Field test research on treatment effect of embankment foundation in class. dead-weight collapsible loess zone along railway passenger dedicated line

The experimental section is located in the class. dead-weight collapsible loess site and is composed of three different kinds of loess foundation treatment measures. The transition sections without foundation treatment exist between them. All 22 m depth of collapsible loess is treated in zone of piles with down hole dynamic compaction. The upper 15 m depth of collapsible loess is treated in zone of cement soil compaction piles. The upper 6 m depth of collapsible loess is treated in zone of dynamic compaction. The results show that the collapsibility of loess within treatment depth has been completely eliminated. Their bearing capacity is higher than the standard value. The composite foundation settlements of piles with down hole dynamic compaction and cement soil compaction piles are less than 15 mm after construction for high-speed railway; but the dynamic compaction foundation can not meet the same requirement. In zone of pile with down hole dynamic compaction, the minimum and average coefficients of compaction are respectively more than the standard values of 0.88 and 0.93; but the average coefficient of compaction and compression modulus of piles are respectively less than the standard values of 0.97 and 100 MPa. In zone of piles with cement-soil compaction piles, the minimum and average coefficients of compaction, or the average coefficient of compaction and compression modulus of piles are also less than the same standard values. Average compression modulus of dynamic foundation is less than the standard value of 15 MPa. The reasonable values of test standard need further study.