Study On The Influence Of High-Speed Railway Vibration On The Bearing Characteristics And Dynamic Response Of Adjacent Belled Piles

Compared with conventional pile foundations,belled piles have more safety reserves for bearing capacity.The full life cycle of the static load generated by the superstructure and the dynamic load of the surrounding train needs to be studied.In many cases,the pile foundation will be affected by the dynamic load of the surrounding.Therefore,based on previous studies,this thesis investigates the impact of belled piles on the static load of the superstructure and the dynamic load of the surrounding,The expected results will help enrich the design,construction,and maintenance of belled piles,and can serve a basis for similar work.The following are some studies conducted in these two areas:Theoretical calculation of belled pile foundation.Summarize the deformation laws of widened bottom piles and the load transfer laws along the pile body;Based on the analysis of standard calculation methods,the settlement calculation formula for the foundation pile and foundation soil when they are expanded as a whole is derived,and the stress analysis of the pile soil model around the train is performed.Indoor model test on bearing capacity and dynamic response of expanded bottom pile.Carry out static load test and dynamic response test of belled pile.Through these two parts of test,the variation of bearing characteristics of the belled pile around the operation line under the influence of various factors during use is analyzed.Finite element analysis of bearing mechanism of belled pile.The numerical simulation is used to make up for the deficiency of model test.The static load on belled piles and the dynamic load on surrounding trains are simulated to completely analyze the bearing mechanism and dynamic response law of belled pile foundations with different specifications under the static environment.Through detailed analysis,the following conclusions are drawn:(1)Selecting belled pile to replace equal diameter pile can simultaneously shorten the pile length to reduce the material cost and effectively avoid existing buildings,greatly increasing the safety reserve;In the actual project,in addition to selecting the size of belled pile according to the specification,it should also consider whether the efficiency of bearing capacity lifting matches the cost of increased materials.(2)The axial force of the belled pile shaft is distributed more evenly,and the deformation of the soil around the pile mainly occurs within the 2D range of the pile;The influence range of belled pile on foundation soil is wider,and the increase of load will cause the whole belled section to be completely separated from the soil around the pile,but the pile shaft constant section always keeps in good contact with the soil.(3)Increasing the belled diameter mainly affects the dynamic response strength of the pile end.When the belled diameter reaches 2d,the influence of the adjacent train load on the pile body becomes significantly smaller;The vehicle speed can directly affect the dynamic response strength of the pile bottom near the belled pile foundation,and the vehicle speed should be controlled to a certain range when it is near the pile foundation.(4)The train load has the greatest impact on the vertical displacement of adjacent piles,and the dynamic stress and vertical velocity of the pile shaft at the burial depth of 1/6L change the most acutely.The vibration load on the subgrade has less impact on the displacement of the foundation soil layer,but has greater impact on the displacement of the pile foundation in the foundation soil layer.