Numerical Simulation Of The Influence Of Squeezing Effect On The Pull-Out Performance Of Rotary Squeezed And Expanded Cast-in-Place Pile

Rotary squeezed and expanded cast-in-place pile is a kind of variable cross-section pile with great application prospect.It changes the bearing mechanism of traditional straight piles in terms of resistance to pull,and has excellent pull resistance characteristics.There is basically no research on the influence of the squeezing effect on the pull-out performance of the rotary squeezed cast-in-place pile.Value of ultimate bearing capacity in existing codes are all based on the straight piles plus the relevant experience bearing capacity of the bearing plate,without considering the impact of squeezing effect on bearing capacity,which leads to a big difference between the bearing capacity in engineering design and the actual bearing capacity.Based on relevant research at home and abroad,this paper uses ABAQUS,adopts the hypoplastic constitutive model,determines the relevant parameters of the hypoplastic model through laboratory tests,and uses numerical simulation to study the effect of squeezing on the bearing capacity of rotary squeezed cast-in-place piles.At the same time,the load transfer mechanism related to the extruded plate pile is analyzed.Finally,the numerical simulation results are verified through indoor small-scale model tests,which provides some suggestions for future engineering design.The research content and related conclusions of this article are as follows:(1)The relevant parameters of the hypoplastic model are measured through experiments,and the subroutine VUMAT of the hypoplastic model is embedded in ABAQUS/Explicit.The ALE meshing method of ABAQUS is used to form a numerical model of the extrusion effect process.And the numerical simulation of the process of squeezed disc forming is carried out,and the changes of the physical and mechanical forms of the soil around the pile at different stages in the process of squeezed disc forming are analyzed.The results show that the physical state variables of the soil around the pile are symmetrical along the horizontal path of the disk tip,and with the extrusion process,the influence range of physical state variables is increasing.(2)The influence of different pile parameters and the squeezing effect on the soil around the pile under the initial density of the soil around the pile is studied,and the pile parameters include the angle and the depth of the plate.Through the study,it is found that the buried depth of the disk has no effect on the physical state variables of the soil around the pile,while the effect of the disk angle on the physical state variables of the soil around the pile is mainly manifested in the vertical direction,and it has no effect on the horizontal direction.The initial compactness of the soil around the pile has a greater impact.The greater the initial compactness is,the larger the impact of the squeezing effect on the physical state variables of the soil around the pile is.(3)The mesh and physical state variables after extrusion are imported from ABAQUS / explicit into ABAQUS / standard,and the uplift simulation of pile is carried out.The results are compared with the cutting pile Through research,it is found that When the compactness of soil around the pile is high,the ultimate bearing capacity of the pile can be increased by 30% due to the compaction effect,and it can also be increased by more than 20% when the compactness is relatively small,and the improvement of the bearing capacity of the pile is mainly reflected in the improvement of the disk resistance,while the improvement of the lateral resistance is relatively small.