Numerical Analysis And In-Situ Test Of Embedded Continuous Pile-Board Structure In Zhengzhou-Xi'an Passenger Dedicated Line

The high-speed railway in China is constructed on large-scale.The key technical problems of the settlement control for the line structure are related to the success of construction high-speed railway due to the high requirements of high speed,safety,regularity and comfort.As the foundation of track,the settlement control of subgrade plays a key role to meet the requirements.It is urgent to control the post-construction settlement at present for high-speed railway subgrade.Genaral ground treatments are difficult to satisfy the requirement of post-construction settlement.The embedded continuous pileboard structure is applied in deep collapsible loess of high-speed railway.Due to the immature design theory of such structure and lack of studies on the service performance and mechanical characteristics of embedded continuous pile-board structure,researches on the embedded continuous pile-board structure are done by numerical analysis and in-situ test in this paper as follows.Firstly,according to the the collected data at home and abroad.the theory of thermal field about the embedded continuous pile-board structure is analyzed, and the thermal conductivity of the graded broken stone is presented between 0.4 W/(m·K) and 0.7W/(m·K),with the thermal load of bearing board about 8.7℃.Meanwhile,the thermal conductivity characteristics of the graded broken stone with standard grading and other groups with different densities,water contents,particle sizes are analyzed on basis of the laboratory test.The thermal conductivity of the graded broken stone increases with the increase of the density. The water content within 9%has little effect on the thermal conductivity. Meanwhile,when the grading of the graded broken stone is changed,its thermal conductivity is less than that with standard grading,no matter the particle becomes bigger or smaller.Secondly,the characteristics of the force and deformation are analyzed in the established planar model of the embedded continuous pile-board structure with the finite element software.The analysis shows that the vertical force,shear force and horizontal displacement at the top of piles at both ends of the structure reaches their maximums under the load of the super-structure and temperature.The major horizontal displacement of the pile distributes in the range of 8m below the pile head.and the major moment and shear in the range of 10m.Thirdly,combined with the engineering practice of the embedded continuous pile-board structure in Zhengzhou-Xi'an passenger dedicated line,the researches are made as follows:the variation law of stress and strain of the board. the displacement variation of the board,the contact stress between board and embankment and between board and graded broken stone layer,the temperature distribution law of board and pile and the stress distribution law of pile.1he characteristics of the force and defomation in this research match well with the numerical analysis results.