A Study On Numerical Methods For Analyses Of Bearing Capacity Behaviour Of Friction-Type Sinle Pile Under Combined Load

It is complex that the bearing mechanism of the single pile under combined load. The current approach is that assume no effect between each load component. The method to design pile foundation under composite load is what according to the small deformation superposition principle, which does not quite conforms to the actual loading situation of single pile. Therefore it is necessary to further study load-bearing characteristics of combined load pile. This article used the finite element method combined with the existing test data to research the load-bearing characteristics of friction-type single pile under combined load. The main research work and conclusions are as follows.By means of retrieval algorithm to adjust parameters of finite element model. The model computation is agreed with the experimental results, which verifies the reasonable effectiveness of the model. For the sake of studying the bearing mechanism of pile under the single direction load, this paper discusses the relationship between ultimate bearing capacity of friction-type single pile and influence factors such as the friction coefficient of piles-soil, pile-soil stiffness ratio, pile diameter, length-diameter ratio, internal friction angle of sandy soil. The results show that vertical ultimate bearing capacity of single pile increases in approximate linear distribution with the increase of friction coefficient; with a wide difference for pile-soil stiffness ratio (i.e., large elasticity modulus of soil around pile), horizontal bearing capacity is controlled by the strength of soil turn to be controlled by the bending strength of pile material; large diameter help to improve the bearing capacity of the pile foundation; with increasing the length-diameter ratio in a certain range, the vertical bearing capacity of single pile can be improved, and have no effect on the horizontal bearing capacity;horizontal displacement of pile-top decreases approximately in a quadratic curve with the increase of internal friction angle of sandy soil.In order to research the influence of loading sequence of the single pile bearing capacity, design five loading scheme of model to compute and study. The vertical load will make more the lateral displacement at the pile top when it was applied after the lateral load. While the lateral load is helpful to reduce the vertical settlement at the pile top. On the other hand, the horizontal load increase the vertical settlement at the pile top when it was applied after the vertical load.For discussing the bearing capacity of single pile under combined load, joint use swipe and fixed displacement ratio method to compute finite element model. Discusses the failure envelope curves of V-H,V-H,H-M loading plane respectively, the compute curves are in good agreement with predecessor research results. Further analysis the effect of different diameter on the failure envelope curve of single pile under V-M load space. Research findings show the pile diameter had no effect on the shape of failure envelope, and affects only the size.To discuss the character of V-H-M failure envelope, compute the envelope and analysis the results. It shows that different vertical load had on effect on single pile H-M failure envelope curves.