed,and the changes of soil stress and displacement with different pile driving depth are studied.