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To built high standard railway in deep soft soil foundation,soft soil consolidation deformation lasting with a long and large process under the effect of load, It has been an important issue in railway construction that how to accomplish the control of roadbed post-construction settlement effectively. Especially in the deep soft foundation area with gravel hardpan, the conventional foundation treatment way is difficult to penetrate the hard layer reinforced by deep soft soil, another problem is that the cost too high to replace railway by bridge with bored pile, site using bag-grouting-pileh can penetrate through the clip hard layer and reinforce the below soft soil.But at present,the mechanism and consolidation deformation character, the settlement calculation methods with using the bag -grouting-pileh to reinforce the foundation, there is still no systematic research achievements, urgently need further research.Paper analysis and summaries the related research achievements in domestic and international, based on the ningbo-taizhou-wenzhou high-speed passenger railway engineering practice, developing field tests, using the method of combining finite element calculation and theoretical analysis to analysis foundation reinforcement effect with bag -grouting-pile, and compared with the existing calculation method, discussed the bag -grouting-pile design calculation method. Main job is as follows:Conducting field tests. Selected typical experimental segment, in view of sub grade relative parameters designed test experiment, embedded components on field, did long-term monitoring of bag -grouting-pileh foundation deformation, pile soil pressure etc. analyzed the test data to get the deformation of variation of bag-grouting-pileh foundation settlement, pile soil pressure distribution and the change rule, through the measured data, studied bag -grouting-pileh foundation reinforcement effect and its working characters.Discussing foundation settlement calculation method,carrying out the bag grouting-pileh foundation calculation method research. Aiming at interlining composite foundation for a special case, put forward a set of bag -grouting-pile settlement calculation method, and got calculated results with experimental data to mutual validation.Based on field survey and indoor test material, reasonably determining the bag-grouting-pile for calculation and analysis of the calculated parameters, using the universal finite element program, PLAXIS, modeled a finite element for clip hardpan under the condition of deep soft soil foundation with bag-grouting-pile foundation roadbed grouting process to simulation analysis.Comparing the test data and the finite element calculation results, the two methods got the results obtained same distribution and the data were quite anatomizes; According to the finite element calculation results, studied bag -grouting-pile displacement field distributions, and thoroughly discusses the foundation settlement and lateral shift, the soil pore water pressure, bag -grouting-pile side horizontal force and pile body deflection with the change rule of sub grade filling, Simulated and analyzed on the same deep foundation conditions without using bag -grouting-pile reinforcement’s foundation, and compared the calculated results with bag grouting-pile foundation.The results show that bag-grouting-pile effective reinforce clip hard layer deep soft soil foundation, satisfying the post-construction settlement control requirements; bag-grouting-pile foundation speed up the drainage consolidation early,late add the effect reinforcement as vertical enhance body of foundation. Research identified bag-grouting-pile reinforcement mechanism, obtained the bag-grouting-pile work traits and design calculation method, be beneficial to popularization and application bag-grouting-pile technology, in order to solve clip hard layer of this special deep soft soii foundation way to handle the problem, enrich the foundation treatment technology.
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