Model Test Of Deformation Of High-Speed Railway Embankment Overlying Mined-Out Area

The mined-out area is commonly avoided in most of the high-speed railway in China at present, and some small mined-out area is controlled considering the straight and smooth of the railway track.There is alreadly some researches about pile-plank structure in soft soil foundation, but the corresponding research of this structure used in mind-out area is rare. In this dissertation, based on the regulation project for mined-out area below the WuFuShan station roadbed of Hefei-Fuzhou high-speed railway, the working mechanism and the settlement of the pile-plank structure were studied by model test. The main achievements of the research are showed as follows:①The axial force gradually decreases with the increment of the pile depth, the maximum axial force appears at the top of the pile, the axial force is constant in the mined-out area; the end bearing capacity gradually decreases with the increment of the pile length.②The skin friction of piles decreases with the increment of the pile depth, it is bigger on the upper section of the pile and is zero in the mined-out area; the load shared by the skin friction increases with the growth of the pile length.③The change regulation of the pile-soil stress ratio is similar to the sharing stress ratio of piles, they both increase with the increment of loads, The pile-soil stress ratio is127and the sharing stress ratio of piles is55.8%at the ultimate load.④The settlement gradually increas with the increment of the load; the settlement in different locations are diverse, but the difference is very small; it turns out to be that the plank is rigid under loads, it is affected by forces and appears to sink as a whole; as the load increases, the settlement curves are steep initially and become gentle later, and remain a stabilized increasing trend finally.⑤The treatment effect of pile-plank structure used for mined-out area is essentially obvious. The overall settlement of the plank is relatively small, and the axial force of the pile is small around the mined-out area and the settlement on the roof of the mined-out area is barely zero value.