Research On Compaction Effect And Bearing Capacity Of The Pre-stressed High Strength Concrete Nodular Pile In Soft Areas

In soft soil areas,the bearing capacity of traditional pre-stressed high-strength concrete(PHC)pipe pile is hampered by poor geological properties and low shear strength of the soil.The pre-stressed high strength concrete nodular pile(PHDC)pile is a new type of PHC pile with variable cross-section,and it can promote the shaft capacity of the pile owing to the nodules along the pile shaft.In order to investigate the bearing capacity,time effect and compaction effect of PHDC pile in soft soil,a series of field tests were carried out and the finite element program ABAQUS was also used to simulate the soil compaction effect in the PHDC pile installation process as well as its load transfer mechanism.The main research work and conclusions are as follows:1?A group of field tests were conducted to investigate the compressive bearing properties of PHDC pile and PHC pipe pile.The results showed that the soil around PHDC pile were greatly disturbed during penetration process,and the time effect on bearing capacity was obvious;Load-displacement curve of PHDC pile was more smooth;Nodules along PHDC pile shaft can increase the bearing capacity of pile.2?The finite element program ABAQUS was used to simulate and calculate the bearing capacities of PHDC pile and PHC pipe pile,respectively.The results showed that the strength of the soil around the PHDC pile was only recovered to about 1/2 of the intact soil strength after being allowed to cure for 40 days;The shaft resistance of pile increased significantly with the increase of soil strength;Nodules along the PHDC shaft accounted most of the shaft resistance of pile.The stress behavior of the lateral soils beside PHDC pile was analyzed through the simulation results.The changes of soil's displacement and stress around the pile were closely related to nodules.The influence of the nodule form,nodule diameter,and nodule vertical spacing on the compressive bearing capacity of the PHDC pile was analyzed by changing the parameters.The bearing capacity of PHDC pile increased with the diameter of nodules increased,but decreased with the vertical spacing of nodules increased.3?The Coupled Eulerian-Lagrangian(CEL)method was used to simulate the pile driving process.Firstly,the reliability of the model was verified by stability analysis.Then,Contrastive analysis was made on the penetration resistance of piles,the soil radial stress,the soil radial displacement,and the surface heave.The results showed that the resistance of PHDC pile was greater than that of PHC pipe pile during penetration;Nodules caused stress fluctuations in the soil at a certain horizontal extent around the pile;Surface soil heaved obliquely upward;The range of the radial displacement of the soil around the PHDC pile was similar to that of PHC pipe pile.