Analysis on Settlement Controlling Effect of pile-net Composite Foundation on Collapsible Loess by Centrifugal Model Tests

On the basis of already-conducted experimental study at home and abroad,the centrifugal model test is used to imitate the pile-net composite foundaton with different pile spacing so as to study the settlement controlling ability of the pile-net composite foundation on collapsible loess ground.The research results show as follows:The collapsible loess ground cannot meet the requirements of settlement after construction of ballasted tracks of high-speed railways and it needs to be reinforced;the settlement after construction,differential settlement,pile-soil load share ratio and negative skin friction of the pile get larger with extending of pile spacing by two to six times of the pile diameter;Settlement settlement rate after construction can be controlled effectively and differential settlement can be reduced by setting of the pile-cap;the neutral point of the relative displacement between the pile and inter-pile soil drops obviously with extending of pile spacing;the value of the relative displacement between the pile and cushion increases with extending of pile spacing in the construction stage and decreases after construction.