Numerical Simulation Analysis Of Deformation Of High-Speed Railway Embankment Overlying Mined-Out Area

Pile-plank structure is a kind of new-type form of basic structure under the rail with the appearance of the construction of railway, the pile-plank structure has a good effect on dealing with the collapsible loess subgrade of Zhengzhou-Xian passenger dedicated line and the soft soil subgrade of Wuhan-Guangzhou passenger dedicated lines, but it is a new research topic that the pile-plank structure is applied to the treatment of subgrade above mined-out area in high-speed railway. For this kind of processing method, there are no norms to be followed and the literature in this area is also very little. For this kind of project, usually just rely on the experience to guide the construction at present,In this dissertation, based on the embankment section of DK499+920and DK499+940in Wufushan railway station, the three-dimensional numerical modeling is built by geotechnical finite difference software FLAC3D, it is analyzed and studied that the settlement and deformation rules of section one and section two under the embankment load and the load transfer mechanism of the pile-plank structure and so on. The main contents and results are as follows:(1) Summarize systematically the present situation of the research on the theory of mining subsidence, the deformation of subgrade above mined-out area, the stability of mined-out area, the disposal technology for mined-out area at home and abroad. At the same time, the numerical simulation methods for subgrade deformation and stability above mined-out area are analyzed.(2) Analyze the numerical value of the two sections, which shows that the pile-plank structure can transmit effectively the upper load to the soil around piles, reduces significantly the pressure on the soil among piles, reduces effectively the amount of compression of the stratum and the total settlement of the ground, and reduces effectively the deformation of subgrade above mined-out area. All above prove that pile-plank structure has good reinforcement effect on subgrade above mined-out area.(3) Study on the settlement and deformation rules of the embankment of the two embankment sections which suggest that settlement of the long pile should be less than the settlement of the short pile in the same embankment load; the settlement of piles through the mined-out area and the other piles which are not through the mined-out area has little difference; the central soil settlement of four piles and two piles is essentially the same under the same embankment load; the settlement of pile top on the shoulder is smaller than that in the centre of the subgrade; the relative displacement between the pile and the soil increase with the increment of the height of embankment fill.(4) Study on the load transfer mechanism of the embankment of the two embankment sections which suggests that the axial force along the pile body is large small distribution under the embankment load, the axial force remains constant in the mined-out area; the distribution of the skin frictional resistance of the pile increases first and then decreases along the pile, the skin frictional resistance of the pile is zero in the mined-out area; both the Pile-soil stress ratio and the pile-soil load share ratio increase gradually with the increment of the height of the embankment fill, and eventually tend to a stable value.