Study On Settlement Characteristics And Optimal Design Of Composite Foundation With Variable Length Piles In Jinan West Railway Station Of High-speed Railway

High-speed railway requires not only the higher strength of embankment, but also higher control of settlement. CFG-pile composite foundation,as a method of processing deep layer of soft soil, controls the settlement of embankment bed effectively and cost savings. Changing the length of the pile, the divergence of settlement will be controlled effectively. In this paper, based on the study of composite foundation settlement test in Jinan West railway station of Beijing-Shanghai high-speed railway, the character of the settlement of railway embankment are analyzed by both ways of monitoring and numerical simulation, which includes:1 .The sedimentation feature of the embankment is analysed in filling phase via observation of CFG-pile composite foundation surface deformation, setelmment of soil between pile and soil stress in field.The result of section test show that:foudation maximum settlement does not occur in the middle of the roadbed because of the changing of pile length.And the result of layered settlement observation shows that the major compression deformation of composite foundation is in the bottom of reinforce area or a certain range on top of the subjacent layer. Pile-soil stress observation test shows the major stress transfers from inter-pile soil to pile cap then to pile top along with the increase of filling soil load.The maximum stress is on the top of the pile,the medial is in the centre of the pile cap and the minimum is in the edge of the pile cap when the filling is finished up to 05.05.2009.2. Aming at the station ebankment,using Drucker-Prager elastic-plastic model,numeric analysis model is established by ANSYS software.Embankment load's influnce depth to composit foundation has been proposed by analyzing,the result of numerical simulation has been validated by observed dataAt last ,the final settlement of the foudation surface after preloading has been predicted by numerical simulation.3. Changing the length of the pile,optimal design model is established .Analyzing the characteristic of distortion in projects of different length of pile through numerical calculation to choose rational design project of optimal lengh of pile. According to the different needs in sinking in different projects,raising a rational design project.