Experimental analysis on settlement controlling of geogrid-reinforced pile-raft-supported embankments in high-speed railway

Centrifugal model tests were performed to investigate the effectiveness of settlement control using geogrid-reinforced pile-raft-supported embankments for high-speed railways on collapsible loess. Firstly, the acceptability of using remolded loess to simulate the behavior of undisturbed collapsible loess in wetting test was examined in centrifugal tests. The settlement of geogrid-reinforced pile-raft-supported embankments under different conditions was then investigated using remolded loess. Experimental results showed that the collapse deformation process of remolded and undisturbed collapsible loesses can be divided into three stages with respect to time. The settlement of embankment built on collapsible loess foundation without improvement does not meet the post-construction settlement constraint for embankment of ballasted track of high-speed railways. The use of rigid piles can significantly reduce embankment settlement and the rate of post-construction settlement. It was also observed that the negative friction developed in the piles varies with pile spacing and pile configurations.