Application Of Jet-grouted Column In Soft Foundation Treatment Of High-speed Rail

The jet-grouted mixed column is formed by organically combining the mixed process of the cement soil mixing pile with the high-pressure jet-grouting technology by innovatively improving the construction machinery and equipment,which can be applied to pile-supported reinforced embankment.This paper relies on a section of Xu-Yan high-speed railway project where jet-grouted mixed columns are applied in soft soil foundation improvement.The article used field experiment,theoretical analysis and numerical simulation to study the reinforcement effect and construction technology of the jet-grouted mixed column reinforced embankment,thereby proposed an appropriate design method for the jet-grouted mixed column composite foundation.The main contents and conclusions of this paper are as following:(1)According to the actual construction situation on site,the construction technology and quality control standard of jet-grouted mixing pile are summarized,construction method,technological process,quality control measures and quality examination meathods were given in detail,which could provide reference for the construction practice of jet-grouted mixing pile under the similar engineering geological conditions.After analyzing the economic benefits of the jet-grouted mixing pile,it is found that the use of jet-grouted mixed column can reduce the construction cost by about 9% under the condition of similar reinforcement effect.(2)Field test study was carried out based on the foundation reinforcement project of XuYan high-speed railway in section XYZQ-?.The deformation of the reinforced embankment and the loading distribution rule between pile and soil under the embankment load were analyzed.The monitoring results show that with the increase of embankment filling,the stress on the pile was always larger than that on the soil and the difference between the two value increased firstly and kept stable finaly;the soil pressure at the center of the embankment was greater than that at the shoulder.The final pile-soil stress ratio was 4.12~10.63 and the load sharing percent was 40.2%~59.4% when the filling height reached 6.6m.(3)Using ABAQUS numerical analysis software,the numerical analysis model was established according to the field conditions.By adjusting the elastic modulus of pile(range from 20 MPa to 81920MPa),the foundation settlement,differential settlement between pile and soil,horizontal displacement,pile-soil stress ratio and excess pore pressure at different depths of 13 groups of jet-grouted mixed column-supported embankments model with different pile strengths were compared and analyzed.The analysis results show that 160 MPa can be taken as the determination limit of flexible pile and rigid pile,which provides a basis for the classification design of the reinforced embankment of the jet-grouted mixing pile.(4)Based on the bearing capacity control principle and combined with the results of field test and numerical analysis results,the design method of reinforced embankment with jetgrouted mixed column was discussed,its rationality was verified by the actual project of XuYan high-speed Railway.