Study On Bearing Capacity Of Branch Pedestal Pile In Transmission Line

Transmission lines often need to pass through the soft soil area with poor soil quality,and bear the influence brought by the special climate in some areas(such as strong winds and icing).The original transmission tower foundation is facing new challenges.Therefore,the research on the foundation of the transmission tower in the soft soil foundation has become an important subject.The branch pedestal pile is formed by manual digging,and the bearing disk is formed at the position of the soil with better mechanical performance.The enlarging head is formed at the bottom of the pile,and the bearing capacity of the soil around the pile is fully utilized through the end bearing action of the supporting plate and the enlarged head.It has high bearing capacity and is very suitable for the foundation of transmission tower with high safety factor.In order to have branch pedestal pile used in transmission tower foundation often subjected to composite loads,according to its characteristics,through the finite element software,ABAQUS,explore the impact of reamed enlarged bottom plate pile diameter,enlarged diameter,plate depth,load ratio,supporting disk belled piles spacing,the proportion of load bearing on the performance.The load displacement rule,the axial force distribution law of pile body,the moment changing rule of pile body,the distribution characteristics of side friction and the percentage of load distribution are studied under combined load.The results show that The bearing capacity of the reamed pile is high,and the vertical bearing capacity of the pile with 16.7m length and 0.6m diameter is 3000~4000kN Under the limit load state,the stress of soil around pile is mainly distributed in the range of 1~3m near the branch plate and the enlargement head,and the length of the pile is about 5m and the radius is about 8~10m.The support plate and the enlargement head play a great role in the bearing of the pile foundation.Under the limit load,the load bearing proportion is up to 87%.The axial force distribution trend of the branch pedestal pile is similar to that of the branch pile.The axial force suddenly changes,and a part of the load is discharged to the soil around the pile through the end bearing effect of the supporting plate,so as to ensure the safety bearing of the pile foundation before the pile end resistance is exerting.The optimum geometric parameters of single pile are disk diameter 2.5D,enlarging head diameter 3D,supporting disc buried depth 6~10m,and the best pile spacing of group piles is 4D(D is the pile diameter).Under the action of horizontal load,the vertical bearing capacity of the pile will be reduced,and the decrease of bearing capacity increases with the increase of the specific gravity of the horizontal load.Based on the principle of bearing capacity of branch pile with enlarged head,this paper puts forward the adjusting coefficient of uplift and compression bearing capacity and pile group effect coefficient under compound load,and modifies the calculation formula of bearing capacity of branch pedestal pile.The branch pedestal pile is a new type of pile that has not been standardized in recent years.The results of this paper show that the branch pedestal pile has good composite load resistance and is suitable for the tower foundation of transmission line.The content of the author's research provides a reference for the application of the branch pedestal pile in the transmission line project.